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01 January 2019, Volume 39 Issue 2 Previous Issue    Next Issue

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Pore Structure Characteristics and Pore Connectivity of Paleogene Shales in Dongying Depression ZHANG Linyan1, BAO Youshu1, XI Chengwei2 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180202 Abstract ( 152 )   PDF (300KB) ( 300 )   Save Base on the combination of total porosity measurement and high-pressure mercury injection for shales, a quantitative study method focusing on shale’s pore structure and pore connectivity is established in this paper. The paper compares the total porosity, effective pore diameter distribution and pore connecting rate among the massive mudstone, laminar shale and laminated shale of Paleogene Shahejie formation in Dongying depression. The study shows that the massive shale has the lowest porosity ranging from 2.7% to 4.5%, laminated shale has the highest porosity ranging from 10.2% to 17.7%, and the porosity of the laminar shale is 5.9%~11.2%. The massive mudstone is dominated by pores of small pore diameter with the the main peak value less than 10.0 nm. The pore diameter of the laminated shale ranges from 3.6 to 10 000.0 nm with the main peak higher than 10.0 nm, and the proportion of pore diameter less than 10.0 nm is relatively low. The pore diameter of the laminar shale is distributed between those of massive and laminated shales, its main peak value is usually about 10 nm, the proportion of the pores with the diameter less than 10.0 nm in the laminar shale is lower than that of the massive mudstone, and the proportion of the pores with the diameter higher than 100.0 nm in the laminar shale is lower than that of the laminated shale. The massive mudstone has the lowest pore connecting rate, the laminated shale has the highest pore connecting rate and the laminar shale has the medium rate. The differences of the shale’s pore structure characteristics are related to sedimentary lithofacies and diagenesis. There are a few primary and syngenetic pores in the massive mudstone, which is not good for the formation of secondary pores. The pore structures of laminar and laminated shales are favorable for the preservation of primary pore and the formation of secondary pore Related Articles | Metrics

Petroleum Distribution in Foreland Thrust Belts and Its Exploration Areas in Midwest China ZHUO Qingong1,2, ZHAO Mengjun1, ZOU Kaizhen3, FU Xiaofei4 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180201 Abstract ( 76 )   PDF (300KB) ( 251 )   Save Large-scale oil and gas fields such as Karamay, Kela-2, Yingdong, Zhongba and Baimamiao have been discovered in the foreland thrust belts around the Qinghai-Tibet Plateau of Midwest China. The paper analyzes and compares the structural characteristics of the foreland thrust belts and its relationship with oil and gas, and summerizes the petroleum distribution in the foreland thrust belts and its exploration areas in the Midwest China. Along the strike, the foreland thrust belt is generally divided into three large structural segments—the mid-segment of the foreland thrust belt is located in the hydrocarbon generation center with enriched oil and gas; from the piedmont area into basin, the foreland thrust belt can be divided into three hydrocarbon enrichment zones such as piedmont nappe belt, footwall covered structure and late inner-basin tectonic belt. Oil and gas accumulated in the paleostructures in the piedmont nappe belt. The footwall covered structure and the late inner-basin tectonic belt are characterized by hydrocarbon accumulation in the near-source and near-fracture areas and oil and gas enrichment in the deep strata. The foreland thrust belt is dominated by structural reservoirs. Additionally, stratigraphic reservoirs such as base rock weathering crust and unconformity barrier are developed in the piedmont nappe belt, and structural-lithological reservoirs are developed in the late inner-basin tectonic belt. Based on the understanding of the petroleum enrichment regularity and the three major exploration fields in the middle and deep of the foreland thrust belt, and combined with the exploration status of the foreland thrust belt in southern margin of Junggar basin, the areas for further exploration are defined as the Qigu fault-fold zone and the lower assemblage in the Wukui anticline zone in the middle segment of the southern margin Related Articles | Metrics

