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01 January 2019, Volume 39 Issue 5 Previous Issue    Next Issue

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Cenozoic Tectonic Deformation Time Sequence and Its Geological Significance in Kekeya Anticline LING Dongming1,2, HAN Yaozu2, BAI Jianpu2 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180501 Abstract ( 95 )   PDF (300KB) ( 291 )   Save Based on the high-resolution 3D seismic data and taking the structure forward modeling and growth strata analysis as constraint conditions, this paper redefines the structural deformation time sequence of the Kekeya anticline. The results show that Kekeya anticline underwent three periods of tectonic activity superpositions, namely Late Miocene, Early Pleistocene and Middle-Late Pleistocene during Cenozoic. The period of Late Miocene was characterized by horizontal overriding, during which a large number of low-angle faults were formed in the Kalatar formation. The Kekeya anticle was located at the lower structural positions in Early Pleistocene and was characterized by receiving deposits; the period of Middle-Late Pleistocene was characterized by high-speed vertical uplifting, during which a large number of high-angle adjusting faults occurred in the core of the anticline, resulting in the uplifting of the Pleistocene thick sediments at the lower positions to the higher positions of the anticline and the forming of the current structural shapes. With the new structure development pattern, several sets of superimposed fault blocks of high-quality reservoirs are found in the core and northern flank of Kekeya anticline. The superposition of multistage faults can effectively improve the physical properties of local reservoirs, and promote oil and gas migration and accumulation into the Kalatar formation, which deepens the understanding of Kekeya condensate reservoirs and provides new targets for further exploration and development Related Articles | Metrics

Diagenesis of Middle Permian Carbonate Rocks in Bijie Area, Northwestern Guizhou LAN Yefang1, HUANG Shuguang2, REN Shuming1, ZHOU Ruxian1 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180502 Abstract ( 89 )   PDF (300KB) ( 54 )   Save Carbonate rocks are well developed and exposed in the Middle Permian Xixia formation and Maokou formation in Bijie area, northwestern Guizhou. Based on field geological section observation and measurement, thin section identification, cathodoluminescence and carbon and oxygen isotope analysis, and combined with the regional background and previous research, the paper summarizes 3 diagenetic characteristics of the Middle Permian carbonate rocks in Bijie area. The first is that limestone and dolomitic limestone with grained textures are mainly developed in the Middle Permian, the rock samples from the stratum exhibit non-luminescence to weak luminescence with the carbon isotope ratio ranging from 1.2‰ to 4.6‰, indicating that the rocks weren’t significantly influenced by meteoric freshwater; the second is that the Middle Permian carbonate rocks suffered from strong diagenesis, and many types of diagenesis such as lithification of micrite under marine phreatic environment, cementation of rimmed, equal-thickness and horse tooth-like calcite under marine vadose environment, equiaxial granulous—blocky cementation and syntaxial overgrowth of calcite under fresh-water vadose and phreatic environments, silicification, dolomitization and dolomite dissolution, rupturing and compaction and pressure dissolution etc. are found and the corresponding diagenetic evolution sequences are established; the third is that silicification and dolomitization may be influenced by local special thermal events, but the influencing degree needs to be studied further. Related Articles | Metrics

Diagenetic Facies Characteristics of Chang 63 Reservoir in Huaqing Oilfield, Ordos Basin LI Pan1, SUN Wei1, LI Changzheng2 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180503 Abstract ( 81 )   PDF (300KB) ( 143 )   Save Exploration and development of Chang 63 reservoir of Yanchang formation in Huaqing oilfield, Ordos Basin has been challenged by strong heterogeneity and complicated microscopic pore structures. Based on the data of cast thin section, SEM, high-pressure mercury injection and constant-rate mercury injection experiments, the paper studies different diagenetic facies and the pore structures of Chang 63 reservoir in Huaqing oilfield. Moreover, logging responses of different diagenetic facies are summarized by combining with production test data. The results show that the throats of the reservoirs of chlorite cementation-intergranular pore facies and illite + chlorite cementation-intergranular pore facies are best developed; the pore throat radius of the reservoirs of illite cementation-intergranular pore facies and illite + chlorite cementation-corrosion facies are relatively small and the reservoir connectivity is poor to medium; the pore structures of tight reservoirs of illite cementation-corrosion facies, illite cementation facies and carbonate cementation facies are poorly developed. Different diagenetic facies have different microscopic pore structure characteristics. Throat radius is the major factor influencing reservoir flowing and storage capacity. The distribution of high quality diagenetic facies is influenced by sedimentary facies, diagenesis and microscopic pore throat characteristics Related Articles | Metrics

