Oil, Gas and Water Separation Research

The exploitation and transportation of deep-sea and remote oil and gas fields have risen to become important components of national energy strategies. The gas–liquid separation and gas blocking caused by the large density difference between the gas and liquid phases are the primary influencing factors for the safe and reliable operation of gas–liquid mixed transportation pump systems. This paper takes the independently designed single-stage helical axial-flow mixed transportation pump compression unit as the research object. Through numerical simulation, the internal flow of the mixed transportation pump is numerically calculated to study the aggregation and conglomeration of small gas clusters in the flow passage hub caused by gas–liquid phase separation, influenced by the shear flow of phase separation, forming axial vortices at the outlet where gas clusters gather in the flow passage. The work performed by the impeller on the gas clusters is insufficient to overcome the adverse pressure gradient formed at the outlet of the flow passage due to the gathering of the liquid phase in adjacent flow passages, resulting in the phenomenon of gas blocking, with vortex gas clusters lingering near the hub wall of the flow passage. Full article

Hydrocyclones can be used to concentrate the entrained sands in sewage and alleviate the clogging and erosion of the drainage network, but in practical application, there are problems such as low concentrations of underflow and a high content of fine particles, which cause a significant load on the subsequent sand dewatering and recycling. This paper designs five spigot structures of hydrocyclones and investigates the separation performance by numerical simulation, aiming to improve the applicability of hydrocyclones in the sewage treatment process by optimizing the spigot structure. The research results show that a large cone spigot delays the external downward swirling flow and reduces fine particle content in the underflow, but its effective separation space is reduced, and the turbulence in the cone section area is more intensive, which influences the separation accuracy. An elongated spigot has a reduced underflow water distribution; fine particles are more enriched in the internal swirling flow, and the underflow recoveries of 1 μm and 5 μm particles drop by 2.34% and 2.31%. The spigot structure affects the downward fluid and air intake states; complicated spigot structures contribute to increasing the resistance of particle discharge through underflow, alleviating fine particle misplacement. Full article

The oil–gas separator of the gas storage compressor serves as crucial equipment in a natural gas storage system to improve gas storage purity and efficiency. Its optimization is also essential to improve the separation efficiency and lifespan. Collision and centrifugal separation are two widely used optimized structures for oil–gas separators, and the enhancement in separation efficiency, as well as the decrease in pressure loss of optimized separators, has been thoroughly discussed. However, the velocity uniformity in the filter inlet has not been considered, which affects the filtration performance. Thus, the overall efficiency of the separator is reduced. Accordingly, optimization of an oil–gas separator with the consideration of velocity uniformity in filter inlets is introduced in this study. The effects of critical dimension parameters of optimized equipment on separator performance were analyzed. The results show that b_b = 0.4, l_b = 3, h_b = 1.5, and k_b = 0.5 and l_e = 0.9 and h_e = 4.11, as well as l_c = 0.5 and d_c = 0.52, are suitable for the case of placing baffles, adjusting the separator height and inlet position, as well as adding an inner cylinder, respectively. Subsequently, the analytic hierarchy process was employed to compare different optimized cases. It is observed that the overall rating for adding an inner cylinder reaches 88.46, which is the more suitable optimized method for the oil–gas separator. This work is relevant for oil–gas systems to improve their separation efficiency and enhance the gas storage performance. Full article

Kazakhstan ranks as the 12th largest oil producer globally and boasts a diverse range of crude oils. This research introduces a method for distinguishing between the different types of crude oils based on biomarker analysis of 28 crude oils from Western and Southern Kazakhstan using gas chromatography-mass spectrometry. Biomarkers serve as valuable tools, especially in forensic investigations of oil spills. These biomarkers effectively retain a significant portion of the original natural product’s carbon structure, providing crucial evidence regarding the origin and identity of the oils under examination. This study identifies a set of biomarkers, including pristine, phytane, n-C₁₇ and n-C₁₈ alkanes, hopanes, bisnorhopanes, iso-copalanes, pregnane, androstane, allopregnane, homopregnane, cholestane, and stigmastane. By examining ratios such as pristane/phytane, pristane/n-C₁₇ alkane, tricyclic/pentacyclic terpanes, and hopane, as well as the distribution of steranes, it was deduced that crude oils from West Kazakhstan exhibited resilience to biodegradation. These findings showed that gas chromatography-mass spectrometry is an effective method for oil biomarkers determination, especially because it provides efficient separation and identification. Additionally, this study delved into the origin conditions and maturity of these oils, contributing to a deeper understanding of their characteristics and analysis that is simple to use and available worldwide. Full article

