• Volume 27,Issue 2,2020 Table of Contents
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    • >ACADEMIC DEBATE·
    • Comment on inaccuracy of relational expression of excess adsorption capacity and absolute adsorption capacity

      2020, 27(2):1-6. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.001

      Abstract (1265) HTML (13) PDF 416.52 K (1112) Comment (0) Favorites

      Abstract:The shale adsorption gas and coalbed adsorption gas are important unconventional natural gas resources. The evaluation of such resources depends on the calculation of the isothermal cumulative adsorption capacity and the determination of the isothermal saturated adsorption capacity under different pressures. The isothermal cumulative adsorption capacity under different pressures needs to be obtained by the relevant calculation methods based on the test data from the adsorption apparatus. Based on the uncertainty of Adamson’s equation of solid-phase adsorption capacity presented in 1976,Donohue and Aranovich cited Adamson’s adsorption equation,and proposed the excess and absolute adsorption capacities and their relational expression that were incorrect in 1998. The excess and absolute adsorption capacities and their relation? al expression proposed by Donohue and Aranovich are cited and confirmed in the paper published by ZHOU Li et al. in 2000,which were also incorrect. From 2015 to 2018,YU Lingjie and other relevant experts followed the relational expression of the excess adsorption capacity and absolute adsorption capacity proposed by ZHOU Li et al. and published many papers in some key Chinese journals. Through the tracking research and comparative analysis in this paper,it is concluded that the excess adsorption capacity and absolute adsorption capacity are two pseudo-words lack of physical definition and use value,and the relational expression of the two is also incorrect. Using the relational expression of the excess adsorption capacity and absolute adsorption capacity,the isothermal adsorption capacity,the isothermal cumulative adsorption capacity,and the isothermal saturated adsorption capacity cannot be obtained at all.

    • >Petroleum Geology
    • Shale oil resource evaluation in complex structural belt of superimposed basin:A case study of middle Permian Lucaogou Formation in Bogda area,southeast margin of Junggar Basin

      2020, 27(2):7-17. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.002

      Abstract (1101) HTML (8) PDF 1.32 M (975) Comment (0) Favorites

      Abstract:The shale oil is the liquid hydrocarbon trapped in various pores of source rock strata,and the studies on the influence of the preservation conditions of different zones on the shale oil loss and its quantitative characterization are inadequate during the shale oil resource evaluation at present. The evaluation of shale oil resource in complex structural areas is of great practical significance to guide shale oil exploration in superimposed basin that experienced multiple tectonic movements in western China. Therefore,taking the shale oil of the Middle Permian Lucaogou Formation in Bogda area,the southeast margin of Junggar Basin as an example,based on the detailed anatomy of geological structure and the division of the preservation evaluation unit,and according to the outcrop section and total organic carbon(TOC)content of the drilling rock sample,pyrolysis hydrocarbon S1 and the measured data of extraction of chloroform bitumen“A”,the relative weight assign? ment quantitation models of preservation coefficients of shale oil in different preservation evaluation units and different lithofacies are established to quantitatively characterize shale oil loss degree in different evaluation unit. Based on the calculation of original shale oil resources,the amount of residual shale oil resources is determined. The results show that:①There are four types of preservation evaluation units in Bogda area,including sag area,structural stability area,thrust transformation area,and surface outcropping area. The oil content of rocks in different units decreases with the increase of tectonic deformation strength and the deterioration of preservation conditions;②The reservoir space type and the pore structure of shale oil reservoir control the difference of TOC and oil content between mudstone and sandstone lithofacies. There is a power function relationship between mudstone and sandstone,and a linear relationship between mudstone and sand? stone shale oil;③Based on the quantitation models of TOC and oil content of shale oil of mudstone and sandstone shales in different preservation and evaluation units,the quantization of the relative weight assignment of preservation coefficient by units and lithofacies is achieved,which lays a foundation for the scientific evaluation of the amount of residual shale oil resources in the tectonic reconstruction area;④Bogda area has abundant shale oil resources. Qitaizhuang,the middle and north of Chaiwopu Sag are favorable shale oil exploration targets,and sandstone shale oil in Lu3 Member is the main exploration interval and target.

