Table of Content

01 January 2019, Volume 37 Issue 5 Previous Issue    Next Issue

For Selected:

Download Citations EndNote Reference Manager ProCite BibTeX RefWorks

Toggle Thumbnails

Fengcheng Alkaline Lacustrine Source Rocks of Lower Permian in Mahu Sag in Junggar Basin: Hydrocarbon Generation Mechanism and Petroleum Resources Reestimation ZHI Dongming1a, CAO Jian2, XIANG Baoli1b, QIN Zhijun1a, WANG Tingting2 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160501 Abstract ( 153 )   PDF (300KB) ( 394 )   Save Hydrocarbon generation characteristics and mechanism of alkaline-lacustrine source rocks are one of the research leading edges and difficulties. Based on a case study in the Lower Permian Fengcheng formation in the Mahu sag of Junggar basin, by using comprehansive methods of artificial section and natural outcrop of the source rocks as well as oil and gas characteristic calibration, the paper studies hydrocarbon generation characteristics and mechanism of the alkaline-lacustrine source rocks, based on which petroleum resources are reestimated. Results show that the Fengcheng alkaline-lacustrine source rocks exhibit some unique characteristics in hydrocarbon generation such as high conversion efficiency, continued hydrocarbon generation, multi-phase generation peaks, long oil-generation window, light oil and high oil to gas ratio, all of which are different from conventional lacustrine high quality source rocks. The unique hydrocarbon generation mechanism should be attributed to organic and inorganic compositions of the source rocks. The bioprecursors in the source rocks are dominated by bacteria and algae, with bacteria much more developed. The unique mineral composition of the Fengcheng formation is characterized by the existence of both alkaline and volcanic minerals that play retarding and catalytic roles on hydrocarbon generation, respectively, which allows early and continued hydrocarbon generation, multi-phase generation peaks and long oil-generation window of source rocks. According to these, the reestimation of petroleum resources in the study area is as follows: the oil generating volume is increased by 25% and the gas generating volume is decreased by 13%, which are more accordant with the present-day exploration results and have significance for making future exploration strategies Related Articles | Metrics

Characteristics of Oil Seepages and Bitumen of Lower Ordovician and Its Hydrocarbon Accumulation History in Southern Guizhou Depression KANG Jianwei1,2, YU Qian2, TIAN Jingchun1, YAN Jianfei2, MEN Yupeng2, QI Minghui3,4 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160502 Abstract ( 42 )   PDF (300KB) ( 78 )   Save Using GC-MS and IRMS testing technologies, the paper analyzes oil seepages and bitumen, correlates their maturity and oil sources,and discusses hydrocarbon accumulation history in Lower Ordovician Honghuayuan formation in southern Guizhou depression. The result shows that the oxidized bitumen in Honghuayuan formation is mainly found in Danzhai-Majiang area in the southern study area; while the Kaili area in the northern study area with oil shows occuing widely, oil shows occur widely, and is of mixture source characteristics by the fact that the major source rocks appear in Niutitang formation of the Lower Cambrian, the secondary hydrocarbon source rocks are found in Wengxiang shale of the Middel-Lower Silurian. Under the influence of multi-stage tectonic activities, the hydrocarbon accumulation history is relatively complex and featured with accumulation-destruction of multicycles, among which the destruction is the strongest during the late Yanshan Movement period Related Articles | Metrics

Maokou Multi-Type Reservoirs in Western Sichuan Basin: Genesis and Implications HU Hao1a,1b, XU Guoming1b, GAO Feng2, SONG Xiaobo1b, LONG Ke1b 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160503 Abstract ( 75 )   PDF (300KB) ( 186 )   Save The strong heterogeneity and complex genesis are observed in the Maokou reservoir of the Middle Permian in Sichuan basin. There are lots of disputes about the understandings of the main controls on reservoir development and reservoir distribution, which brings great trouble to the exploration of Maokou formaion. Using the data of field sections, drilling data in the neighboring area and seismic exploration, the paper demonstrates the reservoir genesis of Maokou formation in Sichan basin from 3 aspects such as lithfacies paleogeography, reservoir characteristics and seismic reservoir prediction. It is considered that the Maokou formation is in the great gentle-slope sedimentary system of carbonate rocks; large-scale shallow-water high-energy reef-flat facies belts occur in western Sichuan basin, which can verify the existence of great deep faults penetrating from Permian strata to basement in Jinma-Yazihe structural belt and Longquanshan buried structural belt; dissolved pore-cavity reservoir and hydrothermal dolomite reservoir may be widely developed in the reef flat sediments at the top of Maokou formation under the actions of both unconformity karstification and fracture-related hydrothermal dolomitization. The above 2 types of reservoirs are the key favorable zones for large-scale gas reservoir exploration in Makou formation in western Sichuan basin Related Articles | Metrics

