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01 January 2019, Volume 38 Issue 2 Previous Issue    Next Issue

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Evolution of Diagenetic Fluids in Reservoirs of Esx3 in Jiangjiadian Area of Linnan Sag CAO Yingchang, WANG Xintong, WANG Yanzhong, YANG Tian, CHENG Xin, WANG Sijia 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170201 Abstract ( 89 )   PDF (300KB) ( 120 )   Save Based on the thin section analysis, fluid inclusion summarizing and microthermometry for more than 70 pieces of samples obtained from more than 10 wells in the Jiangjiadian area of Linnan sag, the paper reveals that the Esx3 reservoir of Shahejie formation underwent multi periods of acid-base fluid evolution and hydrocarbon charging during its burial process: 43.7×106 a — 37.0×106 a ago, the formation fluid was weakly alkaline, the diagenesis was dominated by compaction and a few early pyrites occurred; 37.0×106 a— 28.2×106 a ago, the thermal evolution of organic matter led to the acidity of formation fluid, and feldspar dissolution and the first phase of quartz overgrowth took place; 28.2×106 a—24.6×106 a ago, decarboxylation of organic acid as well as dehydration of gypsum bed in the lower Sha-4 member occurred，thus the formation water became alkaline, and carbonate cementation and quartz dissolution were noted; 24.6×106 a—14.0×106 a ago, thermal evolution of organic matter made the formation water acidic and the second phase of acid dissolution and quartz overgrowth began; 14.0×106 a—2.8×106 a ago, re-evolution and hydrocarbon generation happened to the source rocks, which made the formation water continuously acidic; since 2.8×106 a ago till now, the formation water was acidic and a few late pyrite cements were found Related Articles | Metrics

Characteristics and Formation Periods of Fractures in Ordovician Carbonate Rocks in Hetianhe Gas Field DAI Junsheng, WANG Yukun, FENG Jianwei, LI Shubo, WANG Yongjuan 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170202 Abstract ( 85 )   PDF (300KB) ( 192 )   Save The Ordovician carbonate reservoir in Hetianhe gas field of Bachu uplift, Tarim basin has strong heterogeneity and poor pore throat structure. Most of the karst caves and dissolved pores of the reservoir are filled, and the degree of fracture development becomes the main factor to determine the productivity of the gas field. According to the observation of fissures in the core, it is found that the fractures of the reservoir in the study area are mostly structural fractures. High-angle fractures are developed in the west, and both low-angle and high-angle fractures occur in the east. Based on dissection, occurrence and filling of fractures on the sections of outcrops and the comprehensive analysis on isotopes of oxygen and carbon of the fillings and fluid inclusions, it is considered that the fractures were formed in 3 periods such as early Hercynian movement, late Hercynian movement and Himalayan movement Related Articles | Metrics

Sedimentary Characteristics of Nearshore Subaqueous Fans of Sha-4Sha-3 Member of Shahejie Formation in Daxing Fault Zone of Langgu Sag LIANG Guanzhong1,2, LIU Longsong1, ZHANG Feng2, JI Youliang1, LYU Yahui2LI Yanguo2 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170203 Abstract ( 105 )   PDF (300KB) ( 176 )   Save Conglomerate reservoirs with abundant oil and gas resources have been found in Daxing fault zone successively such as Xing 8 and Xing 9 etc. Most of these reservoirs are mid-fan braided channel of nearshore subaqueous fans. Therefore, it is very important to study the sedimentary characteristics of the nearshore subaqueous fans. Based on the previous research results and the latest core，seismic, well logging and other data obtained in the sag, the sedimentary microfacies are identified and classified in this paper. The vertical and horizontal distributions of the nearshore subaqueous fans are summarized and the depositional models of them are established for debris flow and mud flow, respectively. The debris flow nearshore subaqueous fan is developed in Jiuzhou area with an abrupt contact between the thick conglomerate and mudstone in the fan body. The sediments are mainly composed of particle-supporting conglomerates with little matrix. Whereas, the mud flow nearshore subaqueous fan is found in Gu’an area. Few channel exists in the fan and the sediments are mainly matrix-supporting conglomerates with the matrix dominated by mud. The debris flow nearshore subaqueous fan can be classified into six sedimentary microfacies such as main channel of root fan, interchannel of root fan, braided channel in midfan, braided interchannel in midfan, sheet sand in endfan and mud in endfan, among which the braided channel in midfan is the main body of the midfan and even the debris flow nearshore subaqueous fans. The endfan is relatively undeveloped. The nearshore subaqueous fans are in near NE trending distribution along Daxing fault zone with the lower third member of Shahejie formation being the most developed Related Articles | Metrics

