2024  Vol. 52  No. 3

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Expert Viewpoint
Abstract:

China has abundant shale oil resources and has made significant exploration and development breakthroughs in multiple basins, which unveils a new field for implementing China’s petroleum strategy. However, the exploration and development of shale oil in China has a relatively short history, and the top-level strategic planning and policy guidance are not yet clear. There are a series of issues to be solved such as difficulties in exploration breakthroughs, high development costs, and inefficient organizational operation, etc. To this end, a comprehensive literature review was conducted to explore the current status of shale oil management concept, macro environment, resource allocation, production and operation, science and technology level, and informatization state in China and the U.S, and in-depth considerations were performed to fully understand the pain points, difficulties, and obstacles of shale oil exploration and development in China. It is believed that currently there are four major challenges in shale oil exploration and development in China, including conceptual thinking, technical capabilities, operation management, and green developmentl etc. Based on the national energy strategy, countermeasures and suggestions were proposed to achieve efficient operation of shale oil in China, including implementing shale oil development strategy in a steady manner, building a strategic cooperative community with multi-subject integration under the market mechanism, creating a new mode of production and operation with multi-force collaboration, establishing a new mechanism of iterative technological development and innovation, developing a new information support paradigm empowered by digital intelligence, opening a new landscape of green and low-carbon industrial development, and fostering a new highly compatible and friendly external operation environment.

Drilling & Completion
Abstract:

In order to solve the problems of low rock breaking efficiency of drill bits and low rate of penetration (ROP) caused by great hardness, strong abrasiveness, high in-situ stress, and poor drillability of deep formation rocks, a new method of improving ROP was put forward to release the in-situ stress and reduce the drilling resistance of bottomhole rocks based on the analysis of existing speed increase technologies. Based on this idea, seven new types of drill bits were designed: bottomhole stress-induced unloading drill bits, concentrated energy attack-type unloading bottomhole stress drill bits, differential pressure drill bits, central differential pressure drill bits, drill bits under the joint action of induced unloading and abrasive jet, stairs type drill bits, and coupled self-excited axial impact and induced unloading rock-breaking drill bits. The ROP increase effect of two types of drill bits were verified through laboratory and well-site experiments. The central differential pressure drill bit increased its ROP by 30.01% in laboratory experiments, and the highest ROP increase in well-site experiments was 318.11%. The drill bits under the joint action of induced unloading and abrasive jet increased the ROP of limestone and red sandstone by 59.0% and 336.0% in laboratory experiments, respectively. The proposal of this method and the development of drill bits provide new ways for the ROP increase technology in deep formation with poor drillability.

Abstract:

The Shunbei ultra-deep and ultra-high-temperature fault-controlled oil and gas reservoir complex geology, large burial depth, high formation temperature, and high formation strength. During the drilling and completion process, complex situations such as leakage, collapse, gas invasion, wellbore deviation, and instrument tool failure are encountered frequently, seriously restricting the efficient exploration and development of the oil and gas field. Therefore, in order to improve the drilling speed in the Paleozoic, the drillability of the formation was investigated, and high-efficiency drill bits and long-life screws with large torque were selected, meanwhile pre-bending anti-deviation and fast drilling technology were promoted and employed. To address the issues of high reservoir temperature and difficulty in orientation, the application of high-temperature drilling tools was promoted, along with trajectory design and control technology. To avoid narrow gap leakage, “plugging while drilling + slug loss circulation control” and high-performance water-based drilling fluid were adopted. To address the issue of leakage and overflow in the same layer, managed pressure drilling and bull head method were applied to kill the well. In view of poor quality in long open hole cementing, an ultra-high-temperature cementing slurry system and supporting technology were adopted, and key technologies for improving drilling and completion speed in Shunbei ultra-deep and ultra-high-temperature oil and gas oilfield came into being. The technologies were applied in six wells in different zones of Shunbei, basically solving the problems of difficult drilling speed improvement and simultaneous leakage and overflow in ultra-deep and ultra-high-temperature oil and gas reservoirs. The drilling duration was shortened by 55.0% year on year, and the rate of penetration (ROP) was increased by 184.2%. The research results provided technical support for efficient exploration and development of Shunbei ultra-deep and ultra-high-temperature fault-controlled oil and gas reservoirs.

