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26 October 2022, Volume 12 Issue 5
  • Electricity substitution technology of drilling and completion electrification promote petroleum and gas industry to achieve “carbon peak and neutrality” targets
    ZHANG Liehui,ZHANG An’an,CHEN Yi’n...
    2022, 12(5):  703-710.  doi:10.13809/j.cnki.cn32-1825/te.2022.05.001
    Abstract ( 79 )   HTML( 48 )   PDF (7021KB) ( 48 )   Save

    In recent years, extensive attention has been paid to the decarbonization of petroleum and gas exploration and related technologies at home and broad. The structural transformation of the energy industry of the oil and gas is one of the inevitable ways for China to achieve the “carbon peak and neutrality” targets. Under the prerequisite of energy reform to accelerate the achievement of the targets, the energy reform direction and pathway for the oil and gas technology have been analyzed. Taking the project of the electricity substitution technology in the PetroChina Southwest Oil and Gasfield Company as an example, the changes in terms of environmental pollution and energy consumption before and after the implementation of the project are compared. Then, it focuses on the necessity of the drilling and completion electrification transformation and the advantages of the drilling and completion are emphasized. Based on the analyses and summary of the key and difficulties in the practice process, the key technologies that restrict the development of electricity substitution technology and the breakthrough points of the future researches are put forward, which provides reference for the application of “electricity substitution” technology in oil and gas exploration and development under the “dual-carbon” targets.

    Engineered full flowsheet technology of CCUS and its research progress
    SANG Shuxun,LIU Shiqi,LU Shijian,ZHU Qianlin,WANG ...
    2022, 12(5):  711-725.  doi:10.13809/j.cnki.cn32-1825/te.2022.05.002
    Abstract ( 67 )   HTML( 87 )   PDF (2837KB) ( 87 )   Save

    Cluster deployment is the only way to realize the decarbonization industry development for the carbon capture, utilization and storage (CCUS) technology. The innovation and development for the engineered full flowsheet technology of CCUS is the key and urgent need to complete the scale deployment of CCUS decarbonization industry cluster, serving great significance to China’s energy security and carbon neutrality. In this study, the scientific connotations are clarified. The concept is proposed. The basic mode, application mode and key combination mode are firstly summarized, then the technologically scientific process is analyzed. The key techniques are summarized. The formation mechanisms are investigated. The representative project cases both at home and abroad are summarized. The current challenges and outlook are discussed and analyzed. Current works have shown that the efficient CO2 capture technology, CO2 chemical and bio-utilization, CO2 mineralization, efficient CO2 geological utilization and storage are the core connotation, with CCUS system optimization, source-sink matching and technology matching as the configuration mechanisms. The full flowsheet technology of CCUS is complex and diverse, with five main steps composing in its technical and scientific process. The framework of this technology has been established, and a lot of progress has been made in the field of scientific research and engineering applications. However, there is still a gap between China and developed countries in Europe and America in this field. The main direction of tackling challenges in China includes: accelerating the engineering demonstration of CCUS cluster scale deployment, strengthening the formation mechanism of the engineered full flowsheet technology of CCUS cluster scale deployment technology and scientific research, focusing on the breakthrough of CO2 capture, geological storage, and other key technical links among the engineered full flowsheet CCUS technology.

    Research progress of assistants for reducing CO2-crude oil minimum miscible pressure
    GUO Ping,ZHANG Wanbo,JIA Na,CHEN Fu,LIU Huang,WANG...
    2022, 12(5):  726-733.  doi:10.13809/j.cnki.cn32-1825/te.2022.05.003
    Abstract ( 31 )   HTML( 29 )   PDF (3093KB) ( 29 )   Save