Exploration and Evaluation Methods of Fengcheng Oil Sands in Junggar Basin HUANG Wenhua1a, GUO Rui1b, ZHOU Boyu1a, WANG Dongxue1a, SHI Xiaolei2, Ding Yun1a 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170204 Abstract ( 97 )   PDF (300KB) ( 264 )   Save As oil sands are characterized by shallow burial and high viscosity, its exploration and evaluation methods are different from those of conventional oil and gas. Technologies of small spacing hole drilling and full hole-section coring are used to recognize oil sands, and the effective thickness and reserves are determined on the basis of crude oil mass percentage of oil sands, based on which the exploration and evaluation are carried out for oil sand ores in Fengcheng area of Junggar basin. Selecting a fault block and using 2 exploration methods of hole drilling and well drilling, the comparison analysis shows that the effective thicknesses determined by the 2 methods are congruent and the reserves calculation results are close to each other Related Articles | Metrics

Influences of Dolomitization on Reservoirs of Upper T2l4 of Leikoupo Formation in Western Depression, Sichuan Basin LI Ronga,b, HU Haoa,b, XU Guomingb, WANG Qiongxianb, SONG Xiaobob, LONG Keb 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170205 Abstract ( 63 )   PDF (300KB) ( 250 )   Save The dolomite of upper T2l4 of the Middle Triassic Leikoupo formation is thick and widely distributed in western Sichuan depression. High-yield industrial natural gas flows have been gained from the wells penetrated in the dolomite. Based on the analysis of cores and thin sections and combining with experimental test data, the paper studies the dolomitization in parasyngenetic and shallow-burial stages and discusses its impact on the reservoir development. The result shows that during the deposition period of upper T2l4 of Leikoupo formation, the study area was a restricted platform environment, the sedimentary water was shallow and the sea level changed frequently, dolomitized fluids were mainly seawater of the same period and thus very thick dolomite formed and were laterally distributed steadily; the dolomite stratum formed during the shallow-burial stage and before, dolomicrite, microcrystalline-powder crystalline subhedral-euhedral dolomite and a few powder-fine crystalline subhedral dolomite were found in the stratum. The geochemistry characteristics show that the dolomite formed in the early time; large amount of intercrystalline pores formed during the shallow-burial stage controlled dispersed flow of the corrosive fluids at the late stage, which resulted in the dolomite reservoirs dominated by laminated pore type or needle-like dissolved pore type in the study area Related Articles | Metrics

Research on Sedimentary Facies Based on Modern Sedimentary SystemsA Case from the Second Member of Shawan Formation in Chunguang Area of Chepaizi Swell, Junggar Basin FAN Xiaoyi1a,1b, YAO Guangqing1a,1b, YUE Xinxin2, LI Yanran2, LIU Yuanyuan2 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170206 Abstract ( 64 )   PDF (300KB) ( 199 )   Save Great breakthrough has been achieved in the second member of Shawan formation in Chunguang area of Chepaizi swell, Junggar basin. However，there are a lot of discussions about its depositional system. The uncertainty of its sedimentary facies adds some difficulties to fine description of sandbody and detailed study on sandbody internal configuration and reservoir modeling, which slows down the process of petroleum exploration and development for the lithological reservoirs in the area. Based on the data of core, logging, testing and high-resolution 3D seismic and the analysis of remote sensing images of modern sedimentary systems, the sandbody distributions in the area are compared with those of Maqu river in Gansu province and Lena delta in Russia. The results show that the second member of Shawan formation belongs to braided river delta sedimentary system, where braided river delta plain and braided river delta front are developed, the main sedimentary microfacies can be divided into distributary channel, underwater distributary channel and distributary sand bar and sandbodies are well developed. The reason of the formation of the lithological trap belt in the study area is the lateral continuity of the distributary channel and distributary sand bar resulted from the developed distributary bays, which leads to traps isolated from each other; it is hard to form efficient traps in the southeast of the area due to the lack of transverse breaks of deposits Related Articles | Metrics

