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01 January 2019, Volume 38 Issue 1 Previous Issue    Next Issue

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Characteristics of Sandy Conglomerate Reservoirs and Controlling Factors on Physical Properties of Baikouquan Formation in the Western Slope of Mahu Sag, Junggar Basin QU Jianhua, ZHANG Lei, WU Jun, YOU Xincai 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170101 Abstract ( 169 )   PDF (3180KB) ( 347 )   Save Baikouquan formation in the western slope of Mahu sag, Junggar basin is a set of fan-delta sandy conglomerate depositions. High content of igneous rock debris and the big differences among physical properties of reservoir sections always constrain the petroleum exploration in the area. The reservoir characteristics of Baikouquan formation and the controlling factors are studied based on core observation and thin section identification, and the sandy conglomerate reservoirs of Baikouquan formation in the western slope of Mahu sag are re-classified and denominated. Combined with the grain size distribution of cores in the study area and based on the standard GB/T 17412.2—1998 Rock Classification and Naming Scheme: Sedimentary Rock Classification and Naming Scheme, pebble conglomerate is further divided into fine pebble conglomerate and coarse pebble conglomerate. Based on which, moderate grain size of sandy conglomerate, relatively low content of clay minerals and secondary corrosion are considered as the key factors for high-quality reservoir formation Related Articles | Metrics

Diagenetic Evolution of Cretaceous Ultra-Deep Reservoir in Keshen Belt, Kelasu Thrust Belt, Kuqa Depression LI Ling1, TANG Hongming1, WANG Xi2a, TANG Shenglan2a, FENG Wei2b, WANG Zhufeng1 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170102 Abstract ( 77 )   PDF (4174KB) ( 138 )   Save In order to thoroughly investigate the diagenetic mechanism and environmental evolution of ultra-deep reservoir of the Cretaceous Bashijiqike formation in Keshen belt, by using the thin section observation, cathode luminescence analysis,scanning electron microscope, fluid inclusion microthermometry and laser raman spectum, energy spectrum analysis, the major and trace element analysis and other technical means, combined with diagenetic mineral, this paper portrays the characterization of diagenetic evolution of ultra-deep tight sandstone. The results show that ultra-deep reservoir had experienced alkaline-weak acidic-alkaline-acidic diagenetic environment. The combination of diagenetic fluid and diagenetic mineral: clay coating stained by iron and crystal carbonate in the early stage of alkaline fluid environment; dissolution of plagioclase and quartz overgrowth under the environment of epi-diagenetic; return to the alkaline environment with quartz dissolution, anhydrite cementation, dolomite cementation and feldspar overgrowth; in the late acidic environment with the dissolution of potassium feldspar, micro-crystalline quartz and illite. Alkaline cement products have occupied a large number of pores and the cracks formed in the early stage, which seriously damaged the permeability of the reservoir, the porosity was reduced by 10%~12%. While the acidic fluids carried by lately hydrocarbon charging can dissolute the acid-solube minerals and form dissolved pore and fracture network with the porosity increasing by 2%~3%. Therefore, the effective reservoir space of the ultra-deep reservoir is controlled by early alkaline and late acidic diagenesis environment. The alkaline diagenetic products provide the material basis for the lately acid corrosion, and the late acidic diagenetic environment plays an important role in the late improvement of the physical properties of the ultra-deep reservoir. The acid fluid is mainly controlled by atmospheric water infiltration in epi-diagenetic stage and lately hydrocarbon charging Related Articles | Metrics

Characteristics and Controlling Factors of Low-Resistivity Reservoir of Upper Submember of Es3 in Shanghe Area of Huimin Sag QIU Longwei1, GE Jun1, SHI Zheng2, YANG Yongqiang1, ZHANG Xiaodan2, WANG Man4 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170103 Abstract ( 74 )   PDF (3556KB) ( 202 )   Save Based on the analysis of thin section, X-ray diffraction, formation water data, the characteristics and genesis of the low-resistivity reservoir in upper submember of Es3 are systematically studied in Huimin sag of Baohai Bay basin. In the study area, the resistivity of the low-resistivity reservoir is less than 10 Ω·m, the water saturation is higher than 50% and the resistivity index is lower than 2. The reservoir is dominated by siltstone with relatively high mud content. The clay minerals are mainly composed of kaolinite and illite/montmorillonite mixing layer, with the secondary of Illite. The reservoir space is dominated by primary pores. The porosity is 3.70%~31.60%, averaging 20.63% and the permeability is 0.6~55.4 mD. The samples with the permeability less than 10.0 mD account for 79%. Therefore, the reservoir is classified as mid-high porosity and low-permeability reservoir. The salinity of formation water in the low-resistivity reservoir is relatively high with the average of 31.43 g/L. Multi stages of volcanism and faulting resulted in the upward invasion of high-salinity formation water and then the typical low-resistivity reservoirs formed in the study area Related Articles | Metrics

