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Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "H: Geo-Energy".

Deadline for manuscript submissions: closed (28 April 2023) | Viewed by 14421

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Dr. Zhendong Cui

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Guest Editor

Key Laboratory of Shale Gas and Geological Engineering, Petrophysics and Reservoir Geomechanics Group, Chinese Academy of Sciences, Beijing, China
Interests: rock fracture mechanics; CO2 geological storage;reservoir geomechanics; CO2-enhanced oil/gas recovery (CO2-EOR/ CO2-EGR); shale gas exploitation, tight oil and gas exploitation

Dr. Pingchuan Dong

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Guest Editor

College of Petroleum Engineering, China University of Petroleum, Beijing, China
Interests: oil and gas development geology; reservoir seepage; reservoir geological modeling and digital modeling; enhanced recovery methods; digital core analysis

Dr. Bowen Zheng

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Guest Editor

Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
Interests: engineering geology; rock mass mechanics

Special Issue Information

Dear Colleagues,

With the increasing demand for energy and the increase of exploitation intensity, the exploration and development of deep energy has become a hot issue of concern to the world. However, as the mining depth increases, the complicated geological conditions make it more and more difficulties for the engineering reconstruction, which poses a great threat to the efficient development of deep energy.

This Special Issue will collect original research or review articles on the recent development of geotechnical engineering in deep energy exploitation. The preferred subjects for the Special Issue include latest development of design theories and geotechnical technologies related to deep energy exploitation, such as drilling, reservoir stimulation, geology-engineering integration, and other relevant theories and engineering technologies. All of the theoretical, numerical, experimental, and field studies are welcome.

Dr. Zhendong Cui
Dr. Pingchuan Dong
Dr. Bowen Zheng
Guest Editors

Manuscript Submission Information

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Keywords

geology-engineering integration technology
deep drilling and completion technology
hydraulic fracturing technology
reservoir geomechanics and stimulation technology
CO2-enhanced oil/gas recovery (CO2-EOR/ CO2-EGR)
enhanced geothermal system (EGS) technology
shale gas exploitation
tight oil and gas exploitation
fault reactivation related to oil/gas exploitation
environmental issues and risk evaluation
seepage and fluid flow in reservoirs
other related theories and technologies

Published Papers (8 papers)

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Research

30 pages, 18528 KiB

Open AccessArticle

Numerical Simulation on Shale Fragmentation by a PDC Cutter Based on the Discrete Element Method

by Xiaohui Zhang, Xiaolin Huang, Shengwen Qi, Bowen Zheng, Songfeng Guo and Wei Lu

Energies 2023, 16(2), 965; https://doi.org/10.3390/en16020965 - 15 Jan 2023

Cited by 1 | Viewed by 1545

Abstract

During the guided drilling process as part of shale gas exploration and development, shale is damaged by a polycrystalline diamond compact (PDC) bit cutter. It is essential to carry out research on rock breaking by a PDC cutter. In this paper, we study the mechanism of shale fragmentation by a PDC cutter based on the discrete element method. Additionally, we consider the effects of bedding angle, bedding thickness, cutting depth and cutting rate on the rock-breaking efficiency of a PDC cutter. The results show the following: (1) With the increase in bedding angle, the number and area of microcracks first increase and then decrease, and the proportion of tension cracks is relatively unchanged; there is no significant change in the morphology of the failure zone, and the average particle size of the cutting fragments first decreases and then increases. (2) With the increase in the bedding thickness, microcracks continue to extend in a horizontal direction, the total number of cracks shows a fluctuated change, and the proportion of tension cracks increases. The failure zone extends in a conical shape in the horizontal direction, and the average size of the cutting fragments gradually increases. (3) With the increase in cutting depth and cutting rate, the number and area of microcracks increase, and the proportion of shear cracks increases; the area of the failure zone increases and the size of the cutting fragment decreases. Full article

(This article belongs to the Special Issue Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering)

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24 pages, 18662 KiB

Open AccessArticle

Reservoir Characterization and an Integrated Approach of Reservoir Modeling for Miano Gas Field, Middle Indus Basin

by Chen Yang, Changsheng Zhao, Xiangjuan Meng, Pingchaun Dong, Junxian Chai, Xiaoming Wang, Qihai Nie, Janfang Yang and Wenwen Yu

