Next Article in Journal
Structural Principles of Ion-Conducting Mineral-like Crystals with Tetrahedral, Octahedral, and Mixed Frameworks
Previous Article in Journal
Plagioclase Megacrysts in Mesoproterozoic Amphibolites from the New Jersey Highlands, USA: Indicators of Mixed-Source Magma and Fractionation Interruption in Anorthosite-Dominated Terrains
Previous Article in Special Issue
Genesis and Related Reservoir Development Model of Ordovician Dolomite in Shuntogol Area, Tarim Basin
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Minerals
Volume 14
Issue 8
10.3390/min14080769
minerals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Diagenesis of Cenomanian–Early Turonian and the Control of Carbonate Reservoirs in the Northern Central Arabian Basin

by
Fengfeng Li
*,
Yong Li
,
Haiying Han
,
Wenqi Zhang
and
Lei Li
Research Institute of Petroleum Exploration and Development, Petrochina, Beijing 100083, China
*
Author to whom correspondence should be addressed.
Minerals 2024, 14(8), 769; https://doi.org/10.3390/min14080769 (registering DOI)
Submission received: 20 June 2024 / Revised: 23 July 2024 / Accepted: 25 July 2024 / Published: 29 July 2024
(This article belongs to the Special Issue Dolomitization, Recrystallization, and Cementation in Carbonate Sedimentary Rocks)
Browse Figures
Versions Notes

Abstract

:
The carbonate reservoirs of Cenomanian–Early Turonian in the northeastern Central Arabian Basin hold considerable oil reserves and are great contributors to oil production. Diagenesis have a great impact on carbonate reservoir petrophysical properties, microstructure, and heterogeneity. By integrating cores, cast thin sections, regular core analysis, CT, and isotopes, this study provides an improved understanding of diagenesis in the Cenomanian–Early Turonian and its effect on carbonate reservoirs. The results showed that three diagenetic environments were identified in the Cenomanian–Early Turonian based on texture, structure, cement, crystal form, and crystal size, which were marine environment, meteoric environment, and burial environment. Six diageneses were identified based on residual bioclastic, secondary pores, calcite quantity, dolomite size, and stylolite, namely dissolution, cementation, micritization, dolomitization, compaction, and pressure solution. A micritization model in high energy sediment, a dolomitization model in burrows, and a comprehensive diagenetic model were established. It concluded that dissolution during meteoric environment is most favorable to reservoir physical properties, while cementation is least favorable. The cement content controls the microstructure and petrophysical property. Micritization is detrimental to the petrophysical properties, and the micrite it forms are distributed in the interparticle pores, reducing the reservoir property deposited in high energy environment. Dolomitization is less developed in substrate but widely developed in burrows, which result in the physical properties of the burrows being higher than those of substrate. Compaction and pressure solution have a negative impact on reservoir physical properties.

1. Introduction

The Upper Cretaceous Cenomanian–Turonian stratigraphic interval in the Arabian Plate contains prolific, high-quality conventional carbonate reservoirs in the Mishrif Formation and equivalent units such as the Sarvak and Natih Formations [1] (Figure 1). The Cenomanian–Turonian cycle started with transgressive Ahmadi Formation marl overlain by the Rumaila Formation shelf chalk-bearing carbonate deposits then followed by regressive Mishrif Formation carbonate deposits with rudist bivalves and then open platform facies carbonate deposits of the Khasib and Tanuma Formations [2,3,4]. The Central Arabian Basin is considered as one of the richest petroleum systems in the world. Most of the oil and gas discovered within the basin are in the Cretaceous [5]. During the Cenomanian–early Turonian, the Mishrif Formation within the basin formed as a part of the Wasia Group and has widespread distribution throughout the Arabian plate [6], which is one of the significant carbonate reservoirs throughout the Middle East. The Mishrif Formation is dominated by a shallow-water and shelf carbonate sequence with reservoir porosities exceeding 20% and permeabilities of 100 mD to one Darcy [7]. The study area is in the northeastern Central Arabian Basin, an important oil-producing region in the Middle East, and many giant carbonate oilfields are located here [8,9]. The Cenomanian–Turonian in the Central Arabian Basin is an important oil-producing interval, and the Mishrif Formation is the main reservoir for all of these giant fields.
To date, there are a large number of studies on the Cenomanian–early Turonian, especially the Mishrif Formation, many of them focusing on one or a few fields. The study includes regional geology [10,11], petroleum systems [7,12], tectonism [13,14], source rocks [4], stratigraphy [15], sequences [16,17], sedimentation [18,19], reservoirs origin [20], reservoirs characterization [21,22,23,24], diagenesis [2,25,26,27], and reservoirs rock type [28,29]. The carbonate diagenesis is a significant subject of massive complexity, due to crucial chemical reactivity of the carbonate minerals [30,31]. These minerals react quickly with the acidic or basic waters that either dissolve the carbonates or precipitate new carbonate minerals to bring finally the water into equilibrium with the host carbonate sediments and rocks [30]. The timing and mechanism for porosity formation in deep burial carbonate reservoirs is of great importance and problematic [32].
Many studies on the diagenesis of Cenomanian–early Turonian have been completed. Seven mega sequences (MSQ1~MSQ7) and 18 sequences (K10~K180) were developed in the Cretaceous, and the Cenomanian–early Turonian is one of these mega sequences (MSQ5), with three sequences developed within it (K120~K140) [9,33]. Han, et al. (2022) identified a new maximum flooding surface, K135, between K120 and K140. Therefore, the Cenomanian–early Turonian was finally considered to have developed four sequences within it [34]. At the top of this mega sequence, which is also the top of the Mishrif Formation, is a regional unconformity that can also be well correlated throughout the Arabian Plate. Karstification is commonly developed in the vicinity of the unconformity. Cantrell, et al. (2020) pointed out that while diagenesis has overprinted and altered this initial framework, karsting—resulting in both enhanced reservoir quality due to leaching and reduced reservoir quality due to cementation, brecciation, and fines infiltration—associated with sequence boundaries within and at the top of the Mishrif Formation represents the major flow-significant diagenetic effect in the reservoir [25]. Karstification has two sides to reservoirs, not necessarily forming good reservoirs, but also adversely affecting reservoir physical properties. De Periere, et al. (2017) revealed that fine micrites are likely to be the product of early neomorphic recrystallisation in the lowermost part of the paleo-aquifer associated with the top-Mishrif Unconformity, and were precipitated from meteoric or mixed dysoxic waters which were slightly supersaturated with respect to calcite [35]. Karst is also selective for sedimentary facies. Zhong, et al. (2019) identified that eogenetic karst is developed in the Mishrif Formation of the Halfaya oilfield and pointed out that the occurrence frequency of karstification is high in the relatively high-energy environments such as shoals and low in the low-energy environments such as intershoal sea and open sea [2]. In addition to the karst at the top of the Mishrif Formation, karst can also form at the other sequences boundary within Mishrif. Chen, et al. (2022) identified unconformity at the top of the B21 subzone of the Mishrif Formation and carried out systematic research on karstification within the Mishrif Formation [36]. Both karstification and penecontemporaneous dissolution are important for reservoirs. Mehrabi and Rahimpour-Bonab (2014) pointed out that the most important diagenetic processes that affected the upper Sarvak reservoir carbonates are extensive meteoric dissolution and karstification, karst-related brecciation, and the development of bauxitic-lateritic horizons [37]. The Cenomanian–early Turonian is characterized by multiple diagenetic environments with complex reservoir diagenesis. Chafeet, et al. (2020) identified four diagenetic environments in the Mishrif Formation that were the meteoric vadose, meteoric phreatic, marine phreatic and mixing zone, and revealed diagenesis process such as micritization, dissolution, cementation, compaction, neomorphism, dolomitization, and authigenic minerals [26]. Jodeyri, et al. (2018) pointed out that general diagenetic of Cenomanian–Turonian include micritization, cementation, dissolution, compaction, dolomitization, pyritization, and fracturing [38]. The type and extent of diagenesis is usually influenced by tectonics, climate, sequence, and sedimentation. Newport, et al. (2020) revealed the interaction of tectonics, climate, and eustasy in controlling dolomitization of the Cenomanian–Turonian [39]. Hollis (2011) revealed that the development of a peripheral bulge in late Cenomanian–Turonian, halokinesis, localized influx of channelized clastic material and subregional climatic variability contributed to a heterogeneous pattern of meteoric diagenesis across the Arabian Plate [40].
However, less attention has been paid to some aspect of diagenesis of Cenomanian–Early Turonian and some diagenetic questions remain unanswered. First, the karstification associated with sequence boundary at the end of Cenomanian–Turonian has been clearly described. Penecontemporaneous dissolution, occurring within the sequence or not controlled by unconformity, has a significant impact on the reservoir of the Cenomanian–Early Turonian. Although penecontemporaneous dissolution has been studied, it is much less well understood than karstification. Secondly, dissolution is usually treated independently from cementation, but in fact the two are complementary. The coupled effect of dissolution and cementation on reservoir physical properties is less studied. Thirdly, dolomitization is biased towards mechanisms in matrix or grains, while less research has been completed on dolomite mechanisms in burrows formed by bioturbation which is ubiquitous. Finally, it is puzzling that reservoirs deposited in high energy environments typically contain abundant micrite. Normally, sediments in high-energy environments are supported by grains and no micrite can be seen, but a large number of micrite are present in the pores, and the micrite origin needs further studied.
The objectives of this work, therefore, were to (1) investigate the diagenetic environment of the Cenomanian–Early Turonian; (2) analyze the diagenesis mechanism, characteristics of performance, including dissolution, cementation, micritization, dolomitization, compaction and pressure solution, and establish a micritization model and dolomitization model in burrows; and (3) unravel the effect of diagenesis on reservoir physical properties, especially the combination of dissolution and cementation.