Fluorescence Characteristics of Oil Inclusions of Yingshan Formation in Manan Structural Belt of Maigaiti Slope SI Shanghua1,2, CHEN Honghan2, XIONG Wanling3, LI Peijun2, LU Ziye2 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170207 Abstract ( 47 )   PDF (300KB) ( 175 )   Save In order to understand the hydrocarbon accumulation of Yingshan formation in Ma’nan structural belt of Maigaiti slope, the paper quantitatively describes the fluorescence spectrum of oil inclusions and identifies the oil inclusions with 4 fluorescent colors of orange, yellow-green, blue-green and blue-white by using peak wavelength (λmax), red-green quotient（Q）and QF535 parameters, which represents 4 different stages of oil and gas charging, respectively. The peak wavelength(λmax) and QF535 of oil inclusions are distributed in 4 different areas. The decrease of QF535 value reflects the gradual increase of the maturity of the oil trapped by inclusions. Hydrocarbon charging during stages Ⅰ,Ⅱ and Ⅲ made more contributions to the current oil and gas reservoirs of Yingshan formation than that of stage Ⅳ. The stage Ⅰ is low-maturity oil charging at the early stage and the stages Ⅱ, Ⅲ and Ⅳ are high-maturity oil charging at the late stage Related Articles | Metrics

Accumulation Pattern of Medium Rank Coalbed Methane in Hancheng Mining Area, Ordos Basin YI Wei 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170208 Abstract ( 76 )   PDF (300KB) ( 127 )   Save In order to reveal the accumulation of medium rank coalbed methane (CBM) in Hancheng mining area and using the data of drilling, logging, well testing, coal rock test and production, the conditions and main controlling factors of coalbed methane accumulation in Hancheng mining area are analyzed, based on which the CBM accumulation model is studied. The results show that the CBM accumulation conditions are favorable in Hancheng mining area—the key coal seams are widely distributed in the whole area with the thickness reaching 12 m, CBM content of 6~16 m3/t, relatively high degree of thermal evolution, Ro of 1.91~2.56% and good preservation conditions. The CBM reservoir is mainly controlled by structures, hydrogeological conditions and coal metamorphism. Based on structural morphology, surrounding rock conditions and groundwater dynamic characteristics, the reservoirs in the area can be divided into 5 patterns such as low-angle monocline, nose-like structure, marginal nappe, gentle slope anticline and sealed reverse fault Related Articles | Metrics

Fluid Inclusion Characteristics and Hydrocarbon Accumulation Periods of Triassic Reservoirs in Lunnan Area of Tarim Basin SUN Yifang1, ZHA Ming1, GAO Changhai1, ZHANG Haizu2, ZHAO Haitao2, YAN Wenyuan1 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170209 Abstract ( 56 )   PDF (300KB) ( 134 )   Save There are some disputes about hydrocarbon accumulation periods and times of Triassic reservoirs in Lunnan Area of Tarim Basin, therefore, 51 samples of fluid inclusions are collected from 13 wells in this area. The paper studies the microscopic features and homogenization temperatures of the fluid inclusions based on microscopic observation and microthermometry technology, and determines the hydrocarbon accumulation periods and times combining with the burial history-thermal evolution history matching. Saline inclusions and gas-liquid two-phase hydrocarbon inclusions are mainly developed in the Triassic reservoirs of Lunnan area, most of which occur in the microfissures of quartz. The hydrocarbon inclusions are bright yellow to yellowish green, which indicates a medium maturity of oil and gas in the study area. Homogenization temperatures of associated saline inclusions show a unimodal distribution characteristic with the peak values mainly ranging from 110℃ to 120℃. One period of hydrocarbon charging occurred in the Triassic reservoirs in Miocene in the area Related Articles | Metrics