Energies 2023, 16(2), 856; https://doi.org/10.3390/en16020856 - 11 Jan 2023

Cited by 1 | Viewed by 1845

Abstract

The hydrocarbon-bearing formation of Miano gas field belongs to the Early Cretaceous and it is bounded by two shale intervals, which are considered as maximum flooding surfaces (MFS). The hydrocarbon-bearing interval includes two reservoir units: a tight gas reservoir and its overlying conventional reservoir. Core samples, borehole logs, and well production performance revealed that the two reservoirs present reversed trends in reservoir quality through the gas field without obvious barriers. The average shale volume of the tight gas reservoir changes from 24.3% to 12.2% and the average permeability changes from 32.65 mD to 0.02 mD from the south to north. However, the average effective porosity of the overlaying conventional reservoir increases from 20% to 26% and the average permeability increases from 10 mD to 300 mD. The reversed trends in the two reservoirs lead to challenges in production forecast and development well proposals in the tight gas reservoir. Therefore, reservoir characterization and a predictive reservoir model are essential for further exploitation of Miano gas field. The geological genesis analysis integrating cores, borehole logs, and three-dimensional (3D) seismic data reveals that the producing interval of the tight gas reservoir is tidal-influenced shore facies deposition with intergranular pore space reduced by mineral cementation during burial diagenesis, while the overlaying conventional reservoir is fluvial-influenced deltaic deposition with abundant, well-connected intergranular macropores, which leads to a better reservoir quality. A reservoir model containing both the tight gas reservoir and the conventional reservoir is constructed considering the reservoir nature understanding, and the accuracy of the model is confirmed by reservoir surveillance activities with the simulation model. The study will be critical to the further reservoir development and hydrocarbon production in Miano gas field. Full article

(This article belongs to the Special Issue Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering)

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16 pages, 3622 KiB

Open AccessArticle

Numerical Simulation and Evaluation on Continuum Damage Models of Rocks

by Leilei Zhao, Zhendong Cui, Ruidong Peng and Kai Si

Energies 2022, 15(18), 6806; https://doi.org/10.3390/en15186806 - 17 Sep 2022

Cited by 3 | Viewed by 1196

Abstract

Damage mechanics play an important role in the analysis of rock deformation and failure. Numerous damage variables have been proposed and the corresponding continuum damage models were suggested. Knowing how to apply these theoretical models appropriately in numerical simulations is the key to whether they can be adopted to solve practical problems. The continuum damage models were grouped into empirical damage models, statistical damage models, and elastoplastic damage models in this article. Their applicability and limitations were studied according to some numerical simulations of the most basic uniaxial compression test of a cylinder rock sample. Three representative damage models were chosen from the literature and applied to FEM numerical simulations by introducing a self-developed program. The stress-strain curves due to damage were obtained from the numerical simulation results and compared to those from the experimental results. The damage distribution and evolution of different damage models were investigated to evaluate their influences on rock deformation. It can be concluded that strain-softening stages presented by both the empirical damage models and the statistical damage models are caused by subtracting the elastic modulus gradually while those presented by the elastoplastic damage models are caused by reducing plastic yield stress gradually. Damage-elastic coupling cannot well reflect the irreversibility of damage. The elastoplastic damage models combine damage with plastic history, and thus the irreversibility of damage can be represented. Furthermore, the compulsory reduction of the elastic modulus can probably lead to extreme element distortion and even an unreasonable negative modulus when damage is very serious, which inevitably causes the numerical simulation to fail prematurely under complex stress states. Although the elastoplastic damage models are recommended at present rather than the other models, a more appropriate definition of the damage variable can be expected that should track the whole deformation and failure process. Knowing how to treat the adverse effect of local deterioration due to damage is the challenge numerical simulations have to face when they are applied in the actual project with complex stress states. Full article

(This article belongs to the Special Issue Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering)

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18 pages, 4750 KiB

Open AccessArticle

The Effect of Bedding Plane Angle on Hydraulic Fracture Propagation in Mineral Heterogeneity Model