Abstract:

Well Yuanshen 1 is a key exploration well located in the gentle structural belt of northern Sichuan. The drilling process encountered several technical challenges, including complex formation pressure systems, borehole collapse, drilling fluid loss, strong terrestrial formation abrasiveness, and high risk of well control, etc. Based on the geological characteristics and drilling experiences of adjacent wells, a series of drilling technologies were implemented to increase the rate of penetration (ROP). Foam drilling technology was utilized to improve the ROP in large boreholes within shallow formations. For the highly abrasive terrestrial formations, the technologies of “turbodrill+impregnated diamond bit”and“rotary percussion drilling rig+hybrid drilling bit”were employed to enhance ROP. The combination of high-temperature, leak-proof drilling fluid with “high-efficiency polycrystalline diamond compact (PDC) bit+high torque screw” technology enabled safe and rapid drilling in the complex formations of the marine multi-pressure system. The microcore PDC bit was used to drill into the target zone, enhancing drilling efficiency while meeting the needs of cuttings logging. The well was successfully drilled to a depth of 8 866.00 meters, setting a Sinopec’s record for the deepest vertical well in the Sichuan Basin. This achievement provided technical experience for ultra-deep well drilling in the Sichuan Basin.

Abstract:

Ranging accuracy is a key factor affecting the successful connection between relief wells and accident wells. In order to improve the measurement accuracy of the active magnetic ranging system based on injected current, the electric field distribution in each medium was analyzed, and the current density distribution model of the accident well casing was established. By analyzing the current density distribution law of accident well casing, the calculation model of the optimal distance between the electrode and the probe based on the principle of the maximum magnetic induction intensity at the measuring point was established and the effectiveness of the model was verified by comparison test results. Calculations with examples show that the optimal distance between the electrode and the probe is related to not only the distance between the electrode and the accident well but also the relative well inclination angle. In addition, it has nothing to do with the injected current intensity. The distance between the peak point of the casing current density of the accident well and the coordinate point of the accident well is approximately equal to that between the electrode and the probe in the accident well. The optimal distance between the electrode and the probe is approximately equal to the product of the distance between the electrode and the accident well and the cosecant of the relative inclination angle. According to the calculation results of the optimal distance, a reasonable design of the distance between the electrode and the probe can contribute to the improvement measurement accuracy of the active magnetic ranging system based on injected current.

Abstract:

Due to the characteristics of variable marine environment, complex geological conditions, high operational risks, and high day rates of deepwater drilling operations, it is difficult to choose suitable method for well construction in shallow formation in deepwater. Taking into account all relevant factors, including seabed soil strength, well construction quality, operation efficiency, cost efficiency, drilling safety risk control, and other factors, the adaptability of different well construction methods were analyzed based on the field operation engineering data. A single-dimensional adaptability classification mechanism was established, and a multi-dimensional selection method for well construction in shallow formations of deepwater was formed through quantitative visualization using radar charts. The results show that in the South China Sea with a water depth of 500−1500 meters, the jetting method is the optimal method for well construction in shallow formation during single well operation, and the operation efficiency can be improved by more than 50% compared to the drilling method. This method has achieved good application results in dozens of deepwater wells in the South China Sea, which provides a quantitative evaluation approach for the selection of well construction methods in deepwater complex formations.

