Table of Content

10 June 2025, Volume 47 Issue 3

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SPECIALIST FORUM

Researches on and Prospect of ROP Improvement in Deep and Ultra-deep Oil and Gas Drilling

ZHU Xiaohua

2025, 47(3):  1-9.  DOI: 10.11885/j.issn.1674-5086.2024.09.01.01

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Increasing ROP, controlling complex downhole conditions, and improving drilling-encounter ratio are the three major challenges in deep and ultra-deep oil and gas drilling. Since the “12th Five-Year Plan” period, China has made significant progress in drilling technologies such as rotary steering, precise pressure control, efficient PDC bits, and drilling tools, and a number of ultra-deep wells of about 8 000 meters have been drilled. This paper focuses on the ROP improvement and summarizes the recent research progress in drillstring dynamics, efficient rock breaking and drilling tools, mainly including the review of the development of drillstring dynamics theory, the evaluation methods of drillstring vibration, buckling, and dynamic friction torque. Focusing on the theory of ductile-brittle critical failure of rock, the selection and optimal design method of drill bit based on ductile-brittle critical failure are deeply analyzed. This paper also systematically introduces a series of drilling tools based on impact accelerated crack growth and vibration drag reduction, and the relevant analysis and evaluation method based on CAE numerical calculation. The comprehensive ROP improving method based on efficient energy transfer and utilization is summarized and analyzed. Finally, suggestions are provided for increasing research efforts on downhole power drilling tools and new rock breaking methods. The research work has a certain reference value for improving the drilling speed of deep hard formation and ultra-deep complex structure wells.

GEOLOGY EXPLORATION

Zoning-grading Analysis and 3D Panoramic Characterization of Thrust Strike-slip Faults

OU Chenghua, WANG Zeyu, LIU Jincheng, LI Zhaoliang, MEI Hua

2025, 47(3):  10-24.  DOI: 10.11885/j.issn.1674-5086.2023.09.14.02

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The thrust strike-slip fault is widely distributed in the oil-rich structural zone, and quantitative characterization is of great significance to oil and gas exploration and development of oil-bearing basin, superposed coupling of horizontal extrusion stress and compression shear stress, the thrust displacement and slip displacement occur simultaneously in the thrust strike-slip fault system, which cause formation fragmentation, complex fault system, and disorderly logging and seismic response, and increases the difficulty of fault identification, combination, characterization and modeling. Aimed at the formation mechanism and the complexity of the thrust strike-slip fault system, a zoning-grading analysis and 3D panoramic characterization technology is developed to implement the quantitative analysis and 3D panoramic characterization of the study area—the lower plate of the Youshashan fault system of Yingdong Oilfield in Qaidam Basin. Relying on the zoning formation correlation, the key marked formation cross leading and zoning formation calibration technology is established, and solves the problem of difficult calibration and strong multiple solutions of the fragmentation formation, and the effective calibration of the six key marked formation and the full coverage tracking of the whole study area is implemented. The panoramic characterization, multi-scale and multi-type thrust strike-slip fault-fold step grid modeling and panoramic visualization characterization technology are used to the panoramic visual characterization of the thrust strike-slip fault profile-plane-3D multivision space of the study area.

Interpretation and Identification of Effective Carbonate Reservoir Based on Principal Component Analysis