2. Geological Setting

In the Cenomanian–Early Turonian, the Northern Central Arabian Basin was in a unique carbonate depositional environment. During the Early Cretaceous, the Arabian Plate moved toward the tropics and subtropics, and the Neotethys Ocean continued to rift, forming the Southern Neotethys Ocean at the northern and eastern margins of the Arabian Plate due to mantle subduction during extensional periods [41]. The opening of the Southern Neotethys Ocean led to the cessation of evaporite deposition in the Jurassic Gotina Basin, which has since converted to the Balambo-Garau Basin in the Cretaceous [42,43]. By the Middle Cretaceous, the Neotethys Ocean reached its maximum in rifting [34]. Meanwhile, the Amara uplift was formed by the Hormuz salt diapirism and the reactive of block faults in the Precambrian [44]. In Cenomanian, differential subsidence formed the Najaf Basin in central Iraq, and from the Amara uplift to the Najaf Basin, a broad, shallow-water carbonate ramp was formed [45]. The Najaf Basin filled with fine-grained organic-rich sediments and was rimmed by shallow-marine carbonate sediments that prograded into the basin [25]. The depositional system was typically described as a shallow, rudist buildup-rimmed carbonate platform, fringing the organic-rich sediments of the intrashelf basin [21] (Figure 2). By the Late Cretaceous, this passive margin changed to a convergent margin after north-easterly subduction of Neo-Tethyan oceanic lithosphere [46].
The Northern Central Arabian Basin in Cenomanian–Early Turonian was deposited in a shallow carbonate ramp, and developed supratidal flats, lagoons, tidal channels, mounds, shoals, front shoals, a slope bottom, and an open shelf [47] (Figure 3). During the Cenomanian–Early Turonian, the water was shallow and sensitive to changes in sea level, resulting in frequent changes in diagenetic environment. The depositional hydrodynamics of the shoal, mound, and tidal channel are strong. The depositional hydrodynamics of the front shoal and the slope bottom are moderate, and the depositional hydrodynamics of the lagoon, the open shelf, and the supratidal flat are weak. Diagenesis can differentiate the reservoirs physical properties in the same facies as well as converge the reservoirs physical properties in different facies.

3. Materials and Methods

The paper selected 16 coring wells from 4 carbonate oilfields in the Northern Central Arabian Basin. The coring intervals were mainly concentrated in the Mishrif Formation. In total, about 800 m cores, 1500 cast thin sections, 2000 physical properties, 200 m CT, and 10 isotopes were available in this study. The cores were described and the lithology, pores, and depositional textures such as bioturbation and stylolite were characterized. Cast thin section samples were analyzed using a polarizing microscope. All were stained using Alizarin Red S to differentiate the dolomite from calcium carbonate. The physical property was derived from core plug analysis and used to clarify the effect of diagenesis on the reservoir. The CT were described to recognize mega-pores or stylolite. The isotopes were used to identify the diagenetic environment.
First, the residual bioclastic, cement generation, pore types, dolomite morphology and size were identified via observation of cast thin sections and cores based on expert judgement and then the diagenetic environment was identified. Secondly, diageneses were identified based on the observation of cores, cast thin sections, and CT. The diagenesis characteristics, mechanism, and evolution were analyzed based on the theory of sedimentary, petrology and reservoir geology, and some diagenetic models were established. Finally, the type and effect of diagenesis on reservoirs was investigated via cast thin sections and physical property data, especially the dissolution and cementation. A physical property scatter plot was developed to illustrate the effect of dissolution-cementation on physical properties.

4. Results

4.1. Diagenetic Environment

4.1.1. Marine Environment

Major diagenetic fabrics of marine diagenetic environments of the Cenomanian–Early Turonian include geopetal, fenestral, different generations of calcite, micrite envelope, and bioturbation (Figure 4). As shown in the cast thin sections and core in Figure 4, the geopetal refers to the structure where the lower part of the pore is filled with marine micrite, while the upper part is filled with calcsparite, with a clear boundary between the two (Figure 4a). The fenestral usually develops in a supratidal flat, representing the escape of bubbles generated by the decay of organic matter in marine environments and the subsequent filling of the pores (Figure 4b). The cement in a marine environment is usually fibrous or bladed, while the cement formed in other environments is usually equant, isopachous rims, and grows gradually towards the center of the pores (Figure 4c). Micrite envelope results from micritization in marine environments, where extensive boring leads to the precipitation of micrite. Micrite envelope retains the original contours of bioclastic, which facilitates identification of biology (Figure 4d). Bioturbation is commonly developed in marine environments, especially in low-energy shallow water. On cast thin sections, bioturbation-formed burrows are usually filled with dolomite (Figure 4e), and on cores, the burrows are darker in color than the surrounding rock (Figure 4f).

4.1.2. Meteoric Environment

The meteoric environment of the Cenomanian–Early Turonian is characterized by dissolution and cementation (Figure 5a), which can be subdivided into the vadose zone and the phreatic zone. The phreatic zone underlies the phreatic zone. During sea level regression, sediments are prone to exposure in the vadose zone due to the shallow water setting. Unsaturated fluid has a high capacity for dissolution. Many aragonite or high magnesium bioclasts were dissolved to form a large number of secondary pores. Bioclasts in wackstone are selectively dissolved to form moldic pores (Figure 5b), and bioclasts in grainstone are completely dissolved to form vug pores or interparticle pores (Figure 5c,d). The vadose zone is an open diagenetic system with abundant solute, which is an important period for the development of massive secondary pores. After the sediments are dissolved, Ca2+ in the fluid increase and the fluid is transported by gravity downward to the phreatic zone. The phreatic zone is characterized by saturated fluid and cementation. The cements are usually isopachous, syntaxial and blocky, and are usually greater than 50 μm (Figure 5e,f).
Carbon and oxygen isotopes are important evidence for determining diagenetic environments. These 10 samples originate from the Mishirf Formation in the A field and the lithology includes mudstone, wackstone, packstone, and grainstone (Table 1). In terms of geochemistry, the δ13C values of Cenomanian–Turonian seawater are generally 0‰~3.5‰, while the δ18O values are −0.2‰~−4‰ [48]. The result showed that the δ13C values of 1.84‰~3.97‰ are similar to seawater as a whole, which reflects a stable depositional and diagenetic process, unaffected by significant thermal events. However, the δ18O values of −3.63‰~−5.43‰ are slightly lower than that of seawater. This can be related to a gradual decrease in salinity, increasing temperature of diagenetic fluid, or the influx of freshwater [37]. The Middle Cretaceous was under the domination of a warm and humid tropical climate with heavy rainfall [38]. The study area is deposited in shallow water where the sediments are prone to exposure during the sea level regression. Therefore, the low δ18O values probably result from influx of meteoric freshwater. Furthermore, the precipitation temperature was also calculated based on the Kim and O’Neil equation (1997) [49]. The result showed that the precipitation temperature of all samples was about 20 °C, which was similar to Cretaceous seawater temperature (approximately 25 °C to 30 °C) [50]. According to regional geothermal gradient of 25 °C/km, the present-day temperature of the reservoir was roughly calculated to be between 96 °C and 100 °C. The calculated precipitation temperature indicates no recrystallization during the burial process and this result supports the conclusion that the diagenesis was penecontemporaneous. Therefore, depending on the depth and lithology of the experimental samples, the Mishrif Formation suffered to some extent from meteoric freshwater, regardless of the depositional environment, from deep to shallow.

4.1.3. Burial Environment

The burial environment of the Cenomanian–Early Turonian was characterized by saddle dolomite, ferroan calcite, coarsely crystalline calcite, and stylolite. The time span of the burial diagenetic process was long and the diagenetic setting was stable, the crystals therefore had plenty of time to form [51]. As shown in the cast thin section of the Figure 6, saddle dolomite and coarsely crystalline calcite formed in burial environments with a grain size greater than 200 μm (Figure 6a,b). Furthermore, coarsely crystalline calcite that formed in burial environments are usually uniformly ferroan, resulting in a dark red color (Figure 6c). On the core, the coarsely crystalline calcite, whose size could up to 4 cm, almost filled the cavity (Figure 6d,e). During the burial process, with the increase in temperature and pressure, pressure-solution occurred at the sediment contact to form a stylolite. On the core, the stylolite is widely developed with different morphology (Figure 6f). It is important to note that it is difficult for the burial environment to incur large scale intense dissolution. Ehrenberg (2012) revealed that to increase the porosity of a 100 m thick limestone bed by 1%, 1 m3 of calcite must be dissolved for each square meter of bedding surface. For pore water that is undersaturated by 100 ppm, about 27,000 volumes of water are required to dissolve one volume of calcite. Increasing the porosity by 1% in a 100m thick limestone therefore requires 27,000 m3 of water per square meter [52]. Wang (2018) pointed out that with the increase in depth and temperature, cementation and dolomitization are more prone to occur than dissolution based on in situ simulation experiment [53]. Without a channeling system such as faults or fractures, it is difficult to form an effective supply–drainage system for external diagenetic fluids. Therefore, the burial environment of the Cenomanian–Early Turonian is dominated by cementation and dolomitization, and extensive dissolution is rare.

4.2. Diagenesis

In the Cenomanian–Early Turonian, dissolution, cementation, micritization, dolomitization, compaction, and pressure solution are the most dominant and common diageneses. It should be noted that micritization is one of the forms of recrystallization. Recrystallization usually refers to a process in which the mineralogy remains unchanged and the crystal size increases, whereas degrading recrystallization is the opposite, in which the crystal size decreases. Micritization is known as degrading recrystallization. Dolomitization is one of the forms of replacement, in which calcite is replaced by dolomite.