Characteristics of Micro-Pore Throat Structures in Tight Sandstone Reservoir of the Second Member of Kongdian Formation in Cangdong Sag CHENG QiumengCHEN ShiyueYAN Jihua 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160504 Abstract ( 49 )   PDF (300KB) ( 110 )   Save Based on thin section observation, analysis on SEM, physical property and mercury injection and laser scanning confocal microscope observation, the petrological characteristics, reservoir space type, physical property and pore throat distribution are studied for the tight sandstone reservoir in the second member of Kongdian formation in Cangdong sag of Huanghua depression, Baohai Bay basin. The result shows that the reservoir in the second member of Kongdian formation is dominated by lithic quartz sandstone and lithic sandstone, and the reservoir space is mainly composed of secondary dissolved pores and intercrystalline micro-pores, containing a few residual primary pores and fissures. The porosity and permeability of the reservoir average 7.71% and 0.59 mD, respectively, indicating that the reservoir belongs to super-low porosity and extra-low permeability reservoirs. The reservoir pore throats have relatively poor structures and are mostly distributed separately, so the pore connectivity is poor. The reservoir pore radiuses are similar with the most ranging from 100 to 200 μm. Pore throat radiuses vary largely with the most in micron-nano scale. The filtration capacity of the reservoir is mainly controlled by radius, frequency and distribution pattern of pore throats. Some treatment technologies should be adopted to protect the pore throats in the tight sandstone reservoirs in the second member of Kongdian formation and better development effects can be gained Related Articles | Metrics

Application of Quantitative Grain Fluorescence Technique in Restoration of Hydrocarbon Charging History of Jurassic Reservoirs in Mosuowan Swell, Junggar Basin MA Weijiao1, WANG Ran2, WANG Feng2, LI Xiuli1,3 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160505 Abstract ( 51 )   PDF (300KB) ( 85 )   Save Mosuowan swell in the hinterland of Junggar basin which was located in the high position of the structural anticline during Cretaceous is the favorable area for hydrocarbon migration and accumulation. But little evidence can prove the hydrocarbon accumulation in the paleo-reservoir in Mosuowan swell. This paper selectes the typical exploration Well Moshen-1 in the Wellblock Pencan-2 in Mosuowan swell of Junggar basin, correlates and analyzes 25 cutting samples from the Sangonghe formation of Lower Jurassic in detail using quantitative grain fluorescence technique, and restores the complex reservoir charging process in Wellblock Pencan-2 based on the combined study of log data, structural development, hydrocarbon generation and expulsion history and hydrocarbon accumulation periods. The results show that paleo-reservoir occured in the second member of Sangonghe formation during Cretaceous with the water-oil contact (WOC) at 4 456 m in depth. Himalayan movement resulted in the leakage of the paleo-reservoir at the end of Paleogene and the WOC rose to 4 412 m. In Neogene, Jurassic source rocks charged with oil and gas again resulted in the present WOC at 4 440 m in depth (lower than WOC of the Paleogene) and allowing oil and gas accumulation to appear in sand bodies of the first member of Sangonghe formation under the conditions of no paleo-reservoirs. The research result provides new evidence for the study on hydrocarbon accumulation history of Sangonghe formation in Mosuowan swell Related Articles | Metrics