Shale Reservoir Characteristics and Influencing Factors on Shale Gas Content in Lujiaping Formation of Chengkou Area CUI Nan1,2, ZHANG Ye1,2, LU Zhaohui1,2 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170210 Abstract ( 57 )   PDF (300KB) ( 256 )   Save The paper analyzes the characteristics of geochemistry, petromineralogy, reservoir physical properties and reservoir spaces, gas bearing properties and preservation conditions for the shales of the Lower Cambrian Lujiaping formation in Chengkou area of northeastern Chongqing, and performs correlation analysis of the factors influencing shale gas content with grey correlation theory. The results show that the preservation of the shales in Lujiaping formation is quite good in the study area. The shale reservoir has high organic matter content and maturity and high brittleness, whose kerogen is dominated by Type I; the reservoir spaces are dominated by intergranular pores and large pores are developed in the reservoir with large unit absorbing capacity. But the unfavorable factors such as complicated stratigraphic structures and very high maturity of organic matters of the shales of the Lower Cambrian Lujiaping formation in Chengkou area of northeastern Chongqing may result in the difficulties for future development Related Articles | Metrics

Geological Evaluation of Preferential Steamflooding Pathways in Heavy Oil Reservoirs in Block Qi40 of Liaohe Depression WU Dongsheng, LIU Yangjie, ZHENG Huan 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170211 Abstract ( 60 )   PDF (300KB) ( 179 )   Save In order to determine preferential steamflooding pathways formed during steam drive production in the heavy oil reservoirs in Block Qi40 of Liaohe depression, the parameters for geological evaluation of preferential pathways such as permeability, effective thickness, sedimentary microfacies, coefficient of variation and interlayer frequency are verified by using a combined method of static reservoir description and development performance analysis. Sandbodies of preferential pathways are determined and sample data are extracted on the basis of development performance characteristics. The weights of each parameter are determined by using grey correlation analysis method and fuzzy clustering analysis method is used to classify the steamflooding preferential pathways into 2 types and to obtain these parameters, based on which the standards of geological classification and evaluation are established for preferential steamflooding pathways and then fuzzy pattern recognition method is used to evaluate and predict the spatial distribution of the pathway. The practical application shows that this method is objective and accurate, which can provide basis for steamflooding development plan making Related Articles | Metrics

Reservoir Geological Modeling Technique and Quality Control Method YU Jinbiao 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170212 Abstract ( 110 )   PDF (300KB) ( 139 )   Save Reservoir geological modeling is a process to build a three-dimensional digital model which can characterize structural configuration, petrophysical properties and fluid distribution under the initial reservoir conditions. Geological complexity, limitations of modeling methods and unsufficient modeling data lead to the uncertainties of geological understandings and models. In order to improve the quality of geological models and based on the conventional geological modeling methods and history matching technology in numerical simulation, the paper proposes an integrated modeling method which includes multilevel constraints of dynamic and static data, comprehensive utilization of a variety of information and full-process quality control; systematically summarizes the operation techniques for each modeling procedure and the methods of model quality control. The practical application shows that the quality of geological model is greatly improved, the simulation times for history matching of reservoir numerical simulation are reduced and the efficiency is enhanced as well by using the integrated modeling method and the proposed operation techniques Related Articles | Metrics

Classification and Characterization of Microscopic Pore Structures in Low and Extra-Low Permeability Reservoirs: A Case Study of Reservoirs Chang 2 and Chang 6 in Yanchang Formation of Yanchang Oilfield PANG Zhenyu1, LI Yan1, DUAN Wei1, DONGYue2, DUAN Jingjie1, GAO Qinghua1 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170213 Abstract ( 60 )   PDF (300KB) ( 182 )   Save Using experimental data of constant-rate mercury injection, the paper studies the microscopic pore structures and oil and water distributions in low and extra-low permeability reservoirs in Yanchang oilfield. The results show that throat dominates the development effect. Average radius of throats and number of effective throat per unit volume control the reservoir permeability collectively. In the sequence of effective throat volume per unit volume, main current throat radius, the max. connecting throat radius, their influences on the permeability decrease, which has nothing to do with the mercury injection saturation of throats. The pore throat radius ratio correlates poorly with porosity, but it has a strong negative correlation with permeability. With the decrease of pore throat radius ratio, the development degree of throat becomes better and the fluid permeability increases. Therefore, the oil and gas in the formation are easily displaced through throats, but the correlation between the ratio of pore throat radius and porosity is not obvious and the ratio of pore throat radius does not vary with the change of porosity regularly Related Articles | Metrics