The development of shale gas reservoirs often involves the utilization of horizontal well segmental multi-stage fracturing techniques. However, these reservoirs face challenges, such as rapid initial wellhead pressure and production decline, leading to extended periods of low-pressure production. To address these issues and enhance the production during the low-pressure stage, pressurized mining is considered as an effective measure. Determining the appropriate pressurization target and method for the shale gas wells is of great practical significance for ensuring stable production in shale gas fields. This study takes into account the current development status of shale gas fields and proposes a three-stage pressurization process. The process involves primary supercharging at the center station of the block, secondary supercharging at the gas collecting station, and the introduction of a small booster device located behind the platform separator and in front of the outbound valve group. By incorporating a compressor, the wellhead pressure can be reduced to 0.4 MPa, resulting in a daily output of 12,000 to 14,000 cubic meters from the platform. Using a critical liquid-carrying model for shale gas horizontal wells, this study demonstrates that reducing the wellhead pressure decreases the critical flow of liquid, thereby facilitating the discharge of the accumulated fluid from the gas well. Additionally, the formation pressure of shale gas wells is estimated using the mass balance method. This study calculates the cumulative production of different IPR curves based on the formation pressure. It develops a dynamic production decline model for gas outlet wells and establishes a relationship between the pressure depletion of gas reservoirs and the cumulative gas production before and after pressurization of H10 −2 and H10 −3 wells. The final estimated ultimate recovery of two wells is calculated. In conclusion, the implementation of multi-stage pressurization, as proposed in this study, effectively enhances the production of, and holds practical significance for, stable development of shale gas fields. Full article

The process of storing oil depots and combined station tanks is affected by factors such as process technology, equipment, and management methods. Inevitably, some heavy hydrocarbon components will condense. According to the available literature, the existing detection methods are not enough to accurately measure the component composition so that the proportion of heavy hydrocarbon substances in the lost gas is reduced. In this paper, by inventing a homogeneous reduction device, the lost gas in the entire laboratory process was kept in a homogeneous state so that the gas components were well-retained. Using the homogeneous reduction method and a traditional inspection method, gas chromatography was performed on a standard gas and the on-site lost gas, respectively. The standard gas measurement results show that the mean deviations of the homogeneous reduction method and the traditional test method were −3.45% and −11.62%, respectively, and the reduction degree reached 96.55% with the homogeneous reduction method. The results of the on-site gas loss measurements show that the proportions of most hydrocarbon substances in each lost gas increase to varying degrees after using the homogeneous reduction technology. Therefore, it is proved that these components can be better preserved using the homogeneous reduction method. It can effectively avoid the condensation of components, which is of great significance to the study of oil and gas loss. Full article

The stimulated reservoir volume (SRV) technology extends conventional fracturing technology. Understanding how to effectively and accurately determine modified fracture shape and volume is the key point to evaluating the stimulation effect. Using electromagnetic detection technology can provide a new option for measuring these parameters. By the finite method, the rationality of electromagnetic detection technology to obtain the relevant parameters of reconstruction fracture is testified through forward simulation. This study compared the signals of fractures with different conductivity, volume, and shape collected by electromagnetic detection tool, and the results show that the signals have a specific correspondence with fracture geometric parameters. According to the electromagnetic signal curve of the forward model, the description of propped fractures, including positions and sizes, can be realized. Full article

The phase state prediction methods of condensate gas are relatively mature, but the effect of phase changes on gas–liquid mixture flow behavior and the liquid-carrying capacity of gas has not been researched in detail. This study applied PIPESIM software to predict the fluid phase properties under different development stages of a condensate gas reservoir in Shengli Oilfield and determined the phase diagram and physical properties of the well stream on the basis of the optimized equation of state (EOS). Then the influence of phase change characteristics on wellbore flow behavior and critical liquid-carrying gas velocity was analyzed. The study showed that compared with the early development stage, fewer heavy components are produced and the produced gas–liquid ratio is increased in the late stage of the condensate gas reservoir. In addition, the pressure loss of fluid is decreased, the critical liquid-carrying gas velocity and flow rate are reduced, and the liquid-lifting difficulty is reduced for gas. The reason is that the liquid density decreases obviously due to the phase change, while the gas density is almost unchanged, and the oil–gas surface tension decreases obviously, resulting in a decrease in the critical liquid-carrying gas velocity. At the same time, the variation in the gas compressibility factor is very small, which leads to a decrease in the critical liquid-carrying gas flow rate. Full article