Hydrocarbon Accumulation Mechanism of Lower Es3 in Sanhecun Oilfield, Jiyang Depression ZHANG Bo 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170104 Abstract ( 59 )   PDF (2213KB) ( 156 )   Save In order to identify hydrocarbon accumulation mechanism of the lower Es3 in Sanhecun oilfield of Jiyang depression, Bohai Bay basin, by using drilling and biomarker data and based on the research on petroleum sources and migration pathways, and combined with analysis of hydrocarbon accumulation period, the characteristics of hydrocarbon migration and accumulation of the reservoir are understood. The results show that the oil and gas of the lower Es3 in Sanhecun oilfield originated from the matured source rocks of the upper Es4 in Bonan sag. Faults and unconformities are very developed in the study area. Thick framework sand bodies occur in the lower Es3 where faults, unconformity surfaces and framework sand bodies have relatively good hydrocarbon transport abilities; the hydrocarbon accumulation period of the lower Es3 is the depositional period of Ed, during which the hydrocarbon migrated to the sandy conglomerate fans overlain by thick mudstones in Sanhecun sag through a 3-D transport system composed of faults, unconformities and high-permeable sandy conglomerate fans. As a result, the structural-stratigraphic reservoir was formed. Related Articles | Metrics

Characteristics and Intensity Calculation of Feldspar Dissolution in Chang-8 Reservoir of District DZ-ZY, Xifeng Oilfield LIU Hanlin1, WANG Fengqin1, YANG Youyun1, NAN Junxiang2, YANG Shuo3, CAO Xuegang1 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170105 Abstract ( 67 )   PDF (3395KB) ( 128 )   Save Feldspar dissolution is the main controlling factor of secondary pores in Chang-8 reservoir of District DZ-ZY, Xifeng oilfield. This study uses the thin section, scanning electron microscopy(SEM), electron microprobe (EMPA) and other analytical techniques to analyze the characteristics of feldspar dissolution. Meanwhile, based on the properties of incongruent dissolution and theoretical calculations of secondary porosity and dissolution rate of feldspar, 4 kinds of feldspar dissolution intensity are determined: weak dissolution (dissolution rate <25%), medium dissolution (dissolution rate of 25%~50%), strong dissolution (dissolution rate of 50%~75%) and extremely strong dissolution (dissolution rate >75%). Feldspar dissolution commonly occurs in the study area and the contribution of feldspar dissolution pores to reservoir spaces reaches 60%. But there are significant differences among the dissolution degrees of different feldspar. The degree of dissolution of potassium feldspar is higher than that of plagioclase, and the dissolution pores of potassium feldspar accounts for the largest proportion. The dissolution of feldspar in the study area is dominated by medium dissolution (about 40%) and strong dissolution (about 36%). The contribution rate of potassium feldspar dissolution increases along with the dissolution rate and that of plagioclase is the opposite especially under the conditions of relatively high dissolution intensity Related Articles | Metrics

Study on Reservoir Characteristics and Main Controlling Factors of Ma-55 Submember in Sulige Area DU Jiangmin1, ZHANG Xiaoli2, NIE Wancai3a, XU Houwei4, LUO Chuanyou3b, GUO Ling2 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170106 Abstract ( 64 )   PDF (4406KB) ( 220 )   Save Based on core observation and the analysis on the data of thin section, SEM, mercury injection and petrophysical property and using geophysical and geochemical methods, the paper systematically studies the reservoir characteristics of Ma-55 submember of Ordovician Majiagou formation in Sulige area, analyzes the main controlling factors influencing reservoir formation and development and predicts the distribution of favorable reservoirs. The reservoir of Ma-55 submember is dominated by argillaceous-silty dolomite and silty dolomite with the main reservoir spaces of intercrystalline pores and intercrystalline dissolved pores. The petrophysical properties of Ma-525 are better than those of Ma-515. Sedimentary facies is the material basis for reservoir formation and the microfacies of dolomite flat is the favorable sedimentary facies belt for reservoir development. Diagenesis is a significant guarantee to form favorable reservoir spaces and the constructive diagenesis such as dolomitization and dissolution are favorable to reservoir reconstruction. The tectonism is the effective supplement for reservoir development Related Articles | Metrics