Channel Architecture Element and Its controls on Hydrocarbon Accumulation: A Case Study from Chang-8 Member in Huaqing Area, Ordos Basin XIAO Zhenglu1a, CHEN Shijia1, LIAO Jianbo2, LI Yong1a, WANG Pan1a, DING Zhengang1a 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180504 Abstract ( 65 )   PDF (300KB) ( 153 )   Save The oil-water differential accumulation in the Chang-8 member in Huaqing area of the Ordos basin is the primary problem that has constrained the further development and deployment of the oilfield for a long time. The sand bodies in the underwater distributary channel are the dominant oil reservoirs in Huaqing area, and the fine description for the underwater distributary channel is conducive to solving the complex problems on oil and water accumulation. Based on the concepts and knowledge of channel architecture, the paper selected the typical rock samples of river main body and flanks of the Chang-8 member in Huaqing area, and performed microscopic identification and statistic analysis on lithology and microcapillary mercury injection data. The results reveals the physical properties and pore structures of the main channel sand bodies are far better than those of channel flanks; under the same conditions the main channel sand bodies are more favorable for crude oil charging, channel flanks make reservoir’s heterogeneity strengthened, which influences the differential distribution of oil and water. Based on the establishment of sand body profile and reservoir model, the composite channel sand bodies can be classified into 4 types. The thickness of the main channel sand body is an important index to determine the scale of a reservoir, and the size of the sand body determines the migration and accumulation of crude oil. Limited crude oil migrated along the large-scale channel sand bodies and accumulated at pinchouts or the higher positions of structures Related Articles | Metrics

Unconformity between Lower Ordovician and Overlying Strata in Tarim Basin ZHAO Zhixin, WU Meizhen, LAI Jingrong 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180505 Abstract ( 102 )   PDF (300KB) ( 220 )   Save There are different views on the geological ages and scales of the unconformities within the Ordovician strata in Tarim basin. The Yingshan formation is the key hydrocarbon exploration target in the Ordovician strata of Tarim basin, but up to now, researchers still consider that the Yingshan formation should be classified into the Middle-Lower Ordovician, so the unconformity within the Ordovician strata should be the unconformity between the Middle-Lower Ordovician and the overlying strata in Tarim basin. Based on the study of conodont fossils, the author considers that the largest unconformity within the Ordovician strata in Tarim basin initiated from the late of Early Ordovician and is widely distributed across the basin, which exists between the Yingshan formation and the overlying strata in platform area and is found within Xiangguletage formation in the profile of Kuluketage outcrop in the slope area Related Articles | Metrics

Characteristics and Formation Mechanism of Jurassic Microcrystalline Quartz Coating in Qikou Sag ZHANG Shunli1, LYU Zhengxiang1, XIONG Chenhao1, JI Ping2, QI Yumin3 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180506 Abstract ( 72 )   PDF (300KB) ( 172 )   Save Authigenic microcrystalline quartz coating and quartz secondary overgrowth are the most important authigenic minerals in the Jurassic sandstones of the Qikou sag, Bohai Bay basin. Primary pores related to microcrystalline quartz are well developed in the reservoir with deep burial depth. Based on the analysis of thin section, SEM, cathode luminescence, electronic probe and X-ray diffraction, the paper studies the source, growth pattern and formation mechanism of microcrystalline quartz coating, protection of primary intergranular pores and inhibitory mechanism of quartz secondary overgrowth in the study area, and verifies the diagenetic evolution sequence of the authigenic microcrystalline quartz coating sandstone. The microcrystalline quartz formed in early time, grew parallel to host grains and could rotate arbitrarily along the C axis. The associated primary pores are well developed. The analysis of the genesis of the authigenic microcrystalline quartz coating and its diagenetic evolution sequence is of great significance for the research on forming mechanisms of high-quality deep and ultra-deep reservoirs and petroleum exploration and development in Bohai Bay basin Related Articles | Metrics