4.2.1. Dissolution

Dissolution is the most important diagenesis and is the main cause of secondary pores of the Cenomanian–Early Turonian. The reservoir’s physical properties are greatly improved after intense dissolution. Porosity formed in the subaerial also contributes the development of burial diagenesis [54]; almost all high-quality reservoirs are closely related to dissolution. Based on the process and mechanism, dissolution is categorized into penecontemporaneous dissolution and karstification of the Cenomanian–Early Turonian. Penecontemporaneous dissolution is mainly developed in meteoric environments and marine environments. When sediments are deposited, periodic exposure of the sediments occurs as sea level cycles, and fluids, especially meteoric freshwater, can intensely dissolve the sediments. Sediments are buried and compacted into rock, and tectonics cause the strata to be uplifted and exposed to meteoric environments, and thus subjected to dissolution, weathering, or erosion, which is known as karstification. Thus, penecontemporaneous dissolution and karstification act differently, with the former acting on sediments and the latter on rocks. Penecontemporaneous dissolution occurs in the depositional period, controlled by the low-level sequence, which can strongly dissolve sediments without destroying the stratigraphic fabric, forming a large number of secondary pores, which are commonly developed in the stratigraphy. Karstification is controlled by tectonics or high-level sequences, and the dissolution or erosion usually destroys the stratigraphic fabric, which is mainly distributed in the boundary of high-level sequences.
Penecontemporaneous dissolution of the Cenomanian–Early Turonian is characterized by a large number of pores visible to the naked eyes. On the core, a large number of vug pores created via dissolution could be seen. The core is honeycombed, with pore sizes varying up to the centimeter (Figure 7a,b). On the CT, the pores are black in color, different from the bioclastics. The pores are mainly between 1 mm and 5 mm and are poorly sorted (Figure 7c,d), while some well sorted grainstone have pores less than 1 mm (Figure 7e). On the cast thin sections, Algae and Bivalve wackstone has been completely dissolved forming a large number of moldic pores where the Algae and Bivalves can only be judged by pore outlines (Figure 7f). Bivalves, Rudist, or Benthic Foraminifera in grainstone are dissolved, and the volume of interparticle pores increases dramatically, with significantly better connectivity (Figure 7g,h).
Karstification of the Cenomanian–Early Turonian is characterized by breccia and paleosol and occurs mainly at the regional unconformity, which is the top of Mishrif Formation. Strong dissolution at the meteoric environment leads to the collapse of the strata under a wet climate, forming a large number of breccia. The breccias were poorly sorted and were compacted after reburial. In addition, fluid rich in calcium ionic precipitated during the burial process and formed cement between the breccia. On the core, a large amount of breccia is visible at the top of the Mishrif Formation, which is poorly sorted and mosaicked, with interparticles filled with light green cement (Figure 8a,b). In some fields, the paleosol is visible at the top of the Mishrif Formation, which is the result of strata weathering from long-term exposure (Figure 8c). It should be noted that karstification of the Cenomanian–Early Turonian has an unfavorable effect on reservoir properties, especially when the strata collapse to form breccia. This is why the regional unconformity at the top of the Mishirif forms a dense caprock.

4.2.2. Cementation

The cementation of the Cenomanian–Early Turonian occurred in marine environments, meteoric environments, and burial environments. As mentioned earlier, in marine environments, cementation predominantly forms fibrous calcite, which is chemically unstable and not easily preserved, therefore, it is difficult to see in cast thin sections. Cementation in meteoric environments occurs mainly in the phreatic zone, which underlies the vadose zone. The saturated fluid after dissolution in the vadose zone is transported to the phreatic zone by gravity, where the cementation is intense. The cementation forms equant calcite which is chemically stable. The burial environment where the cementation is also intense is characterized by euhedral calcite, some of which is coarse crystal or ferroan. The cement seen in the cast thin section are the result of the superimposition of multiple phases of cementation. Typically, the intensity of cementation and its effect on physical properties is paid more attention than the cement type.
The intensity of cementation can be judged by the cement content. When the cement fills less than 10% of the pore volume, cementation is almost absent, and the pores are well connected (Figure 9a), which usually occurs in the vadose zone of the meteoric environment. When the cement fills 10%~30% of the pore volume, the cementation is not significant, most of the pores are well connected, and only few pore throats are blocked (Figure 9b), which could occur in the vadose zone or the phreatic zone of the meteoric environment. When the cement fills 30%~50% of the pore volume, the cementation is significant and nearly half of the pore is densely filled (Figure 9c), which usually occurs in the phreatic zone or the shallow burial environment. When the cement fills 50%~70% of the pore volume, the cementation is intense, most of the pores are filled and the throats are blocked (Figure 9d), which usually occurs in the phreatic zone or the shallow burial environment. When the cement fills 70%~90% of the pore volume, the pores only retain a small amount that are disconnected from each other (Figure 9e), which usually occurs in the burial environment. The extreme cementation is represented when the cement occupies greater than 90% of the pore volume and the pores are barely visible to the naked eye in the cast thin sections (Figure 9f), which usually occurs in the burial environment.

4.2.3. Micritization

Micritization is prevalent in Cenomanian–Early Turonian carbonate rock. Micritization originates from microborings that are the penetration traces in hard substrates produced by microorganisms which represent mainly Algae, Bacteria, and Fungi [55]. While micritization can destroy bioclastic fabric, it can also serve to preserve bioclastic contour even though the bioclastic have been completely dissolved. As mentioned earlier, micritization is known as degrading recrystallization. Based on cast thin section, the mechanism of micritization is clarified by establishing a diagenetic model. In high-energy depositional environments, the sediments contain bioclastic such as Rudists and Algae, and the bioclastic is clean and free of micrite, and interparticle pores are developed (Figure 10a). In marine environments, micritization occurs in the biologic shells, forming the micrite envelope. Some organic matter of Rudist was decayed, forming of skeletal pores. Algae were completely dissolved, and only the residual micrite envelope retained the outline. Cementation occurs in marine environments and fibrous calcite encrusts on the outer edge of bioclast or inner edge of the pores (Figure 10b). Meteoric environments are characterized by intense dissolution. Fibrous calcite formed in the marine environments is mostly aragonitic or high-magnesium, which was dissolved during meteoric environments. The micrite envelope was also dissolved and became loose (Figure 10c). As the dissolution continued, the micrite envelopes completely lost their original fabric and the micrite were scattered in the pores. The pore volume was then decreased and some pore throats were partially blocked. The Rudist shell lost the protection of the micrite envelope, and were dissolved to some extent (Figure 10d). Algae lost their micrite envelope and only the pore outlines remained. In burial environments, compaction has less of an effect on Rudist fragments due to its hardness. With increasing burial depth, temperature and pressure favored dolomitization and few Rudist fragments were replaced by dolomite (Figure 10e). Finally, it formed its current appearance in the cast thin sections (Figure 10f).

4.2.4. Dolomitization

The Middle Cretaceous was under the domination of a warm and humid tropical climate with heavy rainfall [37], and penecontemporaneous dolomitization is almost absent, and may be locally developed in the upper of Mishrif Formation. The interval is only 3 m to 5 m thick, with anhedral dolomite and a crystal size of less than 50 μm. Due to the lack of further evidence, penecontemporaneous dolomitization cannot be confirmed based on crystal morphology and size alone. In contrast, burial dolomitization is common in the Cenomanian–Early Turonian.
There are two types of burial dolomitization in the Cenomanian–Early Turonian. One occurs in the bioclastic or matrix. The other occurs in burrows formed by bioturbation. In the bioclastic or matrix, the calcite was replaced by euhedral dolomite whose sizes mostly ranged from 50 μm to 100 μm. On cast thin sections, dolomite was not stained and lots of residual bioclasts, such as Rudist, Bivalves, and Echinoderms can be seen. Since the molar volume of dolomite is smaller than that of calcite, intercrystal pores are formed when calcite is replaced by equal moles of dolomite (Figure 11a–c). Bioturbation is easily recognizable on the core. Burrows are darker in color than the substrate and are patchy, striped, networked, or irregularly formed (Figure 11d). On cast thin sections, the burrows also have significantly different structures and compositions from the substrate. The boundaries between the two are well defined and easily distinguishable (Figure 11e). Dolomitization in burrows also occurred in burial environments. The euhedral dolomite with a size of about 100 μm was unstained, and is easily distinguishable from the substrate (Figure 11e).
It should be noted that dolomitization does not occur in all burrows. The paper established a comprehensive diagenetic model in burrows. The sediment deposited in the low energy environment is characterized by lime mud, and it is easier to burrow through before compaction. The burrows are usually filled with organic matter produced by biological metabolism (Figure 12a). Burrow I and burrow II are in contact with the depositional interface, whose infillings are usually dissolved and the burrow will enlarge, while burrow III is detached from the depositional interface, and whose organic filling is preserved (Figure 12b). If there is sufficient diagenetic fluid, burrow I and burrow II will continue to be dissolved and enlarged. The substrate permeability around the burrow will increase, and the bioclastic near the burrows would be dissolved to form moldic pore (Figure 12c). Meanwhile, the continuous dissolution makes the substrate loose or even forms fractures, which can act as channel of diagenetic fluid (Figure 12d). The dissolved burrows would not remain empty but would be filled with sediments again after, such as coarse infillings in burrow I and fine infillings in burrow II (Figure 12e). The actual cast thin sections are shown in Figure 12g,h. The coarseness of the infillings is mainly controlled by depositional hydrodynamics. During the burial process, burrow I and burrow II would undergone conventional diagenesis while burrow III would have a different process.
The organic matter in burrow III provides material for reducing bacteria. Reducing bacteria can remove SO42− that bind Mg2+ and increase the relative content of Mg2+. Moreover, ammonia in organic matter can reflect with H2O to form an alkaline environment, which promotes dolomitization [56]. Burial environments with exotic Mg2+ through fractures can also promote dolomitization. When sufficient dolomitization had occurred, burrow III was filled with euhedral dolomite with some intercrystal pores (Figure 12f). The actual cast thin sections are shown in Figure 12i.