Genesis of Dolomite in the Lower Ordovician Ma-55 Submember in Eastern Area of Sulige Gas Field JIANG Chuanjie1, DU Xiaohua1; ZHANG Hao1, ZHAO Xinyu1, WANG Jianguo2, JI Yanbo2 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170107 Abstract ( 103 )   PDF (3092KB) ( 139 )   Save The dolomite in Ma-55 submember of the Lower Ordovician Majiagou formation is characterized by large thickness and rapid pinchout laterally, which is significantly different from the relatively thin dolomite with good lateral continuity in Jingbian gas field. The dolomite in Ma-55 submember in the study area is dominated by micritic dolomite, crystal powder dolomite and fine-medium dolomite, whose degree of order is relative low and proportional to crystal size. The Sr content in micrite (algae) of this horizon is far less than that of the contemporary micrite globally and the residual Sr content is affected by many factors such as fresh water and dolomitization. It is found that the higher the dolomitization degree is，the higher the contents of Fe and Mn will be. Carbon and oxygen isotope values are generally negative. The higher the dolomitization degree is，the more negative the carbon-oxygen isotope value tends to be. From the view of petrological and geochemical indices, the genesis of dolomite should be attributed to the combined action of evaporative pumping，seepage reflux and burial dolomitization Related Articles | Metrics

Spectral Characteristics of Oil Sand and Its Relationship with Alkane Contents in Wuerhe Area, Junggar Basin TONG Qinlong1, LIU Dechang1, YU Yongan2, XU Benhong2 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170108 Abstract ( 57 )   PDF (2431KB) ( 124 )   Save By means of spectrometry technology and chemical analysis and test in typical oil and gas seepage areas in Wuerhe area of Junggar basin, the paper discusses the abnormal spectral characteristics caused by the seepage and its relationship with and alkane contents. The results show that on the macroseepage abnormal spectrum of different alkane contents, W-shaped and double absorption peaks ranging from 2 310 to 2 350 nm are stable and single absorption peaks vary largely around 1 725 nm and 1 760 nm; the hydrocarbon absorption characteristics of microseepage are not obvious due to low hydrocarbon contents, but obvious clay alteration can be observed from rock thin sections and spectra. The clayization resulted from oil and gas seepage is dominated by montmorillonitization and illitization in Wuerhe area. Based on the measurement and observation of clay spectra caused by oil and gas seepage of different degrees, it is found that the depth of absorption peak of hydroxyl is large around 2 210 nm on the clay spectrum resulted from strong oil and gas seepage, whereas the depth of absorption peak is relatively small around 2 210 nm on the clay spectrum caused by weak seepage. The depth of absorption peak can reflect the intensity of oil and gas seepage indirectly. Based on the statistics of width, depth, area and symmetry of absorption peaks around 2 310 nm ( the left peak of W-shaped and double absorption peak) on oil sand spectrum and analysis on chromatography-mass spectrometry of saturated hydrocarbons, it is found that there is a linear relationship between the depth of absorption peak and alkane content of oil sand, and alkane contents can be estimated with the parameters of absorption peak depth through a matched linear expression, which could provide references for regional petroleum prospecting Related Articles | Metrics