Abstract:

In the drilling process of Shengli Oilfield, a large amount of drilling waste was generated, with excessive pollutants. However, the pollution control of drilling wastes in Shengli Oilfield focuses on the end treatment, with low waste resource utilization and high cost, which makes it impossible to realize the pollution control in the drilling process and seriously threatens the ecological environment of the oilfield. In order to solve the key technical problems of environmental protection in the drilling process of Shengli Oilfield, theoretical research, equipment development, technical breakthroughs, and integrated application were carried out with the goal of “pollution reduction, harmlessness, and resource utilization”. Three core technologies were formed, including control of drilling pollution source, reduction of drilling waste while drilling in the whole well section, and harm-free treatment and resource utilization of drilling waste at the end. In addition, the environmental protection technology for drilling fluid treatment covering “source control, process reduction, and end treatment” was innovated. During the “Thirteenth Five-Year Plan” period, the environmental protection technology for drilling fluid treatment was widely applied in Shengli, Sichuan, and Xinjiang Oilfields, and a series of green and low-carbon drilling demonstration projects were established in B-105, Y-222, Z-146 blocks of Shengli Oilfield, which provides technical support for the green and low-carbon development of Shengli Oilfield and a useful reference for the green and low-carbon development of onshore oilfields in China.

Abstract:

In order to solve the problems of low transportation efficiency and high environmental protection risks in the process of offshore water-based drilling cuttings recovery, based on the analysis of the characteristics and transportation difficulties of water-based drilling cuttings, a set of efficient closed transportation technologies suitable for offshore water-based drilling cuttings transportation was studied, and the frictional resistance in the transportation process of drilling cuttings was analyzed. Research on resistance reduction and anti-blocking pigging technologies was also conducted. The model calculation results and field test data showed that the closed transportation of water-based drilling cuttings should adopt hydraulic transportation technology, combined with the design of transportation pipeline and pressurized mixer, to effectively reduce resistance and improve the velocity. When the pumping speed was set at 30%−100%, the transportation capacity was 7.5−25.7 m3/h, and the pumping pressure was 1.4−2.8 MPa. The research results show that the closed transportation technology of offshore water-based drilling cuttings solves the problems of efficient, closed, and long-distance transportation of water-based drilling cuttings. It can meet the needs of offshore drilling operations and is of great popularization, application, and commercialization value.

Abstract:

To enhance the low recognition accuracy of traditional intelligent lost circulation models, which suffer from limited samples, this study combined the long short-term memory (LSTM) network and auto-encoder (AE) to create an integrated LSTM-AE-based intelligent lost circulation recognition model. Initially, multiple LSTM-AE models with varying numbers of hidden neurons were trained using normal samples. Several models with better recognition performance were selected as base recognizers based on their reconstruction scores. Subsequently, the recognition results from these base recognizers were fused using ensemble learning. This approach addresses the tendency of a single model to produce false alarms and missed alarms due to overlearning of local sample characteristics, thereby improving the recognition accuracy of the model. The integrated LSTM-AE model was trained and tested using 6000 sets of stand pipe pressure, outlet flow, and mud pit volume data from 18 wells under normal drilling conditions in an oilfield. The results show that the proposed method achieves a recognition accuracy of 94.7%, surpassing the recognition results of other commonly used intelligent models. This approach offers a novel method for lost circulation recognition.

Abstract:

Fractures in tight oil and gas reservoirs are critical fluid seepage channels, and their stress sensitivity significantly influences the production of oil and gas wells. Solid particles play a crucial role in affecting the stress sensitivity of fractures. This study examined the impact of solid particles on fracture stress sensitivity in a laboratory setting under various conditions, including the presence or absence of solid particles, different paving methods of solid particles, and varying particle concentrations. The results indicate that the stress sensitivity of fractures, ranked from highest to lowest, is as follows: no solid particles, fully paved with low-concentration solid particles, fully paved with medium-concentration solid particles, fully paved with high-concentration solid particles, half-filled with medium-concentration solid particles, and high-diversion and paved solid particles. The presence of solid particles effectively reduces the stress sensitivity of fractures, and the damage to the stress sensitivity of fractures is irreversible. These findings provide a theoretical basis for preventing and controlling damage to the stress sensitivity of fractures.