Controlling Factors on Complex Gas-Water Distribution in Xu-6 Tight Sandstone Gas Reservoir in GuangAn Area LI Yong1a, CHEN Shijia1a,1b, WU Bingyan1a, QIU Di1a, LIN Ruopeng1a, LI Junliang2 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170214 Abstract ( 62 )   PDF (300KB) ( 166 )   Save To identify the controlling factors on complex gas-water distributions in tight sandstone gas reservoirs, taking Xu-6 gas reservoir of Guang’an gas field in Sichuan basin as an example, and based on the data of logging, connecting-well section, seismic section and mercury injection, the paper studies the controls of source rock distribution, reservoir physical properties and structural amplitude on gas-water distributions in gas reservoirs comprehensively. The results show that the source rocks interbedded with thin sandstones supply hydrocarbons sporadically, which is the root cause of multi-gas intervals and complex gas-water distributions in Xujiahe formation; with the same hydrocarbon supply conditions, natural gas will first migrate to and accumulate in good quality reservoirs, which results in varied differentiation of gas and water in different blocks; structural amplitude has impacts on gas and water differentiation degrees in tight sandstone gas reservoirs, and the higher the structural amplitude is, the more sufficient the gas and water differentiation will be. Therefore, the gas-water distributions in tight sandstone gas reservoirs are mainly controlled by hydrocarbon source rock distribution, reservoir physical properties and structural amplitude and so on Related Articles | Metrics

Fractal Percolation Law in Fractured-Vuggy Triple Medium Reservoirs LIU Huapu, LIU Huiqing, WANG Jing 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170215 Abstract ( 75 )   PDF (300KB) ( 159 )   Save Fractured-vuggy triple medium reservoirs are characterized by strong heterogeneity and complex pore structures. In order to describe the complex systems more accurately, fractal theory is introduced to establish a fractal mathematical model for fractured-vuggy triple medium reservoirs. By means of Laplace transformation and Stehfest numerical inversion, the bottom hole pressure is obtained; Matlab programming is used to map pressure curves, classify flowing stages and analyze percolation characteristics and fractal parameter sensitivity; percolation parameters are interpreted to verify the accuracy of the model on the basis of drilling and logging data. The results show that the percolation process of the fractal triple medium fractured-vuggy reservoirs can be divided into 5 stages—wellbore storage at the early stage, channeling from caves to fractures, pseudo radial flow between caves and fractures, channeling among matrix, caves and fractures, and the total radial flow. The fractal coefficient could affect the whole percolation process. The fracture tortuosity increases with the increase of fractal coefficient, which results in the increase of flow resistance, more up-shifting of pressure derivative curves and more upwraping of the curves at the total radial flow stage Related Articles | Metrics

Using Geochemical Methods to Evaluate Fault Sealing: A Case Study from Batian Area in Jinhu Sag, Subei Basin WANG Li1a, CHEN Shijia1a,1b, DING Yusheng2, LU Jungang1a,1b, MA Jie1a, LI Yong1a 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170216 Abstract ( 83 )   PDF (300KB) ( 220 )   Save Based on the correlation and analysis of geochemical characteristics of oils from Batian area, surrounding sub-sags, the hanging wall and foot wall of the fault, the paper determines the key subsags for hydrocarbon generation, identifies fault sealing and analyzes the exploration potential of Batian area. The results show that the oil from the periphery of Longgang subsag with the highest maturity is the product of the source rocks of matured stage, and Longgang sub-sag is the key hydrocarbon generating sub-sag in the periphery of Batian area. The differences of geochemical characteristics such as hydrocarbon’s n-alkanes, sterane and terpane distributions and oil maturity in the hanging wall and foot wall of F1 fault reveals that F1 fault is sealed and the matured oil sourced from Longgang sub-sag never migrates across F1 fault to Batian area. The maturity of the extracts from oil-bearing sandstones in Batian area is low, which is similar to the low-maturity products sourced from the slope, Chajian sub-sag and Dongyang sub-sag. The hydrocarbon generating amount from the source rocks of low-maturity stage is limited so that scaled reservoirs are difficult to form. Therefore, the exploration potential is relatively poor in Batian area and the fault block traps neighboring to Longgang sub-sag should be the favorable exploration targets Related Articles | Metrics