XU Wensheng, SUN Yaoxi, LIU Qiguang, PANG Xiongqi, ZHANG Hu

2025, 47(3):  25-36.  DOI: 10.11885/j.issn.1674-5086.2023.09.25.02

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The Kalataer Formation in the Kekeya Area of the Southwest Tarim Depression is a carbonate reservoir, and its pore-fracture system determines the enrichment degree of oil and gas. It is extremely difficult and ineffective to identify and evaluate the pore-fracture system using a single logging parameter. This paper takes the principal component analysis method as the core, couples multiple components under the condition of minimal information loss, and proposes a new method for interpreting and evaluating the storage space of carbonate rock pore-fracture systems based on conventional logging data, aiming to achieve joint quantitative analysis and evaluation of high-density vertical pore-fracture systems in unimaged logging areas. The logging curve data used in this study include sonic logging curves, density logging curves, neutron logging curves, deep lateral logging curves, and shallow lateral logging curves, combined with measured porosity and permeability data, mercury injection test data, etc., to establish a mathematical model for interpreting secondary pore-fracture reservoirs in the Kekeya Area of the southwest Tarim Depression, quantifying the storage space of the carbonate rock pore-fracture system. The research results show that the identification results of the porous-fractured reservoir interpretation model of the Kalataer Formation in the Kerkeya Area are highly consistent with the interpretation results of the imaging logging, with a matching rate of up to 73%, indicating the effectiveness of the method. The research results can provide a solid guarantee for the efficient exploration of tight carbonate oil and gas reservoirs.

Application of Radial Basis Function Multi-attribute Fusion Technology in the Study of Beach-bar Sand Body Distribution Law

LI Bin, LIANG Yu, ZHAO Hu, YANG Hongwei, WEI Guohua

2025, 47(3):  37-47.  DOI: 10.11885/j.issn.1674-5086.2022.03.08.01

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Aiming at the difficulty in effective description with the existing seismic resolution due to thin microfacies sand body of the fast changing facies and reservoir heterogeneity, we take the upper Es₄ sub-member of the Boxing Sag of the Daluhu Oilfield as an example, and use the regional isochronous interface T₇ under constraints, chronostratigraphic slices to extract typical seismic amplitude attributes, and clarify the response characteristics of beach-bar facies on seismic amplitude attributes. Seismic sedimentology is used to explore the characterization of beach-bar microfacies. The study identifies five seismic reflection characteristics of beach-bar facies in the upper part of the fourth member of Shahejie Formation. The cluster analysis method is used to identify the distribution range of beach-bar facies, and to describe the distribution form of beach-bar microfacies based on colored inversion technology, and explored to use of the radial basis multi-attribute fusion method in thickness sand body prediction. The results show that the sand body in the northwest that interferes with the original seismic attributes is not developed, and is dominated by semi-deep lacustrine mudstone. This prediction result is in good agreement with the actual geological understanding, eliminating the ambiguity of a single seismic attribute. Based on the above results, the study has finely described the distribution of beach-bar microfacies in the study area, showing that the bar sand microfacies in the study area is well-developed and distributed in a wide range, and shows the characteristics of multiple parallel rows of sand bars facing the semi-deep lake area. It is a favorable target area with good potential for unconventional oil and gas exploration and development in the next step.

Sealing Evaluation of Air Energy Storage in Underground Brine Mining Salt Cavities in Sichuan Basin

MAO Chuan, LIU Li, ZHAO Xiaoming, WANG Peng, ZHOU Ruiqi

2025, 47(3):  48-64.  DOI: 10.11885/j.issn.1674-5086.2023.12.04.02

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During thousands of years of salt mining in China, a large number of brine-mining salt cavities have been formed. Compared with underground salt cavity gas storage reservoirs, brine-mining salt cavities are characterised by complex geological conditions, extremely irregular cavity morphology, and poor confinement and stability, etc. In order to study the sealing performance of brine-mining salt cavities, this paper with the thin irregular brine mining salt cavity as the research object based on the results of geological, logging and laboratory coretests, a three-dimensional fine geological model and a three-dimensional dynamic geomechanical model of the Y Salt Cavity and wellbore in the Sichuan Basin were established, and numerical simulations of the micro-annularity and fracture extension at the cementing interface were carried out. The results show that: 1) on the basis of clarifying the model permeability and pressure distribution, the simulation results show that the Y Salt Cavity in Sichuan Basin has good closure; 2) the fatigue damage and plastic strain under cyclic loading will be concentrated locally, mainly at the interface between the cement ring and the casing; 3) appropriately lowering the modulus of elasticity of the cement ring and the content of the fibre will enhance the closure ability at the wellbore; 4) when evaluating the closure ability of the salt cavity, the surrounding rock permeability is the main factor. During the construction of the salt cavity gas storage reservoir, a part of the thickness of the top plate of salt rock should be reasonably reserved according to the strength of the closure ability of the rocks in the region to guarantee the cavity tightness.

