Table of Content

10 June 2026, Volume 48 Issue 3

Previous Issue   

GEOLOGY EXPLORATION

Trap Sealing Evaluation and Monitoring Mode Construction Idea of Gas Reservoir-type Gas Storage

HUANG Dan, LI Qiuping, LUO Zhongshan, LIAN Qi, MIAO Shipu

2026, 48(3):  1-15.  DOI: 10.11885/j.issn.1674-5086.2024.05.06.01

Asbtract ( 33 )   HTML ( 4)   PDF (1935KB) ( 19 )  

References | Related Articles | Metrics

The gas reservoir-type gas storage is the focus of the national energy strategy deployment, which undertakes the arduous task of natural gas peak shaving and supply guarantee. Trap tightness is the primary prerequisite to ensure the safe operation of gas storage. However, the evaluation methods for trap tightness of gas reservoir-type gas storage are quite different, and a systematic and complete evaluation model has not been established. On the basis of a large number of domestic and foreign gas storage tightness evaluation and monitoring research, based on the characteristics of Huangcaoxia gas storage traps, a “static-dynamic” combination of gas storage reservoir trap tightness evaluation model was established, focusing on both caprock sealing and fault sealing. Also, a “monitoring well and microseismic” monitoring method was formed, and the working parameters of the gas storage can be dynamically adjusted in a timely manner based on the monitoring data. Through the constructed evaluation and monitoring model, the trap tightness of Huangcaoxia gas storage is preliminarily evaluated and monitored, and it is considered that the trap tightness is good. The research results have certain reference value for improving the evaluation and monitoring system of gas reservoir-type gas storage tightness at home and abroad.

Evalution of Geological Sweet Spot Around Well in Shale Oil: Taking Qingcheng Oilfield as An Example

WANG Zhongliang, XU Wenyuan, ZOU Huabao, QIAN Chen, WU Siwei

2026, 48(3):  16-26.  DOI: 10.11885/j.issn.1674-5086.2025.02.10.02

Asbtract ( 24 )   HTML ( 1)   PDF (4215KB) ( 8 )  

References | Related Articles | Metrics

Shale oil, as one of the important fields in unconventional oil and gas exploration and development, has gradually become a major research object for domestic and foreign oilfields. We take the Chang 7 sections of the Qingcheng Oilfield as the research objects, which pose many difficulties such as strong heterogeneity of the reservoir, numerous vertical interlayers, and that in characterizing geological sweet spots. The four-property evaluation using logging data has a long history and can quantitatively characterize geological sweet spots from the wellbore. However, with the continuous deepening of exploration and development practices, the evaluation of geological sweet spots only from the wellbore perspective can no longer meet the needs of the oilfield. In response to this situation, the logging-while-drilling gamma imaging is used to analyze the positional relationship between the wellbore trajectory and the formation and calculate the formation dip angle. The logging-while-drilling resistivity probe is used to determine the boundary range of the formation and pick up the changes in the structural dip near the wellbore. The logging-while-drilling nuclear magnetic resonance is used to accurately measure the porosity and fluid saturation of the reservoir in real time and evaluate the physical properties of the reservoir, forming a geological sweet spot evaluation technology around the wellbore for shale oil. This technology has important guiding significance in the geological steering and perforation cluster optimization of horizontal wells in the Qingcheng Oilfield's shale oil, and has good promotion value in other unconventional oil and gas reservoirs.

Application of Stress Field-constrained Multi-information Fracture Modeling Technology in the Development of Shale Oil

ZHANG Wen, WANG Qun, ZHOU Dongyan, YAO Juqin, CAO Yang, YU Jianglong

2026, 48(3):  27-38.  DOI: 10.11885/j.issn.1674-5086.2025.03.14.01

Asbtract ( 19 )   HTML ( 1)   PDF (30723KB) ( 13 )  