4.2.5. Compaction and Pressure Solution

Compaction and pressure solution occur primarily in burial environments and are characterized by brittle fracture and stylolite Cenomanian to Early Turonian. After the sediments are detached from the depositional interface, the overlying sediments continue to increase, intergranular water is removed from the pores under pressure, and sediments are compacted and become tighter. It should be noted that the early filling of cement between bioclastic can effectively resist compaction. Mud-supported sediments show the greatest volume reduction during compaction. Grain-supported sediments show a relative low volume reduction under compaction, but brittle fractures of bioclasts can be seen in cast thin sections (Figure 13a). Pressure solution is commonly developed in the Cenomanian to Early Turonian and is most notably marked by stylolite. On cast thin sections, different bioclasts such as Rudist, Bivalves, and Echinoderms are closely compacted and some stylolite developed locally. Stylolite can act as fluid-transport channels in buried environments, so diagenesis is more active near stylolite. As shown in Figure 13b,c, dolomite is commonly seen near stylolite, and stylolite can be filled with bitumen. On the core, the stylolites and fractures have different morphology, with the former being irregularly shaped and jagged (Figure 12d–f), and whose scales range from a few centimeters to tens of centimeters, while the latter are usually flat in section.

5. Discussion

5.1. Effects of Dissolution and Cementation on Reservoirs

Dissolution and cementation in penecontemporaneous stage are the most important diagenetic affecting the carbonate reservoirs of the Cenomanian to early Turonian. Dissolution is the most favorable diagenesis for reservoirs, while cementation is the least favorable diagenesis. Dissolution and cementation usually coexist and are in opposition to each other. The results of the two diageneses are reflected in the cement content and reservoir microstructure. The combination of dissolution and cementation was classified into three types based on the cement content of 30% and 70%.
The first one is intense dissolution and rare cementation (Figure 14a), whose cement content is less than 30% of the pore volume. Dissolution dominates the reservoir microstructure. The reservoir is dominated by interparticle pores, vug pores, and few moldic pores; the pores are well connected (Figure 14b,c). The second one is medium dissolution and medium cementation (Figure 14d), whose cement contents range between 30% and 50% of the pore volume. Some pores are filled with calcite and some are retained. The pore throat was severely blocked and the pores were usually isolated from each other (Figure 14e,f). The last one is rare dissolution and intense cementation (Figure 14g), whose cement content is greater than 70% of the pore volume. Cementation dominates the reservoir microstructure. The pores are almost entirely filled with calcite, with a small amount of isolated pore remaining (Figure 14h,i).
Eight depositional facies in the Cenomanian–Early Turonian developed, which are supratidal flat, lagoon, tidal channels, mound, shoal, front shoal, slope bottom, and open shelf. Different depositional facies have different physical properties, but the degree of physical property superposition of different depositional facies is severe (Figure 15a). There are fewer data on open land sheds and supratidal flats, and their physical properties are relatively concentrated. The physical properties of other high energy facies such as shoal, tidal channel, and mound, are overall dominated by medium–high porosity and medium–high permeability, however, these facies also develop some poor reservoirs with low porosity and low permeability. Depositional facies such as front shoal, lagoon, and slope bottom all span large physical property intervals. Overall, sedimentation has limited control over reservoir physical properties. Different diageneses of the same depositional facies can result in differentiation of physical properties, while the physical properties of different depositional facies can converge after diagenesis.
Samples that are identical to the depositional facies were selected and divided according to diagenesis. As shown in the Figure 15b, diagenesis has a clear control on reservoir physical properties and different combinations of dissolution and cementation corresponding physical properties are clearly distinguishable. The intense dissolution and rare cementation correspond to the best reservoir, whose porosity is usually greater than 20% and permeability is mostly greater than 10 mD, up to 1000 mD. The medium dissolution and medium cementation correspond to medium reservoir, with porosity ranging from 10 to 25%, permeability less than 10 mD, and the majority ranging from 1 to 10 mD. The rare dissolution and intense cementation correspond to the worst reservoir, with porosity less than 10% and permeability less than 1 mD (Figure 15b).

5.2. Effects of Micritization on Reservoirs

The effect of micritization on reservoir quality is thought to be minimal [25]. However, micritization in the Cenomanian–Early Turonian has an adverse effect on physical properties. As explained above, micritization has different forms. When the biological shell has undergone micritization to form a micrite envelope, the micrite exists completely at the edge of the shell, the micritization therefore has almost no effect on the physical properties (Figure 16a,b). When the micrite envelope structure is destroyed and micrite fills the pores reducing the pore volume or blocking the pore throat, micritization has a negative effect on the reservoir (Figure 16c–e). Although a small number of micropores develop in the micrite envelope (Figure 16f), the micropores are insignificant compared to the pores occupied by the micrite. It should be noted that micritization occurs in marine environments, and the micrite envelopes formed are usually collapsed in meteoric environments, and then the micrites are usually distributed in the pore. Therefore, micritization in the Cenomanian to Turonian usually act as unfavorable diagenesis.

5.3. Effects of Dolomitization on Reservoirs

Dolomitization occurring in the bioclastic and matrix can form intercrystal pores, which are usually favorable to reservoir physical properties and are not discussed here. The focus here is on the effect of dolomitization on physical properties in burrows.
Dolomitization could completely change mineralogical, structural, and petrophysical properties of burrows, which are different from that of substrate (Figure 17a). The substrate is usually mudstone, wackstone, or packstone. The physical properties of the substrate are poor and the pores are not visible to the naked eye at all (Figure 17b). As the fluid rich in magnesium ironic in the burrows percolates into the substrate, dolomitization also occurs in the substrate adjacent to the burrows, and a small amount of dolomite is visible in the substrate. Furthermore, the blue haze caused by micropores can be seen in the substrate near the burrows (Figure 17c). The dolomitization in the burrows is sufficient, and the original structure and components are almost completely replaced by dolomite. Since the molar volume of dolomite is smaller than that of calcite, a large number of intercrystal pores are formed after dolomitization (Figure 17d). Permeability of the lime mudstone–wackstone matrix that surrounds the dolomitized burrows is commonly below 1 millidarcy, in comparison, the permeability of the burrow-associated dolomite ranges between 1 and 350 mD [57]. The bulk reservoir permeability is influenced by the volume of bioturbation and magnitude of permeability difference between the burrows and matrix. The more adequate the bioturbation, the higher permeability of the burrows, and the higher the bulk reservoir permeability, but the more heterogeneous the reservoir microstructure.

5.4. Effects of Compaction and Pressure Solution on Reservoirs

Compaction has unfavorable effects on reservoir physical properties. During the burial process, the particles and matrix of the mudstone, wackstone, or packstone are compressed greatly and the pore volume is greatly reduced. The grainstone or rudstone, on the other hand, is more resistant to compaction and loses relatively little pore volume during the burial process. Pressure solution has little impact on the reservoir’s physical properties, but in some cases, stylolite can act as a channel for diagenetic fluids in the burial environment and dolomitization near the stylolite is common.

5.5. Comprehensive Diagenetic Model

Based on the tectonic setting, sequence, and basin burial history in southeastern Iraq, a comprehensive diagenetic model for the Cenomanian–Early Turonian has been established on the basis of the above-mentioned studies on the diagenetic environment and diagenesis (Figure 18). During the sea level cycle, the Mishrif Formation underwent full penecontemporaneous diagenesis during the deposition. The micritization and cementation occurred in the marine environment. The micrite envelope is ubiquitous in the Mishrif Formation, but the fibrous cement could not be seen as they struggle to preserve. During the sea level regression, the sediments were intensely dissolved in the vadose zone of the meteoric environment and a large number of secondary pores therefore could be seen on the cores and cast thin sections. There are multiple seal level cycles in the Mishrif Formation, therefore, the cumulative thickness of the dissolution interval is thick. As sedimentation continued, the sediments of the lower Mishrif Formation were buried but at shallow depths and suffered from slight compaction. During the burial process, intense cementation occurred when the sediments were in the phreatic zone of meteoric environment. Primary pores from sedimentation and secondary pores formed by dissolution would have been substantially filled during that period. At the end of middle Cretaceous, tectonism uplifted the shallowly buried Mishrif Formation to the subaerial, and the top of the Mishrif Formation suffered intense karstification, forming a large amount of breccia and paleosol. This exposure continued until the beginning of the Late Cretaceous. The top of the Mishrif Formation was heavily eroded or weathered while the lower section of the Mishrif Formation was less affected. The remnants of the Mishrif Formation were again buried. During shallow burial, cementation dominated, accompanied by compaction. With the increase in burial depth, cementation, compaction, and pressure solution dominated, all of which are unfavorable to the reservoir’s physical properties. The diagenesis formed a large number of brittle fractures, coarse crystalline calcite, and stylolite. During the burial process, three phases of tectonic uplift occurred, but the Mishrif Formation was not uplifted to the subaerial, and no karstification occurred. However, the tectonic uplift formed some faults locally, and the faults, as the transportation channel of diagenetic fluids, can promote the buried dissolution or dolomitization [58].

6. Conclusions

(1)
Three diagenetic environments were identified in the Cenomanian–Early Turonian based on texture, structure, cement, and crystal form and size, which were marine environment, meteoric environment, and burial environment. The vadose zone of meteoric environments is characterized by intense dissolution, where there developed a large amount of secondary pores due to the shallow depositional environment.
(2)
Six diageneses were identified in the Cenomanian–Early Turonian according to residual bioclastic, secondary pores, calcite quantity, dolomite form and size, and stylolite, which were dissolution, cementation, micritization, dolomitization, compaction, and pressure solution. The diagenesis mechanism and characteristics of performance were analyzed. A micritization model and a dolomitization model in burrows were established.
(3)
During the Cenomanian–Early Turonian, dissolution in the meteoric environment was the most beneficial to the reservoir and cementation was the most unfavorable. The combination of them was classified into three types based on the cement content of 30% and 70%, which had a clear control on the reservoir’s physical properties and the different combinations of dissolution and cementation corresponding to physical properties are clearly distinguishable. Micritization is detrimental to the petrophysical properties, and is the main micrite origin of the reservoir deposited in a high energy environment. Dolomitization is widely developed in burrows, resulting in the physical properties of the burrows being higher than those of the substrate. Compaction and pressolution are destructive to the reservoir’s physical properties. A comprehensive diagenetic model of the Cenomanian–Early Turonian was established.