Quantitative Characterization of Architecture Units for Braided River Reservoir in Su36-11 EOR Test Area ZHAO Zhongjun, LI Jinbu, MA Zhixin, WU Xiaoning, FU Bin, WANG Wensheng 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170109 Abstract ( 45 )   PDF (3615KB) ( 50 )   Save Braided channel bar and braided channel are important oil and gas reservoir sandbodies, which are characterized by rapid lateral variation, poor continuity and connectivity, strong reservoir heterogeneity and obvious differences of sandbody scale among different areas and different types. These features seriously constrain the development of the braided river reservoir. Based on the reservoir architecture theory, the paper quantitatively characterizes the architecture units of the braided river reservoir of the lower He-8 section (i.e. H8x) in Su36-11 EOR test area of Sulige gas field and analyzes the effective sandbody distribution. The result show that the width of a single braided channel ranges from 100 to 550 m, and the length and width of braided bars are 1 350~4 300 m and 480~1 950 m, respectively. Finally, based on the development scale and distribution of sedimentary microfacies units and combined with production performance data, the comprehensive evaluation of effective sandbodies indicates that channel bars and braided channels are distributed continuously in H8x1-3 and H8x2-3 so that they are considered as the most favorable areas and target horizons with high drilling rate of effective sandbodies. The channel bars in H8x1-2 and H8x2-2 have high effective sandbody drilling rate and island-like channel bars are favorable reservoir sandbodies. Gas may be discovered in only a few channel bars in H8x1-2 and H8x2-2 so that the risks to develop the 2 horizons will be the highest Related Articles | Metrics

Orthogonal Test Design and Numerical Simulation Optimization of CO2 Flooding in Extra-Low Permeability Reservoirs LI Nan1, PAN Zhijian1, SU Ting1, FEI Yongtao2 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170110 Abstract ( 108 )   PDF (921KB) ( 475 )   Save Low permeability reservoirs are the main contributors to the discovered and proved reserves in China currently, among which extra-low permeability reservoirs are widely distributed and account for a large proportion of the reserves. However, extra-low permeability reservoirs are characterized by poor physical properties, so it is difficult to enhance single well production by conventional waterflooding method significantly. CO2 flooding can expand oil volume, reduce oil viscosity, lower interfacial tension and capillary resistance and finally improve oil displacement efficiency. In order to develop extra-low permeability reservoirs reasonably and efficiently, based on numerical simulation and orthogonal design methods, CO2 flooding models are established for extra-low permeability reservoirs, and technical and economic evaluations are carried out for the factors influencing CO2 flooding. The analysis indicates that the parameters influencing development effect from high to low are reservoir type, well spacing density and injected CO2 volume. Considering daily well production and internal rate of return and so on, the optimum way to develop extra-low permeability reservoirs is the combination of CO2 flooding in horizontal wells and the corresponding parameters Related Articles | Metrics

Analysis on Paraffin Deposition of High-Waxy Condensate Oil with Gas Injection in Condensate Gas Reservoirs of Dalaoba Gas Field, Tarim Basin SUN Lei1, LUO Qiang1, XU Shenhao2, PAN Yi1, LENG Jie1, LI Lijian3 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170111 Abstract ( 93 )   PDF (1301KB) ( 157 )   Save In order to study formation fluids in the high-wax condensate gas reservoirs in Dalaoba gas field, experiments and tests are carried out for wax appearance temperature（WAT）and on-line wax precipitation amount of condensate oil with a laser test device and in-line filters connected to high-temperature and high-pressure DBR-PVT tester. Meanwhile, gas is injected to test WAT after multiple backward contacts. The paper compares the results with those obtained from the theoretical calculation model for paraffin deposition. The analysis shows that if paraffin components are considered as adjustable parameters, the modeling results of WAT and wax precipitation amount could match with the experimental results very well. If the mole fractions of paraffin components are put into the theoretical model, WAT and wax precipitation amount before and after multiple backward contacts could be well predicted. Using this fluid system to perform modeling and calculation, the changes of fluid compositions with different contact frequencies and wax precipitation amount at different temperatures can be obtained after gas injection in Well DL4. The injected gas mainly plays the role of extraction, which will result in the increase of heavy component content in the fluid and the rise of WAT. The results can provide basis for calculation of wax precipitation amount before and after gas injection in condensate gas reservoirs Related Articles | Metrics