References | Related Articles | Metrics

The shale oil in the Fengcheng Formation of the Mabei Area has emerged as a key successor field for reserve and production growth in the Junggar Basin. The matrix physical properties of the Fengcheng Formation reservoirs are relatively poor, with fractures serving as the primary controlling factor for high production. Additionally, differentiated supporting fracturing technologies are required for reservoirs with varying degrees of fracture development. Traditional well-seismic joint fracture modeling methods exhibit low accuracy and struggle to quantitatively characterize multi-scale, azimuthally distributed fractures. This paper innovates methods in the following aspects: 1) azimuthal fracture modeling based on well data and seismic information is conducted to enhance the pertinence of the research; 2) tectonic evolution analysis and multi-constraint stress field inversion are performed to simulate the distribution of fracture development in different geological stages driven by paleotectonic stress field; 3) through the method of deep learning, the fracture information from well logging, seismic data, and stress fields is effectively integrated into a unified framework, enabling precise characterization of fractures of different scales and periods. The application of these methods raises the accuracy of natural fracture prediction to more than 80%, providing technical support for the fracturing design of 6 wells in the M Area. The daily production capacity of individual wells has increased by more than 22%, contributing to cost reduction and efficiency enhancement in the oilfield.

A Seismic Source Separation Method Based on Hybrid Optimization and Improved U-Net

LI Yan, Lü Xiaoyu, LIU Yangchao, ZHANG Quan, PENG Bo, TANG Shuhang

2026, 48(3):  39-52.  DOI: 10.11885/j.issn.1674-5086.2025.08.16.01

Asbtract ( 15 )   HTML ( 0)   PDF (10294KB) ( 9 )  

References | Related Articles | Metrics

Traditional single-source seismic exploration has problems of low efficiency and insufficient anti-interference ability. Although multi-source technology improves the exploration efficiency, the data quality deteriorates due to the interference of aliasing noise. For this reason, this paper proposes two optimization methods to solve the source separation problem. Method 1: A dynamic weighted hybrid optimization algorithm (ALFT) is constructed by integrating the FISTA algorithm and the ALBM algorithm. This algorithm improves the convergence speed while ensuring accuracy. By combining the advantages of the filtering method and the inversion method, a process of “initial value pre-judgment-iterative correction” is formed. The experimental results show that, compared with the direct iteration method, this method can increase the signal-to-noise ratio by 10%～25% and reduce the iteration time by 33%. Method 2: A CSA-Unet deep learning network model is proposed. Based on the U-Net network architecture, this model introduces an attention local contrast (ALC) module to enhance the ability to capture the characteristics of effective signals, and combines a local entropy discrete point suppression mechanism to eliminate the interference of auxiliary sources. The validation results demonstrate that CSA-UNet achieves a significantly higher separation signal-to-noise ratio than ALFT_a and U-Net on both the simulated dataset (Sigsbee2B) and the real dataset, while also effectively preserving the structure of the formation reflection signals. The methods proposed in this paper provide an efficient and high-precision solution for multi-source seismic exploration and are of great significance in imaging practices under complex geological conditions.

OIL AND GAS ENGINEERING

The Remediation Mechanism of Subcritical or Supercritical Water for Fracturing Fluid Damage in Normal-pressure Shale Gas Formation

CHEN Mingjun, LI Peisong, KANG Yili, CHEN Zhangxing, YOU Lijun, YAN Maoling

2026, 48(3):  53-67.  DOI: 10.11885/j.issn.1674-5086.2024.09.11.01

Asbtract ( 16 )   HTML ( 0)   PDF (7334KB) ( 8 )  

References | Related Articles | Metrics

The weak formation energy and retained fracturing fluid in the normal-pressure gas shale formation tend to cause formation damage, resulting in a rapid decline in the production of shale gas wells and low ultimate recovery after hydraulic fracturing. In this research, the normal-pressure shale gas formation in southeast Chongqing is considered as the research object. A scientific conception of relieving fracturing fluid damage by subcritical or supercritical water stimulation is innovatively proposed after clarifying the formation damage mechanisms of fracturing fluid invasion and the solution to relievie such formation damage. This method can improve the aqueous phase mobility and the gas flow capacity in shale matrix. The engineering and geological characteristics of shale gas reservoirs after hydraulic fracturing are considered, so the scientific conception is qualified as practical. Furthermore, dissolving minerals/organic matter and inducing fractures in the shale matrix via sub-and supercritical water remediation are investigated through experiments. The results show that the porosity and permeability of shale samples are greatly enhanced due to a large number of submicron-micron intragranular and interparticle dissolution pores generated. A high-temperature thermophysical effect and a subcritical or supercritical water catalytic oxidative dissolution effect are considered as the main mechanisms of relieving aqueous phase trapping damage in a shale gas reservoir. The application prospect of subcritical or supercritical water remediation is forecasted from the aspects of synergizing with hydraulic fracturing and the green and low-carbon concept in shale gas development.