Mesozoic Sporopollen Assemblages and Their Stratigraphical Significance in Well Shimo-1 of Junggar Basin Aliya AMUTI, XIAO Jinan, SHI Tianming, WENG Yuexin 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180203 Abstract ( 61 )   PDF (300KB) ( 55 )   Save To solve the problems existed in stratigraphic classification and correlation in Shimo area, the paper systematically studies the Mesozoic sporopollen fossils in Well Shimo-1. The sporopollen fossils can be divided into 195 species of 98 genera, and 5 sporopollen assemblages are identified, including the Concavissimisporites-Classopollis-Rugubivesiculites assemblage corresponding to the Lower Cretaceous Qingshuihe formation, Cyathidites-Cerebropollenites-Piceaepollenites assemblage corresponding to the Lower-Middle Jurassic Sangonghe formation, Osmundacidites-Cycadopites-Protoconiferus assemblage corresponding to the Lower Jurassic Badaowan formation, Dictyophyllidites-Aratrisporites-Alisporites assemblage corresponding to the Upper Triassic Baijiantan formation-the Lower Jurassic Badaowan formation, and Punctatisporites-Converrucosisporites xinjiangensis-Parataeniaesporites pseudostriatus assemblage corresponding to the Middle-Upper Triassic Karamay formation. The characteristics of the 5 sporopollen assemblages can be correlated with the assemblages in the Qingshuihe formation, Sangonghe formation, Badaowan formation, Huangshanjie formation and Haojiagou formation, and Karamay formation in the southern margin of Junggar basin, respectively. The data of the sporopollen fossils show that the strata of Jurassic are incompletely developed in the wellblock with the absences of Toutunhe formation, Qigu formation and Kalazha formation; the age of Sangonghe formation may be the late of Early Jurassic-the early of Middle Jurassic, the stratigraphic boundary between Middle Jurassic and Lower Jurassic should be located between the upper and lower member of Sangonghe formation; the age of the bottom of Badaowan formation may be the late Triassic, and the stratigraphic boundary between Triassic and Jurassic should be the lower Badaowan formation Related Articles | Metrics

Geochemical Characteristics of Hydrocarbons Occluded in Asphaltene and Oil Source Identification in Tahe Oilfield TAO Guoliang, LIU Peng, LI Maowen, CAO Tingting, John VOLKMAN, Lloyd SNOWDON 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180204 Abstract ( 93 )   PDF (300KB) ( 247 )   Save To solve the disputes on oil source in Tahe oilfield of Tarim basin, the paper selects the oil obtained from Well TK772 in the major area of the oilfield to comparatively study the geochemical characteristics of the crude oil and the hydrocarbons occluded in the asphaltene oxidation products. The results show that the hydrocarbons occluded in asphaltene are characterized by even carbon preference in N-alkanes, low pristane to phytane ratio, low C29/C30 hopane ratio, low C35/C34 hopane ratio, low maturity, high Ts/(Ts+Tm) ratio and high gammacerane index and so on, indicating that its oil source was formed in an evaporite environment with restricted platform, high salinity, strong reduction and zonal water body, which represents the oil charging characteristics at the earliest stages in Tahe oilfield. The characteristics of the biomarkers of saturated hydrocarbon in Well TK772 which is significantly different from that of the hydrocarbons occluded in asphaltene reflects that its oil source was formed in a depositional environment of carbonate rocks with broad water body and low salinity, representing the characteristics of the most oil in Tahe oilfield. Based on these newly obtained geochemical evidence and combined with the previous research results on the relationship between source rock distribution and sedimentary facies in the northern Tarim basin, it is considered that the oil accumulated in 3 periods in Tahe oilfield, the first-period oil originated from the Cambrian source rocks of evaporite facies in the platform; the second-period oil from the Upper Ordovician carbonate source rocks and the third-period from the high-maturity light oil charging at the late stage in the periphery of Tahe oilfield Related Articles | Metrics