Characteristics of Fluvial Sedimentary Sequences of Guantao Formation in the Southern Gentle Slope Belt, Huanghekou Sag CHEN Rongtao, NIU Chengmin, WANG Qingbin, YANG Bo, WANG Feilong, WANG Jun 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180507 Abstract ( 51 )   PDF (300KB) ( 164 )   Save Guantao formation in Huanghekou sag is dominated by braided-river deposits and is lack of mudstone cap rocks, enough attention has not been paid to the exploration in the formation. Based on the comprehensive analysis on the data of core, logging and seismic, it is considered that the braided-river deposits and meandering river deposits are developed in the southern slope belt of Huanghekou sag. Using the sequence stratigraphy analysis method, the paper establishes a sequence stratigraphic framework for the Guantao formation in the study area, and classifies two 3-order sequences, namely SQG2 and SQG1, each of which contains a high accommodation system tract (HAST) and a low accommodation system tract (LAST). Based on which, the paper summarizes the characteristics of the sedimentary sequence evolution of Guantao formation in the study area. The study area was dominated by braided river deposits which mainly contained multi-period composite braided river sandbodies during the development of the low accommodation system tract of SQG2; during the development of the high accommodation system tract of SQG2, the study area was dominated by meandering river deposits which mainly contained isolated point-bar sandbodies and a high proportion of flood plain mud. The evolution characteristics of SQG1 sequence was similar to that of the lower Guantao formation. During the development of SQG1 sequence, the accommodation maintained a high level, so the grain size and sandstone percentage of the sandbodies in SQG1 were lower than those of Guantao formation. The 2 sets of meandering river deposits in Guantao formation of the southern gentle slope belt in Huanghekou sag can be the good cap rocks and provide good conditions for oil and gas accumulation. Guided by the study, oil and gas have been discovered successively in the study area Related Articles | Metrics

Pore Structure and Its Fractal Features of the Shale in Taiyuan Formation of Linxing Area, Ordos Basin WU Hongchen1,2, HE Jinxian1,2, ZHANG Xiaoli1, REN Zeqiang1, ZHOU Taotao1, WANG Aikuan1 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180508 Abstract ( 67 )   PDF (300KB) ( 114 )   Save The material composition of the shale of Taiyuan formation in Linxing area, Ordos basin is studied through the analysis of organic geochemistry and X-ray diffraction. The paper uses high-pressure mercury injection method to discuss pore size distribution of the shale, and analyzes mercury injection data with fractal theory to discuss the its pore heterogeneity. The results show that the TOC of the shale is 1.59%~22.58%, averaging 2.77%; the contents of brittle minerals ranges from 21.92% to 74.45%, averaging 44.55%; the contents of clay minerals ranges from 19.43% to 78.08%, averaging 52.70%. According to the result of mercury injection experiments, it is found that the pore size distribution in partial shale samples has a feature of “double peaks” , among which the larger main peak corresponds to micron-sized cracks and the smaller main peak corresponds to macropores and mesopores, while partial samples only have the main peak corresponding to cracks. Based on the matching results, fractal dimension of the pores can be divided into 2 sections, one section corresponds to micron-sized cracks with the fractal dimension ranging from 2.326 2 to 2.610 3 and the other corresponds to nano-pores such as macropores and mesopores with the fractal dimension ranging from 2.704 1 to 3.697 1. In the shale of Taiyuan formation, nanopores act as the main reservoir spaces of adsorbed gas while micro-sized cracks act as the main reservoir spaces of free gas and flowing passages. The shale samples with high content of clay minerals and low content of brittle minerals have larger fractal dimension and stronger absorption capacity to methane, which means that fracturing operation will be more difficult. Related Articles | Metrics