Early Stable Production Technology Policy for Low Permeability Fractured and Caved Carbonate Gas Reservoir Development

OU Jiaqiang, CHEN Lin

2026, 48(3):  68-76.  DOI: 10.11885/j.issn.1674-5086.2024.10.07.32

Asbtract ( 17 )   HTML ( 0)   PDF (1714KB) ( 5 )  

References | Related Articles | Metrics

Carbonate rock oil and gas fields play a vital role in the global development of oil and gas resources, and the oil and gas output from carbonate reservoirs accounts for over 60% of the world's total production. Taking the Deng4 Gas Reservoir in the Moxi Block of Anyue Gas Field as an example, this reservoir features low matrix porosity, well-developed fractures and vugs, and strong heterogeneity. It is a typical low-permeability fractured-vuggy carbonate gas reservoir. During production, prominent challenges frequently emerge, including frequent gas well blockage, high risks of water influx and liquid loading, large variations in the stable production capacity of individual wells, and unbalanced reserve utilization. To achieve early stable production of the gas reservoir, systematic research was conducted focusing on blockage removal, water influx monitoring, hierarchical classification of gas wells, production allocation optimization and balanced reserve production. Two sets of blockage removal technologies for wellhead and downhole operations were established. Dynamic monitoring of water influx and identification of liquid loading were implemented. Gas wells were managed by hierarchical classification based on the K-means clustering algorithm. Combined with 3D geological modeling and numerical simulation, single-well production allocation was optimized and replacement production wells were deployed. Field application results show that the blockage removal treatments restored daily gas production by (148×10⁴ m³), with a cumulative incremental production of (1.83×10⁸ m³). After production allocation optimization, the stable production period of the gas reservoir was extended by 5.2 years, and the recovery factor during stable production rose from 6.14% to 9.45%. A total of 16 replacement production wells were deployed according to the distribution of remaining reserve abundance, which provides solid support for improving reserve utilization efficiency and realizing sustained stable production.

An Analysis of Linear Water Invasion Characteristics of Carbonate Edge-water Reservoirs

ZHU Songbai, WANG Shengjun, ZHAO Ji, WANG Hui, DENG Jun

2026, 48(3):  77-86.  DOI: 10.11885/j.issn.1674-5086.2024.06.18.01

Asbtract ( 15 )   HTML ( 0)   PDF (627KB) ( 8 )  

References | Related Articles | Metrics

The unsteady linear water invasion models of fractured carbonate reservoir and fracture-vuggy carbonate reservoir were deduced and established respectively, assuming the reservoir was rectangular and the closed water body was linearly distributed on one side of the reservoir. Then the models were solved by modern mathematical methods, and the linear water invasion curves of carbonate edge-water reservoir were plotted. The water invasion curves of two kinds of carbonate edge-water reservoirs were compared and analyzed, and the water invasion curves of infinite water body were also drawn. In addition, the characteristics and rules of water invasion were analyzed by drawing water invasion curves of fracture-vuggy carbonate reservoirs under different parameters. Finally, the water invasion model was applied and analyzed combined with the field data of fracture-vuggy carbonate edge-water reservoir from Tarim Basin. The results show that: 1) There is one ascending stage in the late stage of water invasion curve for fracture carbonate reservoir, and two ascending stages in the late stage of water invasion curve for fracture-vuggy carbonate reservoir. 2) The interporosiy flow coefficient affects the occurrence of the ascending stage of water invasion curve. 3) Storage coefficient affects the position of the corresponding stage of water invasion curve. 4) Water distance affects the position of all stages in the late stage of water invasion curve. 5) It is an important guarantee for the rational and efficient development of carbonate reservoir to fully understand the characteristics and rules of water invasion.