Abstract:

In order to investigate the cuttings removal rule of rotary drill pipes in slim-hole horizontal well washing, a similar test design was carried out according to the washing condition of long slim-hole horizontal wells in the deep Triassic system of Mahu Sag, so as to investigate the cuttings start-up velocity and cuttings bed removal efficiency. The test found that the cuttings bed presented three transport modes: stable transport, dune wave-type transport, and overall transport when washed with different flow rates. The effects of particle size of cuttings, flow rate, and rotational speed on start-up velocity of cuttings in stable transport state of cuttings bed were studied through tests, as well as the effect law of the rotational speed of drill pipe on the height of cuttings bed and the time required to form a stable cuttings bed. The effects of particle size of cuttings, flow rate, and initial mass of cuttings bed on the removal efficiency of cuttings bed in overall transport state were investigated. The results show that the smaller particle size of cuttings indicates a smaller start-up velocity, and the equivalent start-up velocity of cuttings will be reduced by 45.5% after the drill pipe rotates. The increase in rotational speed of the drill pipe will shorten the time required to form a stable cuttings bed and improve the removal efficiency of cuttings. When the cuttings bed is in overall transport state, the removal speed of the cuttings bed is less affected by the particle size of the cuttings at low flow rates, and the transport speed of the cuttings bed with large particle size is faster at high flow rates. The flow rate and rotational speed of the drill pipe are the key to improving the removal efficiency of cuttings during well washing process. However, the rotational speed of the drill pipe is currently low during well washing process and can be appropriately increased to improve the well washing efficiency.

Abstract:

In order to solve the problem of wellbore instability in hard and brittle shale formations, nano-micro plugging agents have been developed in China and abroad by emulsion polymerization method. However, the nano-micro size of the plugging agent during application is difficult to maintain, and the drilling fluid is easy to foam. To this end, styrene and methyl methacrylate were used as monomers for polymerization, and divinylbenzene was used as an internal crosslinking agent for polymerization, with starch nanoparticles as emulsion stabilizers. A raspberry-like nano-micro plugging agent (i.e. raspberry-like crosslinked P (St-co-MMA) microspheres with starch nanoparticles adsorbed on the surface) was prepared by Pickering emulsion polymerization method for water-based drilling fluids. The particle size, morphology, and structure characteristics of crosslinked P(St-co-MMA) microspheres were characterized and analyzed, and their performance was evaluated in laboratory tests. The results show that the crosslinked P (St-co-MMA) microspheres can significantly reduce the American Petroleum Institute (API) filtrate loss and permeability plugging apparatus (PPA) filtrate loss of polymer potassium chloride drilling fluid and effectively plug the micron pores of the formation. The foaming problem of drilling fluid is solved, and the rheological property of drilling fluid is less affected, which can meet the needs of wellbore stability of shale oil and gas formation.

Oil & Gas Exploitation
Abstract:

A horizontal well with severe fluid loss in a fractured-vuggy carbonate reservoir in the eastern part of the South China Sea faced challenges such as early water production and rapid water breakthrough. Owing to the bottom water communicated by the fractured-vuggy network, the traditional mechanical and chemical water control methods were unable to solve the water discharge problem in the wells in this reservoir. Therefore, a water control technology, i.e., particle huff and puff, was proposed. Taking advantage of the leakage of the fractured-vuggy network of the carbonate formation, a large number of low-density (1.05 g/cm3) particles with stable physicochemical properties, mainly resins, were“swallowed”, so as to improve the heterogeneity of the formation. After put into production, some of the particles in the network would be gradually “spit back” to the annulus of the wellbore and its adjacent wells, so as to mitigate the water channeling. The results of particle huff and puff simulation experiment demonstrated that particles can enter the experimental fracture when the flow rate is greater than 0.003 3 m/s and can “spit back” from the experimental fracture when the flow rate is greater than 0.009 0 m/s. The particle huff and puff condition is easily met in the field. The technology was applied to three new wells and one old well in a fractured-vuggy reservoir, and the water cut was reduced by 5−10 percentage points compared with the adjacent wells or the wells themselves before the measures. The cumulative oil increase for a single well was 3×104 m3 to 8×104 m3, indicating obvious water control and oil increase effects. The proposed particle huff and puff technology provides a new water control solution to the water discharge problem of horizontal wells with severe fluid loss in fractured-vuggy carbonate reservoirs.