Genesis and Sweet Spot Prediction of Jurassic Tight Sandstone Reservoir in Central Sichuan Basin ZOU Juan1, LE Yuan1, JIN Tao1, LI Xiuqing1, LI Xuesong2, WEI Tengqiang1 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180509 Abstract ( 72 )   PDF (300KB) ( 204 )   Save The reservoirs of Jurassic Lianggaoshan formation and Sha-1 member of Shaximiao formation in Sichuan basin are typical extra-low porosity and extra-low permeability reservoirs with strong heterogeneity and great difficulties to predict sweet spots. To predict the favorable areas of sweet spot, the paper studies the reservoir characteristics and its forming mechanism based on the analysis of core, thin section, SEM, X-ray diffraction and inclusion. The study results show that the Jurassic tight sandstone reservoirs are the products of the dissolution of facies-controlled sandbodies during the middle diagenetic period in the Sichuan basin and the structural fractures formed in the middle and late periods can improve the reservoir capability. The sweet spots in the reservoirs are controlled by sedimentary sandbody, diagenetic dissolution and structural fractures, and mainly distributed in the areas where microfacies such as beach bar, distributary channel and river mouth bar, hydrocarbon charging phases and fractures superimpose with each other. The sweet spots of Lianggaoshan formation are mainly found in the areas of Gongshanmiao, Longgang-Yingshan, Lianchi-Chongxi etc.; and the sweet spots of Sha-1 member are mainly distributed in the areas of Gongshanmiao, Wellblock Longgang-9, Shuijiacao and Dacheng-Guang’an etc Related Articles | Metrics

Formation Mechanism of Carbonate Cement in Tight Sandstone: A Case from the Sandstone of Shaximiao Formation in the Piedmont of Longmen Mountain in Middle Section of Western Sichuan Depression YANG Yongjian, ZHANG Shihua, YANG Yingtao, ZHu Li, YAN Lini, ZHANG Ling 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180510 Abstract ( 59 )   PDF (300KB) ( 90 )   Save Carbonate cement is the most important cement in the reservoir of the Middle Jurassic Shaximiao formation in the western Sichuan depression and is also one of the key factors of reservoir densification. Carbonate cement is very developed in the piedmont of Longmen mountain and its average content is about 12% in the area. Taking the sandstone of Shaximiao formation in the piedmont of Longmen mountain as the research object, the paper studies the formation mechanism of the carbonate cement based on the microscopic observation on samples and the analysis of carbon and oxygen isotopes in the carbonate cement and electronic probe. The study shows that the carbonate cement in Shaximiao formation in the area is dominated by intergrown and microcrystalline calcites with the δ13CPDB of -7.69‰~-2.13‰ and the δ18OPDB ranging from -15.34‰ to -9.60‰. The inorganic carbon acts as the main source of the carbonate cement. The cement formed at the temperature of 56.1~101.3 ℃, indicating an early diagenesis stage. Relatively low FeO and MnO contents in the intergrown calcites and relatively high FeO and MnO contents in a few microcrystalline calcites indicate that the carbonate cement was mainly formed at the early diagenesis stage. There are also some calcite cements developed at the late diagenesis stage whose formation is related to Fe and Mn rich fluids in the deep strata Related Articles | Metrics

Logging Evaluation of Advantageous Lithology of Metamorphic Reservoir in Moliqing Fault Depression, Yitong Basin BAI Songtao1,2, YU Limin3, AN Jixing1, WAN Jinbin1, LI Yang1, XU Siyong1, JIN Xiaohui1 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180511 Abstract ( 68 )   PDF (300KB) ( 173 )   Save Based on the observation of cores obtained from the basement metamorphic rocks in Moliqing fault depression, Yitong basin and guided by geological understandings, the paper uses the conventional logging and FMI logging data to systematically summarize the logging responses and its validity identification method of the lithologies of the 4 types of metamorphic rocks in the area. Effective identification is conducted by using porosity logging and FMI technologies and a method combined with multiple logging charts is proposed for the lithology identification of metamorphic rocks. The identification, calculation and validity analysis are performed for the fractures in the metamorphic reservoir by using FMI and NMR logging technologies, and finally the advantageous lithofacies of the metamorphic rocks are determined in the study area. Logging data from many wells in the study area are evaluated and relatively good results have been obtained, which provides technical support for the exploration of the metamorphic rocks in the area Related Articles | Metrics