Optimization Method of Deep Paleokarst Reservoir Model Based on Production Dynamic Information

Lü Xinrui, LI Hongkai, SONG Suihong, WANG Zhelin

2026, 48(3):  87-97.  DOI: 10.11885/j.issn.1674-5086.2024.07.11.01

Asbtract ( 12 )   HTML ( 0)   PDF (2366KB) ( 5 )  

References | Related Articles | Metrics

The construction of geological models that accurately characterize the strong heterogeneity of different types of reservoir groups is the geological basis for efficient development deep paleokarst reservoirs. Currently, the geological model constructed by the paleokarst classification modeling method is mainly based on static data, which is not fully consistent with the actual production dynamics. There are problems such as the local inconsistencies between the model connectivity characteristics and the measured inter-well connectivity, the uncertainties in physical properties parameters of unfilled caves, and the great differences between model-calculated well control reserves and dynamic reserves of single wells. To improve the coincidence degree between the geological model and the production dynamic information of deep paleokarst reservoirs, a model optimization method and workflow based on annealing simulation method are constructed with the constraints of dynamic connectivity and dynamic reserves. In this paper, based on the connectivity characteristics of tracer and production dynamic discrimination, the mathematical model of fracture tracer conduction is established, and the objective function that characterizes the relationship between tracer conduction data and fracture attributes is constructed. The location of part fractures is optimized locally, so that the model connectivity is quantitatively consistent with the dynamic connectivity data. Taking the dynamic reserves of single well or well group as the target, the porosity, storage volume or co-optimization of the reservoir within its control range are carried out to improve the porosity accuracy of unfilled karst caves and reduce the difference between well controlled reserves and dynamic reserves of the model. The results show that the agreement between tracer simulation and measured curves after optimization of the geological model of a typical block reaches 86.3%, and the combined compliance rate between single well control reserves and dynamic reserves in the model is increased to 88.5%. The purpose of optimizing the model based on dynamic information is realized, the uncertainty of the model is reduced, and the effect is remarkable.

Mechanical Deterioration Characteristics and Damage Evolution Mechanism of Shale Under Thermal Gradient Effects

ZHOU Chengxiang, LI Chengying, GAO Maoping

2026, 48(3):  98-110.  DOI: 10.11885/j.issn.1674-5086.2024.11.27.02

Asbtract ( 14 )   HTML ( 0)   PDF (10283KB) ( 2 )  

References | Related Articles | Metrics

Shale gas development is faced with challenges such as difficulties in reservoir stimulation and low permeability. Liquid nitrogen fracturing, as a waterless reservoir stimulation technology, can circumvent the water sensitivity damage and environmental pollution issues associated with traditional hydraulic fracturing. However, the mechanism by which its thermal shock effect influences the mechanical degradation of shale remains unclear. To investigate the mechanical strength variation and fracture morphology characteristics of deep shale gas reservoirs under liquid nitrogen freezing, uniaxial compression experiments were conducted to measure the mechanical strength of shale at different temperatures and liquid nitrogen cycling times. The failure modes of shale at various temperatures were compared, and microstructural changes before and after liquid nitrogen freezing were analyzed. The results show that the deterioration and damage characteristics of shale are governed by cooling time, preheating temperature, and thermal gradient effects, manifested as microcrack propagation, increased fracture network complexity, and reduced mechanical strength. A higher thermal gradient enhances the deterioration effect of liquid nitrogen on the mechanical strength of the rock. Increased cycling times further exacerbate matrix damage and strength weakening, although the effect diminishes and stabilizes over time. The failure mode of shale is significantly influenced by bedding angles, with a minimum compressive strength observed at 60°, and a 90° bedding angle exhibits higher mechanical strength. In the case of strong non-homogeneity of shale, liquid nitrogen can effectively form a complex network of seams and reduce the mechanical strength. The synergistic damage model of “temperature-circulation-structure” established in this study provides a key theoretical support for the time regulation, optimization of circulation parameters, orientation of layers and non-homogeneous effect of liquid nitrogen fracturing in deep shale reservoirs.