by Weige Han, Zhendong Cui, Zhengguo Zhu and Xianmin Han

Energies 2022, 15(16), 6052; https://doi.org/10.3390/en15166052 - 20 Aug 2022

Cited by 3 | Viewed by 1390

Abstract

The bedding planes of unconventional oil and gas reservoirs are relatively well developed. Bedding planes directly interfere with hydraulic fracture expansion. Determining how bedding planes influence hydraulic fractures is key for understanding the formation and evolution of hydraulic fracturing networks. After conducting X-ray diffraction analysis of shale, we used Python programming to establish a numerical model of mineral heterogeneity with a 0-thickness cohesive element and a bedding plane that was globally embedded. The influence of the bedding-plane angle on hydraulic fracture propagation was studied. Acoustic emission (AE) data were simulated using MATLAB programming to study fracture propagation in detail. The numerical simulation and AE data showed that the propagation paths of hydraulic fractures were determined by the maximum principal stress and bedding plane. Clearer bedding effects were observed with smaller angles between the bedding surface and the maximum principal stress. However, the bedding effect led to continuous bedding slip fractures, which is not conducive to forming a complex fracture network. At moderate bedding plane angles, cross-layer and bedding fractures alternately appeared, characteristic of intermittent dislocation fracture and a complex fracture network. During hydraulic fracturing, tensile fractures represented the dominant fracture type and manifested in cross-layer fractures. We observed large fracture widths, which are conducive to proppant migration and filling. However, the shear fractures mostly manifested as bedding slip fractures with small fracture widths. Combining the fracture-network, AE, and fractal dimension data showed that a complex fracture network was most readily generated when the angle between the bedding plane and the maximum principal stress was 30°. The numerical simulation results provide important technical information for fracturing construction, which should support the efficient extraction of unconventional tight oil and gas. Full article

(This article belongs to the Special Issue Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering)

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19 pages, 30892 KiB

Open AccessArticle

A Novel Borehole Cataloguing Method Based on a Drilling Process Monitoring (DPM) System

by Peng Guo, Zhongjian Zhang, Xuefan Wang, Zhongqi Yue and Maosheng Zhang

Energies 2022, 15(16), 5832; https://doi.org/10.3390/en15165832 - 11 Aug 2022

Cited by 6 | Viewed by 1577

Abstract

Borehole cataloguing is an important task in geological drilling. Traditional manual cataloguing provides the stratification of underground boreholes based on changes in core lithology. This paper proposes a novel borehole cataloguing method using a drilling process monitoring (DPM) system. This DPM cataloguing method stratifies a borehole according to the drilling speed through the rock. A 102 m borehole was drilled and cored in Baota district, Yan’an city, Shaanxi Province, China. The rock-breaking response parameters of the drill bit displacement, drill rod rotation speed and inlet pipe and outlet pipe oil pressures were monitored throughout the drilling process, and the drilling depth-penetration rate curve during the net drilling process was obtained. The changes in drilling speed show that the DPM cataloguing can identify the depths of the layer interfaces of the borehole and describe the stratification. The interface depth values obtained by DPM have little difference from the interface depth values obtained by manual cataloguing, and the errors are between −0.04% and 4.29%. From the DPM stratification results, the engineering quality evaluation of the rock mass can be realized without coring. DPM is fast, convenient, accurate, can greatly improve the efficiency of existing catalogues, and can be applied to scientific research in any underground space. DPM is a measurement-while-drilling technology. According to DPM data, the operating state of a drilling rig and the parameter changes while drilling can be obtained in situ and in real time throughout the drilling process. Full article

(This article belongs to the Special Issue Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering)

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13 pages, 5093 KiB

Open AccessArticle

Effect of In-Situ Stress on Hydraulic Fracturing of Tight Sandstone Based on Discrete Element Method

by Hongjian Wang, Wanlin Gong, Guangxiang Yuan, Xiaodong Wang, Jitao Zhao, Yujie Su and Yuchen Wang

Energies 2022, 15(15), 5620; https://doi.org/10.3390/en15155620 - 3 Aug 2022

Cited by 1 | Viewed by 1735

Abstract

The tight sandstone reservoir in the Qianfoya formation of well PL-3 of the Puguang gas field in Sichuan, China, obtained a high-yield gas flow after a volume fracturing treatment. However, the stimulated reservoir volume (SRV), fracture morphology, scale and formation law still remain unclear. Based on particle flow discrete-element theory in this paper, we carried out a few trials of the Brazilian splitting test, uniaxial compression and triaxial compression of rock mechanics. Meanwhile, the research also testified to the conversion relationship between macroparameters and microparameters, established the numerical simulation on hydraulic fracturing through PFC^2D discrete element software, and finally analyzed the influence of difference coefficients on the fracturing effect, in terms of different in-situ stresses. The conclusions are as follows: firstly, the influence of in-situ stress is essential for the direction, shape and quantity of fracture propagation, and the fractures generated by hydraulic fracturing are mainly tension fractures, accounting for over 90% of the total longitudinal fractures. Secondly, it is indicated that when the difference coefficient is small in the in-situ stress, the fractures formed by hydraulic fracturing expand randomly around the wellbore. When the difference coefficient K_h of in-situ stress is above 0.6, the development of hydraulic fractures is mainly controlled by in-situ stress; as a result, the fractures tend to expand in the vertical direction of the minimum horizontal principal stress and the fracture shape is relatively singular. When the difference coefficient of in-situ stress was 0.3, in total, 3121 fractures were generated by fracturing, and the fractal dimension D value of the fracture network complexity was 1.60. In this case, this fracturing effect was the best and it is the easiest to achieve for the purpose of economical and effective development on large-scale volume fracturing. Full article