Research and Identification of Gas and Water Characteristics in Ma-55 Submember in the Southern District of Sulige Gas Field ZHENG Xiaopeng, WANG Shujie, HAO Long, HU Weiwei, LIU Daotian, WANG Ye 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180205 Abstract ( 70 )   PDF (300KB) ( 190 )   Save Marine carbonate reservoirs are developed in Ma-55 submember of the Lower Ordovician Majiagou formation in the southern district of Sulige gas field, which have no obvious gas-water interface. But gas wells produce water during the development process. Based on indepth analysis of chemical characteristics of formation water, logging curve overlapping and cross-plot methods, the paper determines the formation water type and distribution pattern. The results show that the formation water in Ma-55 submember belongs to well-sealed ancient residual seawater and 3 distribution patterns exist in the submember including retained water at the bottom, gas and water in the same layer and lenticular water, among which the boundary of deep lateral resistivity between aquifer and gas-water zone is 266 Ω·m and that between gas-water zone and gas zone is 710 Ω·m Related Articles | Metrics

Classification of Low-Permeability Sandstone Reservoirs and Permeability Evaluation by Well Logging: A Case from the Reservoir of Toutunhe Formation in Wellblock Shinan-21 FENG Lijuan, JIANG Zhibin, QIAN Chuanchuan, SU Haibin, WANG Jie, LIU Gang 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180206 Abstract ( 58 )   PDF (300KB) ( 229 )   Save The low-permeability sandstone reservoir of Toutunhe formation in Wellblock Shinan-21 of Junggar basin is characterized by strong heterogeneity and great physical property differences in profile. Based on physical property analysis and the data of mercury injection and casting thin section, regarding microscopic pore-throat structures of the reservoir, the reservoir can be divided into 4 types through parameter optimization by using cluster analysis method. The Toutunhe formation in Wellblock Shinan-21 is dominated by Type Ⅱ and Type Ⅲ reservoirs that are mainly influenced by shale content. The larger the shale content is, the poorer the pore structure and the lower the permeability will be. The error of permeability of shaly sandstone reservoir interpreted with conventional model is relatively large. According to shale content and combining with reservoir classification, the paper establishes 4 permeability interpretation models for the 4 types of reservoirs, respectively. The actual application shows that the new models can well match with core analysis data, the interpretation accuracy is improved by 7.8% compared with that of the conventional model and good effects have been gained, which can be widely used for other low-permeability shaly sandstone reservoirs Related Articles | Metrics

Fine Multiparameter Evaluation for Polymer Flooding in Conglomerate Reservoirs and Its Application: A Case Study from Lower Karamay Formation in District Qidong-1, Karamay Oilfield XU Houwei, WANG Haiming, LIU Rongjun, XU Changfu, WANG Xiaoguang, LYV Jianrong 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180207 Abstract ( 77 )   PDF (300KB) ( 258 )   Save The two difficulties such as injected polymer molecular weight optimization and fine multiparameter reservoir evaluation have become the key problems to be solved urgently in the process of polymer flooding. Taking the conglomerate reservoir of the lower Karamay formation in District Qidong-1 of Karamay oilfield as the study object, the paper uses physical simulation methods to identify the relationship between recovery factor and polymer molecular weight, that is, the recovery factor will decrease gradually after the polymer molecular weight reaches 1 500×104. Based on which, taking the radial amplitude difference between of compensated density log and neutron porosity log as a regressive parameter, a model is established to calculate shale content. The permeability model established by using porosity and shale content can evaluate the seepage property of the conglomerate reservoir more accurately. Based on the results of physical simulation experiments and reservoir multiparameter interpretation, the optimal injected polymer molecular weights in different subregions are determined for the conglomerate reservoir of the lower Karamay formation in District Qidong-1, good application effects have been gained and the daily oil production has been improved from 149.2 t to 515.8 t after the implementation of polymer flooding program in the study area Related Articles | Metrics