Mechanisms of Multiscale Mechanical Parameter Degradation in Carbonate Rocks During Supercritical CO2 Acid Fracturing

LIU Chao, TAN Yawen, LIN Jin, WU Jinqiao, GAO Yang

2026, 48(3):  111-122.  DOI: 10.11885/j.issn.1674-5086.2025.11.12.01

Asbtract ( 23 )   HTML ( 0)   PDF (21395KB) ( 5 )  

References | Related Articles | Metrics

To overcome the issues of conventional acid fracturing in deep, high-temperature carbonate reservoirs with low pressure coefficients-namely overly rapid reactions, short effective penetration distances, low fracture conductivity, and difficult post-fracture flowback-this study performed soaking experiments on tight carbonates of the Majiagou Formation at 110 ℃ and 30 MPa using supercritical CO₂ (SC-CO₂) and SC-CO₂ plus formation water. Integrating X-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation, and uniaxial compressive tests, we constructed a coupled mineral-microstructure-micro/macro-mechanics evolution framework. The results indicate that pure SC-CO₂ is characterized by de-dolomitization accompanied by secondary calcite precipitation; with the addition of formation water, the regime shifts to carbonic-acid-dominated dissolution, manifested as preferential dissolution of calcite with relative enrichment (and possible recrystallization) of dolomite. The soaking process exhibits staged evolution: early de-dolomitization with secondary precipitation; a middle stage of intensified calcite dissolution with dolomite enrichment/recrystallization; and a late stage marked by increased porosity and connectivity and the emergence of channelization (wormholing). SEM shows surface evolution from pitting to grooves and through-going pores, with calcite more reactive than dolomite. Nanoindentation reveals power-law decay in hardness and elastic modulus-pronounced early softening followed by a short-term rebound and subsequent re-softening. At the macroscale, mechanical properties degrade concurrently: compressive strength and elastic modulus decrease markedly, Poisson's ratio increases, the load-bearing framework weakens, and ductility is enhanced.

Research and Application Progress of Nano-particles in Enhanced Oil Recovery

LU Cong, ZHU Qiuyan, GUO Jianchun

2026, 48(3):  123-132.  DOI: 10.11885/j.issn.1674-5086.2024.01.22.02

Asbtract ( 15 )   HTML ( 0)   PDF (6691KB) ( 4 )  

References | Related Articles | Metrics

For low porosity and low permeability reservoir, heavy oil reservoir and other reservoirs, chemical flooding, gas flooding and other methods are limited by reservoir conditions, and nanoparticles can be introduced to improve the technology. In order to make the industry further understand how to improve oil recovery, the mechanism of nanoparticles is described, including reducing the interfacial tension, structural disjoining pressure, improving the wettability and fluid properties, and pore channels plugging. On the one hand, nanoparticles adsorbed on the oil-water interface can reduce the interfacial tension of oil and water to improve oil recovery, on the other hand, they can form a steric barrier to improve the stability of emulsion or foam. When the nanoparticles gather in the three phase contact area of oil, water and rock, they rely on Brownian motion and electrostatic repulsion to produce structural separation and compression, so that the oil droplets are removed from the rock surface and adsorbed on the rock surface to improve the wettability. Nanoparticles can also improve crude oil rheology by adsorption of asphaltene and extend displacement range by pore channels plugging. In addition, the research development and field application of enhanced oil recovery of nanoparticles at home and abroad are also introduced.