(This article belongs to the Special Issue Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering)

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17 pages, 5706 KiB

Open AccessArticle

Study on Fatigue Life Prediction and Acoustic Emission Characteristics of Sandstone Based on Mesoscopic Crack Propagation Mechanism

by Kai Si, Zhendong Cui, Ruidong Peng and Leilei Zhao

Energies 2022, 15(13), 4807; https://doi.org/10.3390/en15134807 - 30 Jun 2022

Cited by 2 | Viewed by 1129

Abstract

Even when the maximum stress is less than the peak stress under conventional loading, fatigue failure of rock is likely to occur, thereby showing its unique characteristics. The present study summarized the factors affecting rock fatigue life from the perspective of phenomenology and studied the fatigue damage process of rock from the microscopic perspective. However, the meso-mechanical mechanism of fatigue–tension failure of rocks is still not very clear, and there are few studies on rock fatigue life that use meso-crack propagation models. In this paper, a mesoscopic model considering wing crack propagation is introduced to examine the fatigue failure of sandstone. A fatigue life prediction formula of sandstone was deduced via a combination with the Paris formula. This formula can quantitatively characterize the impact of upper limit stress and lower limit stress on the fatigue life of sandstone and explain the reason why upper limit stress has a greater influence on the fatigue process of sandstone. Such a prediction formula is applicable only under the condition of low confining pressures, which mainly cause tensile failure due to mesoscopic wing crack propagation. Acoustic emission signals during fatigue failure were monitored and then analyzed using a clustering method and a moment tensor inversion method. Therefore, the tensile or shear properties of mesoscopic failure could be distinguished according to acoustic emission characteristics in different stages of fatigue crack propagation. The results showed that crack sources causing sandstone fatigue failure are mainly tension-type when confining pressure is less than 10 MPa, which further verifies the proposed prediction model of sandstone fatigue life under low confining pressures. Full article

(This article belongs to the Special Issue Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering)

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15 pages, 3640 KiB

Open AccessArticle

Prediction Model for the Viscosity of Heavy Oil Diluted with Light Oil Using Machine Learning Techniques

by Xiaodong Gao, Pingchuan Dong, Jiawei Cui and Qichao Gao

Energies 2022, 15(6), 2297; https://doi.org/10.3390/en15062297 - 21 Mar 2022

Cited by 12 | Viewed by 3155

Abstract

Due to the presence of asphaltene, the flow assurance of high viscosity crude oil becomes more challenging and costly to produce in wellbores and pipelines. One of the most effective ways to reduce viscosity is to blend heavy oil with light oil. However, the viscosity measurement of diluted heavy crude is either time-consuming or inaccurate. This work aims to develop a more accurate viscosity model of diluted heavy crude based on machine learning techniques. A multilayer neural network is used to predict the viscosity of heavy oil diluted with lighter oil. The input data used in the training include temperature, light oil viscosity, heavy oil viscosity, and dilution ratio. In this modeling process, 156 datasets were retrieved from the available iterature of various heavy-oil fields in China. Part of the data (80%) is used to train the developed models using Adam optimizer algorithms, while the other part of the data (20%) is used to predict the viscosity of heavy oil diluted with lighter. The performance and accuracy of the machine learning models were tested and compared with the existing viscosity models. It was found that the new model can predict the viscosity of diluted heavy oil with higher accuracy, and it performs better than other models. The absolute average relative error is 10.44%, the standard deviation of the relative error is 8.45%, and the coefficient of determination is R² = 0.95. The viscosity predicted by the neural network outperformed existing correlations by the statistical analysis used for the datasets available in the literature. Therefore, the method proposed in this paper can better estimate the viscosity of diluted heavy crude oil and has important promotion value. Full article

(This article belongs to the Special Issue Deep Energy Exploitation : Latest Advances and Prospects of Geotechnical Engineering)

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