Matching Relationship among Key Indices of Production Rate and Productivity Construction WANG Xiaolin1,2, KUANG Ming2, DOU Hongen2 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170112 Abstract ( 81 )   PDF (635KB) ( 210 )   Save During annual oilfield development plan making, productivity contribution rate, productivity implementation rate, production decline rate, recovery factor and production rate are the key indices to determine reserves, production and productivity. According to the relationship between initial production and productivity of brought-in blocks, based on exponential, hyperbolic and harmonic equations of production decline and combined with recovery factor indices, the paper establishes a matching relationship among the key indices of annual oilfield development plan making, and analyzes the influences of productivity contribution rate, productivity implementation rate, initial decline rate, decline exponent and recovery factor on production rate. The established relationship could provide theoretical basis for reasonable selection of the key indices of annual oilfield development plan and can be used for production and productivity optimization during annual or mid-long tern planning Related Articles | Metrics

Application of Nitrogen Foam Flooding in Heavy Oil Reservoirs in Karamay Oilfield XIANG Xiangxing1CHEN Jing1HOU Junwei2QIAO Qi1YANG Ziyue3LIU Hongfei2 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170113 Abstract ( 59 )   PDF (971KB) ( 49 )   Save The heavy oil reservoir of the Upper Jurassic Qigu formation in Well block J-230 of District No.9, Karamay oilfield is characterized by serious heterogeneity, thin oil layers and low natural energy. As the oilfield development is at the mid-late stage, the oil saturation of the reservoir significantly decreases, the residual oil distribution is complex, the formation pressure is low and there are more and more high water-cut wells, which results in the difficulties of development and sharp decrease of oil production rate and economic benefit. A field test of nitrogen assisted steam huff and puff technology was carried out in 1995 and the results showed that nitrogen injection could replenish formation energy effectively, elongate huff-puff time and improve the development effect of thermal heavy oil recovery. Whereas, because steam channeling is serious in injectors after multi cycles of nitrogen assisted steam injection, experimental studies are conducted on nitrogen foam assisted steam huff and puff and its profile control and flooding. The results show that high-temperature foaming agents with good foaming ability and stability can be used for common heavy oil reservoirs with strong heterogeneity, with which the oil recovery factor can be significantly improved Related Articles | Metrics

Waterflooding Experiment and Micro-Distribution of Remaining Oil in JIV Reservoir in Lunnan-2 Oilfield HE Qiaolina, GUAN Zengwub, ZUO Xiaojuna, WU Lina, XING Xinga, HUANG Lana 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170114 Abstract ( 59 )   PDF (4480KB) ( 226 )   Save Based on the analysis of cast thin-section, conventional physical properties, SEM and mercury injection, the pore structures of JIV reservoir of the Lower Jurassic Yangxia formation are classified. Microscopic waterflooding experiments for sandstone cores are carried out in the reservoirs with 4 main pore structures. The experiment results show that the reservoirs with different pore structures have different percolation features. Fine-throat, low-permeability reservoir and microfine-throat, super-low permeability reservoir are dominated by finger-like percolation, relative fine-throat, high-permeability reservoir by finger-like-net-like percolation and fine-throat, medium-permeability reservoir by net-like-uniform percolation. The remaining oil after waterflooding are mainly in sheet-like and cluster-like distributions resulted from by-pass oil with the secondary of scattered columnar, angular and film-like distribution. The analysis on micro-percolation features of waterflooding in reservoirs with different pore structures could provide basis for reasonable and efficient development of the oilfield Related Articles | Metrics

Variations of Rock Resistivity in Water-Flooded Zones of Water Injection Oilfield ZHANG Hengrong, TAN Wei, WANG Lijuan, DING Lei 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170115 Abstract ( 93 )   PDF (1030KB) ( 209 )   Save The changes of electrical properties of water flooded reservoirs are complex, which brings great difficulty to the identification of water flooded zone and the evaluation of remaining oil saturation. In this paper, simulated waterflooding experiments under reservoir conditions are carried out by using sealed coring samples, the variations of rock resistivity are analyzed for the situations when the water of different salinities is injected to displace oil and the influences of changes of pore structures, and formation water salinity on rock electrical parameters are discussed. The experimental results show that when high-salinity water or formation water is injected to displace oil, the rock resistivity always monotonously decreases and exhibits a “L” shape, and the better the physical properties are, the larger the decrease amplitude of rock resistivity will be; when low-salinity water is injected to displace oil, the rock resistivity generally displays a “U” or “S” shape and the better the physical properties are, the resistivity will change to monotonous increase from monotonous decrease, and the higher the water saturation at the first inflection point will be. The changes of pore structure resulted from the changes of injected water volume have no significant impact on rock electrical parameter. With the increase of formation water salinity, cementation index and saturation index will gradually increase. The influence of the difference of formation water salinity at different waterflooded stage on rock electrical parameters should be considered when calculating residual oil saturation Related Articles | Metrics