    • Origin and evidence of calcite in shale oil reservoir of Dongying Sag

      2020, 27(2):18-25. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.003

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      Abstract:In order to clarify the origin of calcite minerals and the diagenetic characteristics of reservoirs in Dongying Sag,the calcite veins in Well Niuye1 are analyzed with thin section,X-ray diffraction and carbon-oxygen isotope. It is discovered that they can indicate top-bottom structure and have mechanical twin crystals characteristics,which provides the evidence that they are products of the in-situ stress generated by geological tectonic movement acting on the shale,and they provide carrier minerals for the study of in-situ stress in shale formation. Through comparative analysis of carbon and oxygen isotopes of micrite calcite and sparry calcite in shale of the study area,it is found that micrite calcite in shale mainly belongs to carbonate related to biogas generated by methane bacteria. The sparry calcite veins are likely to be the product of precipitation and recrystallization of the mudstone calcite after dissolution. The micro-fractures caused by hydrocarbon generation and pressurization are the prerequisite for the formation of the calcite veins,and the dissolution and reprecipitation of argillaceous calcite by organic acid is a necessary condition. Based on the four petrological characteristics and the carbon-oxygen isotope,the syngenetic evolution of the hydrocarbon-generating pressurization,micro-fracture formation,organic acid discharged from thermal evolution of organic matter,dissolution of micrite calcite,recrystallization of calcite,and formation of calcite veins are described. The source of carbon pool of shale and adjacent sandstone and the process of synergistic diagenesis of sandstone and mudstone are discussed as well.

    • Control of slope break zone on sandy debris flow deposition:A case study of Jurassic Sangonghe Formation in west sag of Well Pen-1 and its periphery in Junggar Basin

      2020, 27(2):26-34. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.004

      Abstract (656) HTML (14) PDF 4.15 M (968) Comment (0) Favorites

      Abstract:In recent years,there has been no significant breakthrough in the exploration of Sangonghe Formation in the west sag of Well Pen-1 and its periphery in Junggar Basin. The analysis shows that the insufficient understanding of the favorable reservoir distribution rules restricts the exploration process in this area. Based on the previous research work and the core,logging and seismic data,the palaeogeomorphology before sedimentation of Sangonghe Formation is restored. Then,the geological characteristics of deep-water sediments are systematically analyzed,and the control of paleogeomorphology on the sedimentary system is summarized. The results show that the typical deep-water sandy debris flow deposit is developed in Sangonghe Formation of the central area in the west sag of Well Pen-1,there are thick-massive sandstones with floating mud-gravel and argillaceous tear debris in the reservoir,and the top/bottom abrupt contacts are common. Four sedimentary units,such as underwater low uplift,underwater gully,slope and deep-water sag are developed before sedimentation of Sangonghe Formation. Two-stage slope break zones in the slope area,which obviously controls the sedimentary system. There are two-stage slope break zones in the slope area,which obviously control the sedimentary system and by which the research area is divided into shallow-water delta front,prodelta,and shallow lake-semi-deep lake facies. The sandy debris flow is developed in the shallow lake-semi-deep lake sedimentary zone in the west of M17-QS1. The exploration practice has proved that the sandy debris flow reservoirs have good physical properties,a relatively large oil and gas reservoir can be formed in the case of good oil and gas source and matching conditions,which is the best field for exploration prospect of“lower sag”in the west sag of Well Pen-1.