    The minimum miscible pressure (MMP) of CO2 flooding is a crucial parameter to judge whether miscible flooding is attainable. In order to reduce the application threshold of miscible flooding, the MMP between CO2 and crude oil needs to be reduced urgently. Adding miscible flooding assistants to oil reservoir is an effective means for minimum miscible pressure reduction. At present, according to the elements contained, the miscible flooding assistants can be divided into three categories including fluorocarbon, siloxane, and hydrocarbon (oxygenated). In order to reduce the cost and improve the MMP reduction performance, the hydrocarbon structure should be added to the fluorocarbon assistants to make the assistants develop in the direction of mixing type. The hydrocarbon assistants have sound MMP reduction performances and room for improvement. The key is to find a suitable CO2-phlic structure. Computer simulation is also a vital means to study micro mechanism and assist structure designing. Compared with fluorocarbon and siloxane, the cost of hydrocarbon (oxygenated) is lower, and it has the most application potential from the prospective of cost. At present, the main factor affecting the large-scale application of miscible assistants is the limitation of cost. The promotion and application in the future needs the close cooperation of petroleum and chemical practitioners. In this paper, the mechanisms of CO2 miscible flooding assistants reducing MMP are introduced. The structures of existing miscible flooding assistants, MMP reduction effectiveness are summarized, and the influencing factors on MMP reduction efficiency are analyzed. The developing directions CO2 miscible flooding assistants designing are prospected.

    Mechanism and calculation model of EOR by CO2 flooding
    WANG Gaofeng,LIAO Guangzhi,LI Hongbin,HU ZhiMing,W...
    2022, 12(5):  734-740.  doi:10.13809/j.cnki.cn32-1825/te.2022.05.004
    Abstract ( 44 )   HTML( 43 )   PDF (1466KB) ( 43 )   Save

    The proved reserves of natural gas in place in China is huge. However, realizing the long-term large scale stable production of natural gas faces a series of challenges such as enhanced gas recovery(EGR) of complex gas reservoirs, especially for those unconventional resources such as shale gas, coalbed methane and tight sand gas. Under the background of carbon neutralization, CCUS-EGR technology has broad application prospects due to owing the functions of increasing gas rate and carbon reduction. The main EGR mechanisms for CO2 flooding are summarized into three types: substitution due to dominant adsorption of carbon dioxide, continuous convective displacement and gas reservoir energy supplement. Under the consideration that the classification of occurrence states of the adsorbed, free and dissolved natural gas are applicable to all types of the gas reservoirs. The prediction method of increased natural gas ultimate recovery factor by CO2 flooding is further deduced. It is found that CO2 flooding is expected to improve shale gas recovery of more than 20 percentage points by this method. In order to break through the technology of greatly improving natural gas recovery, it is suggested to evaluate the potential of CO2 flooding to improve natural gas recovery for gas reservoirs with good geological sequestration conditions, assess the economic feasibility of CCUS-EGR technology applying in target gas reservoirs, and carry out major pilot tests of CO2 flooding in various types of gas reservoirs. The synergistic displacement effect of flue gas components and the technology of expanding CO2 sweeping volume should be focused especially.

    Prediction method of migration law and gas channeling time of CO2 flooding front: A case study of G89-1 Block in Shengli Oilfield
    CUI Chuanzhi,YAN Dawei,YAO Tongyu,WANG Jian,ZHANG ...
    2022, 12(5):  741-747.  doi:10.13809/j.cnki.cn32-1825/te.2022.05.005
    Abstract ( 29 )   HTML( 12 )   PDF (2977KB) ( 12 )   Save

    CO2 gas channeling time prediction is of great significance for CO2 gas channeling prevention and enhanced oil recovery. Current studies rarely involve quantitative characterization of the gas channeling time. According to the parameters of the target block reservoir, the crude oil viscosity, reservoir permeability, gas injection rate and injection-production well spacing and other factors impact on the moving rule of the CO2 drive front is analyzed by the numerical simulation method, then the characterization formula of gas flow time and gas flow influence coefficient considering multiple factors is established, and the accuracy of the formula is verified by comparing with the field practice. The results show that under the condition of constant pressure production, the sweep efficiency decreases with the increase of crude oil viscosity. When the crude oil viscosity is greater than 3 mPa·s, the increase of gas emergence time slows down. When the reservoir permeability increases, the seepage resistance decreases, the displacement front moves faster, and the oil well breaks out earlier. When the gas injection velocity increases, the leading edge movement speed increases and the gas appearance time advances. When the gas injection velocity is 2 500 m3/d, the sweep efficiency is the minimum. When the injection-production well spacing increases, the moving speed of gas front slows down, and the gas emergence time of oil well prolongs. When the injection-production well spacing is larger than 250 m, the well spacing continues to increase, and the sweep efficiency increases slightly.