Architectural Styles and Depositional Processes of Cenozoic Deep-water Channels in the Lower Congo Basin, West Africa

CAO Shuchun, LIU Fei, BU Fanqing, QI Mingming, GUAN Hong

2025, 47(3):  65-75.  DOI: 10.11885/j.issn.1674-5086.2025.02.28.02

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The Lower Congo Basin has developed large-scale deep-water channel deposits, which are the primary type of hydrocarbon reservoirs. To address the unclear understanding of the internal channel unit stacking patterns and migration modes, a study on deep-water channel deposition models was conducted. This research utilized three-dimensional seismic data and RGB spectral decomposition attribute fusion techniques to investigate the sedimentary characteristics of different channel architectural levels and reconstructed the depositional process of turbidite channels in the study area. The key findings are as follows: the study area is characterized by a down-stepping confined channel system, comprising three phases of aggradational and progradational complex channels. The lower complex channels exhibit planar straight geometries with vertically stacked individual channels, while the middle complex channels form low-sinusosity belts with laterally stacked individual channels. The upper complex channels show high-sinusosity and meandering planar geometries, with individual channels laterally connected or isolated. These three phases of compound channels correspond to three stages: erosional base, main deposition, and late abandonment. Reservoir formation occurred during the main depositional stage of the channel system. This study clarifies the sedimentary characteristics and stacking patterns of different channel architectural units, and establishes a depositional model for deep-water channels in the study area. The findings hold significant geological implications for the development strategies and efficient production of similar hydrocarbon reservoirs.

Seismic Wavefield Forward Modeling Study Under Complex Conditions in the Southwest Foreland Belt of the Tarim Basin

PEI Guangping, SHEN Tianjing, PENG Gengxin, JIANG Zelei, CHEN Feixu

2025, 47(3):  76-87.  DOI: 10.11885/j.issn.1674-5086.2023.05.24.01

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The surface and subsurface structural patterns in the region in front of the southwest foothill area of the Tarim Basin are highly complex, with diverse lithological and structural features. This area is a typical case of “dual complexity” in both surface and subsurface geology, leading to complex seismic wavefields and significant challenges in data processing and imaging accuracy. To clarify the seismic wavefield propagation characteristics in this region and provide a theoretical basis for subsequent data processing, this study constructs a dual-complexity velocity model representative of the area's geological features, based on field seismic data, well logging data, and near-surface outcrop information, and conducts seismic wavefield simulation analysis. During the modeling process, a near-surface velocity model was first developed using near-surface tomography data and elevation information. Then, a structurally complex model was constructed and refined based on seismic interpretation results. These models were subsequently integrated to form the final velocity structure model. To accurately characterize the Q value distribution within the target area, this study proposes a method for constructing a Q model based on sparse well data. Seismic wavefield forward modeling was conducted using the developed velocity and Q models to analyze the effects of surface elevation variation and near-surface velocity distribution on the subsurface wavefield. The findings are expected to provide a theoretical basis for optimizing seismic acquisition system parameters and improving seismic imaging quality in the study area.

OIL AND GAS ENGINEERING

A Feasibility Study of CO₂ and Associated Gas Mixture Flooding in High Water-cut Reservoirs

ZHANG Lingfeng, LIAO Xinwei, ZHANG Qi, DONG Peng, YANG Zepeng, HOU Shanze

2025, 47(3):  88-100.  DOI: 10.11885/j.issn.1674-5086.2024.06.23.01

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The Shanshan Block in the Tuha Oilfield has entered a high-water-cut development stage, limiting additional oil recovery by waterflooding, it is imperative to explore novel EOR technologies. Although CO₂ flooding is proven effective by reseaches home and abord, but it is highly costly for Shanshan Block due to the lack of CO₂ resources. This study examines mixing hydrocarbon-associated gas with CO₂ to reduce injection expenses. Minimum miscibility pressures were tested using crude oil, cores, and associated gas in Shanshan Block. Under high temperature and pressure, cores were waterflooded and then displaced with gas mixtures at varying CO₂ concentrations, tracked by nuclear magnetic resonance and computed tomography. Results show that miscibility occurs above 43% CO₂ content. At approximately 50% CO₂, displacement performance is comparable to pure CO₂ flooding and surpasses pure associated gas, Microscopic analysis reveals that the hybrid CO₂-associated gas flooding effectively mobilizes remaining oil at the pore scale, demonstrating economic feasibility and technical efficacy. Hence, it offers a promising method for Shanshan Block.