    • Characteristics of strike-slip faults and its control on hydrocarbon accumulation in Changdi area of Jiyang Depression

      2020, 27(2):35-42. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.005

      Abstract (1011) HTML (4) PDF 6.86 M (1783) Comment (0) Favorites

      Abstract:A large number of buried hill oil reservoirs are developed in the inner uplifts of Jiyang Depression. However,hydrocarbon accumulates in shallow layers instead of the low uplift in Changdi area. At present,research on the genetic mechanism of hydrocarbon accumulation is insufficient in this area. The structure is an important factor controlling the hydrocarbon accumulation. For this reason,based on the detail seismic data interpretation and hydrocarbon geochemical data analysis,the characteristics of the strike-slip faults and their control on the hydrocarbon are analyzed. The results show that Changdi fault is formed in the Cenozoic,with obvious dextral strike-slip. The middle part of Changdi fault is pressurization flexure in“S”shape of the strike-slip fault caused by pressure increasing,the fault plane is tightly closed,and the strata are compressed and uplifted to form small anticlines and fault-nosed traps. The southern and northern part of Changdi fault is depressurization flexure in“S”shape of the strike-slip fault caused by pressure releasing,the fault plane is opened and destroys the early traps,which is not conducive to hydrocarbon accumulation. The hydrocarbon accumulation mode in strike-slip compressed sections in Changdi low uplift is mainly characterized by shallow hydrocarbon accumulation,multihydrocarbon sources supply and multi-transportation pathways.

    • Diagenesis characteristics and evolution of porosity of Chang7 tight sandstone reservoir in Dingbian Oilfield,Ordos Basin

      2020, 27(2):43-52. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.006

      Abstract (723) HTML (5) PDF 4.33 M (986) Comment (0) Favorites

      Abstract:Chang7 reservoir in Dingbian Oilfield of Ordos Basin has abundant oil reserves,but its tightness and anisotropy restrict the effective exploration and development. Based on thin section,scanning electron microscope(SEM)analysis,the rock compositions,pore types,physical properties,and diagenesis of Chang7 tight reservoir are studied. The porosity evolution model of tight sandstone reservoir are established at Chang7 by using the diagenetic evolution events and geological comprehensive response,to clarify the evolution of diagenesis and porosity. Meanwhile,influences of diagenesis at different depths on the porosity are compared,which provides a theoretical basis to explore the relatively dominant reservoirs in the study area. The results show that:The clastic rocks of Chang7 tight reservoirs in the study area are mainly feldspar sandstone and feldspar lithic sandstone,mainly containing clay minerals,carbonate,and other cement. The effective pore types are mainly secondary dissolved pores and residual intergranular pores,indicating a typical tight sandstone reservoir with ultra-low porosity and ultra-low permeability. The diagenetic evolution of Chang7 reservoir in the study area has gone through stages of rapid compaction-early cementation,cementation-early dissolution,mainly dissolution-pore increase,compaction-late cementation,etc. This suggests that Chang7 oil reservoir in the research area is currently in the middle diagenetic stage A. Compaction is the main controlling factor leading to pore decrease and tight reservoir formation,with an average pore reduction of 20.4%. The average pore reduction by cementation is 14.02%,and the cementation in the late stage is the key to form tight reservoirs. The dissolution increases the porosity by 5.87% on average,which delays the densification. The sandstone compaction and cementation in the bottom of Chang71 and middle of Chang72 are relatively weak,and the dissolution increasing pore volume is relatively strong,which indicates a preferred reservoir for exploration and development in this area.

    • Method for exploration target optimization in blank region of main oil-bearing beds in mature exploration area-A case study of Es3 Member in south slope,Bonan Subsag

      2020, 27(2):53-61. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.007

      Abstract (1053) HTML (4) PDF 1.22 M (852) Comment (0) Favorites

      Abstract:The exploration of Jiyang Depression has reached in mature or over-mature stage. In view of the increasing of reserve blank area of main oil-bearing beds in mature exploration area,a method,which is suitable for optimizing petroleum exploration target in the main oil-bearing beds of mature exploration area,is established focusing on the Es3 Member in south slope,Bonan Subsag being defined as“seven-step processes”. This method is used to predict the potential of remaining resources in the blank area under the guidance of the“Pareto Geological Probability Model”,and the lithologic structural reservoir is determined as the main exploration target in the south slope according to“Oil and Gas Reservoirs Orderly Distribution”theory. On the basis of fine dissection on“structure,provenance,sedimentation and reservoir”,a fine geological model with multi-source,multi-fan and multi-stage superimposition in blank area is established for the Es3 Member in the south slope,Bonan Subsag. The statistical analysis of reservoir-forming conditions in“9 pictures and 1 table”of mature exploration area is carried out at the same time. The reservoir-forming characteristics of the Es3 Member in the south slope,Bonan Subsag are sorted out,including migration with sand,layer-by-layer distribution,fault sealing,and enrichment with excellent facies. Through comparison of the“positive-negative ratio”between successful and unsuccessful exploration wells,the three major failure reasons for undeterminable reserves are undeveloped reservoir,unsealed fault,and inaccurate oil height. Targeted research is carried out to establish the key technologies in reserve blank area,including the fine reservoir modeling,fault sealing evaluation and prediction of trap oil-bearing height. Through quantitative characterization of reservoir-forming factors,favorable traps are optimized,and exploration deployment is carried out for key targets,and good exploration results are achieved.