Author Contributions

Conceptualization, F.L.; methodology, F.L.; software, Y.L.; validation, Y.L.; formal analysis, H.H.; investigation, H.H.; resources, W.Z.; data curation, W.Z.; writing—original draft preparation, F.L., Y.L., H.H., W.Z. and L.L.; writing—review and editing, F.L., Y.L., H.H., W.Z. and L.L.; visualization, L.L.; supervision, L.L.; project administration, Y.L.; funding acquisition, Y.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by CNPC project: “Joint study of AIBION carbonate reservoirs, grant number 2021DQ0407“ and CNPC projects “Research and application of key technologies for water injection development in thick carbonate reservoir, grant number 2023ZZ19-01”.

Data Availability Statement

Data are contained within the article.

Acknowledgments

Jiquan Yin, and Zhaohui Xia from RIPED are thanked for their insightful discussions. PETROCHINA is thanked for access to the data and permission to publish.

Conflicts of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. Bromhead, A.D.; Van Buchem, F.S.P.; Simmons, M.D.; Davies, R.B. Sequence stratigraphy, palaeogeography and petroleum plays of the Cenomanian–Turonian succession of the Arabian Plate: An updated synthesis. J. Pet. Geol. 2022, 45, 119–161. [Google Scholar] [CrossRef]
  2. Zhong, Y.; Tan, X.; Zhao, L.; Guo, R.; Li, F.; Jin, Z.; Chen, Y.; Xiao, D. Identification of facies-controlled eogenetic karstification in the Upper Cretaceous of the Halfaya oilfield and its impact on reservoir capacity. Geol. J. 2019, 54, 450–465. [Google Scholar] [CrossRef]
  3. Alsharhan, A.S.; Nairn, A.E.M. A review of the Cretaceous formations in the Arabian Peninsula and Gulf: Part II. Mid-Cretaceous (Wasia Group) stratigraphy and paleogeography. J. Pet. Geol. 1988, 11, 89–112. [Google Scholar] [CrossRef]
  4. Al-Khafaji, A.J.; Hakimi, M.H.; Najaf, A.A. Organic geochemistry characterisation of crude oils from Mishrif reservoir rocks in the southern Mesopotamian Basin, South Iraq: Implication for source input and paleoenvironmental conditions. Egypt. J. Pet. 2018, 27, 117–130. [Google Scholar] [CrossRef]
  5. Zhou, C.; Zhang, Q.; Yang, P.; Duan, H. Main controlling factors of hydrocarbon accumulation in Mesopotamia Basin. Pet. Geol. Exp. 2013, 35, 296–301. [Google Scholar]
  6. Mahdi, T.A.; Mustafa, J. Facies Modelling of Mishrif Formation in Selected Wells of Tuba Oil Field, Southern Iraq. Int. J. Adv. Eng. Res. Sci. 2018, 5, 237355. [Google Scholar] [CrossRef]
  7. Al-Ameri, T.K.; Al-Khafaji, A.J.; Zumberge, J. Petroleum system analysis of the Mishrif reservoir in the Ratawi, Zubair, North and South Rumaila oil fields, southern Iraq. GeoArabia 2009, 14, 91–108. [Google Scholar] [CrossRef]
  8. Aqrawi, A.A.M.; Thehni, G.A.; Sherwani, G.H.; Kareem, B.M.A. Mid-Cretaceous rudist-bearing carbonates of the Mishrif Formation: An important reservoir sequence in the Mesopotamian Basin, Iraq. J. Pet. Geol. 1998, 21, 57–82. [Google Scholar] [CrossRef]
  9. Sadooni, F.N.; Aqrawi, A.A.M. Cretaceous sequence stratigraphy and petroleum potential of the Mesopotamian Basin, Iraq. SEPM Spec. Publ. 2000, 69, 315–334. [Google Scholar]
  10. Abdelhady, A.A.; Farouk, S.; Ahmad, F.; Elamri, Z.; Al-Kahtany, K. Impact of the late Cenomanian sea-level rise on the south Tethyan coastal ecosystem in the Middle East (Jordan, Egypt, and Tunisia): A quantitative eco-biostratigraphy approach. Palaeogeogr. Palaeoclimatol. Palaeoecol. 2021, 574, 110446. [Google Scholar] [CrossRef]
  11. Jaballah, J.; Negra, M.H.; Reijmer, J.J.G. Middle Cenomanian–Turonian sequence stratigraphy of central-southern Tunisia: Regional and global control on depositional patterns. Cretac. Res. 2020, 111, 104446. [Google Scholar] [CrossRef]
  12. Van Buchem, F.S.; Razin, P.; Homewood, P.W.; Oterdoom, W.H.; Philip, J. Stratigraphic organization of carbonate ramps and organic-rich intrashelf basins: Natih Formation (middle Cretaceous) of northern Oman. AAPG Bull. 2002, 86, 21–53. [Google Scholar]
  13. Ali, M.Y.; Farid, A. Cretaceous–neogene structural evolution of Se abu dhabi, united Arab Emirates. J. Pet. Geol. 2016, 39, 221–245. [Google Scholar] [CrossRef]
  14. Alavi, M. Regional stratigraphy of the Zagros fold-thrust belt of Iran and its proforeland evolution. Am. J. Sci. 2004, 304, 1–20. [Google Scholar] [CrossRef]
  15. Grélaud, C.; Razin, P.; Homewood, P.W.; Schwab, A.M. Development of incisions on a periodically emergent carbonate platform (Natih Formation, Late Cretaceous, Oman). J. Sediment. Res. 2006, 76, 647–669. [Google Scholar] [CrossRef]
  16. Nasser, M.E. Stratigraphic Sequence and Basin development of the Mishrif Formation in Selected Oil fields in the Mesopotamian Zone, Southeastern Iraq. Int. J. Adv. Eng. Res. Sci. 2018, 5, 237462. [Google Scholar] [CrossRef]
  17. Saber, S.G.; Salama, Y.F.; Scott, R.W.; Abdel-Gawad, G.I.; Aly, M.F. Cenomanian-Turonian rudist assemblages and sequence stratigraphy on the North Sinai carbonate shelf, Egypt. GeoArabia 2009, 14, 113–134. [Google Scholar] [CrossRef]
  18. Mahdi, T.A.; Aqrawi, A.A.M. Role of facies diversity and cyclicity on the reservoir quality of the mid-Cretaceous Mishrif Formation in the southern Mesopotamian Basin, Iraq. Geol. Soc. Lond. Spec. Publ. 2018, 435, 1–21. [Google Scholar] [CrossRef]
  19. Al-Mimar, H.S.; Awadh, S.M.; Al-Yaseri, A.A.; Yaseen, Z.M. Sedimentary units-layering system and depositional model of the carbonate Mishrif reservoir in Rumaila oilfield, Southern Iraq. Model. Earth Syst. Environ. 2018, 4, 1449–1465. [Google Scholar] [CrossRef]
  20. Liu, H.; Tian, Z.; Liu, B.; Guo, R.; Yang, D.; Deng, Y.; Yu, Y.; Shi, K. Pore types, origins and control on reservoir heterogeneity of carbonate rocks in Middle Cretaceous Mishrif Formation of the West Qurna oilfield, Iraq. J. Pet. Sci. Eng. 2018, 171, 1338–1349. [Google Scholar] [CrossRef]
  21. Zhang, L.; Li, R.; Deng, H.; Fu, M.; Hu, L.; Guo, X.; Xie, X.; Zhao, C. Identification, Distribution Characteristics, and Effects on Production of Interlayers in Carbonate Reservoirs: A Case Study from the Cretaceous Mishrif Formation in Halfaya Oilfield, Iraq. J. Pet. Sci. Eng. 2021, 202, 108571. [Google Scholar] [CrossRef]
  22. Li, R.; Chen, Q.; Deng, H.; Fu, M.; Hu, L.; Xie, X.; Zhang, L.; Guo, X.; Fan, H.; Xiang, Z. Quantitative evaluation of the carbonate reservoir heterogeneity based on production dynamic data: A case study from Cretaceous Mishrif formation in Halfaya oilfield, Iraq. J. Pet. Sci. Eng. 2021, 206, 109007. [Google Scholar] [CrossRef]
  23. Al-Musawi, F.A.; Idan, R.M.; Salih, A.L.M. Reservoir characterization, Facies distribution, and sequence stratigraphy of Mishrif Formation in a selected oilfield, South of Iraq. J. Phys. Conf. Ser. 2020, 1660, 012073. [Google Scholar] [CrossRef]
  24. Grant, S.R.; Hughes, M.J.; Olatoke, O.J.; Philip, N. Stochastic inversion by trace matching for carbonate reservoir property prediction: A Mishrif Reservoir case study. Lead. Edge 2019, 38, 27–34. [Google Scholar] [CrossRef]
  25. Cantrell, D.L.; Shah, R.A.; Ou, J.; Xu, C.; Phillips, C.; Li, X.L.; Hu, T.M. Depositional and diagenetic controls on reservoir quality: Example from the upper Cretaceous Mishrif Formation of Iraq. Mar. Pet. Geol. 2020, 118, 104415. [Google Scholar] [CrossRef]
  26. Chafeet, H.A.; Raheem, M.K.; Dahham, N.A. Diagenesis processes impact on the carbonate Mishrif quality in Ratawi oilfield, southern Iraq. Model. Earth Syst. Environ. 2020, 6, 2609–2622. [Google Scholar] [CrossRef]
  27. Hussain, S.A.; Al-Obaidi, M.; Khwedim, K.; Ahmad, K. Facies Architecture, Diagenesis and Paleoceanography of Mishrif (Late Cretaceous) in Selected Wells of West Qurna Oil Field, Southern Iraq. J. Phys. Conf. Ser. 2020, 1664, 012137. [Google Scholar] [CrossRef]
  28. Wang, R.; Wang, Z.; Osumanu, A.; Zhang, G.; Li, B.; Lu, Y. Grid density overlap hierarchical algorithm for clustering of carbonate reservoir rock types: A case from Mishrif Formation of West Qurna-1 oilfield, Iraq. J. Pet. Sci. Eng. 2019, 182, 106209. [Google Scholar] [CrossRef]
  29. Kelishami, S.B.A.; Mohebian, R. Petrophysical rock type (PRT) and evaluation of Cenomanian–Santonian lithostratigraphic units in southwest of Iran. Carbonates Evaporites 2021, 36, 13–29. [Google Scholar] [CrossRef]
  30. Awadeesian, A.M.; Al-Jawed, S.N.A.; Saleh, A.H.; Sherwani, G.H. Mishrif carbonates facies and diagenesis glossary, South Iraq microfacies investigation technique: Types, classification, and related diagenetic impacts. Arab. J. Geosci. 2015, 8, 10715–10737. [Google Scholar] [CrossRef]