Identification of Thin Interlayer and Potential Tapping of Residual Oil in Channel Sand Bodies JIANG Zhenhai 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180208 Abstract ( 76 )   PDF (300KB) ( 203 )   Save Inefficient or invalid circulation of the injected water occur in partial high-permeable zones within channel sand bodies after long-term waterflood development in reservoirs, and remaining oil accumulates near interlayers. It is still difficult to identify thin interlayer in channel sand bodies, which goes against the remaining oil potential tapping. Taking the western area of District Beier of Daqing placanticline oilfield as an example and using the data obtained from sealed coring wells with small well spacings, the paper carries out fine description of thin interlayer within channel sand bodies, classifies and evaluates the logging response characteristics of the interlayer and determines its controls on residual oil distribution. The study results show that the interlayers in the study area can be divided into lithological interlayer and physical-property interlayer, both of which are dominated by mudstone and siltstone, mainly distributed at the top of the sedimentary cycle vertically and mainly located in the sedimentary facies transformation zones in the plane. The remaining oil concentrates in the vicinity of the interlayers. Based on the identification results of the thin interlayers and according to the characteristics of the residual oil distributed in different channel sand bodies, different methods are adopted to realize the adjustment of potential tapping in thick sand layers, and the effects of increasing oil production and decreasing water production are significant, which can be the references for the secondary development in similar blocks Related Articles | Metrics

Reservoir Architecture and Remaining Oil Distribution in Shallow-Water Delta, Xingshugang Oilfield SONG Jinpeng1, LIN Chengyan1,2, REN Lihua1,2, LYU Duanchuan1, YOU Chunmei3 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180209 Abstract ( 72 )   PDF (300KB) ( 166 )   Save At present there are no mature research thinking and methods for hierarchical architecture analysis on distributary channel sand bodies of shallow-water delta facies in China and abroad. Taking the close spacing area in the middle of Xingshugang oilfield as a case, combining the data of seismic, logging, core, XRF and physical property analysis and test, the paper quantitatively characterizes the distributary channels of shallow-water delta facies hierarchically. The results show that 8 architectural levels are classified for the sand body of shallow-water delta facies in the study area. The single-period distributary channels in the 5th architectural elements are various and of different sizes, and stable interlayers are mostly developed between the distributary channels formed in different periods, which controls the general effect of waterflood development. The distribution characteristics of the different types of the 4th architectural elements are significantly different and the remaining oil saturation are various greatly in single wells and in the plane. The 3rd architectural elements are developed in different periods with the interface mostly being the stable physical interlayers, which controls the efficiency of ASP flooding and vertical distribution of remaining oil. The hierarchical analysis on the reservoir architecture can provide basis for fine characterization of shallow-water delta distributary channel sand body in the study area and potential tapping of remaining oil at extra-high water cut stages in mature oilfields Related Articles | Metrics

Controlling Factors of Well Productivity in Volcanic Reservoirs of Wellblock A, Chepaizi Oilfiled KONG Chuixian, BA Zhongchen, YAN Xiaolong, HUA Meirui, ZHOU Yang, SHI Yanling 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180210 Abstract ( 48 )   PDF (300KB) ( 217 )   Save The Carboniferous volcanic rocks in Wellblock A of Chepaizi oilfiled belong to the pore-fracture dual-media reservoirs, in which hydrocarbon accumulation and well productivity are affected by multiple factors including fault, lithology, lithofacies, porosity and fracture, leading to the complex hydrocarbon accumulation law and unstable well productivity. Based on the data of geology, well logging, lab analysis and seismic interpretation, the paper analyzes the configuration relationship between the productivity and reservoir factors such as lithology, lithofacies, matrix physical property and fracture, and confirms the hydrocarbon production characteristics of the Carboniferous volcanic reservoir. The results show that both the explosive facies and effusive facies near the volcanic vent are the predominant lithofacies where volcanic breccia and stomatal basalt are the favorable lithologies with good matrix physical properties and developed fractures. In the wellblock there are many high-yield wells whose logging curves are characterized by both negative anomaly in SP and a certain overlapping area between Rt and DEN. Considering well productivity and its controlling factors, three types of favorable reservoirs are classified in the plane and the type I is the best. On the basis of the above, combined with the logging curve characteristics, 9 existing wells are proposed to carry out formation test and 11 new development wells are suggested to be deployed on the C3 and C4 volcanic rock mass Related Articles | Metrics