    • Sedimentary forward numerical modeling at different sedimentary scales:Progress and hydrocarbon significance

      2020, 27(2):62-71. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.008

      Abstract (1584) HTML (5) PDF 1.13 M (1021) Comment (0) Favorites

      Abstract:Sedimentary forward numerical modeling is a key method to study depositional processes supported by numerous numerical models. However,the model selection and application are difficult. This review summarized model features,including sedimentary time scales,driving mechanism,channel evolution,following rules,sedimentary outcomes,and applicable objects. The mathematical principles,parameter selection,simulation outcomes and restrictions of Delft3D and DIONISOS are illustrated as well. It shows that the sequence evolution controlled by lake level change hierarchy correspond to the sedimentary scales. Combining the characteristics of sediment components and simulation objectives is the basic principle of optimizing the numerical model. The well-seismic data and geological modeling algorithm are the necessary means to verify and optimize the training model. The deep-learning and reinforcement-learning numerical models based on big data and AI are main trends for sedimentary forward numerical modeling.

    • Controlling mechanism of antithetic fault and reverse fault on hydrocarbon accumulations in Tamtsag Basin

      2020, 27(2):72-79. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.009

      Abstract (848) HTML (20) PDF 946.49 K (797) Comment (0) Favorites

      Abstract:Tamtsag Basin is an important overseas hydrocarbon production base of Daqing Oilfield. Based on the dynamic properties and the tectonic evolution characteristics of the tectonic movement in the basin,the basin is divided into three structural strata from the bottom to the top,including fault-depression,fault-depression transformation,and depression.During the fault-depression,the passive rifting titled and uplifted the strata,to form a large number of antithetic faults which were opposite to the stratigraphic tendency. At the end of the deposition of Yimin Formation,the basin was strongly reversed under the action of regional compressive and torsional stress field,and many faults were formed with extension,compression,and torsion step by step. By analyzing the types and distribution of drilled hydrocarbon reservoir in the basin, it is believed that antithetic faults and reverse faults control the hydrocarbon accumulation.According to the configuration relationship of source-reservoir-caprock association,the basin is divided vertically into upper,middle,and lower three sets of hydrocarbon systems. The distribution of hydrocarbon in different systems is complementary,the lower hydrocarbon system dominated by the first member of Nantun Group is the most important producing layer,and the reservoir type is mainly blocked by reverse fault. In the plane,hydrocarbon distributions are controlled by faults. Hydrocarbon is mainly arranged as a“strip”along the antithetic fault in the lower system and gathered near the reverse fault in the upper system. By analyzing the controlling mechanism of antithetic faults and reverse faults,two kinds of hydrocarbon accumulation mode are summarized,including the lower uplift hydrocarbon accumulation backed by antithetic fault and the secondary hydrocarbon accumulation controlled by the reverse fault in research area.