An Experimental and Numerical Study of In-situ Generated Solvent Assisted SAGD in Heavy Oil Reservoir

CHENG Haiqing, YANG Simin, ZHAO Qinghui, ZAHNG Yong, SU Lei

2025, 47(3):  101-111.  DOI: 10.11885/j.issn.1674-5086.2023.05.30.01

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In order to solve the problems of low thermal efficiency and high steam consumption in the middle and late stages of steam injection in heavy oil reservoirs, this study proposes an in-situ generated solvent assisted steam assisted gravity drainage technique. This paper studies the feasibility of this new method through a combination of numerical simulation and physical simulation. By conducting experiments on Liaohe Du84 heavy oil, the mechanism of solvent generation during catalytic crac-king of heavy oil was studied. A reaction kinetics model was established based on reaction kinetics theory, and the mechanism of solvent enhanced SAGD in situ production of heavy oil was studied using numerical simulation methods. The research results indicate that over 5% of heavy oil is in-situ converted into solvents in a steam injection environment through catalytic cracking reaction. The solvent composition includes light hydrocarbons and non condensable gases, which have the characteristics of being a solvent medium for SAGD. The concentration also meets the solvent requirements of expanding solvent-SAGD technology. The generated light oil components and gases are recycled in the steam chamber as a solvent medium for gravity drainage, thus improve both recovery efficiency and oil steam ratio.

Micro Mechanism of Oil Displacement by Water Gas Dispersion System

SHANG Zhenhao, WU Jiazhong, XIONG Wei, ZHANG Moxi, CHEN Xinglong

2025, 47(3):  112-123.  DOI: 10.11885/j.issn.1674-5086.2022.09.30.02

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Low permeability reservoirs have small pores, fine throats and large seepage resistance, and the recovery percent of conventional water drive is only about 20%. Gas injection development is not only limited by gas sources, but also seriously affected by gas channeling and other problems; therefore, it is urgent to develop key technologies to continuously improve oil recovery in low permeability reservoirs. The oil displacement technology of water gas dispersion system is a new technology to improve oil recovery. This technology can realize the control of seepage resistance and supplement energy at the same time, thus greatly improving the water displacement efficiency of low permeability reservoirs. In order to understand the micro oil displacement mechanism of water gas dispersion system, the flow characteristics and distribution laws of fluid in the displacement process were recorded, identified and quantitatively calculated through water drive, gas drive and water gas dispersion system oil displacement experiments by means of micro etching model, high-speed camera acquisition and ImagePro-Plus6.0 software identification. The experimental study shows that the main producing area of water drive is the main channel, and the remaining oil is mainly distributed in the edges and corners of the model; the characteristics of CO₂ gas channeling are obvious, the gas mainly flowing in the pore center and forming a water/oil film on the pore wall; the most remarkable feature of water gas dispersion system for oil displacement is that it mixes with the oil phase “highly” after entering the pores. The mixed microbubbles can not only produce “plugging” effect, increasing the seepage resistance of the main channel, but also promote the subsequent fluid to change direction and enter the small pores that are not swept by water drive or gas drive, with obvious effect of expanding the swept volume. And it can significantly displace the remaining oil at the edges and corners, and even recover all the residual oil in the blind end. The oil recovery efficiency of water drive, gas drive and water gas dispersion system drive is 71.6%, 82.0% and 91.0%, and water gas dispersion system plays a prominent role in improving oil displacement efficiency.