Diapiric Hydro-Dynamic Balance System and Gas Reservoir Model in Yinggehai Basin SONG Ruiyou, YU Junfeng, HAN Guangming, HAO Defeng, YANG Baocheng 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160506 Abstract ( 71 )   PDF (300KB) ( 178 )   Save The central diapir zone is the key gas-producing area in Yinggehai basin. Material compositions and activities of the diapir directly control the natural gas accumulation course and features. For probing the course and features, this paper demonstrates the main intrusion pattern, emphasizes and summarizes the diapiric hydro-dynamic balance system and analyzes the gas reservoir characteristics under the control of dynamic balance of fluids. According to material compositions and intrusion pattern, diapirs in the study area can be classified into 4 types such as slow wedging, continuous penetrating, periodic collapsing and mixed breakthrough. The former 3 types belong to stepping diffusion system dominated by mud diapir, penetrating fragment system induced by fluid front and periodic collapsing dynamic balance system dominated by fluid column, respectively. In a dynamic balance system, gas reservoirs are charged with multi-stage mixed gas and overlapped with each other in different charging degrees. The structure of syntectonic stratum is complex and several petroleum systems can coexist. Petrochemical components of natural gas exhibit delamination and inversion of carbon isotope value could be found. It is necessary to distinguish intrusion pattern of diapirs during gas reservoir exploration. Integrated analysis should be conducted regarding target trap type, relationship between sand body and diaper and the neighboring gas reservoirs to identify gas-bearing properties of the traps Related Articles | Metrics

Analysis of Hydrocarbon Potential of Carboniferous Tuffite in Beisantai Swell, Junggar Basin HOU Maoguo1, ZHA Ming1, CHEN Hong2, GAO Changhai1, QU Jiangxiu1, DING Xiujian1 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160507 Abstract ( 77 )   PDF (300KB) ( 185 )   Save To identify hydrocarbon potential of the Carboniferous source rocks in Beisantai swell of Junggar basin, abundance, type, maturity and distribution of organic matter in Carboniferous tuffite and dark shale in the study area are correlated and analyzed on the basis of geochemical parameters such as rock pyrolysis, carbon isotope and biomarkers, etc., based on which oil-source correlation and analysis are carried out. The result shows that the Carboniferous tuffite and dark shale have relatively high organic matter abundance with organic matter type dominated by Type Ⅱ2-Ⅲ that have entered into the matured phase of large amount of oil and gas generation. The tuffite mainly occurs in the central Beisantai swell and is a set of thick and moderate-good quality source rocks. The dark shale is of less thickness, which may constrain the rock to be the key source rock. The results of oil-source correlation and analysis also exhibit that the oil in Xiquan-3 reservoir is sourced from the Carboniferous tuffite, which can further verify the capability of hydrocarbon generation and expulsion of this tuffite as effective source rocks Related Articles | Metrics

Geochemical Characteristics and Genesis of Buqu Dolomite in Longeni-Angdaercuo Area, Tibet CHEN Hao1,2,3, WANG Jian2,3, WANG Yuke1,2,3, CHEN Ming2,3 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160508 Abstract ( 70 )   PDF (300KB) ( 152 )   Save The Buqu dolomite of the Middle Jurassic in Longeni-Angdaercuo area in Tibet is a sequence with petroliferous prospect. To understand its genesis is very significant for accurate evaluation of petroliferous potential in the study area. This paper analyzes the fluid inclusion, carbon and oxygen isotopes in oil-bearing dolomite in this area, showing that the homogenization temperature mainly ranges from 130℃ to 170℃ and the salinity mainly ranges from 3.5% to 4.5% of fluid inclusion in dolomite zones, which indicates that the dolomite zone-formed environment temperature and salinity are all relatively high and they should be the products of deep-burial to late-stage diagenesis. All the δ18OPDB values of dolomite are less than zero (migrating toward negative values) and vary largely, indicating the low-temperature and high-temperature genesis of dolomite. Based on the combination of field survey and indoor test and analysis, it is considered that the dolomite in the study area experienced a complex genesis—at least the compound of 3 stages of genesis, namely low-temperature penecontemporaneous dolomitization at the early stage, high-temperature and deep-burial dolomitization at the middle stage and structural dolomitization at the late stage Related Articles | Metrics

Polymer Flooding for Sandy Conglomerate Reservoir in District Qidong-1, Karamay Oilfield: Experiment and Evaluation TANG Hongming1aZHANG Yaqi1bWANG Junjie1bWANG Xiaoguang2CHEN Yukun2WANG Zhufeng1b 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160509 Abstract ( 84 )   PDF (300KB) ( 200 )   Save Sandy conglomerate reservoir is characterized by mixed rock grains, strong heterogeneity and complex pore structures. Waterflooding in the sandy conglomerate reservoirs in Karamay oilfield encounters some problems such as water channeling and watered out, high overall watercut and low recovery factor etc., so indoor experiment and evaluation should be carried out for the sandy conglomerate reservoirs to provide guidance for reasonably making development scheme. This paper takes the sandy conglomerate reservoir in T2k1 of Karamay formation in District Qidong-1, Karamay oilfield as the research object, describes the characteristics of different pore structures in the reservoir on the basis of mercury injection and casting thin section analysis. Some typical cores are selected for waterflooding and polymer flooding experiments. Oil displacement efficiency and oil producing rule during displacement process and residual oil distribution after polymer flooding are determined by NMR. The results show that big differences among different types of pore structures result in different polymer flooding potentials, the highest oil displacement efficiency is obtained in Type Ⅱ pore structures; the highest oil producing degree by waterflooding is observed in the pore throats with the radius larger than 10.0 μm. The effective pore throat radius ranges from 1.0 to 10.0 μm for polymer flooding. The pores with the pore throat radius less than 1.0 μm make the lowest contribution for polymer flooding and the oil displacement efficiency of polymer flooding can be improved by 13.09% on average Related Articles | Metrics