    • Identification of effective fractures in tight clastic reservoirs in Hilbert space

      2020, 27(2):80-86. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.010

      Abstract (1019) HTML (4) PDF 597.70 K (731) Comment (0) Favorites

      Abstract:Fractured tight clastic rock is an important hydrocarbon reservoir,and identification and prediction of its fracture development section is important. Research indicates that the principal component analysis method is effective in fracture identification. In order to further improve the defect of principal component analysis in dealing with data non-linear structure,the method is projected into the Hilbert space,to form the kernel principal component analysis(kernel PCA)utilizing the kernel function,which effectively improves the ability of non-linear data analysis and the accuracy of data extraction and identification. The effective fractures of the tight clastic reservoir of Shanxi Formation in south Qinshui Basin are identified. The cumulative contribution rate of the principal component 1 and 2 is increased to 94.800%,which is 6.240% higher than that of the traditional principal component analysis(PCA). Using the optimized kernel PCA to identify the effective fractures can more effectively distinguish the fractured stratum and the non-fractured stratum of the dense clastic rock,and can further identify the unfilled,the half-filled,and the full-filled fractured formation,which improves the identification accuracy of the effective fracture in dense clastic rock reservoirs.

    • >Petroleum Recovery Efficiency
    • Progress on synthesis and application of polyhedral oligomeric silsesquioxanes for oil displacement

      2020, 27(2):87-97. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.011

      Abstract (1181) HTML (11) PDF 1.23 M (907) Comment (0) Favorites

      Abstract:Chemical flooding has been paid more and more attention by petroleum researchers for its high cost performance.New functional materials for oil displacement are one of the key issues in chemical flooding. In recent years,a novel monomer for oil displacement functional materials,polyhedral oligomeric silsesquioxane(POSS),has attracted extensive attention of material scientists because of its good three-dimensional structure and excellent physicochemical properties,which makes it an ideal basic unit for constructing organic/inorganic nanocomposite materials for oil displacement. Based on the preliminary work,this paper systematically reviews the synthesis methods of the nano-POSS monomers,and uses these methods to design and synthesize monofunctional,multifunctional and difunctional POSS monomers. These functional monomers are modified,grafted or polymerized to further design and synthesize organic/inorganic nanocomposite materials for oil displacement with powerful functions and various properties. The relationship between the structure and performance of POSS monomers and the application of POSS monomers in tertiary oil recovery are further elaborated. And the development trend and prospect of POSS monomer in new materials for oil displacement are also discussed.

    • Application and prospect of nano-cellulosic materials in the development of oil and gas field

      2020, 27(2):98-104. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.012

      Abstract (1293) HTML (21) PDF 1.98 M (984) Comment (0) Favorites

      Abstract:Materials are the foundation and guarantee for the development of oil and gas reservoirs. Actively drawing on the latest progress in material science,improving the economic benefits of oil and gas resources development,and reducing the pressure on environmental protection are the inevitable requirements and the only way for the development of petroleum engineering. As a high-performance biopolymer material,the nano-cellulosic(NC)material has the advantages of low cost,wide sources,no pollution,and renewable,as well as physical properties such as high strength,low density,strong toughness,and easy modification. It is widely used in the fields of biomedicine,food packaging and photoelectric materials. The latest researches show that the NC material also has broad application prospects in the development of oil and gas reservoirs,and has gradually attracted the attention of Chinese and foreign scholars. The research progress of NC in drilling,fracturing and EOR in recent years has been summarized in detail,and the technical issues and solutions encountered in practical applications have been analyzed in depth. Based on the recent research on NC dispersions,NC high-stability foams,NC emulsions and NC hydrogels,the application potential and development direction of NC materials in oil and gas field development are prospected in the future.