New Methods of Modified Pareto Distribution Model Applied in Petroleum Resources EvaluationConcurrent Review of 3 Incorrect Pareto Distribution Models CHEN Yuanqian 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170217 Abstract ( 93 )   PDF (300KB) ( 151 )   Save Pareto presented a negative exponent power function in 1897 to describe the distributions of reserves scale of oil and gas fields in petroliferous regions or basins, which is called Pareto distribution model or Pareto law. However, the original Pareto distribution model has some flaws in theory—N(0) approaches to infinite when x equals to zero. Furthermore, the constants in the distribution model can’t be determined because there is usually a nonlinear relationship between reserves scale and its serial number on double-logarithm coordinate. Therefore, Pareto distribution model can’t be applied effectively in oil and gas resources evaluation. Chen Yuanqian presented a modification of the original Pareto distribution model in 2008 to overcome the theoretical flaws and established effective estimation methods. Then the methods to calculate Pareto distribution density, cumulative distribution and adverse cumulative distribution, total resources and 3-level resources are obtained based on the modified Pareto distribution model. At the same time, this paper reviews the 3 incorrect Pareto distributions presented by Jin Zhijun, Lee and Chen-Richard, respectively. The actual application indicates that the new methods are practical and effective Related Articles | Metrics

Simulating Experiment of Sulfur Occurrence during Pyrolysis of Solid Bitumen in Carbonate Rocks LUO Houyong1,2 ?ZHANG Dayong3, ?LIANG Mingliang4, ?LIU Wenhui2, ?HU Wenxuan1 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170218 Abstract ( 70 )   PDF (300KB) ( 69 )   Save In order to clarify the changes of sulfur occurrence during the pyrolysis of solid bitumen and thermochemical sulfate reduction(TSR) in carbonate reservoirs, some solid sulfur bitumen samples of low maturity were acquired from the Lower Cambrian stratum in Kuangshanliang area of northwestern Sichuan province, and evolutions of hydrocarbon generation and expulsion were simulated with a semi-open experiment system; by using synchrotron radiation technology, the chemical occurrence of sulfur in solid products was detected accurately. The results showed that oxidation reaction mainly occurred during the direct pyrolysis of the solid bitumen; the generated H2S and large amount of CO2 due to the existence of dissolved sulfate indicated that TSR occurred in the pyrolysis process; with the increase of experimental temperature and pressure, the yield of H2S and sulfate increased, which reflected that both oxidation and reduction reactions might occur in the experiment. The calcium sulfate generation and its enrichment showed that the acid fluids associated with TSR would corroded dolomite reservoirs obviously, as a result, the secondary gypsum might be produced and the gypsum in high-sulfur reservoirs could be the reactant of TSR Related Articles | Metrics

Derivation and Application of CO2 Flooding Characteristic Curves in Low Permeability Reservoirs CHEN Liang, GU Hongjun, LIU Rongjun, QU Huailin, DONG Haihai, ZHAO Yiqing 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170219 Abstract ( 63 )   PDF (300KB) ( 159 )   Save Based on the theory of Type-A waterflooding characteristic curves, because the percolations of CO2 and oil during CO2 flooding in low permeability reservoirs are in accordance with the power exponent law, the paper derives the CO2 flooding characteristic curves for low permeability reservoirs, establishes a relationship between quasi-content of CO2 and recovery percent of reserves and obtains a series of methods to predict recoverable reserves and recovery factor of CO2 flooding in low permeability reservoirs. The characteristic curves of CO2 flooding in low permeability reservoirs show that the modified relationship between cumulative CO2 production and cumulative oil production is semi-logarithmic. The field application indicates that the dynamic indices such as recoverable reserves and recovery factor by CO2 flooding in low permeability reservoirs can be better predicted with the characteristic curves, which is helpful for block development evaluation Related Articles | Metrics