Study on Displacement Degree and Sweep Efficiency Variation of Water-Drive Reservoirs at High Water-Cut Stage XUE Jiangtanga, LIU Zhenb, XUE Longlonga, LIAO Huaweia, ZHANG Haixiaa, SHU Kuna 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180512 Abstract ( 100 )   PDF (300KB) ( 208 )   Save To accurately characterize the displacement degree and sweep efficiency variation of water-drive reservoir at high water-cut stage, a relationship among waterflooding displacement degree Ed, volumetric sweep efficiency Ev and water cut fw has been established based on previous researches about oil/water relative permeability variations at high water-cut stage, and the comparison of the method before and after the improvement has been conducted by taking Sanjianfang reservoir in Shanshan oilfield as an example. The results show that when the reservoir enters the high water cut stage, the fw vs. Ed curve goes from an up-concave shape to a down-concave shape and Ed changes faster with the change of the water cut ; the Ev vs. fw curve changes from a down-concave shape to an approximate flat shape and Ev changes more slowly with the change of the water cut. The variations of these parameters at the high water cut stage revealed by the study can reflect the underground status of the waterflooding, which is of great significance for the development performance prediction at high water-cut stage Related Articles | Metrics

Main Controlling Factors on Liquid Productivity Index for Polymer Flooding in Offshore Multi-Layered Heavy Oil Reservoirs WEI Zhijie1,2, KANG Xiaodong1,2, HE Chunbai1,2, ZHANG Jian1,2, SHENG Han3 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180513 Abstract ( 74 )   PDF (300KB) ( 199 )   Save To address the apparent decline of liquid productivity index during polymer flooding in some offshore heavy oil wells, a sophisticated mathematical model to predict productivity behavior in multi-layered reservoirs is established, then the main controlling factors on the variations of liquid productivity index of polymer flooding are studied. The results show that the productivity index after conversion into polymer flooding undergoes 4 phases — rise, decline, stabilization and rise again; the largest drop of the dimensionless liquid productivity index is significantly influenced by polymer viscosity, polymer injection timing and permeability ratio, and the trough timing is highly impacted by crude oil viscosity, permeability ratio, relative thickness of low-permeability zone and absorption capacity. Based on which formulas to calculate the largest drop of dimensionless liquid productivity index and trough timing are proposed. Under the typical polymer flooding conditions in offshore oilfields, the average largest drop of liquid productivity index is 53.1%, and the average cumulative injection pore volume corresponding to the trough timing is 0.250 PV. The research results are of guiding significance for the liquid productivity index prediction, program design and adjustment for polymer flooding. Related Articles | Metrics

Reservoir Pore Types and Flowing Characteristics of Oil Displacement by Water in the Chang-8 Member of Zhenbei Oilfield, Ordos Basin HUI Wei1,2,3, LIU Yicang2, WANG Lianguo2, HOU Changbing2, REN Dazhong3 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180514 Abstract ( 74 )   PDF (300KB) ( 104 )   Save Regarding the complex microscopic pore structures and the weak understanding on water flooding regularity, the paper studies the microscopic pore structures and the flowing characteristics of oil displacement by water in the reservoir of the Chang-8 member by using sandstone waterflooding model, cast thin section and SEM analysis in Zhenbei oilfield, Ordos basin. The results show that the accumulation spaces of the Chang-8 reservoir in the study area can be divided into residual intergranular pores, dissolved pores and microcracks; the displacement types are dominated by network displacement and finger-like displacement and even displacement seldom occurs. Different types of waterflooding have different displacement efficiencies, the efficiency of even displacement is the highest and that of finger-like displacement is the lowest. The waterflooding efficiency highly correlates with the permeability with the correlation coefficient of 0.84 and the correlation coefficient between the waterflooding efficiency and porosity is 0.51. Reservoir heterogeneity is also an important factor influencing the waterflooding efficiency. Related Articles | Metrics