    • Effect of oil-water emulsification capability on oil film displacement

      2020, 27(2):105-111. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.013

      Abstract (757) HTML (14) PDF 2.00 M (975) Comment (0) Favorites

      Abstract:In order to have a better understanding of the mechanism of oil film displacement,the oil film displacement experiments are conducted. Considering the effects of emulsifying speed and emulsification amount,the emulsification index(EI)is used to quantitatively characterize the emulsification capability of the chemical flooding agents. For the low and medium viscosity oil used in experiments,three kinds of oil displacement agents are screened,which have the strong emulsification capability and ultra-low interfacial tension(IFT),strong emulsification capability and low IFT,and weak emulsification capability and ultra-low IFT,respectively. And then,the three kinds of oil displacement agents are used to conduct the oil film displacement experiments based on the glass rod bundle model. For the low viscosity crude oil,the oil film displacement efficiencies of the oil displacement agents with higher emulsification capability(EI are 0.667 and 0.706 respectively)are about 90% no matter the IFT of displacement agents is ultra-low,while the oil film displacement efficiency of the oil displacement agent with weak emulsification capability and ultra-low IFT(EI=0.244)is less than 70%. For the medium viscosity oil,the oil film displacement efficiencies of the oil displacement agents with higher emulsification capability(EI are 0.534 and 0.602 respectively)are about 83% no matter the IFT of oil displacement agents is ultra-low,while the oil film displacement efficiency of oil displacement agent with weak emulsification capability and ultra-low IFT(EI=0.258)is less than 65%. The research results show that the oil film displacement efficiencies mainly depend on the emulsification capability of the oil displacement agents.

    • Optimization of injection-production pattern for polymer flooding in S offshore Oilfield

      2020, 27(2):112-117. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.014

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      Abstract:The plane heterogeneity of S offshore Oilfield is strong. After years of polymer flooding development,areal drainage degrees are heterogeneous,and the effect of water-controlling and oil-increasing is weakened. In particular,the remaining oil distribution after the polymer flooding is complex,so the development effect of oilfield needs to be further improved by optimizing injection-production pattern. According to the relationship between the distribution characteristics of sedimentary facies and well pattern in S Oilfield,the plane heterogeneous conceptual models from the high,medium and low permeability zones are established. Based on the above models,a physical simulation model with the plane permeability ratio of 3 is established. Five groups physical simulation experiments of different well spacing are carried out under the same injection-production conditions. Then the reservoir geological models corresponding to the laboratory physical models at five permeability ratios are established by using the reservoir numerical simulation. Eight simulation schemes of well spacing are designed for each geological model,so that the total number of simulation schemes of well spacing are equal to 40.The experiment results show that when the plane permeability ratio is 3,the cumulative oil production is the highest when the ratio of well spacing is 1.8. And pressure gradients in the low and high permeability reservoirs are basically the same,so microelectrode saturation test shows that the low permeability layer and the high permeability layer are both produced effectively. Through deeper analysis of reservoir simulation results,the optimal well spacing under different plane permeability ratios is obtained. The optimal well spacing ratio gradually increases with the increase of plane permeability ratio. Finally,based on the optimal results,it is concluded that horizontal injection well and vertical production well form the best well pattern through the physical simulation experiment and reservoir numerical simulation.

    • Research on interwell connectivity of oil reservoirs based on Kalman filter and artificial neural network

      2020, 27(2):118-124. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.015

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      Abstract:The understanding of interwell connectivity of oil reservoirs is of great significance for the formulation of reasonable development and adjustment plans and the improvement of water-driven reservoir recovery. Based on dynamic data of injection-production well,an analysis method combining Kalman filter and artificial neural network is established to quantitatively characterize the dynamic interwell connectivity in reservoir. Considering the noise pollution of the injection data and the time-lag effect of the injection signal in the formation propagation process,the Kalman filter algorithm and the nonlinear diffusion filter are used to pre-process the injection-production data,thereby reducing the effect of injection-production data on the machine learning model,and improving the accuracy of connectivity analysis. Based on the pre-processed historical injection and production data,the artificial neural network taking the oil production rates of producers as the response and the water injection rates of injectors as the input is trained and the parameters are optimized,and the interwell communication relationship in the injection and production system is simulated and excavated. Through the parameter sensitivity analysis of the trained model,the degree of interwell connectivity in reservoirs is quantified. The model is applied to analyze the interwell connectivity in four types of reservoirs with representative characteristics such as homogeneity,anisotropy,closed faults,high permeability zones and one real heterogeneous reservoir. The calculation results are highly consistent with the reservoir geological features,indicating that this method has good practicability and reliability. It can be applied to effectively quantify the connectivity of injection and production system.