Optimization of Pressure-bearing and Plugging Drilling Fluid System in Mahu 401 Well Area

ZHOU Zenan, WANG Luyi, RONG Kesheng, REN Tao, LIU Xinguo

2025, 47(3):  124-134.  DOI: 10.11885/j.issn.1674-5086.2023.05.17.06

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This paper focuses on the problems such as “leakage before flowback” and “leakage in the same layer” when drilling in the horizontal member of Sankai Baijiantan Formation in Mahu 401 Well area, which makes it difficult to greatly improve the pressure bearing capacity. It is found that the Baijiantan Formation has the characteristics of strong permeability and micro-fracture development, and it is easy to produce micro-cracks with the increasing well depth, stress and external force. After the intrusion of drilling fluid filtrate into the well wall, micro-cracks continue to expand, resulting in frequent complications such as well loss. Considering that the crack width of the sampled core of Baijiantan Formation in Mahu 401 Well Area ranges from 1 to 30 μm, multi-micron grade plugging materials are used for optimization, and combined with the optimization of other treatment agents, a set of pressure plugging water-based drilling fluid system and supporting construction technology suitable for this well area are established. The application shows that the maximum leakage velocity, leakage volume and plugging times of the test well are significantly reduced, which indicates that the plugging material has formed an effective sealing and plugging slug, thus improving the pressure bearing capacity of the formation, and its leakage prevention and plugging effect is remarkable.

Design Optimization of Mixed Gas Source Natural Gas Pipeline Network for Collaborative LNG and PNG Supply

ZHENG Zhuo, ZHOU Jun, ZHANG Shuzhong, LI Xiaoxiao, LIANG Guangchuan

2025, 47(3):  135-144.  DOI: 10.11885/j.issn.1674-5086.2024.09.04.04

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China' vigorous promotion of the construction of LNG import and LNG receiving stations, will from will form a natural gas pipeline network structure mainly for LNG and PNG supply in coastal cities. This research is aimed at the problem of collaborative LNG and PNG supply of natural gas pipeline network design optimization. On the basis of pipeline network design optimization, the influence of collaborative LNG and PNG supply on the pipeline network is included in the constraints, and the lowest annual equivalent cost is the objective function to establish a general MINLP model for the design and optimization of the natural pipeline network of the mixed gas source of LNG and PNG. Taking a coastal area as an example, two solution strategies, hierarchical optimization and overall optimization, are proposed to solve the above model. In the first stage of hierarchical optimization, the layout optimization will take the minimum flow length and the objective function line, and the mathematical programming solver GUROBI for solution, and in the second stage, the mathematical programming solver CONOPT is used. The overall optimization uses incremental piecewise linearization to linearize the pressure drop constraint, and the mathematical programming solver DICOPT for solution. Finally, two pipeline network design schemes of hierarchical optimization and overall optimization were obtained. The analysis found that the overall optimization solution time was longer than that of hierarchical optimization. The annual equivalent cost of overall optimization was reduced by RMB 7.4916 million per year, a decrease of 1.41%, which verified the reliability of the established general model, and can provide a reference for the design of the natural gas pipeline network for the collaborative supply of LNG and PNG.

The Development and Evaluation of Leakage Source Localization Model in Natural Gas Stations Based on TDLAS Methane Detector

CHEN Xuezhong

2025, 47(3):  145-155.  DOI: 10.11885/j.issn.1674-5086.2024.12.24.02

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In the operation of natural gas stations, emergency response to sudden gas leakage accidents highly depends on the accurate acquisition of critical information such as leakage location and volume. Currently, most natural gas stations are equipped with TDLAS methane detectors capable of sensing minor leaks. However, due to the absence of integrated gas plume tracking and search algorithms, autonomous leakage source identification remains unachievable. To address this issue, this study established a global source model based on real-time concentration (GSRC) and a spherical source model based on real-time concentration (SSRC), with their effectiveness and advantages evaluated through numerical simulations and field tests. The results demonstrate that the GSRC and SSRC models, based on real-time gas plume concentration and search algorithms, enable cloud-based laser methane detectors to autonomously search and locate leaks. Furthermore, key model parameters were determined through in-depth analysis of influencing factors. Meanwhile, a full-scale CFD leakage dispersion model was developed for a natural gas station in western China, and the simulation found that the SSRC model has the smallest search path length and average search time, and the highest search efficiency. Field tests conducted after embedding the SSRC model into the detector's industrial control platform revealed that 86% of leakage incidents (within 10~60 m³/h leakage rates) could be located within 4 min, with positioning errors ≤2 m in 44% of cases and ≤ 4 m in 72% of cases. The developed leakage source search models significantly enhance localization accuracy, providing critical technical support for emergency response and recovery operations.