Dynamic Simulation of Gas-Lift Dead-Lift Unloading Process in Waterflooded Gas Wells of Kelameili Gas Field ZHONG Haiquan1, ZHANG Feng2, FENG Dianfang2, WANG Xiaolei2, WANG Zhengming2, HONG Jiangling2, CHEN Wei2 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180211 Abstract ( 112 )   PDF (300KB) ( 224 )   Save Because of its strong adaptability and flexibility, gas lift is widely used in dewatering gas recovery of water-producing gas wells or restoring production of water-flooded gas wells. However, the unloading process of gas lift is very complicated, and its unloading methods or process parameters are mostly determined by experience, especially for gas-lift dead-lift process. A mathematical model based on mass conservation and momentum conservation is established to describe the unloading process of gas-lift dead lift and the finite difference method is used to solve the model. Taking the DX180X water-flooded gas well in Kelameili gas field for example and considering nitrogen gas lift and natural gas lift, dynamic simulation is performed for unloading process of normal lift and reverse lift, the influencing factors including nitrogen and natural gas injection, and normal and reverse lift are analyzed, and the changes of wellhead pressure and downhole pressure with time during unloading process are modeled. To lower the starting pressure and reduce liquid flowback time or flowback quantity, nitrogen-injection normal lift method is recommended, which is particularly applicable in deep wells and waterflooded wells with relatively high formation pressure or in which coiled tubing and gas-lift dead-lift are needed. Case modeling and analysis could provide references for feasibility study, design and compressor selection etc. of gas-lift dead-lift process Related Articles | Metrics

An Analytical Model for Water Swept Area in SAGD Wells GAO YanfangCHEN MianLIN BotaoJIN Yan 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180212 Abstract ( 83 )   PDF (300KB) ( 223 )   Save Steam Assisted Gravity Drainage（SAGD）technology is widely adopted for the development of terrestrial heavy oil reservoirs in Fengcheng oilfield. Due to the strong heterogeneity and low permeability of the reservoirs, the reservoir stimulation by water injection has been adopted to shorten the subsequent preheating period in SAGD wells. To quantitatively evaluate the shape of the stimulated region, the article proposed the concepts and calculation methods of floodable coefficient and squeezed fluid permeability in the swept area by water injection, derived the analytical solutions of the swept area in a single horizontal well and two horizontal wells, respectively, and finally used the model to predict the effects of field practices and verified the results by combining finite element calculation. It was concluded that the floodable coefficient in the studied reservoirs was about 0.27~0.30. Both the water swept radius and area of the dual-well injection system increased with the increase of the well spacing between the 2 wells, effective water permeability, horizontal section length and injection pressure under constant displacement conditions, and decreased with the viscosity of injected fluid. The viscosity of the injected fluid should be reduced as far as possible during field liquid-squeezing operation in SAGD wells. Meanwhile, the injection pressure and the near-wellbore reservoir permeability should be increased gradually to optimize the effect Related Articles | Metrics

Evaluation of Modified Bio-Polymers Suitable for High-Temperature High-Salinity Conditions in Hade Oilfield XU Haixia1, YUAN Xu2, YUAN Zebo1, REN Lihua1, CHENG Fang3, ZHAO Jing2 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180213 Abstract ( 64 )   PDF (300KB) ( 166 )   Save Problems such as serious contradiction between layers, water injection adjustment and fingering occurred during waterflooding in the double-step horizontal wells in Hade oilfield. Controlled hydrophobic modification for different carbon chains (C12, C14 and C16) in biopolymers was conducted for 8 biopolymers, and the biopolymers that have the characteristics of thermal thickening and salt thickening, and can be used for high-temperature high-salinity conditions for deep profile modification were composed and selected. The results showed that for the solutions of BP-14-036 and BP-12-012 with the mass fractions of 1.0%, their viscosities were about 10 000 mPa·s; when the salinities increased to 250 g/L, the viscosities exceeded 12 000 mPa·s, indicating the solutions were salt thickening; when the temperature reached 130 ℃, the viscosity of BP-14-036 solution with the mass fractions of 1.0% was over 14 000 mPa穝, indicating the solution was thermal thickening. Therefore, the 2 biopolymer solutions could transfera the extreme conditions of reservoir into the favorable factors to improve profile control effect to a certain extent, which could be used to solve the problems of weak thickening properties and poor tolerabilities of profile control and flooding agent, fracturing fluid and drilling fluid in high-temperature high-salinity oilfields Related Articles | Metrics