Abstract:

In order to reveal the opening conditions and extension law of natural and hydraulic fractures in fractured reservoirs and reduce the risk of water channeling, in-situ stress test, natural fracture observation, hydraulic fracture extension test, and simulation were used. In addition, the opening conditions and extension law of natural and hydraulic fractures, the effect of horizontal stress difference on the extension of hydraulic fractures, and the net pressure of communication between natural and hydraulic fractures were systematically studied. The results show that the vertical stress σv in the study area is higher than the maximum horizontal principal stress σH, which is higher than the minimum horizontal principal stress σh. The gradients of vertical stress, maximum horizontal principal stress, and minimum horizontal principal stress are 0.025, 0.020, and 0.017 MPa/m, respectively. The critical pressure gradient of fracture sliding in the tight sandstone of the study area ranges from 0.018 to 0.020 MPa/m, with an average value of 0.019 MPa/m. When the critical pressure gradient in the natural fracture exceeds 0.020 MPa/m, all the ineffective fractures are transformed into effective fractures. As the horizontal stress difference increases from 0 to 10 MPa, the length of hydraulic fractures increases gradually. The length of hydraulic fractures formed under the stress difference of 10 MPa is about 1.52 times that of hydraulic fractures formed under the stress difference of 0 MPa and 5 MPa. The fracturing experiment results show that the hydraulic fracture will be deflected to a certain extent when encountering locally developed gravel particles and then continue to extend along the original direction. In the study area, the net pressure gradient of fracture communication under the condition that natural fractures in the target layer open to form branch fractures is 0.003 MPa /m, and the net pressure of fracture communication is 4.5–9.0 MPa. It is concluded that the construction of an unsteady extension mode of hydraulic fractures in fractured reservoirs should consider the horizontal stress difference, natural fracture development, lithology characteristics, and fracturing operation conditions.

Abstract:

In order to reduce the throttling loss of the valve group caused by the inconsistent demand pressure of each water injection well, a mathematical model of partial-pressure periodic water injection under time-of-use (TOU) electricity price was established. The model took the lowest total energy consumption cost of the pump station as the objective function and the service requirements of the pump assembly in the station and water injection well outside the station as the constraint conditions. Modeling programming was performed with mathematical planning and a optimization general algebraic modeling system (GAMS). The embedded branch-and-reduce optimization navigator (BARON) solver was called to solve the problem. According to the actual water injection situation, two operation schemes of cross water injection and sequential water injection were considered in each pressure range, and the best water injection scheme was determined by comparative analysis. The results show that after optimization, the average throttling loss of low-pressure and medium-pressure water injection well group is reduced by about 7 MPa and 3 MPa, respectively. The partial-pressure periodic water injection under TOU electricity price has good economic benefits, which can reduce the energy consumption cost within one period by about 13000 yuan and greatly reduce the energy consumption cost caused by throttling loss in site. Compared with cross water injection, sequential water injection has better practical value and operability and can provide some reference for the actual operation and production of the site.