Well Test Interpretation Model for Deviated Wells in Tri-Porosity-Media and Homogeneous Composite Carbonate Gas Reservoirs MENG Fankun1, LEI Qun1, HE Dongbo1, YAN Haijun1, DENG Hui2, XU Wei2 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180515 Abstract ( 59 )   PDF (300KB) ( 134 )   Save In the deviated wells drilled in the carbonate gas reservoirs in Gaoshiti—Moxi area, because fractures and karst caves are developed in the near wellbore areas and matrix is extensively distributed in the areas far from wellbore, the paper comprehensively uses the methods of Laplace transformation, Fourier transformation and inverse transformation, and point-source function combination, takes the influences of wellbore storage coefficient and skin factor into consideration, establishes a well test model for deviated wells in tri-porosity-media and homogeneous composite gas reservoirs and uses Stehfest numerical inversion method to obtain the solution of the model. Compared with the solution obtained from a well test model for vertical wells in tri-porosity-media and homogeneous composite gas reservoirs, the validity of the established model is verified. Based on the classified flowing phases, the influences of wellbore storage coefficient, skin factor, interporosity flow coefficient, inner zone radius and hole deviation angle on well test curves are analyzed. A typical well test curve can be divided into 7 phases, the increase of wellbore storage coefficient will cover up the influence of well deviation on the curve, interporosity flow coefficient will bring impact to the appearance of channeling phase and the inner zone radius can determine the time of pressure arriving at the interface between the inner and out zones. When the hole deviation angle is lower than 50°, skin factor will decrease with the increase of the deviation angle and the well test curves will have the same characteristics; when the hole deviation angle is higher than 50°, obvious radial flow in the vertical direction will occur. Related Articles | Metrics

A New Method for Logging-Seismic Sequence Interpretation of Underwater Progradation Complex in Sandy Conglomerate Fan Deltas WANG Jian1, QU Yongqiang2, PAN Jianguo2, YIN Lu2, XU Duonian2, TENG Tuanyu2 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180516 Abstract ( 67 )   PDF (300KB) ( 134 )   Save In order to detailedly characterize the reservoirs in fan deltas and improve the success rate of hydrocarbon exploration, and taking the first and the second members of the Triassic Baikouquan formation on the western slope of the Mahu sag, Junggar basin as examples, the paper proposes a new method for logging-seismic sequence interpretation aiming at discovering the favorable underwater reservoirs in delta fan front. The fine description of the distribution of ancient grooves is carried out for the first and the second members of the Baikouquan formation by using a new method of ancient landform restoration. The logging data and stratigraphic dip are used to judge and characterize the paleocurrent directions. A totally new seismic interpretation model combined with logging-seismic combination technology is applied to find progradation complexes along river flowing directions in ancient grooves. Meanwhile, the favorable underwater reservoirs in the study area are identified by using lake shoreline determination method. The study shows that the fan-delta-front progradation on the slope belt is commonly found, especially in the ancient grooves. Based on the data analysis of seismic inversion, actual core measurement, logging interpretation, NMR, production test and post-drilling evaluation, it has been proved that the new model of progradation complex is reasonable Related Articles | Metrics