    Prediction model of minimum miscible pressure in CO2 flooding
    PAN Yi,ZHAO Qiuxia,SUN Lei,LIU Jiang,WANG Tao,GUO ...
    2022, 12(5):  748-753.  doi:10.13809/j.cnki.cn32-1825/te.2022.05.006
    Abstract ( 25 )   HTML( 18 )   PDF (1450KB) ( 18 )   Save

    Based on the analysis of the factors influencing the minimum miscibility pressure in CO2 flooding and 36 groups of tubule experimental data, the correlation degree of each factor influencing the minimum miscibility pressure in CO2 flooding of crude oil is calculated by the grey correlation method. The prediction model of minimum miscible pressure in CO2 flooding for crude oil is fitted by the MATLAB (Matrix Laboratory) software, which is related to the reservoir temperature, relative molecular weight of C5+, volatile hydrocarbon component (N2+CH4) content and intermediate hydrocarbon component (CO2+H2S+C2—C4) content. The fitting correlation coefficient reaches 0.900 9. The data of the minimum miscible pressure test of three wells in an oilfield are used to verify the new prediction model. The average error of calculation is 3.57 %, which can be used to guide the field development of the reservoirs.

    Mathematical model and numerical analysis for leakage of fluid along geological fault during CO2 storage
    ZHANG Lisong,JIANG Menggang,LI Wenjie,ZHANG Shiyan...
    2022, 12(5):  754-763.  doi:10.13809/j.cnki.cn32-1825/te.2022.05.007
    Abstract ( 25 )   HTML( 24 )   PDF (2072KB) ( 24 )   Save

    The leakage of fluid (CO2, brine and freshwater) along fault is a crucial issue that cannot be ignored during CO2 geological storage. For this reason, the equations to describe the fluid leakage rate along faults in different stages are derived. Then, these equations are combined with mass and energy conservation equations to establish the fluid leakage model in CO2 storage processes by considering geologically activated faults. In such case, the crucial parameters (i.e., leakage time and leakage amount) for fluid leakage along a fault are obtained. The results of the effects of different parameters on leakage time and amount show the advanced initial time of CO2 leakage, the extended duration and the increased leakage amount of CO2, with CO2 injection rate and reservoir permeability increasing. Meanwhile, the initial time and duration of CO2 leakage are unchanged while the leakage amount of CO2 is increased, when increasing the fault permeability. In addition, the fault permeability has the greatest impact on the leakage amount of brine and freshwater, compared to CO2 injection rate and reservoir permeability. The numerical results show that brine starts to leak earliest, followed by CO2, freshwater. Meanwhile, the duration of CO2 leakage along a fault is the longest, while the duration of brine leakage is the shortest. Additionally, the leakage amount of CO2 is the largest, followed by brine leakage amount and the freshwater leakage amount.

    Laboratory experiment of front migration and gas channeling of CO2 immiscible flooding
    KONG Weijun,CUI Chuanzhi,WU Zhongwei,LI Lifeng,SU ...
    2022, 12(5):  764-776.  doi:10.13809/j.cnki.cn32-1825/te.2022.05.008
    Abstract ( 27 )   HTML( 14 )   PDF (3630KB) ( 14 )   Save

    Currently, there are few works on the laws of front migration and gas channeling with laboratory experiments from the aspect of CO2 sweep efficiency. Therefore, a visual physical simulation device is used to carry out the physical simulation experiment of CO2 immiscible flooding of slab core. The influences of factors such as crude oil viscosity, reservoir permeability, reservoir heterogeneity and injection rate on the migration of CO2 immiscible flooding front and gas channeling laws are analyzed. The study found that under the conditions of constant flow injection in injection wells and constant pressure production in production wells, the viscosity of crude oil decreases, the permeability decreases, the reservoir is homogeneous, and the injection speed increases, which will lead to an increase in the recovery degree of CO2 immiscible flooding. Meanwhile, the decrease in the viscosity of crude oil, the lower the permeability, and the increase in the injection rate, also lead to the enhancement of the ability of the oil well to continue to expand sweep factor after gas breakthrough, that is, it can alleviate gas channeling. It is concluded that under the condition of constant flow injection in injection wells and constant pressure production in production wells, high injection rate development can alleviate gas channeling and obtain better development results. When the injection rate increased from 0.1 mL/min to 2 mL/min, the recovery increased from 15.4 % to 35.3 %, and the sweep factor difference increased from 8.3 % to 26.2 %. This research is of great significance for CO2 immiscible flooding gas channeling suppression and enhanced oil recovery.

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