Abstract:

In order to clarify the distribution of microscopic remaining oil in different oil displacement stages and guide the exploration of remaining oil potential in the late stage of water injection development in mature oilfields, cores with different permeability levels from typical blocks were selected for oil displacement experiments. Liquid nitrogen refrigeration technology was used to prepare core slices, and high-pressure mercury lamp fluorescence microscopy was used to analyze the microscopic remaining oil occurrence status during the saturated oil stage, the initial water breakthrough stage, and the post water flooding stage. Through image processing, the occurrence state of remaining oil were further categorized, and the proportions of remaining oil in different states were calculated. The results show that water flooding in medium-permeability core mainly utilizes free-state residual oil, and there is more free residual oil remaining after water flooding, which can be used as a potential target for further exploration. The free-state microscopic residual oil in low-permeability cores was further reduced during the water flooding process, and then the membrane-shaped residual oil in bound state and the throat-shaped residual oil in semi-bound state after water flooding can be used as alternative development resource. The microscopic observation method by high-pressure mercury lamp fluorescence provides a new quantitative approach for the remaining oil analysis and a good reference for the exploration of remaining oil potential in mature oilfields.

Abstract:

The throttling slip base made of soluble magnesium alloy often fails due to its rapid degradation rate during downhole service. Therefore, the surface of soluble magnesium alloy was modified to solve the problem. In order to understand the corrosion resistance of the surface-modified soluble magnesium alloy, the microstructure of surface-modified magnesium alloy before and after corrosion was observed with scanning electron microscopy(SEM). The phase structure of surface-modified magnesium alloy before and after surface corrosion was analyzed by X-ray diffraction (XRD) and infrared spectrometer. The corrosion resistance of the alloy in simulated well fluids at pH 3.0, 7.2, and 9.0 was evaluated by electrochemical and immersion tests. Compared with magnesium alloy, the corrosion potential of surface-modified magnesium alloy was positively shifted by about 1.1 V; the corrosion current density was reduced by three orders of magnitude, and the corrosion rate was reduced by about 3 mm/a in the simulated well fluids at different pH values. Compared with the simulated well fluid at pH 7.2, the charge transfer resistance of the surface-modified magnesium alloy decreased from 9.13×106 Ω·cm2 to 1.91×106 Ω·cm2 in the simulated well fluid at pH 3.0. The results show that compared with magnesium alloy, the corrosion resistance of surface-modified magnesium alloy in simulated well fluids at pH 3.0, 7.2, and 9.0 is significantly improved, while the corrosion resistance of surface-modified magnesium alloy in acidic simulated well fluids is greatly reduced and easy to degrade. The field test of the throttling slip base of the surface-modified magnesium alloy shows that the pressure performance and corrosion resistance of the slip base meet the requirements, and it is easy to be salvaged. The research and field test show that the corrosion resistance of the surface-modified magnesium alloy meets the requirements of soluble slip base, which provides a basis for its application in downhole throttling.

Well Logging & Surface Logging
Abstract:

Wireline logging in horizontal wells in high resistivity formations faces high risk,and its logging data are subject to serious lackage, which restricts accurate geosteering drilling and high-quality reservoir identification. Therefore, a novel electrode system of azimuthal lateral resistivity logging while drilling based on the non-contact coupling principle was proposed, with radial, longitudinal, and circumferential detection abilities. The effects of wellbore size, flushed zone resistivity, formation inclination, layer thickness, and surrounding rock resistivity on the detection results were investigated by using the three-dimensional finite element simulation method. The electrode system size and detection characteristics were determined, and the ambient impact calibration diagram was established. The simulation results show that the toroidal coil excitation instrument for azimuthal lateral resistivity logging while drilling has a shallow detection depth, which is generally less than that of the cable-type instrument, but it is less affected by intrusion during the drilling process. It can meet the needs of logging while drilling, has good longitudinal zone identification ability, and can define 0.5 m thin layers under the condition of high resistivity formation. With the help of quad azimuthal measurement, the position of high and low resistivity abnormal bodies can be well identified, and the formation inclination can be determined. The research results have important guiding significance for the structural parameter design of instruments for azimuthal lateral logging while drilling and exploring for high resistivity reservoirs.