Production Splitting Method for Multi-layer Commingled Gas Wells and Its Application in Yanchang Gas Field

ZHANG Xiaofeng, HE Jianying, WANG Shuai, LI Jing

2026, 48(3):  133-143.  DOI: 10.11885/j.issn.1674-5086.2024.02.01.01

Asbtract ( 14 )   HTML ( 0)   PDF (1057KB) ( 3 )  

References | Related Articles | Metrics

Multilayer commingled production is a common development method for multi-layer gas reservoirs. Reasonable splitting of gas production in each layer is a key factor for fine description of gas reservoirs and single-layer productivity evaluation of gas wells. The existing production splitting methods have some shortcomings and defects. The KH method and the mutation theory are of large errors and poor applicability. The numerical simulation method is complicated and takes a long time. The direct measurement method has high cost and cannot reflect the change of the yield contribution rate of each layer in the production process. In order to improve the accuracy of the production splitting results of multi-layer commingled gas wells, a new production splitting method based on node analysis is established by using the dynamic and static data of gas wells. Considering the constraints of reservoir properties of each layer on production, the grey correlation analysis method and analytic hierarchy process are used to quantitatively evaluate the reservoir properties of each layer. Based on the analysis method of multi-layer commingled production nodes in gas wells, the measured gas production is fitted by modifying the productivity coefficient of each layer and the constrained particle swarm optimization algorithm, and then the gas production and yield contribution rate of each layer are obtained. This method is applied to the Yanchang Gas Field. The results show that the error between the yield contribution rate fitted by this method and the production profile test is smaller, and it can reflect the change of the yield contribution rate of each layer with the production time. This method is suitable for commingled gas wells with abundant production data and no production profile test data, and provides more accurate data for single-layer productivity evaluation of gas wells.

Inversion Method of Deep Horizontal In-situ Stress Based on Borehole Deformation

MA Tianshou, CHEN Jie, LIU Yang, JIA Lichun, XU Honglin

2026, 48(3):  144-154.  DOI: 10.11885/j.issn.1674-5086.2024.03.11.03

Asbtract ( 18 )   HTML ( 0)   PDF (2036KB) ( 6 )  

References | Related Articles | Metrics

Based on the relationship between borehole deformation and in-situ stress state under non-uniform horizontal in-situ stress, an inversion method of deep horizontal in-situ stress was proposed based on borehole deformation. Firstly, based on the classical Krisch borehole stress equation and constitutive model, the inversion model of the horizontal in-situ stress was derived by using borehole deformation. Secondly, the inversion model was verified by finite element method. Then, the effects of wellbore pressure, formation lithology, horizontal differential stress, borehole size and inclination on the inversion of horizontal in-situ stress were analyzed using the finite element method. Finally, the applicability of this method is validated using measured data from two vertical wells in Alberta, Canada. The results indicate that the borehole deformation under the action of nonuniform horizontal in-situ stress is elliptical, and the inversion of the horizontal in-situ stress is related to the major and minor axes of the ellipse. The accuracy of the inversion model is verified by finite element simulation, and the inversion errors of the maximum and minimum horizontal in-situ stress are 0.001% and 0.052%, respectively. Different wellbore pressure, horizontal differential stress, borehole size and formation lithology have little effect on the inversion of horizontal in-situ stress, and the inversion error is <0.1%. However, borehole inclination has a significant effect on the in-situ stress inversion, and the inversion error of the horizontal in-situ stress is <0.4% when the borehole inclination is 65°. The analysis results of two case wells show that the inversion errors of the maximum and minimum horizontal in-situ stress are <5.5%, which further verifies the accuracy of this method. This study provides a new approach and method for in-situ measurement and inversion of horizontal in-situ stress in deep oil and gas wells.

PETROLEUM MACHINERY AND OILFIELD CHEMISTRY

Model Experiment on the Interaction Between the Buried PE Pipeline with Joint and Foundation Soil Under the Vertical Load

LU Jianguo, TAO Rui, LI Pengcheng, WANG Daguo, LI Chaolang

2026, 48(3):  155-164.  DOI: 10.11885/j.issn.1674-5086.2024.06.11.04

Asbtract ( 16 )   HTML ( 0)   PDF (1512KB) ( 7 )  