A New Method to Fast Forecast Layered Production Indexes in Waterflooding Wells DONG Chi1, SONG Kaoping1, SHI Chengfang2, ZHU Menggao3, CUI Xiaona1, LIU Zhu1 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170220 Abstract ( 73 )   PDF (300KB) ( 216 )   Save As the matured waterflooding oilfields in China are mostly at high/ultra-high water cut stages, and plane and interlayer conflicts become more serious, remaining oil distribution is highly dispersed and economic and efficient production becomes more and more difficult. In order to meet the requirements to identify preferential flow paths quickly and accurately and to control the ineffective and low effective circulation for oilfields, this paper puts forward a new method to fast forecast layered production indexes for individual wells based on the conventional numerical simulation technology and the method of water flooding curves. In this paper, 10 relative permeability curves of natural cores selected by Daqing oilfield are studied, it is found that the recovery percent of reserves and water-oil ratio exhibit a good linear relation in semi-log coordinate system with the correlation coefficient greater than 0.99. Based on this, the functional relationship among the slope and intercept of the expression and permeability is calculated by using parameter regression, and then the relationship between recovery percent of reserves and water cut (or water fractional flow) under various permeability is obtained. Combining single well production split with the above formula, the paper establishes a new forecasting model of layered production indexes for individual wells, and simultaneously proposes a production correction method using actual production data. Compared with the calculation results obtained from Eclipse numerical simulation software, the maximum error between the waterflooding recovery factors obtained from the 2 methods is 2.72%. The calculation results of the dynamic index of the actual production block shows that the method is simple and easy to learn, which can forecast the layered production indexes of water flooding reservoirs efficiently and accurately, and can solve the problems such as time-consuming, complex computation and human intervention in previous forecast methods Related Articles | Metrics

Methods of Parameter Sensitivity Analysis for History Matching Based on Adjoint Model WANG Yong1, ZHANG Zhang2, SUN Yeheng1, LIU Wei2 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170221 Abstract ( 73 )   PDF (300KB) ( 111 )   Save In view of the problems of huge computations, incapacity to deal with large scale reservoirs and unqualified computational accuracy of the current sensitivity analysis methods in numerical reservoir simulation, this paper proposes an adjoint model-based parameter sensitivity analysis method for history matching. Based on the adjoint system theory, an adjoint model with the adjoint variables independent of simulated variables is established and direct resolution of gradient equation can be avoided; coefficient matrices of the adjoint model are constructed according to the state equation of the reservoir percolation model and solving methods of the numerical reservoir simulator. Adjoint variables are acquired by solving the adjoint equations and sensitive coefficient calculation equations are established. The sensitive coefficient matrices of objective functions with respect to control variables are solved by using the adjoint variables. Compared with the commonly used gradient simulator methods and experimental design methods, the advantages of this method are as follows: the coefficient matrices of the adjoint model can be directly derived from the results of the state equation; the amounts of calculations to solve the gradient equation only depend on the quantity of the observation data rather than the number of model parameters. In order to obtain the derivatives of particular observation data with regard to all model parameters, it only needs to construct and solve one corresponding adjoint equation. With high calculation ability; the sensitive coefficients of all producing time for each grid parameter could be acquired simply by forward modeling an original model and inverting an adjoint model only once, thus the efficiency of parameter sensitivity analysis is greatly improved Related Articles | Metrics

Abiogenesis of Hydrocarbon Gas and Its Identification Index XU Wang1,2, ZHENG Guodong1, MA Xiangxian1, FAN Qiaohui1, David R Hilton1,3, XU Sheng1 2017, 38 (2):  1-1.  doi: 10.7657/XJPG20170222 Abstract ( 75 )   PDF (300KB) ( 158 )   Save The paper summarizes and reviews some typical viewpoints, latest researches and developments about abiogenic hydrocarbon gases. Based on the theory of serpentinized abiogenic hydrocarbon, the possible geological backgrounds for the formation of abiogenic hydrocarbon gases are analyzed. The discovered formation and migration of abiogenic hydrocarbon gases are mostly located in the areas with intense tectonic activities and complex geological environments. How to match the chemical reaction mechanisms and the reaction conditions with the specific geological conditions is essential to the accumulation of abiogenic hydrocarbon gases. Various identification indices and classification patterns are discussed for abiogenic gases. Although the typical distribution intervals of δ13C values of methane are significant for abiogenic gas identification, a reasonable explanation should be given in combination with the specific geological background. Actually, δ13C values of abiogenic methane may have a wider distribution range. The case analysis results show that the comprehensive utilization of carbon and hydrogen isotopes has obvious advantages in identifying hydrocarbon gas genesis Related Articles | Metrics