Abstract:

Conventional electromagnetic logging while drilling is an important method for evaluating stratigraphic fluids, but it does not have azimuth property. In this paper, a new modular electromagnetic logging while drilling instrument was proposed with good azimuth detection property. In order to accurately understand the influence of modular electromagnetic logging while drilling instrument on the measured voltage signal, a 3D model was established using the finite element method, and the influence laws of various instrument parts were explored. The results show that with the increased resistivity of the drill collar and antenna slot filling material, the received voltage signal has a sudden change, which is closely related to the frequency and geometric size of the instrument. The resistivity of the cover plate material has a great influence on the intensity of the received signal, and the cover plate should be selected with a little lower resistivity than metal. The measurement signal increases with the increasing resistivity of the sensor body, so the non-metallic material should be selected as the sensor body. When the resistivity of the instrument structure such as drill collar and filling material is low, the received voltage signal has obvious attenuation, and its influence can be ignored when the resistivity of the filling material is high. By deducting the instrument response in the air medium, the influence of the instrument structure can be well eliminated. After deducting the influence of the instrument structure, the magnetic flux in the coil decreases, resulting in a smaller instrument signal than before. The research results can provide a theoretical basis for the design and manufacture of actual logging instruments.

Low-Carbon & Emission Reduction
Abstract:

The integrated development of oil & gas resources and new energy is an important feature of building a new energy system. This study analyzes the main advantages of integrating depleted oil & gas reservoirs with new energy sources and reviews research progress in utilizing these reservoirs for geothermal energy, energy storage, hydrogen storage, hydrogen production, and lithium metal mining, both in China and abroad. The research results show that due to the different degrees of technology portability and reference, the technology maturity of integrated development of depleted oil & gas reservoirs and new energy is different. The feasibility of exploiting geothermal resources by utilizing depleted oil & gas reservoirs has been fully verified, the energy storage of depleted oil & gas reservoirs is currently undergoing verification, while hydrogen storage in depleted oil & gas reservoirs is in the early exploratory stage. Researches into extracting hydrogen and lithium from depleted oil & gas reservoirs have been carried out by a few companies, with the feasibility unproven. Based on the survey results, the main suggestions for promoting the integrating depleted oil & gas reservoirs with new energy are put forward: surveying current depleted oil & gas reservoirs to establish the relevant information sharing platform; conducting extensive collaborative research to promote rapid technological breakthroughs; implementing demonstration and pilot projects to form utilization standards for the resources of depleted oil & gas reservoirs; exploring the business modes for resource utilization of depleted oil & gas reservoirs to achieve low-carbon development.

Abstract:

During the 14th Five-Year Plan period, the huge peak shaving gap and resource degradation of underground gas storage (UGS) in China have formed a sharp contrast. UGS construction faces challenges, such as a lack of storage site resources and upgrading of technical difficulties. Therefore, through systematical research and analysis of the types and characteristics of global UGS, new change trends in Chinese UGS sites were proposed, and development strategies for UGS construction from the perspectives of new modes, theoretical technologies, and supporting policies were explored. In response to the characteristics of separation between natural gas resources and markets in China, the coexistence of multiple peak shaving methods, and regional differences in UGS types, an overall layout and digital development direction for UGS construction were proposed. Chinese UGS sites present four new trends, namely diversification, large scale, complexity, and digitalization. The new mode of “three zones” in large-scale low-permeability lithological gas reservoirs and collaborative construction of oil reservoir gas drive and UGS can activate a batch of site resources and greatly improve peak shaving capacity. New technologies such as dynamic sealing evaluation of gas storage geological bodies, seepage mechanism and storage design of high-speed interactive injection and production, and new technology for complex salt cavity building and space utilization improvements, can significantly improve operational efficiency and reduce safety risks. The research results provide scientific support for fully excavating site resources and guiding the efficient design of complex UGS.