Establishment and Application of Integrated Near-Surface and Subsurface Q Model in Desert Area JIANG Li, WANG Xiaotao, TAN Jia, XIAO Yanling, CHEN Yong, ZHANG Jin 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170116 Abstract ( 63 )   PDF (4143KB) ( 100 )   Save The hinterland of Junggar basin is covered by desert. The majority of middle-high frequency energy in seismic reflection waves is absorbed by near-surface sand dunes. To improve seismic data resolution, the paper proposes a method to build an integrated near-surface and subsurface, prestack Q model. Firstly, the method calculates the relative near-surface Q field at shot and receiver points with simplified spectral ratio based on amplitude and main frequency of seismic data and seismic travel time on the surface; then uses formation quality factors at near-surface shot-receiver points to modify average sub-surface Q model and establishes a pre-stack average Q model containing near-surface variations, which could further compensate seismic data of one-step pre-stack Q model. The seismic data resolution obtained from the model in the desert area is better than that obtained from conventional subsurface Q compensation method and deconvolution method. The results of synthetic seismogram calibration and pre-stack inversion are better than those of conventional methods as well. Therefore, the model has good prospects for application Related Articles | Metrics

Interpretation of Logging Lithology in Carbonate Reservoirs Based on Markov Chain Probability Model YUAN Zhaowei1a, DUAN Zhengjun1b, ZHANG Chunyu2, TAN Maojin1a, GAO Shichen1c 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170117 Abstract ( 60 )   PDF (3522KB) ( 205 )   Save The influences of deposition and diagenesis result in the complexity and diversity of the carbonate reservoirs of the fifth section of the Lower Ordovician Majiagou formation in Sudong 41-33 block, Sulige gas field. Therefore, lithology recognition is a key step in the process of reservoir evaluation. Analysis of log and logging data shows that 7 types of reservoirs are mainly developed in the fifth section of Majiagou formation such as limestone, dolomite, dolomitic limestone, calcite dolomite, argillaceous dolomite, argillaceous limestone and mudstone. Based on the analysis of sensitivity parameters, 4 kinds of parameters of GR, density, PEF and CNL which could reflect reservoir lithologies are selected, and Na-ve Bayesian method constrained by Markov chain probability method is used to perform multi-parameter comprehensive interpretation. The results of analysis and comparison of logging and log data show that the accuracy of lithology recognition reaches 85.34%. Compared with the traditional Na-ve Bayesian method, the accuracy of lithology recognition could be improved by 12.39%. High accuracy model for logging lithology interpretation of carbonate reservoirs can be obtained by using this method. The method is an effective way for complex lithology identification Related Articles | Metrics

Application of Digital Core Technology in Elastic Modulus Calculation for Shale ZHANG Yuliang1a, FAN Cuijie1b, XIE An1b, QI Hongyan1a, YANG Bai2 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170118 Abstract ( 62 )   PDF (4004KB) ( 267 )   Save Elastic modulus is an important parameter for sweet-spot discovery in shale gas exploration and development, and also an significant index to determine hydraulic fracturing effect. It is very difficult for conventional experiment method of rock mechanics to measure elasticity features of shale due to its extremely high brittleness. To predict elastic modulus, up-to-date digital petrophysical method combined with scanning electron microscope imaging, quantitative mineral component determination of shale and finite element numerical simulation is used. Based on modeling the stress-strain response process of digital shale cores in the range of linear elasticity, effective elastic parameters of the digital cores can be calculated. Through comparison of the modeling calculation results of the calculated areas with different sizes, the sampling by this method is verified to be representative. The comparison of modeling calculation results and the actual logging data can also prove the effectiveness of the method Related Articles | Metrics