Analytic Model of Oil-Based Drilling Fluid Density and Wellbore Liquid Column Pressure in Deep Wells YANG Hu 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180214 Abstract ( 71 )   PDF (300KB) ( 140 )   Save During the drilling and completion in high-temperature and high-pressure deep wells, there are differences between the measured drilling fluid density on the ground and actual drilling fluid density in wellbore because the drilling fluid is affected by both temperature and pressure, which will lead to the difficulties in accurate calculation of the drilling fluid pressure in the wellbore. Based on the investigation on the prediction models of oil-base drilling fluid density at home and abroad, it is considered that all the previous models are not general and the calculation accuracy can’t meet the demands of deep wells, especially ultra-deep wells because they are empirical models using a few experimental data under the condition of specific formulas. Therefore, the paper uses a mathematical analytical method to establish a precise model to predict drilling fluid density and drilling fluid column pressure. Compared with the empirical models of many scholars, it is concluded that most empirical models are the simplified forms of the newly-established analytical model which can reflect the influences of temperature and pressure on drilling fluid density more fully and accurately. In the actual application, regarding the oil-based drilling fluid as the mixture of base oil, salt water and solid material, the prediction for oil-based drilling fluid density and wellbore liquid column pressure with different formula and oil-water ratio can be performed Related Articles | Metrics

Evaluation of Surfactant Performance in Reservoirs of Wellblock B21, Karamay Oilfield LI Kai, LI Zhihong, LIU Xiaoli, CHEN Liyan, WAN Qingshan, XU Renjun 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180215 Abstract ( 68 )   PDF (300KB) ( 110 )   Save To evaluate the feasibility of oil displacement using HW surfactant in Type Ⅱ conglomerate reservoirs in Wellblock B21, Karamay oilfield, the paper investigates the interfacial activity, stability, emulsifying property and simulated oil displacement performance of the surfactant. The results show that the magnitude of interfacial tension of HW surfactant concentration is 10-2 mN/m and the minimum interfacial is 0.006 0 mN/m when the mass fraction of HW surfactant is in the range of 0.1%~0.5%; the surfactant has good stability and its interfacial tension will not change during a long-term placement, which is in favor of enhancing oil recovery through reducing interfacial tension; the mass fraction and water-oil ratio of the surfactant have significant impact on emulsifying ability which increases with the increase of mass fraction, the water after demulsification is clear with distinct interface, which can help oil-water separation after oil displacement. The oil displacement experiment result shows that the surfactant solution with the mass fraction of 0.3% can improve the recovery factor by 10.5% Related Articles | Metrics

Triassic Channel Sand Body Identification and Efficient Well Placement in Tahe Oilfield CHEN Shuyang, ZHENG Haini, XIAN Wei, DENG Feng 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180216 Abstract ( 65 )   PDF (300KB) ( 143 )   Save The channel sand body in the 4th member of Triassic Akekule formation in Tahe oil field is characterized by ultra deep burial, thin sand body and narrow river channel. With the guidance of the study on sedimentary microfacies, a set of channel sand body identification and description technologies have been established, which uses forward modeling technology to determine marker, seismic multi-attribute identification technology to determine boundary, stratigraphic slicing technology to determine period and pseudo-sonic well-log-constrained impedance inversion technology to determine thickness. Based on which, a set of efficient well placement technologies combining pilot evaluation and step-like horizontal well development has been formed regarding segment reservoir accumulation of channel sand body with wide distribution of interlayer and barrier, which can reduce the risk in reservoir evaluation and improve reserves producing degree of channel sand body reservoir. Good application effects have been gained and the technologies can be the references for similar lithological reservoir development Related Articles | Metrics