Integrity Risk Assessment and Countermeasures for Gas-coal Cooperative Exploitation of Sulfur Gas Wells

GUO Runsheng, YU Xiaozhong, GAO Fei

2025, 47(3):  156-169.  DOI: 10.11885/j.issn.1674-5086.2022.11.05.01

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Coal mining disturbance and formation subsidence in Ordos Basin seriously threaten the wellbore integrity of adjacent natural gas wells, resulting in nearly 30% of production Wells in the development zone facing the risk of underground and surface leakage of natural gas, which brings huge security risks to the production of natural gas and coal mines in this region. In order to effectively reduce the safety production risks of natural gas wells in coal mining areas, based on the analysis of factors affecting wellbore integrity, the coupling model of structural unit elements and potential risk factors of wellbore integrity is constructed by using WBS-RBS matrix, and the index system of wellbore integrity risk evaluation is established. The combined weight coefficient is determined by analytic hierarchy process and entropy weight method. Based on the regret theory, the wellbore integrity risk assessment model is established to determine the main controlling factors and risk levels of natural gas wells in coal mining areas. The model validation analysis was carried out with Well PG14 as an example, and corresponding management countermeasures were proposed. The results show that the results of wellbore integrity risk assessment based on regret theory are basically consistent with field practice, indicating that the method is feasible in the field of natural gas well integrity risk assessment in coal mining areas, and can effectively improve the objectivity of evaluation results, so as to guide the integrity risk management of natural gas wells in coal mining areas.

PETROLEUM MACHINERY AND OILFIELD CHEMISTRY

Numerical and Experimental Study of Coriolis Flowmeter Based on Fluid-structure Interaction

XI Zhandong, DENG Yong, XIONG Ming, ZHAO Huaigang, ZHOU Zhaoming

2025, 47(3):  170-178.  DOI: 10.11885/j.issn.1674-5086.2022.11.27.01

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The vibration characteristics of the Coriolis mass flowmeter in the fluid-structure coupling state were studied in order to solve the metering error problem. Taking a typical CMF300 Coriolis mass flowmeter in a pipeline station as an example, the fluid-structure coupling modal vibration analysis and experimental study of Coriolis flowmeter are carried out by using ANSYS finite element method. The results are as follows: 1) the calculated natural frequency of the second order mode is the excited frequency of Coriolis mass flowmeter, and the natural frequency of the sixth order mode is the Coriolis force frequency; 2) the excitation frequency of finite element modal analysis is 80.043 Hz, and that of experimental test is 83.820 Hz; 3) the excitation frequency and driving frequency of CMF300 are tested, and the experimental results are in good agreement with the finite element model; 4) the numerical model and modal test method can obtain the actual natural frequencies of different Coriolis mass flowmeters at each station. The research conclusion provides a theoretical basis for eliminating the external interference to the metering error of the flowmeter.

Research and Application of Foam Plugging in Horizontal Wells Steam Flooding of Offshore Oilfield

TANG Xiaoxu, WANG Cheng, HAN Xiaodong, YUAN Yujing, REN Lei

2025, 47(3):  179-186.  DOI: 10.11885/j.issn.1674-5086.2023.07.28.01

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Foam plugging can improve steam profile and expand steam sweeping area, which is an effective measure to improve the development effect of steam flooding. In view of the characteristics of steam flooding of N Oilfield in Bohai, such as complex offshore environment, high operation and construction risk, and difficulty in plugging for horizontal wells with large spacing, the research on foam plugging for steam flooding in offshore horizontal wells with large well spacing was carried out. The key performance indexes of high temperature resistant foaming agent were evaluated through laboratory experiments. The RFA-1 foaming agent can withstand temperature up to 350 ℃, and the resistance factor can reach 44 in high temperature environment, which has good plugging and adjusting performance. The field tests verified the effectiveness of foam plugging to improve the development effect of steam flooding. Foam plugging can effectively control water and improve steam profile. In application, the water cut of the cross-flow well decreased significantly from 81.7% to 47.0%, and the oil was increased by about 800 t.