Application of Single-Point Deliverability Formula in S Gas Field of Right Bank Block, Amu Darya MENG Zhonghua1,2, ZHAO Liqiang1, LIU Pingli1, GAO Pengyu3, LIU Ronghe2, ZHANG Wenbiao2 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170119 Abstract ( 67 )   PDF (589KB) ( 209 )   Save Besides the advantages such as short test time, relatively simple process and low cost etc., the single-point well test method can not only reduce the amount of released air during test, but also effectively evaluate deliverability, so the method can be widely used in productivity evaluation for gas fields. However, the value of α in the single-point formula is quite different in different gas fields. The single-point deliverability formula is modified for the application in S gas field of the Right Bank Block of Amu Darya and a unique single-point deliverability formula is established for the gas field. According to the deliverability test results from 42 wells in S gas field, an average α value of 0.28 is obtained for the formula. Because the well deliverability varies greatly, α values should be classified and calculated according to different deliverability ranges. The single-point deliverability formula using the average α value of 0.28 and α values for different ranges can verify that the open flow capacities obtained from α values for different deliverability ranges are more accurate Related Articles | Metrics

Research Progress on Brittleness of Shale Reservoirs ZHANG Chenchen1, DONG Dazhong1,2, WANG Yuman1, JIANG Shan1, GUAN Quanzhong3 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170120 Abstract ( 75 )   PDF (1816KB) ( 183 )   Save Brittleness is a key indicator to select favorable fracturing intervals. Mineral-based method and elastic parameter-based method are generally used to evaluate shale brittleness. The marine shales in South China are characterized by various sedimentary environment, complex lithofacies and large range of burial depth. The paper analyzes the theoretical defects and the limitations during application on the basis of case study. Based on the research results on shale mechanical properties, the paper summarizes the influences of mineral composition, organic matter, bedding and confining pressure on shale brittleness, and demonstrates the relationship between brittleness and fracability. The comprehensive analysis shows that mineral-based method is more applicable but has a detect that there is not a unified definition for brittle minerals yet. Elastic parameter-based method can perform logging and seismic prediction effectively, but this method can’t reflect the influence of confining pressure and it is difficult to characterize the brittleness differences between deep and shallow shales with the method. Combined with the lithofacies and burial depth range of marine shales in South China and based on the differences among different mineral components, quartz, dolomite and pyrite are proposed to be considered as brittle minerals; based on the influence of confining pressure on brittleness, the paper suggests that strength or fracture toughness should be added to the elastic parameter-based indices as a confining pressure-indicator to apply to the deep-burial shale brittleness evaluation. Profound understandings on the influences of mineral composition, organic matter, bedding and burial depth on brittleness and the relationship between brittleness and fracability can promote detailed lithofacies characterization of shales and sweep-spot optimization Related Articles | Metrics

Geochemical Characteristics and Favorable Areas for Shale Prospecting in Second White Specks Formation, Western Canada Basin LIN Houfei1, HUANG Haiping1,2, JIANG Wenlong3, MA Li1, CHAI Chengyu1 2017, 38 (1):  1-1.  doi: 10.7657/XJPG20170121 Abstract ( 67 )   PDF (2272KB) ( 115 )   Save Based on the data analyses of rock pyrolysis, gas chromatographic mass spectrometry(GC-MS), organic geochemistry and X-ray diffraction on core samples from 9 wells, this paper discusses the geochemical characteristics and the favorable areas for shale oil exploration. GC-MS analysis of saturated hydrocarbon shows that the hydrocarbon is dominated by short-chain n-alkanes（nC9—nC19）with the predominance of ααα20RC27 steranes and relatively low content of oleanane. The organic matter is dominated by algae and plankton. Maturity has a little impact on Pr/Ph, which basically records the oxidation and deoxidation environment during deposition and early diagenesis stage. The relationship between dibenzothiophene/phenanthrene and pristane/phytane indicates that the sedimentary environment-lithofacies of Second White Specks formation vary largely from east to west. Strong reducing environment occurs in the east of Alberta, weak reducing environment in the middle-west and relatively strong reducing environment in the west. On the other hand, the pyrolysis products in the lab usually contain large amount of polar, high-molecular compounds, which results in the over-estimation of hydrocarbon potential obtained by mass balance model counting inert carbon. A new method of dead carbon correction is used to reconstruct the original organic carbon content and original hydrocarbon potential of matured-high matured source rocks in Second White Specks formation. The favorable areas for shale oil production are discussed, and it is concluded that the vitrinite reflectance of the source rocks is greater than 0.5 in 5 wells of the middle-western part of the study area and the residual oil in other wells can’t meet the commercial production requirement Related Articles | Metrics