  31. Qiao, Z.; Janson, X.; Shen, A.; Zheng, J.; Zeng, H.; Wang, X. Lithofacies, architecture, and reservoir heterogeneity of tidal-dominated platform marginal oolitic shoal: An analogue of oolitic reservoirs of Lower Triassic Feixianguan Formation, Sichuan Basin, SW China. Mar. Pet. Geol. 2016, 76, 290–309. [Google Scholar] [CrossRef]
  32. Qiao, Z.; Yu, Z.; She, M.; Pan, L.; Zhang, T.; Li, W.; Shen, A. Progress on ancient ultra-deeply buried marine carbonate reservoir in China. J. Palaeogegraphy 2023, 25, 1257–1276, (In Chinese with English Abstract). [Google Scholar]
  33. Sharland, P.R.; Casey, D.M.; Davies, R.B.; Simmons, M.D.; Sutcliffe, O.E. Arabian Plate Sequence Stratigraphy. GeoArabia 2004, 9, 199–214. [Google Scholar] [CrossRef]
  34. Han, H.; Guo, R.; Wang, J.; Qin, G.; Sun, X.; Yu, Y.; Su, H.; Gao, Y. Sequence stratigraphic framwork and sedimentary evolution of the Cretaceous in Southern Iraq. Earth Sci. Front. 2023, 30, 122–138, (In Chinese with English Abstract). [Google Scholar]
  35. De Periere, M.D.; Durlet, C.; Vennin, E.; Caline, B.; Boichard, R.; Meyer, A. Influence of a major exposure surface on the development of microporous micritic limestones-Example of the Upper Mishrif Formation (Cenomanian) of the Middle East. Sediment. Geol. 2017, 353, 96–113. [Google Scholar] [CrossRef]
  36. Chen, P.; Guo, L.; Li, C.; Tong, Y. Karstification characteristics of the Cenomanian-Turonian Mishrif Formation in the Missan Oil Fields, southeastern Iraq, and their effects on reservoirs. Front. Earth Sci. 2022, 16, 435–445. [Google Scholar] [CrossRef]
  37. Mehrabi, H.; Rahimpour-Bonab, H. Paleoclimate and tectonic controls on the depositional and diagenetic history of the Cenomanian–early Turonian carbonate reservoirs, Dezful Embayment, SW Iran. Facies 2014, 60, 147–167. [Google Scholar] [CrossRef]
  38. Jodeyri-Agaii, R.; Rahimpour-Bonab, H.; Tavakoli, V.; Kadkhodaie-Ilkhchi, R.; Yousefpour, M.R. Integrated approach for zonation of a mid-Cenomanian carbonate reservoir in a sequence stratigraphic framework. Geol. Acta Int. Earth Sci. J. 2018, 16, 321–337. [Google Scholar]
  39. Newport, R.; Segura, M.; Redfern, J.; Hollis, C. The interaction of tectonics, climate and eustasy in controlling dolomitization: A case study of Cenomanian–Turonian, shallow marine carbonates of the Iberian Basin. Sedimentology 2020, 67, 2223–2247. [Google Scholar] [CrossRef]
  40. Hollis, C. Diagenetic controls on reservoir properties of carbonate successions within the Albian–Turonian of the Arabian Plate. Pet. Geosci. 2011, 17, 223–241. [Google Scholar] [CrossRef]
  41. Ahmad, K.I.; Hussain, S.A.; Al-Obaidi, M. Paleoceanographic reconstruction of Upper Cretaceous, black shale succession, Northeastern Iraq using Geochemical proxies to indicate paleoredox and paleoenvironment conditions. Diyala J. Pure Sci. 2018, 14, 237–264. [Google Scholar]
  42. Wang, H.; Shi, K.; Ma, Y.; Liu, B.; Song, X.; Ge, Y.; Liu, H.; Hoffmann, R.; Immenhauser, A. Control of depositional and diagenetic processes on the reservoir properties of the Mishrif Formation in the AD oilfield, Central Mesopotamian Basin, Iraq. Mar. Pet. Geol. 2021, 132, 105202. [Google Scholar] [CrossRef]
  43. He, Z.; Jin, Z.; Li, S.; Bai, G.; Lv, X.; Guo, J.; Gao, J.; Yin, J.; Li, Y.; Zheng, D. Prototypes, modifications, and hydrocarbon enrichment variations in basins influenced by Tethyan evolution: A comparative analysis of the Persian Gulf Basin and the Sichuan Basin. Sci. China Earth Sci. 2023, 66, 2871–2897, (In Chinese with English Abstract). [Google Scholar] [CrossRef]
  44. Aqrawi, A.A.M.; Gof, J.C.; Horbury, A.D.; Sadooni, F.N. The Petroleum Geology of Iraq; Buck Scientific Press: Beaconsfield, UK, 2010. [Google Scholar]
  45. Sherwani, G.H.M.; Aqrawi, A.A.M. Lithostratigraphy and environmental considerations of Cenomanian-Early Turonian shelf carbonates (Rumaila and Mishrif formation) of Mesopotamian basin, central and southern Iraq (Abastract). AAPG Bull. 1987, 71, 614. [Google Scholar]
  46. Kalanat, B.; Vaziri-Moghaddam, H.; Bijani, S. Depositional history of the uppermost Albian–Turonian Sarvak Formation in the Izeh Zone (SW Iran). Int. J. Earth Sci. 2021, 110, 305–330. [Google Scholar] [CrossRef]
  47. Li, F.; Li, L.; Chen, J. Characteristics of high flow zones and a balanced development strategy of a thick bioclastic limestone reservoir in the Mishrif Formation in X Oilfield, Iraq. Energies 2023, 16, 1451. [Google Scholar] [CrossRef]
  48. Veizer, J.; Ala, D.; Azmy, K.; Bruckschen, P.; Buhl, D.; Bruhn, F.; Garden, G.; Diener, A.; Ebneth, S.; Godderis, Y.; et al. 87Sr/86Sr, δ13C and δ18O evolution of Phanerozoic seawater. Chem. Geol. 1999, 161, 59–88. [Google Scholar] [CrossRef]
  49. Kim, S.T.; O’Neil, J.R. Equilibrium and nonequilibrium oxygen isotope effects in synthetic carbonates. Geochim. Cosmochim. Acta 1997, 61, 3461–3475. [Google Scholar] [CrossRef]
  50. Gu, Q.; Xing, F.; Wen, J.; Liu, Z.; Feng, S. Research progress on carbonate factory. Acta Sedimentol. Sin. 2022, 7, 1–30, (In Chinese with English Abstract). [Google Scholar]
  51. Qiao, Z.; Shao, G.; Luo, X.; Cao, P.; Sun, X.; Shen, A. Genetic classification and large-scale reservoir development law of burial dolomite: Cognition based on LA-ICP-MS trace elemental mapping and U-Pb dating. Nat. Gas Ind. 2021, 41, 46–56, (In Chinese with English Abstract). [Google Scholar]
  52. Ehrenberg, S.N.; Walderhaug, O.; Bjorlykke, K. Carbonate porosity creation by mesogenetic dissolution: Reality or illusion? AAPG Bull. 2012, 96, 217–233. [Google Scholar] [CrossRef]
  53. Wang, M.; Chen, C. In-situ Simulations and Experiments of Deep Carbonate Rocks and Its Implications for Exploration: Take Permian Samples in Northeast Sichuan as an Example. Mar. Orig. Pet. Geol. 2018, 23, 10–16, (In Chinese with English Abstract). [Google Scholar]
  54. Qiao, Z.; Shen, A.; Zhang, S.; Hu, A.; Liang, F.; Luo, X.; Shao, G.; Wang, Y.; Zhao, J.; Cao, P.; et al. Origin of giant Ordovician cavern reservoirs in the Halahatang oil field in the Tarim Basin, northwestern China. AAPG Bull. 2023, 107, 1105–1135. [Google Scholar] [CrossRef]
  55. Salamon, K.; Kołodziej, B.; Löser, H. Diverse nature of ubiquitous microborings in Cenomanian corals (Saxonian Cretaceous Basin, Germany). Cretac. Res. 2021, 126, 104888. [Google Scholar] [CrossRef]
  56. Gingras, M.K.; Pemberton, S.G.; Muelenbachs, K.; Machel, H. Conceptual models for burrow-related, selective dolomitization with textural and isotopic evidence from the Tyndall Stone, Canada. Geobiology 2004, 2, 21–30. [Google Scholar] [CrossRef]
  57. Baniak, G.M.; Gingras, M.K.; Pemberton, S.G. Reservoir characterization of burrow-associated dolomites in the Upper Devonian Wabamun Group, Pine Creek gas field, central Alberta, Canada. Mar. Pet. Geol. 2013, 48, 275–292. [Google Scholar] [CrossRef]
  58. Qiao, Z.; Shen, A.; Liang, F. Magnesium isotope-based forming process of large sized burial dolomite: A case study of the Penglaiba Formation in Tarim basin. Acta Geol. Sin. 2023, 97, 2293–2310, (In Chinese with English Abstract). [Google Scholar]
Minerals 14 00769 g001
Figure 1. Chronostratigraphy of the Middle East, modified from [3].
Figure 1. Chronostratigraphy of the Middle East, modified from [3].
Minerals 14 00769 g001
Minerals 14 00769 g002
Figure 2. Cenomanian paleogeography of study area, modified from [42,43].
Figure 2. Cenomanian paleogeography of study area, modified from [42,43].
Minerals 14 00769 g002
Minerals 14 00769 g003
Figure 3. Depositional model of Cenomanian to Early Turonian. (Modified from [47]).
Figure 3. Depositional model of Cenomanian to Early Turonian. (Modified from [47]).
Minerals 14 00769 g003
Minerals 14 00769 g004
Figure 4. Indicated symbol of marine diagenetic environment. (a) D oilfield, D-4 well, cast thin section, single polarized light, undyed, geopetal structure; (b) A oilfield, A-1 well, cast thin section, single polarized light, dyed, fenestral structure; (c) A oilfield, A-1 well, cast thin section, single polarized light, dyed, calcite of different generations; (d) D oilfield, D-5 well, cast thin section, single polarized light, dyed, micrite envelope; (e) A oilfield, A-1 well, cast thin section, single polarized light, dyed, bioturbation, dolomite in burrows; and (f) C oilfield, C-3 well, cores, white light, bioturbation.
Figure 4. Indicated symbol of marine diagenetic environment. (a) D oilfield, D-4 well, cast thin section, single polarized light, undyed, geopetal structure; (b) A oilfield, A-1 well, cast thin section, single polarized light, dyed, fenestral structure; (c) A oilfield, A-1 well, cast thin section, single polarized light, dyed, calcite of different generations; (d) D oilfield, D-5 well, cast thin section, single polarized light, dyed, micrite envelope; (e) A oilfield, A-1 well, cast thin section, single polarized light, dyed, bioturbation, dolomite in burrows; and (f) C oilfield, C-3 well, cores, white light, bioturbation.