A New Form of Material Balance Equation for Condensate Gas Reservoirs with Oil Rings WANG Nutao1, ZHANG Wu2, LI Chen2 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160510 Abstract ( 75 )   PDF (300KB) ( 128 )   Save Material balance equation is one of the most commonly-used methods to calculate dynamic reserves of gas reservoirs, but for condensate gas reservoirs with oil rings, their dynamic reserves are not only related to oil and gas production, but also to retrograde condensation degree. Since mass conversion occurs among different products, it is difficult to accurately calculate the amount of conversions and to establish material balance equation with volume balance or molar balance. Also, conversion from wellhead oil and gas flow rate to bottom-hole inflow rate can’t be realized by the direct use of the volume factor and the gas-oil ratio, hence the material balance equation for conventional gas reservoirs greatly differs from that for condensate gas reservoirs with oil rings. On the basis of the law of mass conservation, this paper proposes a general formula of the material balance equation for natural water-drive condensate gas reservoirs with oil rings under production conditions, in which multi-phase flow displacement theory and oil saturations corresponding to curve interpolation are used to get the dynamic reserves of such reservoirs with oil rings by optimizing the objective function through non-linear regression, without converting condensate oil into equivalent gas with empirical formula and without by means of concepts of two-phase deviation factor and state equation of liquid. Therefore, the new formula can avoid the variations in oil and gas components and their volumes resulted from complicated phase changes. The obtained material balance equation has a stronger theoretical foundation and can better reflect the actual status of condensate gas reservoirs Related Articles | Metrics

Impact of Volumetric Adiabatic Exponent on Calculation of Choke Flow Rate WANG Faqing, YANG Shuzhen, CAO Xianping, CHEN Defei, QIN Han 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160511 Abstract ( 100 )   PDF (300KB) ( 427 )   Save Choke flow rate is often needed to be calculated during oil and gas field production and the volumetric adiabatic exponent used as a constant in the calculation is often assumed to be 1.3. In fact, the volumetric adiabatic exponent as a function of temperature and pressure should be used for choke flow rate calculation, and the exponent can be considered as a constant only under the conditions of low pressure. Based on the analysis of the impact of temperature and pressure on the exponent, it is concluded that the volumetric adiabatic exponent can be considered as a constant when the inlet pressure is lower than 10 MPa. When the inlet pressure is more than 10 MPa and outlet to inlet pressure ratio is less than 0.9, there is a big difference between the specific heat ratio and the volumetric adiabatic exponent, so the specific ratio can’t substitute the exponent. Under the same pressure and temperature, dry gas flow rate is larger than condensate gas flow rate from chokes of same size. The higher the condensate content is, the lower the gas flow rate will be Related Articles | Metrics

Productivity Prediction of Zipper-Like Fracturing Horizontal Wells in Shale Gas Reservoirs with Considering Microscopic Flow PU Xieyanga, HU Yongquana, ZHAO Jinzhoub, LI Zhiqianga 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160512 Abstract ( 68 )   PDF (300KB) ( 169 )   Save On the basis of considering multiple migration mechanisms, a nano-pores gas flow model and an apparent-permeability model are established for shales, based on which a gas reservoir-fracture-wellbore coupled flow model is established through fracture space dispersion and by means of pressure drawdown superposition principle, and matrix analysis method and numerical iteration method are used to solve the model. The factors influencing the productivity of zipper-like fracturing horizontal wells in shale gas reservoirs are analyzed by the model. The result shows that the production considering the microscopic flow of shale gas is higher than that without considering the microscopic flow. Slipping flow contributes the most to the gas production with the secondary of surface diffusion and Knudsen diffusion makes the minimum contribution. The incremental gas production gradually decreases with the increase of well spacing, and there is an optimal value of well spacing. The larger the overlap ratio of stimulated reservoir volume is, the less the gas production will be, but there is an optimal overlap ratio of stimulated reservoir volume with the gradual increase of amplitude of gas production decrease Related Articles | Metrics