    • Delaying gelation time of in-situ polymerization gel system based on SR&NI ATRP initiation mechanism

      2020, 27(2):125-130. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.016

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      Abstract:The gelation of the in-situ polymerization gel is rapid and the concentration of active free radical in the polymerization system is hard to be controlled,which are caused by thermal decomposition initiator. In view of this problem,simultaneous reverse and normal initiation ATRP(SR&NI ATRP)is applied to control the gelation time. The ferric trichloride,ligand and sodium chloroacetate are added into the in-situ polymerization gel to convert the mechanism of free radical polymerization into SR&NI ATRP initiation mechanism to control the concentration of free radicals and prolong the gelation time.Experiment results show that the gelation time of the in-situ polymerization gel using thermal decomposition radical initiator is less than ten hours at 50-80 ℃. Compared with EDTA and 1,10-phenanthroline,2,2’-bipyridines is more suitable for the ligand of SR&NI ATRP. The gelation time can be longer than 25 h when its mass fraction is between 0.05% and 0.09% at 60 ℃. In addition,the gelation time of in-situ polymerization gel could be controlled to be greater than 20-40 h by adjusting the mass fraction of ferric trichloride,2,2’-bipyridine and sodium chloroacetate,which could meet the requirements of deep profile control of the in-situ polymerization gel.

    • EOR mechanism of viscosity reducer flooding in heavy oil reservoirs

      2020, 27(2):131-136. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.017

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      Abstract:In order to systematically study the mechanism of enhanced oil recovery(EOR)of viscosity reducer flooding,which is a new development method,a single-tube sand-packed model,a three-dimensional sand-packed model,and a microscopic glass etching model were used to test the oil displacement efficiency and the sweep efficiency of the viscosity reducer flooding,and analyze its causes. The experimental results show that the viscosity reducer flooding enhances oil recovery by increasing the oil displacement efficiency and the sweep efficiency. Compared with water flooding,the viscosity reducer flooding improves the oil displacement efficiency by 13%,and the mechanisms are as follows:①the crude oil is dispersed and emulsified to form small oil-in-water droplets,which is conducive to reducing the apparent viscosity of crude oil through a narrow throat;②the interfacial tension is reduced,the number of capillaries is increased,and the residual oil saturation is reduced. Simultaneously,the viscosity reducer flooding increases the sweep efficiency from 18.8% to 39.9%.The mechanisms are as follows:①emulsion profile control and flooding. The dispersed and emulsified crude oil enters the water channeling channel,which causes the water percolation area to decrease and the resistance to increase,and the subsequent injected liquid enters the previously unswept area;②Jamin effect. The small viscosity-reduced and emulsified oil drops aggregate to form large oil drops blocked at the throat,and the surrounding displacement fluid turns. This study clarifies the EOR mechanism of viscosity reducer flooding,and lays the foundation for the subsequent studies of the development technical limit and field application.

    • Gas production path of coalbed methane reservoir:A case study of Mabidong Block,southern Qinshui Basin

      2020, 27(2):137-142. DOI: 10.13673/j.cnki.cn37-1359/te.2020.02.018

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      Abstract:In order to clarify the gas production path of coalbed methane in the process of drainage,samples that collected from No.3 coal seam of Mabidong Block,southern Qinshui Basin are studied,and the parallel and series experiments composed of fractured and matrix samples are designed to simulate the different combination mode of matrix and fractures. By analyzing the relationship between gas flow rate,core permeability and displacement pressure difference in each case,the mechanism of coalbed methane production at different driving pressure differences is explored. The experimental results show that the coalbed methane follows the series path from the matrix pores to the natural micro-fractures and then to the artificial fractures during the drainage process,and it also follows a parallel path that composed of the matrix,natural micro-fractures and artificial fractures. The production of gas in the series path is mainly affected by the permeability of the matrix,and the production of gas in the parallel path is mainly affected by the artificial fractures. The equivalent permeability of the series path is much lower than that of the parallel path. When the pressure difference across the core is reduced from about 4.5 MPa to 2 MPa,the equivalent permeability of the parallel path is reduced from 30 times to 16 times the equivalent permeability of the series path. Therefore,in the process of drainage of coalbed methane wells,the influence of the parallel path on the production of coalbed methane should be further considered.

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