A Rock Static Brittleness Index Calculation Method Considering Burial Depth Correction: A Case Study of Permian Lucaogou Formation in Jimsar Sag LI Guoxing1, MAO Rui2, WANG Zhenlin2, MU Liwei2 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180517 Abstract ( 77 )   PDF (300KB) ( 178 )   Save Based on the data of dynamic and static rock mechanics experiments and other supporting experiments, the ratio of Young’s modulus to Poisson’s ratio is preferred as the method to characterize the static brittleness index, a dynamicstatic brittleness index conversion model based on porosity and clay content is established and the static brittleness index can be calculated. Finally, the influence of burial depth on brittleness indexes is studied, burial depth correction is performed, and then a relatively sophisticated rock static brittleness calculation method considering burial depth correction is established on the basis of logging data. The calculation results of the rock brittleness are consistent with the results of core static brittleness experiment in the study area, and the method has been widely used in production Related Articles | Metrics

Lower Limits of Physical Properties of Jurassic Tight Sandstone Reservoirs in Block 4 of Central Junggar Basin WANG Jiandong1a, WANG Chang2, CAO Haifang1a, LI Jing2, MA Ji1b, ZHENG Jinkai2 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180518 Abstract ( 44 )   PDF (300KB) ( 129 )   Save Taking the tight sandstone reservoir of Middle Jurassic Toutunhe formation in Block 4 of central Junggar basin as an example, and based on the data of logging interpretation and formation testing, the lower limits of effective reservoir physical properties in the study area are determined by comprehensive consideration of empirical statistical method, distribution function curve method, formation test method, porositypermeability method, positiveinverse cumulative method and mud content method. The study results show that the lower limit of effective reservoir porosity is 4.52%, the lower limit of permeability is 0.14 mD; the porosity and permeability exhibit a relation of power function and the lower limits of the effective reservoir physical properties decrease with the increase of depth. The weighted average algorithm of the reliabilities of all the methods is used to determine the lower limits of effective reservoir physical properties, which can effectively avoid the randomness and uncertainty of a single method Related Articles | Metrics

Prediction of Cave Filling Degree in Ordovician Carbonate Reservoirs Based on BP Neural Network in Lungu Oilfield, Tarim Basin YU Congling1a, CAI Zhongxian1, YANG Haijun2, ZHU Yongfeng2, WANG Hui1 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180519 Abstract ( 74 )   PDF (300KB) ( 182 )   Save In order to predict the filling performance of caves in carbonate reservoirs, using the feature that the BP neural network can realize the linear mapping between input and output targets, and based on the detailed characterization of underground river network, ancient landform, ancient drainage system and passageways of underground river, the paper classifies the underground rivers, uses the data of logging, 3D seismic and cores to describe the cave filling degree penetrated by a single well, and predicts the filling degree of the underground river in Lungu oilfield by combining with the correspondence relationship between the cave filling degree and through-well underground river. The dissection of the underground rivers in the study area shows that there are 6 factors which can control the filling degree of the underground river such as the level and type of underground river, cave type, the relationship with the underground river passageways, the relationship with hall-like caves and cave collapse. Using the 6 factors as the input parameters, a prediction model is established for the underground river filling degree. The prediction results show that the relative error is about 10% by using the BP neural network to predict the underground river filling degree. The method can be applied in the evaluation of caved carbonate reservoirs Related Articles | Metrics

Development Methods of Aryskum Oilfield with Large Gas Cap, Thin Oil Rim and Edge/Bottom Water LIU Wangdong, YANG Zhigang, Aini MAIMAITI, LU Zhiming, XU Jialong 2018, 39 (5):  1-1.  doi: 10.7657/XJPG20180520 Abstract ( 116 )   PDF (300KB) ( 260 )   Save Aryskum oilfield is a complicated oil and gas reservoir with large gas cap, thin oil rim and edge/bottom water. To determine the rational development method for this reservoir, based on extensive investigations of development methods for analogous reservoirs both at home and abroad, the author adopted the method of gas injection into the gas cap and barrier waterflooding to avoid gas channeling and water encroachment. Horizontal well was adopted to develop the thin oil rims and the well patterns were perfected for progressive and extensional development in the south and north of the oilfield. After implementation, the gas channeling in the gas cap has been effectively controlled and the formation pressure has been maintained and kept rising steadily, while the oil production of the oilfield increased year by year. Therefore, the method has been determined as the effective development method for such complicated oil and gas reservoirs Related Articles | Metrics