Application of High-Precision Three-Parameter Wavelet Spectrum Analysis in Thin Reservoir Prediction PENG Jun, ZHOU Jiaxiong, MA Guangke, SUI Bo, WANG Yu, TANG Xu 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180217 Abstract ( 69 )   PDF (300KB) ( 364 )   Save 3 tunable parameters are used to control the construction of wavelet basis function, allowing the wavelets to better match with seismic signals and in favor of obtaining more accurate time-frequency analysis results, which is an effective method to identify thin reservoirs. Theoretical research and composite signal spectrum analysis prove that the high-precision three-parameter wavelet spectrum analysis method can effectively improve the identification precision of thin reservoirs because it focuses on high-frequency energy and has high resolution. The combination of the method with the non-linear e-index attenuation gradient matching highly improves the accuracy of frequency attenuation gradient calculation and the reliability of fluid property identification results. The combined method is applied in the reservoir prediction and fluid property identification of Ⅳ section of the second member of Zhuhai formation, Wenchang A oilfield in the western South China Sea, and the prediction results are in accordance with the actual drilling status. The effective application of the method has improved the potential tapping of Wenchang A oifield and is helpful for oil recovery enhacement Related Articles | Metrics

Using Micro-CT Scanning Technology to Study Characteristics of Pore Structures in Sandy Conglomerate: A Case from Baikouquan Formation in Mahu Sag, Junggar Basin XIONG Jian1, TANG Yong2, LIU Xiangjun1, QU Jianhua2, LIU Kai1, YOU Xincai2 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180218 Abstract ( 82 )   PDF (300KB) ( 322 )   Save Taking the sandy conglomerate reservoir of Baikouquan formation in Mahu sag as the study objects, micro-CT scanning technology is used to investigate the characteristics of the 2D and 3D pore structures of the rock in the sandy conglomerate reservoir. The results indicated that the sandy conglomerate sample obtained from Baikouquan formation in Mahu sag is dominated by residual intergranular pores, dissolved pores and micro-cracks. The shapes of the pores are irregular, the pore throats are of different sizes and their distributions are mainly contiguous and isolated; microscopic heterogeneous pore distribution is noted and even obvious in the samples with poor physical properties; equivalent pore radius is mainly in unimodal distribution and mostly less than 50 μm, and the proportion of small pores in the samples with relatively poor physical properties is higher than that in the samples with good physical properties Related Articles | Metrics

Modern Petroleum Geology: Mantle Hydrocarbon Theory CUI Yongqiang 2018, 39 (2):  1-1.  doi: 10.7657/XJPG20180219 Abstract ( 260 )   PDF (300KB) ( 193 )   Save The theories and experiments of modern science, space detection and achievements of exploration and development practices have proved that the large-scale existence of oil is not premised on the existence of living matter. Petroleum originates from the deep strata 100 km below the earth surface and is synthetized from the pre-existing carbon and hydrogen elements. Under any conditions, the biological molecules belonging to the C-H-O system can not be transformed into the hydrocarbon molecules of the C-H system heavier than methane. Hydrocarbon is part of mantle hydrocarbon alkali fluid which will have an alkaline metasomatism with surrounding rocks during its going upward and will transform into petroleum hydrothermal fluid containing metal, non metal and rare earth elements at the critical temperature. The petroleum hydrothermal fluid differentiates in the upward channel and metal, nonmetal, rare earth and hydrocarbon reservoir are formed. The upward channels of hydrocarbon in the faulted basins are the small fault-throw strike-slip faults in basement, petroleum accumulates within the flower-like fracture systems controlled by the strike-slip faults and is distributed no more than 2 km from the flower-like fractures. The upward channels of hydrocarbon in the compressional basins are the thrust faults between obduction-type orogenic belts and the basins, and the hydrocarbon reservoirs are formed in the vicinity of the thrust faults. Chemical sedimentary formation and oil zones are formed after the differentiation of hydrocarbon hydrothermal fluid entering the faulted basins, and the oil zones will further convert into petroleum asphalt due to hydration and oxidation. Petroleum asphalt undergoing burial and pyrolysis will convert into coal seam. Hydrocarbon entering the bottom of oceans and tundras will change into natural gas hydrates under appropriate temperature and pressure. Oceanic hydrothermal vents, oceanic and terrestrial mud volcanoes are the windows of modern earth’s degassing. Basins and reservoirs are receiving the deep oil and gas supplies Related Articles | Metrics