Minerals 14 00769 g004
Minerals 14 00769 g005
Figure 5. Indicated symbol of meteoric diagenetic environment. (a) A oilfield, A-1 well, cast thin section, single polarized light, dyed, dissolution and isopachous calcite; (b) C oilfield, C-01 well, cast thin section, single polarized light, dyed, selective dissolution; (c) A oilfield, A-1 well, cast thin section, single polarized light, dyed, intense dissolution; (d) A oilfield, A-1 well, cast thin section, single polarized light, dyed, dissolution; (e) A oilfield, A-1 well, cast thin section, single polarized light, dyed, isopachous equant calcite; and (f) A oilfield, A-1 well, cast thin section, single polarized light, dyed, isopachous equant calcite.
Figure 5. Indicated symbol of meteoric diagenetic environment. (a) A oilfield, A-1 well, cast thin section, single polarized light, dyed, dissolution and isopachous calcite; (b) C oilfield, C-01 well, cast thin section, single polarized light, dyed, selective dissolution; (c) A oilfield, A-1 well, cast thin section, single polarized light, dyed, intense dissolution; (d) A oilfield, A-1 well, cast thin section, single polarized light, dyed, dissolution; (e) A oilfield, A-1 well, cast thin section, single polarized light, dyed, isopachous equant calcite; and (f) A oilfield, A-1 well, cast thin section, single polarized light, dyed, isopachous equant calcite.
Minerals 14 00769 g005
Minerals 14 00769 g006
Figure 6. Indicated symbol of burial diagenetic environment. (a) A oilfield, A-1 well, cast thin section, single polarized light, dyed, saddle dolomite; (b) A oilfield, A-1 well, cast thin section, single polarized light, dyed, saddle dolomite and coarsely crystalline ferroan calcite; (c) A oilfield, A-1 well, cast thin section, single polarized light, dyed, coarsely crystalline ferroan calcite; (d) C oilfield, C-6 well, core, white light, coarsely crystalline calcite; (e) C oilfield, C-2 well, core, white light, coarsely crystalline calcite; and (f) C oilfield, C-3 well, core, white light, stylolite.
Figure 6. Indicated symbol of burial diagenetic environment. (a) A oilfield, A-1 well, cast thin section, single polarized light, dyed, saddle dolomite; (b) A oilfield, A-1 well, cast thin section, single polarized light, dyed, saddle dolomite and coarsely crystalline ferroan calcite; (c) A oilfield, A-1 well, cast thin section, single polarized light, dyed, coarsely crystalline ferroan calcite; (d) C oilfield, C-6 well, core, white light, coarsely crystalline calcite; (e) C oilfield, C-2 well, core, white light, coarsely crystalline calcite; and (f) C oilfield, C-3 well, core, white light, stylolite.
Minerals 14 00769 g006
Minerals 14 00769 g007
Figure 7. Characteristics of penecontemporaneous dissolution in Cenomanian–early Turonian. (a) C oilfield, C-7 well, core, white light, vug pores; (b) C oilfield, C-4 well, core, white light, vug pores; (c) C oilfield, C-8 well, CT, vug pores; (d) C oilfield, C-8 well, CT, vug pores; (e) C oilfield, C-8 well, CT, well sorted pores; (f) C oilfield, C-5 well, cast thin section, single polarized light, dyed, moldic pores; (g) D oilfield, D-5 well, cast thin section, single polarized light, dyed, intergranular pores were expanded via dissolution; and (h) D oilfield, D-5 well, cast thin section, single polarized light, dyed, intergranular pores were expanded via dissolution.
Figure 7. Characteristics of penecontemporaneous dissolution in Cenomanian–early Turonian. (a) C oilfield, C-7 well, core, white light, vug pores; (b) C oilfield, C-4 well, core, white light, vug pores; (c) C oilfield, C-8 well, CT, vug pores; (d) C oilfield, C-8 well, CT, vug pores; (e) C oilfield, C-8 well, CT, well sorted pores; (f) C oilfield, C-5 well, cast thin section, single polarized light, dyed, moldic pores; (g) D oilfield, D-5 well, cast thin section, single polarized light, dyed, intergranular pores were expanded via dissolution; and (h) D oilfield, D-5 well, cast thin section, single polarized light, dyed, intergranular pores were expanded via dissolution.
Minerals 14 00769 g007
Minerals 14 00769 g008
Figure 8. Karstification in Cenomanian–early Turonian. (a) B oilfield, B-1 well, core, white light, breccia; (b) A oilfield, A-1 well, core, white light, breccia; and (c) C oilfield, C-1 well, core, white light, breccia.
Figure 8. Karstification in Cenomanian–early Turonian. (a) B oilfield, B-1 well, core, white light, breccia; (b) A oilfield, A-1 well, core, white light, breccia; and (c) C oilfield, C-1 well, core, white light, breccia.
Minerals 14 00769 g008
Minerals 14 00769 g009
Figure 9. Cementation characteristics in Cenomanian–early Turonian. (a) D oilfield, D-1 well, cast thin section, single polarized light, dyed, cementation, the cement fills 10% of the pore volume; (b) D oilfield, D-1 well, cast thin section, single polarized light, dyed, cementation, the cement fills 30% of the pore volume; (c) D oilfield, D-2 well, cast thin section, single polarized light, dyed, cementation, the cement fills 50% of the pore volume; (d) D oilfield, D-1 well, cast thin section, single polarized light, dyed, cementation, the cement fills 70% of the pore volume; (e) D oilfield, D-3 well, cast thin section, single polarized light, undyed, cementation, the cement fills 90% of the pore volume; and (f) C oilfield, C-1 well, cast thin section, single polarized light, dyed, cementation, the cement fills 100% of the pore volume.
Figure 9. Cementation characteristics in Cenomanian–early Turonian. (a) D oilfield, D-1 well, cast thin section, single polarized light, dyed, cementation, the cement fills 10% of the pore volume; (b) D oilfield, D-1 well, cast thin section, single polarized light, dyed, cementation, the cement fills 30% of the pore volume; (c) D oilfield, D-2 well, cast thin section, single polarized light, dyed, cementation, the cement fills 50% of the pore volume; (d) D oilfield, D-1 well, cast thin section, single polarized light, dyed, cementation, the cement fills 70% of the pore volume; (e) D oilfield, D-3 well, cast thin section, single polarized light, undyed, cementation, the cement fills 90% of the pore volume; and (f) C oilfield, C-1 well, cast thin section, single polarized light, dyed, cementation, the cement fills 100% of the pore volume.
Minerals 14 00769 g009
Minerals 14 00769 g010
Figure 10. Micritization evolution in Cenomanian–early Turonian. (a) Primitive sediments; (b) diagenesis in marine environment; (c) diagenesis in meteoric environment I; (d) diagenesis in meteoric environment II; (e) diagenesis in burial environment; and (f) the final structure showed in the microscopes.
Figure 10. Micritization evolution in Cenomanian–early Turonian. (a) Primitive sediments; (b) diagenesis in marine environment; (c) diagenesis in meteoric environment I; (d) diagenesis in meteoric environment II; (e) diagenesis in burial environment; and (f) the final structure showed in the microscopes.
Minerals 14 00769 g010
Minerals 14 00769 g011
Figure 11. Dolomitization characteristics in Cenomanian–early Turonian. (a) C oilfield, C-3 well, cast thin section, single polarized light, dyed, dolomitization; (b) C oilfield, C-1 well, cast thin section, single polarized light, dyed, dolomitization; (c) C oilfield, C-1 well, cast thin section, single polarized light, dyed, dolomitization; (d) B oilfield, B-1 well, core, white light, bioturbation, burrows could be seen on core; (e) B oilfield, B-1 well, full size cast thin section, single polarized light, dyed, bioturbation, dolomitization in burrows; and (f) B oilfield, B-1 well, cast thin section, single polarized light, dyed, dolomitization.
Figure 11. Dolomitization characteristics in Cenomanian–early Turonian. (a) C oilfield, C-3 well, cast thin section, single polarized light, dyed, dolomitization; (b) C oilfield, C-1 well, cast thin section, single polarized light, dyed, dolomitization; (c) C oilfield, C-1 well, cast thin section, single polarized light, dyed, dolomitization; (d) B oilfield, B-1 well, core, white light, bioturbation, burrows could be seen on core; (e) B oilfield, B-1 well, full size cast thin section, single polarized light, dyed, bioturbation, dolomitization in burrows; and (f) B oilfield, B-1 well, cast thin section, single polarized light, dyed, dolomitization.
Minerals 14 00769 g011
Minerals 14 00769 g012