References | Related Articles | Metrics

Vertical load, as a common yet easily overlooked hazard factor, can cause the failure of buried PE pipeline. Based on the independently developed pipeline-soil interaction test platform, this paper carried out a model test of the interaction between the foundation soil and buried PE pipe with joint, and and explored the mechanical response of buried PE pipeline with joints under vertical loads and the mechanism of pipe-soil coupling processes. The results showed that the failure of buried PE pipeline systems under vertical loads was prone to start at the joint. Firstly, micro-cracks emerged from the weld seam of the joint. Then, under the continuous action of vertical load, the cracks expanded along the weld seam. Additionally, under the action of vertical load, the horizontal displacement of the pipeline intensified the deformation of the pipeline. Buried PE pipelines, under the action of vertical load, underwent overall tensile deformation along the axis. The longitudinal strain of the pipeline was mainly manifested as tensile strain at the top of the pipeline, and the compressive strain at the bottom of the pipeline. Due to the dissipation effect of soil on vertical load, increasing the burial depth of pipelines can effectively reduce the destructive effect of vertical loads on pipelines.

Simulation of Cement Sheath Integrity Based on the CDP and the Interface Separation Criterion

DENG Kuanhai, LUO Kaihuai, LIU Qiaoping, SONG Weichun, ZHOU Niantao, AL-SHAIBANI Sinan Ihsan, ZHANG Jingyi

2026, 48(3):  165-177.  DOI: 10.11885/j.issn.1674-5086.2024.11.02.01

Asbtract ( 17 )   HTML ( 0)   PDF (13592KB) ( 7 )  

References | Related Articles | Metrics

To investigate the failure process and damage form of cement sheath integrity under alternating pressure, the experimental results of the stress-strain ontological relationship and mechanical parameters of cement stone under uni/triaxial and cyclic loading are used to establish a three-dimensional mechanical model of the“production casing-cement sheath-technical casing” under alternating pressure. The mechanical response under alternating pressure was analyzed and verified by using full-size cement sheath integrity failure experiments. The CDP and interfacial separation criterion were used to simulate and analyse the cement sheath body integrity and interfacial integrity respectively. The results show that the degree of damage to the cement body increases with both peak pressure and the number of cycles, and the growth rate of tensile damage is higher. After the tensile damage value reaches its maximum value, the compressive damage value continues to increase as the number of cycles increases, and the cracks continue to extend. As the peak of pressure increases, the number of cycles required is gradually decreases for interfacial integrity damage to sprout and its evolution to form a micro-annular gap. The increase in the peak of pressure and the cycle times can both lead to damage to the integrity of the cement sheath, but the impact of the peak of pressure is more significant, directly damaging its integrity, while the cycle times further exacerbate the integrity damage and evolve into failure. The brittle characteristics of cementite and differences in tensile and compressive strengths are key factors in the differences in the rate of growth of damage.

Preparation and Performance Study of A New Selective Liquid Water Plugging Agent

LAN Xitang, LIU Yigang, GAO Shang, ZHANG Yunpeng, PAN Dingcheng

2026, 48(3):  178-186.  DOI: 10.11885/j.issn.1674-5086.2023.10.13.01

Asbtract ( 16 )   HTML ( 0)   PDF (2588KB) ( 12 )  

References | Related Articles | Metrics

With the development of water injection and over exploitation of oil and gas reservoirs, the problem of water production from oil and gas wells has become increasingly prominent. Water plugging operations are usually used to enhance oil recovery and water drive efficiency. Among them, selective water plugging agents have received widespread attention due to their ability to achieve precise water plugging and reduce damage to the reservoir. However, the strength and temperature resistance of the selective water plugging agents currently in use are limited, which greatly restricts its application in high-temperature and high-pressure formations. Therefore, based on the idea of the non-solvent-induced phase inversion method (NIPI), a new type of selective liquid water plugging agent with high-temperature resistance and high-strength has been developed based on plant fibers and high-strength polymer blends. The water plugging agent can achieve a phase transition from a low-viscosity liquid to a high-strength solid material upon contact with water, thus achieving precise water plugging. At the same time, the selective plugging success rate, temperature resistance, and compressive properties of the water plugging agent were evaluated. The study showed that the water plugging agent has good fluidity and can achieve precise selective water plugging of the water layer. At the same time, its temperature resistance can reach 120 ℃, pressure resistance can reach 9.99 MPa, and water blocking rate to 100%.