Influence of In-Situ Stress on Water Production in Kela-2 Gas Field, Tarim Basin CHEN Sheng, ZHANG Hui, WANG Haiying, WANG Yimin, LIU Xinyu, YUAN Fang 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160513 Abstract ( 66 )   PDF (300KB) ( 173 )   Save An in-situ stress analysis method is introduced to understand the reason for increase of water-breakthrough wells and the mechanism of mismatch of gas-water contact rising at different structural positions. After the establishment of a 3D dynamic in-situ stress field model, shear stress and effective normal stress on the surfaces of faults and fractures are extracted, variation of shear stress to effective normal stress ratio is calculated, mechanical activity performances of faults and fractures during stress field evolution are evaluated, by which the corresponding relation with water-breakthrough in gas production wells could be found and the mechanism of water-breakthrough in them could be clearly understood. . The study shows that the enhancement of fault and fracture activities during the dynamic change process of in-situ stress is the main reason for water production in the gas field. Additionally, the differences of mechanical activity performances of faults and fractures at different structural positions result in the mismatch of gas-water contact rising at different structural positions Related Articles | Metrics

Forecast of Initial Horizontal Well Productivity in Tight Reservoirs by Volumetric Fracturing Process WANG Wei 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160514 Abstract ( 81 )   PDF (300KB) ( 228 )   Save Aiming at the difficulties in initial well productivity forecast after volumetric fracturing, the article analyzes the influencing factors of initial well productivity after fracturing based on the data of geology, engineering and production performance by volumetric fracturing process in District Long-26 and Yuanping-1 of Daqing oilfield. Gray correlation analysis method, multiple correlation coefficient method and entropy evaluation method are used to analyze the degree of correlation between the initial well productivity after volumetric fracturing and the influencing factors, then the main factors are determined. The study result shows that the main factors influencing the initial well productivity after volumetric fracturing include sand adding volume, liquid adding volume, formation pressure and permeability, based on which the support vector machine (SVM) method is used to forecast the initial well production after fracturing. The actual fracturing effect verifies that SVM method can more accurately forecast the initial production after fracturing than conventional multiple linear regression (MLR) method, which may provide guidance and reference for similar tight oil and gas reservoir development Related Articles | Metrics

Optimization Technology for Horizontal Well Track and Staged Fracturing Based on In-Situ Stress Characteristics: A Case from Carbonate Reservoirs in Tazhong Area, Tarim Basin JU Yan, FAN Kunyu, ZHAO Wei, XIE En, XU Qiuyun, ZHANG Wen 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160515 Abstract ( 53 )   PDF (300KB) ( 396 )   Save Previous technologies for horizontal well track and staged fracturing optimization in carbonate reservoirs could not be used to predict the complexity of reservoir stimulation and the connections of favorable fractures around wellbores, due to lack of comprehensive analysis data of in-situ stress. On the basis of reservoir in-situ stress characteristics, a 3D in-situ stress model based on wave impedance inversion data cubes is established for the carbonate reservoirs, which integrates horizontal well track and staged fracturing optimization technologies, including the drilling rate of fracture zones, borehole stability and reservoir stimulation at the late stage. The method is applicable for heterogeneous carbonate reservoirs in Tazhong area, Tarim basin and can provide basis for horizontal well track design and staged fracturing stimulation Related Articles | Metrics