Waterflooding reservoir interwell connectivity characterization is the fundamental work in oil development, aiming to inverse the vital connecting channels between injectors and producers. In this paper, we endow an artificial neural network (ANN) with strong interpretability through the ordinary differential equation (ODE) of the material balance equation, proposing a physical knowledge fusion neural network (PKFNN). In addition, the proposed model could inherit the knowledge learned from different injector–producer pairs, fully improving the training efficiency. In this way, PKFNN combines the merits of both physical and machine learning approaches. Firstly, based on the physical control law and the ODE of the material balance equation, we endow the model with highly transparent modular architectures in the framework of feedforward neural network. In this way, our work has both high interpretability and excellent approximation ability, combining the merits of the physical and machine learning approaches. The proposed model shows great performance on productivity forecast and interwell connectivity reflection in several reservoir experiments. PKFNN provides a novel way to enhance the interpretability and robustness of the data-driven-based interwell connectivity-analyzing models by integrating the physical knowledge of waterflooding reservoirs. Full article

Nowadays, most oilfields have entered the high water cut stage of waterflood development. The importance of oil–water separation technology becomes more obvious. Gravity separation is one of the most commonly used treatment techniques for produced fluid. The gravitational separator has a large processing capacity and a wide application range, but its structure is relatively simple and the separation efficiency gradually falls behind to meet current production needs. The key difficulties to improve the separation efficiency are to analyze the flow field and coalescing components inside the separator. Aiming at these difficulties, this paper reports an innovatively designed series-parallel multistage multiphase separation system (MMSS). A horizontal separator is connected in series with a vertical separator, and the vertical separator consists of five discrete pipes connected in parallel. Different coalescing components are then set inside the vertical separator. The separation effect of the MMSS is studied by numerical simulation and laboratory experiments. The oil phase volume distribution cloud diagrams of coalescing components are analyzed by numerical simulation, including semicircle baffle, spiral track plate, four-hole plate and seven-hole plate. Laboratory experiments show that MMSS has a high separation efficiency, and the water content at the oil outlet is 3.0% less than that of the horizontal separator. By observing the shape of oil droplets at the outlet and measuring the oil cut and water cut at the sampling outlet, the separation effect of four coalescent plates is obtained. According to the statistics, when the volumetric flow at the inlet of the separator is 1.5 m³/h, the average particle size of oil drops in the blank pipe, semicircular baffle, four-hole plate, spiral track and seven-hole plate increases in turn. A continuous oil layer appears at the outlet of the vertical separator in the fully open state. The water content at the oil outlet of the semicircular baffle coalescing component is always at a high level under different flow rates. When the inlet volumetric flow rate is less than 1.6 m³/h, the performance of the spiral track coalescing component is better. With the increase of the inlet volumetric flow rate, the separation efficiency of the spiral track is lower than that of the orifice. The results show that the semicircular coalescing component has the worst performance, the spiral track coalescing component is superior at small volumetric flow rates, and the orifice coalescing component is superior at large volumetric flow rates. Full article

The periodic injection-production process of natural gas in underground gas storage make the rock bear alternating load under the gas-solid coupling. The alternating load changes the physical properties of rock, and then influence the critical production pressure drop of injection-production wells in gas storage. In the case of gas-solid coupling, the decisive factors affecting the alternating load are the number of injection-production cycles and the injection-production differential pressure. Therefore, a discrete element numerical simulation model is established to simulate the gas-solid coupling process of gas storage wells under different injection-production cycle and differential pressure. The influence mechanism of injection-production cycle and differential pressure on particle cementation and primary crack is analyzed microscopically and also the influence law of injection-production cycle and differential pressure on rock mechanical properties is analyzed from the macroscopic. Finally, the influence law of injection-production cycle and differential pressure on the critical production pressure drop of injection-production wells due to gas-solid coupling can be obtained. The results show that under the influence of gas-solid coupling, the number of bonded contact cracks and micro cracks in the model increase gradually, both the elastic modulus ratio and the cohesion ratio decrease gradually with the increase of injection-production cycle and the higher the injection-production differential pressure, the greater the decline range. Then, with the injection-production cycle increasing the Poisson’s ratio increases gradually and the higher the injection-production differential pressure, the greater the increase range. Finally, the internal friction angle ratio increases greatly in the initial stage, after that decreases and then shows a linear increase. According to the influence law, the relationship model between the critical production pressure drop of injection-production wells in gas storage and the injection-production cycle and differential pressure under the gas-solid coupling will be established, which is used for the dynamic prediction of the critical production pressure drop of injection-production wells in the whole life cycle of gas storage. Full article