Figure 12. The diagenesis in burrows formed by bioturbation. (a) Primitive burrows; (b) burrows were dissolved and enlarged; (c) burrows were dissolved and enlarged again, some bioclastic around burrows were dissolved; (d) some fracture may be induced by dissolution; (e) the dissolved pores were filled by new fillings; (f) dolomitization occurred in burial environment. (g) B oilfield, B-1 well, cast thin section, single polarized light, dyed, burrows filled with coarse infillings; (h) B oilfield, B-1 well, cast thin section, single polarized light, dyed, burrows filled with fine infillings; and (i) A oilfield, A-1 well, cast thin section, single polarized light, dyed, burrows filled with dolomites.
Figure 12. The diagenesis in burrows formed by bioturbation. (a) Primitive burrows; (b) burrows were dissolved and enlarged; (c) burrows were dissolved and enlarged again, some bioclastic around burrows were dissolved; (d) some fracture may be induced by dissolution; (e) the dissolved pores were filled by new fillings; (f) dolomitization occurred in burial environment. (g) B oilfield, B-1 well, cast thin section, single polarized light, dyed, burrows filled with coarse infillings; (h) B oilfield, B-1 well, cast thin section, single polarized light, dyed, burrows filled with fine infillings; and (i) A oilfield, A-1 well, cast thin section, single polarized light, dyed, burrows filled with dolomites.
Minerals 14 00769 g012
Minerals 14 00769 g013
Figure 13. Compaction and pressolution in Cenomanian–early Turonian. (a) C oilfield, C-3 well, cast thin section, single polarized light, dyed, compaction; (b) D oilfield, D-1 well, cast thin section, single polarized light, dyed, compaction and pressure solution; (c) C oilfield, C-2 well, cast thin section, single polarized light, dyed, compaction and pressure solution; (d) C oilfield, C-4 well, core, white light, stylolite; (e) C oilfield, C-2 well, core, white light, stylolite; and (f) C oilfield, C-1 well, core, white light, stylolite.
Figure 13. Compaction and pressolution in Cenomanian–early Turonian. (a) C oilfield, C-3 well, cast thin section, single polarized light, dyed, compaction; (b) D oilfield, D-1 well, cast thin section, single polarized light, dyed, compaction and pressure solution; (c) C oilfield, C-2 well, cast thin section, single polarized light, dyed, compaction and pressure solution; (d) C oilfield, C-4 well, core, white light, stylolite; (e) C oilfield, C-2 well, core, white light, stylolite; and (f) C oilfield, C-1 well, core, white light, stylolite.
Minerals 14 00769 g013
Minerals 14 00769 g014
Figure 14. Correlation of cement quantity and petrophysical property. (a) Intense dissolution and rare cementation; (b) D oilfield, D-2 well, cast thin section, single polarized light, dyed, rare cement; (c) A oilfield, A-1 well, cast thin section, single polarized light, dyed, rare cement; (d) medium dissolution and medium cementation; (e) D oilfield, D-1 well, cast thin section, single polarized light, dyed, the pores were partially filled by cement; (f) D oilfield, D-1 well, cast thin section, single polarized light, dyed, the pores were partially filled by cement; (g) rare dissolution and intense cementation; (h) C oilfield, C-3 well, cast thin section, single polarized light, dyed, the pores were almost filled by cement; and (i) C oilfield, C-3 well, cast thin section, single polarized light, dyed, the pores were almost filled by cement.
Figure 14. Correlation of cement quantity and petrophysical property. (a) Intense dissolution and rare cementation; (b) D oilfield, D-2 well, cast thin section, single polarized light, dyed, rare cement; (c) A oilfield, A-1 well, cast thin section, single polarized light, dyed, rare cement; (d) medium dissolution and medium cementation; (e) D oilfield, D-1 well, cast thin section, single polarized light, dyed, the pores were partially filled by cement; (f) D oilfield, D-1 well, cast thin section, single polarized light, dyed, the pores were partially filled by cement; (g) rare dissolution and intense cementation; (h) C oilfield, C-3 well, cast thin section, single polarized light, dyed, the pores were almost filled by cement; and (i) C oilfield, C-3 well, cast thin section, single polarized light, dyed, the pores were almost filled by cement.
Minerals 14 00769 g014
Minerals 14 00769 g015
Figure 15. Effect of diagenesis on reservoir physical property. (a) Correlation of depositional facies and physical property; (b) correlation of dissolution/cementation and physical property.
Figure 15. Effect of diagenesis on reservoir physical property. (a) Correlation of depositional facies and physical property; (b) correlation of dissolution/cementation and physical property.
Minerals 14 00769 g015
Minerals 14 00769 g016
Figure 16. Effect of micritization on petrophysical property. (a) C oilfield, C-3well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope can be seen; (b) C oilfield, C-1 well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope can be seen; (c) C oilfield, C-3 well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope cannot be seen; (d) C oilfield, C-3 well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope can be seen; (e) C oilfield, C-3 well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope almost were destroyed; and (f) C oilfield, C-3 well, cast thin section, single polarized light, dyed, micritization, micropores could be seen on the micrite envelope.
Figure 16. Effect of micritization on petrophysical property. (a) C oilfield, C-3well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope can be seen; (b) C oilfield, C-1 well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope can be seen; (c) C oilfield, C-3 well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope cannot be seen; (d) C oilfield, C-3 well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope can be seen; (e) C oilfield, C-3 well, cast thin section, single polarized light, dyed, micritization, the pores were partial filled by micrite and the micrite envelope almost were destroyed; and (f) C oilfield, C-3 well, cast thin section, single polarized light, dyed, micritization, micropores could be seen on the micrite envelope.
Minerals 14 00769 g016
Minerals 14 00769 g017
Figure 17. Dolomitization in burrows and effect on petrophysical property. (a) B oilfield, B-1 well, full size cast thin section, single polarized light, dyed, bioturbation; (b) B oilfield, B-1 well, cast thin section, single polarized light, dyed, substrate; (c) B oilfield, B-1 well, cast thin section, single polarized light, burrow boundary; and (d) B oilfield, B-1 well, cast thin section, single polarized light, dolomitization in burrow.
Figure 17. Dolomitization in burrows and effect on petrophysical property. (a) B oilfield, B-1 well, full size cast thin section, single polarized light, dyed, bioturbation; (b) B oilfield, B-1 well, cast thin section, single polarized light, dyed, substrate; (c) B oilfield, B-1 well, cast thin section, single polarized light, burrow boundary; and (d) B oilfield, B-1 well, cast thin section, single polarized light, dolomitization in burrow.
Minerals 14 00769 g017
Minerals 14 00769 g018
Figure 18. Comprehensive diagenetic model of the Cenomanian–Early Turonian.
Figure 18. Comprehensive diagenetic model of the Cenomanian–Early Turonian.
Minerals 14 00769 g018
Table 1. Carbon and oxygen isotope samples and data.
Table 1. Carbon and oxygen isotope samples and data.
SampleDepth
/m		StrataLithologyδ13C‰
(VPDB)		δ18O‰
(VPDB)		Precipitation
Temperature (°C)
12862.33MishrifMudstone1.84−5.1420.823
22864.71MishrifWackstone2.64−4.5920.820
32879.48MishrifMudstone2.14−4.5320.820
42919.33MishrifPackstone3.34−3.6320.816
52921.77MishrifMudstone2.76−3.9120.817
62928.58MishrifWackstone3.06−4.1820.818
72935.81MishrifWackstone2.90−3.8320.817
82979.66MishrifGrainstone2.66−4.3820.819
93003.18MishrifGrainstone3.97−5.4320.824
103016.40MishrifGrainstone3.58−4.9720.822
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Li, F.; Li, Y.; Han, H.; Zhang, W.; Li, L. Diagenesis of Cenomanian–Early Turonian and the Control of Carbonate Reservoirs in the Northern Central Arabian Basin. Minerals 2024, 14, 769. https://doi.org/10.3390/min14080769

AMA Style

Li F, Li Y, Han H, Zhang W, Li L. Diagenesis of Cenomanian–Early Turonian and the Control of Carbonate Reservoirs in the Northern Central Arabian Basin. Minerals. 2024; 14(8):769. https://doi.org/10.3390/min14080769

Chicago/Turabian Style

Li, Fengfeng, Yong Li, Haiying Han, Wenqi Zhang, and Lei Li. 2024. "Diagenesis of Cenomanian–Early Turonian and the Control of Carbonate Reservoirs in the Northern Central Arabian Basin" Minerals 14, no. 8: 769. https://doi.org/10.3390/min14080769

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop