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01 January 2019, Volume 37 Issue 6 Previous Issue    Next Issue

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Depositional Characteristics and Hydrocarbon Exploration Significance of Shallow-Water Deltas : A Case Study of Upper Sha-1 Member in Chaheji Structural Belt of Baxian Sag, Bohai Bay Basin LYU Chuanbing1,2CHENG Tongran1ZHANG Feng2JI Youliang1LIANG Guanzhong2LI Yanguo2 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160601 Abstract ( 121 )   PDF (2063KB) ( 280 )   Save Reservoirs of shallow-water delta facies are the dominant oil and gas reservoirs in the upper Sha-1 member of Shahejie formation in Chaheji structural belt of Baxian sag in Jizhong depression, Bohai Bay basin. Based on the analyses of petrological feature, sedimentary structural characteristics, grain sizes and fossils, the paper studies the sedimentary characteristics and sedimentary facies distribution of shallow-water delta systematically, summarizes the depositional model of shallow-water delta and describes the favorable accumulation conditions of shallow-water delta. The study results show that in the upper Sha-1 member, the distributary channel of shallow-water delta is well developed, river mouth bar does not occur and large-area sheet sands are extensively distributed. The cyclic variations of lake level result in sandstone interbedded with mud at multi-stages, which is the main controlling factor of sand body distribution. The sedimentary characteristics of shallow-water delta could determine that in this facies there exist pretty good reservoir-caprock assemblages and various traps are then formed due to faulting to sandbodies. The upper Sha-1 member in Chaheji structural belt has good oil and gas accumulation conditions Related Articles | Metrics

Gas-Controlling Characteristics of Structural and Hydrogeological Factors in Xishanyao Formation of Western Fukang Block, Junggar Basin LI Sheng1,2, GE Yanyan1,2, YANG Xuesong2,3, LI Xin4, FU Xuehai4 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160602 Abstract ( 72 )   PDF (2646KB) ( 187 )   Save In order to understand the geological gas-controlling functions in the coalbeds of the Middle Jurassic Xishanyao formation in western Fukang block, Junggar basin, the block is divided into 2 structural units according to the regional hydrogeological boundary--Chigang reverse fault and CBM-rich units are classified based on methane weathering zone and hydrogeological conditions. Based on the analysis of structural and hydrogeological features, the paper discusses the coupled structural-hydrogeological gas-controlling mechanism. The study results show that the enrichment of CBM in the Xishanyao formation of western Fukang block should be the product of the coupled functions of structure and hydrogeology conditions. Tectonic movements resulted in dynamic metamorphism and plutonic metamorphism in coalbeds, which are helpful for the generation of thermogenic gas; the sealed folds and thrust faults resulted from horizontal compression in the late Yanshan movement and Himalayan movement contributed to CBM preservation, whereas the tectonic uplift in the early Yanshan movement was not conductive to primary biogenic gas preservation; CBM accumulation by hydraulic seal occurred due to the lateral charging of groundwater into the stagnation areas with high salinity. CBM losses in the coalbeds with the burial depth lower than 600 m in the middle-upper Xishanyao formation were caused by tectonic uplift, relatively strong seasonal runoff and evaporation. Meanwhile, high-salinity formation water due to arid climate restrained the generation of secondary biogenic gas, resulting in the low content of CBM Related Articles | Metrics

Formation Mechanism and Evolution Characteristics of Ultra-High Pressure in Lucaogou Formation of Jimsar Sag, Junggar Basin LAI Ren, ZHA Ming, GAO Changhai, QU Jiangxiu, DING Xiujian 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160603 Abstract ( 91 )   PDF (2016KB) ( 285 )   Save Ultra-high pressure generally occurs in the Middle Permian Lucaogou formation of Jimusar sag, Junggar basin. This paper analyzes the present formation pressure features and the ultra-high pressure formation mechanism and reconstructs the paleopressure evolution of Lucaogou formation by using logging, drilling, formation testing data combined with basin modeling technology. The study results show that the present pressure structure can be categorized into four zones from top to bottom such as normal pressure zone, shallow ultra-high pressure zone, transitional zone and deep ultra-high pressure zone. Lucaogou formation is located in the deep ultra-high pressure zone which is continuous laterally. Most residual pressures range from 10 to 20 MPa and the pressure coefficient is 1.10~1.50. The paleopressure evolution of Lucaogou formation experiences three and a half cycles of pressurization—decompression and there is a good matching relationship among the pressure cycle, sedimentation rate, hydrocarbon generation and expulsion and tectonic uplifting. Undercompaction resulted from the rapid burial of sediments is the main reason causing the first stage of ultra-high pressure. After reaching the hydrocarbon generation threshold in Late Triassic, hydrocarbon-generating pressurization was the key mechanism for the second and third stages of ultra-high pressure Related Articles | Metrics

Analysis of Mesozoic Prototype Basin in Kuqa Depression, Tarim Basin YU Haibo1,2QI Jiafu1YANG Xianzhang3SUN Tong1LIU Qiyao3CAO Shujuan3 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160604 Abstract ( 102 )   PDF (6658KB) ( 385 )   Save Using the data of seismic, surface outcrop, drilling, logging and non-seismic geophysics, the paper investigates the basin structure, tectonic style and regional tectonic evolution of Mesozoic strata in Kuqa depression, Tarim basin. Stratum trend thickness method is adopted to calculate the Mesozoic denudation thickness and the genesis of the Mesozoic prototype basin is analyzed in Kuqa depression with sedimentary data. The residual Mesozoic strata in Kuqa depression are generally of a geologic framework characterized by thick in the north and thin in the south, denudating in the north and overlapping in the south, strong angular unconformity developed on the Hercynian fold belt of the southern Tianshan Mountain in the north and slight angular unconformity distributed on the Cambrian-Ordovician series. The Mesozoic prototype basin in Kuqa depression is a down-wrapped basin overlying the Hercynian orogenic belt of the southern Tianshan Mountain and the transitional zone at the margin of Tarim craton. The isostasy may provide the main force for the subsidence of the basin. The Hercynian movement resulted in the uplift of the southern Tianshan folds. Strong volcanism occurred in Tarim craton and southern Tianshan Mountain during the early Permian allowed the formation of proto-Kuqa depression basin on the basin-mountain transitional zone. The balanced subsidence of the earthcrust started in Triassic period, the orogenic belt collapsed and the depression basin was developed on the basin-mountain transitional zone. The successive development of the depression occured in Jurassic and Cretaceous, but the basin axis, sedimentation and depositional center slightly migrated and the regional uplift-denudation occurred in the Late Cretaceous Related Articles | Metrics

Influence of Abnormal Thermal Effect on Carbon Isotope Characteristics of N-Alkanes in Crude Oil: A Case from Tarim Basin LI Di1ZHENG Zhaoyang1WANG Yu2ZHOU Wenxi1SU Jin2CAI Yuwen2 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160605 Abstract ( 75 )   PDF (1898KB) ( 90 )   Save Analysis on n-alkane carbon isotope curves of oil is an important method for oil-oil and oil-source correlation. The study shows that n-alkane carbon isotope curves tend to be changed due to several secondary actions. Mantle plume event in Permian reformed the oil accumulation conditions, meanwhile the associated abnormal thermal effect brought significant influences to geochemical features and physical-chemical properties of the oil in Tarim basin. Based on the evidences of abnormal thermal effect in Well TZ421, TD2, ZS1(ZS1c) and TZ62 and the analysis of the changes of n-alkane carbon isotope curves of the oil in these wells, it is found that the curves record various abnormal thermal events occurred in Tarim basin and could reflect the reformation of the original carbon isotope characteristics of oil. Through the analysis on the changed n-alkane carbon isotope characteristics caused by abnormal thermal effects, 3 characteristics can be identified, which reflects their differential reformations caused by thermal effects of hydrothermal solution and magma, sulfate thermochemical reduction reaction and thermal alteration, respectively, and reveals the influences of different thermal effects on n-alkane free-carbon isotope fractionation. Using n-alkane carbon isotope characteristics as the basis for marine end-member oil division should be carefully considered in Tarim basin Related Articles | Metrics

Karst Paleogeomorphology and Development Model of Karst Fracture-Cave Bodies of Ordovician in Halahatang Sag ZHANG Qingyu1,2, LIANG Bin2, QIN Fengrui2, CHEN Lixin3, DAN Yong2, LI Jingrui2 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160606 Abstract ( 82 )   PDF (4308KB) ( 264 )   Save In view of different geological features of buried-hill weathering crust areas in the north and buried karst area in the south of Halahatang area in the northern Tarim basin, the Ordovician paleolandform and ancient drainage systems are restored using impression method and a combination method of paleostructure and residual impression. The karst fracture-cave body development characteristics and its formation mechanism are studied under 4 different paleo-landform environments, and 4 karst fracture-cave body development patterns are established such as buried-hill weathering crust zone, upper karst slope, lower karst slope and karst basin. The buried-hill weathering crust zone is dominated by surface-karst fracture-cave system; large fracture-cave bodies of Yijianfang formation-Yingshan formation and underground river channel systems mainly occur in the upper-karst slope; 2 sets of large fracture-cave bodies namely Liang-1-Liang-2 member and Yijianfang formation-Yingshan formation are developed on the lower karst slope; and karst fracture-cave bodies are distributed along faults in the karst basin Related Articles | Metrics

Geochemical Characteristics of Crude Oil and Oil-Source Correlation in Halahatang Sag LI Zhongxuan1, XU Zhiming1,WANG Zhaoming2, CHEN Yunchuan3, XIAO Zhongyao2 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160607 Abstract ( 100 )   PDF (1641KB) ( 204 )   Save The Halahatang sag in Tarim basin is abundant in petroleum resources with the proved reserves over one hundred million tons. In order to confirm the major source rocks of Ordovician reservoirs in Halahatang sag, systematic geochemical analyses are performed for oil samples from Well ZS1 and Halahatang sag and characteristics of light hydrocarbons and biomarkers are further studied. The results show that the Halahatang oil samples are characterized by high content of n-alkanes and poor content of aromatic hydrocarbons, which are similar to those of oil samples from Well ZS1, indicating the typical sapropelic origin. The aryl isoprenoid compounds detected in the oil samples from Halahatang sag are the markers for strong reducing sedimentary environment. Combined with the characteristics of source rocks and geological settings in Halahatang sag, it is considered that the marine oil in the study area mainly originates from the Cambrian to Lower Ordovician source rocks instead of the Middle to Upper Ordovician source rocks Related Articles | Metrics

Composition Characteristics and Geochemical Significance of Aromatic Hydrocarbon in Crude Oils in Eastern Wushi Sag, Beibu Gulf Basin HAO Xin1, REN Yongjun1, XU Xinde2, LIU Hongyan3, YANG Xibing2 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160608 Abstract ( 62 )   PDF (1640KB) ( 132 )   Save In order to identify the oil source, depositional environment, thermal maturity and possible source rocks of the oil in eastern Wushi sag of Beibu Gulf basin, chromatography and mess-spectrometric techniques are used to systematically analyze aromatic hydrocarbon compositions in oil samples. The results show that aromatic hydrocarbon in the oil of eastern Wushi sag is characterized by high content of aphthalene and phenanthrene series, low content of biphenyl, threefluorene and triaromaticsterane series. Compositions such as 1,2,5,6 methyl naphthalene, retene and triaromatic sterane indicate that the organic matters in the source rocks are of double contributions from both aquatic organisms and terrestrial higher plants and form in reduction and weak reduction-weak oxidation environments of fresh water-saline water lacustrine facies. Vitrinite reflectances obtained from methyldibenzothiophenes ratio and distribution index, methyl naphthalene ratio, methylphenanthrene index and distribution fraction respectively show that the crude oil belongs to moderate maturity oil. Based on the compositions of aromatic hydrocarbons in the oil, the oil in the study area can be divided into 3 subgroups of 2 types, which includes type Ⅰ oil originated from the source rocks of the upper and lower El2; type Ⅱ1 oil from the lower El2 and type Ⅱ2 oil from the lower El2 and possibly El3 Related Articles | Metrics

Characteristics of Palaeogene Hydrocarbon Source Rocks and Controls on Its Organic Matter Abundance in Liaozhong Sag HUANG Xuefeng1, WU Wei1, WANG Xing2, BAI Wanbei1 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160609 Abstract ( 58 )   PDF (3319KB) ( 129 )   Save According to the characteristics of geochemistry, petrology and sedimentology, the paper evaluates the organic matter-rich mudstones in the Paleogene Shahejie formation, Ed3 and the lower Ed2 from organic matter abundance, type and maturity, and analyzes their hydrocarbon potential, repectively. Meanwhile, the paper studies the controls of structural subsidence, sedimentary rate, dilutive effect and sedimentary facies on organic matter abundance. The result shows that the organic matter abundance of Es3 source rocks which is featured with rich algae, rapid subsidence and high ratio of mudstone thickness to gross thickness is relatively high in the southern and middle Liaozhong sag, moderate in the northern sag. The organic matters are mostly Type Ⅱ with large hydrocarbon potential. The source rocks of Es1 and Es2 developed during thermal subsidence stage have high-highest organic matter abundance with the organic matter of Type Ⅰ and Ⅱ, and being low mature-mature. The source rocks of Ed3 which was rapidly deposited during extensional rifting stge have relatively high organic matter abundance in the southern and middle Liaozhong sag, moderate in the northern sag. The organic matters are dominated by TypeⅡ1 and Ⅱ2, being immature-low mature. The dilutive effect of the lower Ed2 is obvious so that the organic matter abundance is not high, indicating the source rocks in the lower Ed2 being immature-low mature Related Articles | Metrics

Diagenetic Facies Classification of LowPorosity and LowPermeability Sandstones Based on Porosity Evolution Simulation: A Case Study from Permian Strata in Jinxi Flexure Belt,Ordos Basin CHEN Yulong, ZHANG Chong, NIE Xin, SHI Wenrui, LIU Jingqiang, GUO Jining 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160610 Abstract ( 42 )   PDF (1972KB) ( 103 )   Save The key to exploration of low?porosity and low?permeability reservoirs is to predict the reservoirs with relative good physical properties to find favorable petroliferous areas. In a certain sedimentary environment, diagenetic facies is the core factor controlling the physical properties of reservoirs. The diagenetic facies which can be used to classify petroliferous areas should consider the influence of diagenesis on pore spaces of reservoirs. Based on rock components, surface porosity and petrophysical properties and through porosity evolution simulation, porosity variations before and after diagenesis such as compaction, cementation and corrosion are simulated on the basis of primary porosity. Apparent compaction rate, apparent cementation rate and apparent corrosion rate are used to represent the construction and destroy degrees of pore spaces caused by diagenesis and the degrees could be digitalized. Based on the data of apparent compaction rate, apparent cementation rate and apparent corrosion rate, diagenesis can be divided into 3 types, namely strong, moderate and weak diagenesis. Based on the intensities of compaction, cementation and corrosion, diagenetic facies can be classified quantitatively. With this method, the Permian diagenetic facies in Jinxi flexure belt of Ordos basin are classified as strong cementation and strong corrosion facies,strong cementation and moderate corrosion facies and moderate cementation and moderate corrosion facies, which is in accordance with the results from thin section analysis Related Articles | Metrics

Study on Miscible CO2 Flooding Test in Strong Water-Sensitive Reservoirs in Sudert Oilfield CHENG Jiecheng1, JIANG Hongfu2, LEI Youzhong1, PANG Zhiqing1, WANG Yanyong1, AN Ping2 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160611 Abstract ( 74 )   PDF (662KB) ( 148 )   Save In view of the actual situations such as strong water sensitivity and poor water injection effect of the Lower Jurassic Hinggan reservoir in Sudert oil field, the Block B14 was selected for miscible CO2 flooding test in 2011. The obtained minimum miscible pressure of crude oil and CO2 is 16.6 MPa from slim tube test in laboratory, 1.0 MPa lower than the original formation pressure, which indicates that miscible CO2 flooding could be realized. The field test result shows after the implementation of miscible CO2 flooding, the injectivity and the oil production are significantly improved, the reservoir producing degree are increased and the structural high and artificial fracture strikes are the predominant directions; miscible CO2 flooding can replenish energy for strong water-sensitive reservoirs effectively, so it could be a new method to improve development effect and enhance oil recovery Related Articles | Metrics

Air Foam Flooding in Tight Reservoirs: Simulation Experiment and Application XU Darong, LI Xiangfang, LI Yuansheng, YU Pengliang, XIA Jun, JIANG Mingjie 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160612 Abstract ( 63 )   PDF (1325KB) ( 137 )   Save The original natural elastic energy of reservoirs are main energies for tight reservoir development and the ultimate recovery factor is generally less than 10%. Air foam flooding can replenish energy for tight reservoir development to improve the ultimate recovery factor. Based on experiments with single-barreled cores and double-barreled cores, the paper studies flow characteristics and displacement effect in tight reservoirs by air foam flooding, discusses the influences of different factors on the air foam flooding effect and concludes that the optimal gas-liquid ratio is 3:1 and the optimal size of foam liquid slug is 0.05 PV. The results show that the air foam flooding can obviously improve oil production and good water control effect can be gained. Taking 15 typical producers as examples, the average oil production per month is 198.1 t and 240.0 t before and after injection, respectively, and the oil production is increased by 21%; the average water cut is 28.8% and 28.9% before and after injection, respectively, and the water cut only increases by 0.1% Related Articles | Metrics

Physical Plugging Removal of Binary Combination Flooding in Conglomerate Reservoirs in Karamay: Experimental Study and Application LYU JianrongaSUN NanbNIE ZhenrongaLIU WentaoaZHOU Yuhuia 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160613 Abstract ( 67 )   PDF (2211KB) ( 124 )   Save Regarding the problems of poorer experiment effect than the designed one due to plugging in deep layers at the initial binary combination injection stage into the conglomerate reservoirs in the lower Karamay formation in District Qizhong of Karamay oilfield, Xinjiang, the microscopic distribution and genesis of the plugging are studied using electron-probe X-ray microanalyzer. The result shows that the binary combination system with excessive molecular weight and mass concentration matches poorly with the reservoir and mainly occurs in complex pores and pore throat where clay minerals accumulate, which results in poor physical properties of the conglomerate reservoir and poor mobility during the oil displacement process. Large amount of kaolinite in the conglomerate reservoir tends to drop off at relatively high injection rate and reacts with the injected binary combination system, resulting in the plugging of reservoir pores. Based on the above understanding, experimental study on physical plugging removal is carried out. Typical natural cores with different physical properties are selected, and binary combination systems with high, moderate and low molecular weights and mass concentrations are injected in to the cores. Resistance coefficient and residual resistance coefficient are calculated under steady pressure and then the mobility could be determined. The result shows that physical plugging removal in the conglomerate reservoir has a permeability limit that the plugging in moderate and high permeability reservoirs (>50 mD) could be effectively relieved by gradually decreasing the molar weight and mass concentration of the binary combination system, but it doesn’t work for the plugging in low permeability reservoirs (<50 mD) . After field formula adjustment, injection pressure decreases steadily, liquid production increases and plugging is effectively relieved. It is predicted that the binary combination flooding in the conglomerate reservoir could improve recovery factor by 15% in the study area Related Articles | Metrics

A Method for Full-Cycle Alternative Injection-Production Performance Evaluation of Hutubi Underground Gas Storage CHEN Chao, PANG Jing, LI Daoqing, CUI Guoqiang, YAN Liheng 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160614 Abstract ( 125 )   PDF (1708KB) ( 274 )   Save An underground gas storage (USG) has two functions of seasonal peak shaving and strategic energy storage with gas wells acting as both injectors and producers. Compared with gas production process, high-pressure gas injection is more risky and there is no available performance evaluation method. Evaluation of gas injection performance is one of the core technology to guarantee the safe operation of USG and the evaluation accuracy will directly affect the capacity and peak shaving ability of gas storage. Based on the alternative injection-production operation law and by means of unsteady gas production analysis method, the paper presents a flow model suitable for gas injection of Hutubi USG, establishes 2 dimensionless gas-injection analysis charts and a dynamic matching method through a series of mathematical transformation, then puts parameters such as gas injection radius, skin factor and permeability etc. obtained from the unsteady gas injection analysis into the unsteady gas injection equation to realize full-cycle injection-production history matching for single wells, and finally performs well pressure prediction according to the actual situations of emergency peak shaving and surface facilities. The practice shows that the method could realize not only the quantitative evaluation of gas injection capacity of UGS, but also the accurate pressure prediction, which could provide the basis for optimization of gas injection allocation. Related Articles | Metrics

Water Discharge from Coalbed Methane (CBM) Well May Not Be Equal to Water Production from Coalbed DENG PengPENG XiaolongZHU Suyang, WANG Chaowen 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160615 Abstract ( 99 )   PDF (1073KB) ( 261 )   Save The water discharge from CBM well is usually regarded as the water production from coalbed during dynamic analysis of this kind of wells. Based on wellbore storage effect, the paper analyzes the relationship between water discharge from wellbore and water production from coalbed, compares the 2 water productions with different working fluid levels, concludes that wellbore water discharge may not be equal to water production from coalbed and establishes a modified formula of coalbed water production. Then the calculation results of the production data from Well XX of TS well group, Qinshui basin show that there is an obvious gap between wellbore water discharge and coalbed water production during the first production stage with the peak value difference reaching 72% of wellbore water discharge; the maximum coalbed water production is 25% higher than the maximum wellbore water discharge due to sharp pressure variations at the second and third production stages. Meanwhile, the influence of the difference between wellbore water discharge and coalbed water production on production is simulated with a mechanism model and based on production data in Well XX of TS well group, Qinshui basin. The result shows: if the wellbore water discharge is considered to be equal to the coalbed water production, coal seam pressure drop rate will be accelerated, the gas breakthrough time will be 79 days in advance and the peak of gas production will be reached 180 days in advance as well. It is concluded that the water discharge from CBM well is not equal to the water production from coalbed when the pressure changes in the coal bed. Otherwise, dynamic analysis, production system determination and implementation and numerical simulation for CBM wells will be wrong Related Articles | Metrics

Application of Petrophysical Modeling Technique in Favorable Reservoir Prediction in Western Slope of Mahu Sag, Junggar Basin YU Baoli1, ZHAO Xiaohui1, QU Jianhua2, CAO Xiaolu1, DENG Yong1, WANG Xiaohui1 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160616 Abstract ( 75 )   PDF (3876KB) ( 371 )   Save The Triassic Baikouquan formation in the western slope of Mahu sag, Junggar basin is a set of fan-delta front sandy conglomerate deposits. Conventional post-stack wave impedance inversion can’t be used to distinguish effective reservoir and tight reservoir, which constrains well placement and reserves calculation. Analysis on the available elastic parameter crossplots obtained from logging data shows that vp/vs ratio is an effective elastic sensitive parameter to classify tight reservoir and effective reservoir. Based on accurate calculation of shale content, effective porosity, water saturation and other parameters, a reasonable petrophysical model is selected and the accuracy of S-wave velocity estimation is improved significantly, which could provide fundamental data for prestack inversion of elastic sensitive parameters in the study area. With the optimized parameters of vp/vs ratio, effective reservoirs can be identified and exploratory well success rate can reach 80%, which provides basis for well placement and reserves confirmation in the study area Related Articles | Metrics

Optimal Quantitative Logging Analysis on Mineral Components of Complex Clastic Rocks HAN HaodongPENG Jun 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160617 Abstract ( 65 )   PDF (3462KB) ( 226 )   Save To obtain continuous stratigraphic sedimentation sections of Silurian Kepingtage formation in Tazhong area, TarimBasin, a multi-mineral model is established using the data of thin section identification and X-ray diffraction analysis. Quasi-Newton method is used to process the 8 logging curves and mineral components of clastic rocks, pore fluid content and the corresponding theoretical calculated logging curves are gained in the study area. Verification of the theoretical calculated curves by means of confidence interval method and objective function value method shows that the relative error between theoretical and actual logging curves averages 7.88%; analyses on thin section identification and X-ray diffraction data show that the mineral component contents obtained from the optimal logging interpretation match well with that from practical analysis data. The calculated results can provide quantitative data for detailed lithology classification, oil and water layer identification, depositional environment analysis and diagenesis study Related Articles | Metrics

Logging Identification Method for Lithology: A Case Study of Baikouquan Formation in Wellblock Fengnan, Junggar Basin ZHAO Ning1, WANG Liang1, TANG Yong2, QU Jianhua2, LUO Xingping2, SIMA Liqiang1 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160618 Abstract ( 104 )   PDF (3581KB) ( 206 )   Save The tight sandy conglomerate reservoir in Baikouquan formation of Wellblock Fengnan, Junggar basin is characterized by various types of rocks, large range of grain size and severe heterogeneity, all of which have significant impacts on reservoir development effect. On the basis of the reference on national standard (GB/T 17412.2-1998) Classification and Nomenclature Schemes of Sedimentary Rocks, the rocks in Baikouquan formation can be classified as mudstone, moderate-fine sandstone, coarse sandstone, fine conglomerate, small pebble conglomerate, large pebble conglomerate and coarse conglomerate. The analysis on lithological and petrologic features of different rocks shows that there are differences in sedimentary environment, grain size, matrix content, physical property and pore structure among different lithologies. Coarse sandstone, fine conglomerate and small pebble conglomerate are dominant reservoir lithologies with the secondary of large pebble conglomerate. Dry layer or non-reservoir is mainly composed of mudstone, moderate-fine sandstone and coarse conglomerate. Based on lithological and petrologic features and their logging responses, interval transit time-deep lateral resistivity cross plot chart are established and a combined identification method of -ND and the plot is developed. The lithology obtained from logging identification matches well with that from cores, which could be widely used in the study area Related Articles | Metrics

Application of Tool-Free Staged Acid Fracturing Technology in Horizontal Wells, Tahe Oilfield SONG Zhifeng1, HU Yajie1,2, WU Tingxin3 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160619 Abstract ( 70 )   PDF (532KB) ( 159 )   Save Abundant OOIP is discovered in the low-quality reservoirs of Tahe oilfield. But this kind of reservoirs can’t be economically developed because of low well productivity after preflush acid-fracturing and high cost of staged acid fracturing with tools in horizontal wells. Tool-free, temporary-plugging staged acid fracturing method is used in fracture-cave carbonate reservoirs, that is using steering acid and degradable fiber at fissure vents as barriers, which could force fracture initiation from the next section and then the reservoirs could be connected with each other. Thus the single fracture-cave pattern of preflush acid-fracturing is changed and several reservoirs in a single well can be produced effectively through one-time acid fracturing. Field application result shows that the average acid fracturing cost for a single section in one well can be reduced by 47.8% and well productivity can be increased to 1.8 times of that in neighboring wells. Consequently, the development benefit is significantly improved Related Articles | Metrics

Hydrocarbon Accumulation Differences of Tight Oil between Williston Basin and Western Gulf of Mexico Basin LI Qian1, LU Shuangfang1a, LI Wenhao1a, XU Siyong2, ZHANG Han1, HU Ying1 2016, 37 (6):  1-1.  doi: 10.7657/XJPG20160620 Abstract ( 91 )   PDF (2424KB) ( 452 )   Save Based on the analysis of petroleum exploration data combined with thin-section identification and organic geochemical data, the paper studies the geological and geochemical features of shales of Bakken formation in Williston basin and Eagle Ford formation in Western Gulf of Mexico basin, and analyzes the reason causing hydrocarbon accumulation differences between the two formations. Different rock associations result in the differences of hydrocarbon accumulation patterns between Bakken formation and Eagle Ford formation -- the former is dominated by outer-source accumulation and the latter by inner-source accumulation. The overpressure caused by hydrocarbon-generation in shales of Bakken formation is larger than that of Eagle Ford formation, which allows greater hydrocarbon expulsion forces and is helpful for oil and gas expulsion from the shales. Therefore, less oil and gas retain in shales of Bakken formation than that of Eagle Ford formation (with most oil and gas retaining in shales). The physical properties of middle Bakken formation are better than those of the upper and lower Bakken formations due to more developed connecting pores and larger pore throats, and the middle Bakken formation is the main interval for oil and gas occurrence. Shales and limestones in Eagle Ford formation with well developed pores contribute significantly to hydrocarbon storage. Tight oil reservoirs in both Bakken and Eagle Ford formations are continuous or quasi-continuous reservoirs. The tight oil reservoirs in Bakken formation mainly migrate vertically, leading to the formation of continuous large-area tight oil regions in the middle Bakken reservoir. Whereas, vertical and lateral migrations occur in Eagle Ford tight reservoirs, resulting in the overlapping of shales and tight limestones vertically, which could act as the source rock and reservoir simultaneously featured by interconnection and superimposition Related Articles | Metrics