Application of Constraint Analysis Method to Establishing In-Situ Stress Model YANG Minghe1ZHANG Yang1YANG Hu2WEN Qianbin2SHI Jiangang2CHEN Weifeng2 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160516 Abstract ( 73 )   PDF (300KB) ( 151 )   Save The accurate establishment of in-situ stress model is an important basis for oil and gas exploration and development. The constraint analysis method is used to establish in-situ stress model, whose essence is to analyze the constraint boundaries of vertical principle stress, the max. horizontal principle stress and the min. horizontal principle stress, narrow the computing boundaries and improve computing accuracy. On the basis of the fault pattern theory proposed by E. M. Anderson, 4 types of in-situ stress boundaries and the corresponding constraint equations are obtained. The frictional strength on the original fault surface determines the upper limit of stress differences between the max. and min. horizontal principle stress; formation pore pressure can give the lower limit of the min. horizontal principle stress; the width of borehole breakout or drilling-induced fractures can be used to determine the upper limit of the max. horizontal principle stress; the min. horizontal principle stress can be measured by hydraulic fracturing tests and the max. horizontal principle stress can be estimated as well; the vertical principle stress can be gained through density logging curve integral. The actual application shows that the constraint analysis method is an effective way to establish in-situ stress model and to determine the 3 principle stresses (especially the max. horizontal principle stress) combined with the results from laboratory stress experiments Related Articles | Metrics

Application of Conventional Gas-Component Monitoring Technique in Fire Flooding in Wellblock Hongqian-1, Hongshanzui Oilfield, Junggar Basin HUANG Jihong, HUANG Ling, ZHU Wenguang, LI Tao, PAN Weiqing 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160517 Abstract ( 56 )   PDF (300KB) ( 149 )   Save Taking the fire-flooding pilot test area in Wellblock Hongqian-1 of Hongshanzui oilfield, Junggar basin as an example and on the basis of data analysis of field gas component monitoring, whether the reservoir is ignited and is in a high-temperature combustion state can be rapidly determined. In view of no effective front-line monitoring technique up to now, the article proposes a new method by which the air distribution can be verified on the basis of data analysis of gas component monitoring. The result can be used to provide basis for production performance adjustment of fire-flooding and to identify abnormal status of production wells in time. The re-understanding of H2S variations during in-situ combustion process in Wellblock Hongqian-1 can provide data for surface engineering planning during the industrilization of fire flooding Related Articles | Metrics

Analysis on Application Effect of NMR Logging Data in Igneous Rocks in District Dixi SHI Feizhou1, WANG Yanchun1, SUN Wei2, FANG Yuan3 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160518 Abstract ( 58 )   PDF (300KB) ( 145 )   Save There are big differences among igneous reservoirs with similar physical and fluid properties, but the reason for the differences is not clear. Taking the Carboniferous igneous rocks in District Dixi of Junggar basin as an example, the paper analyzes the application effect of NMR data from 3 wells and discusses the differences of the NMR data application effect from 3 aspects such as ferromagnetic mineral content, quartz content and shale content. The result shows that the application effect of NMR data in acidic igneous rock study is better than that in intermediate-basic igneous rock study. The calculated porosity obtained from NMR logging decreases with the increase of ferromagnetic mineral content, which is closer to the actual formation porosity with the increase of quartz content and becomes larger with the increase of shale content. The variation of the porosity is less than 10% Related Articles | Metrics

Application of Modified Morlet Wavelet Transform in Reservoir Prediction QI Yu, LIANG Jianshe, LIU Yinghong, YU Ziliang, CHEN Silu 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160519 Abstract ( 94 )   PDF (300KB) ( 280 )   Save Morlet wavelet possesses the highest resolution in time frequency domain. This article presents a wavelet transform method, selects Morlet wavelet as mother wavelet, introduces a parameter c2 controlling the bandwidth of wavelet functions which will be modified later, and studies the influences of c2 variation on wavelet functions. After the application of modified Morlet wavelet transform in seismic physical modeling, the seismic data after frequency division processing can provide more clear description of objectives. The case study shows that the modified frequency division processing method of Morelet wavelet transform can effectively improve the accuracy of reservoir prediction Related Articles | Metrics

A New Method to Calculate Shale Gas Reserves Considering Dissolved Gas in Kerogen YANG LongMEI Haiyan ZHANG MaolinYUAN En 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160520 Abstract ( 68 )   PDF (300KB) ( 137 )   Save Predecessors did not consider the dissolved shale gas in kerogen when calculating the shale gas reserves. But it has been proved by some researchers that large amount of shale gas dissolved in kerogen can not be ignored in the calculation. The reserves calculation method ignoring the dissolved gas in kerogen can’t be used to truly and accurately calculate the reserves in shale gas reservoirs. Based on the previous calculation methods for shale gas reserves, a new material balance equation is established considering adsorbed phase density, volumetric variations of matrix and fracture pores with pressure, changes of adsorbed phase volume with pressure and dissolved gas in kerogen. Case study shows that dissolved gas accounts for about 4.69% of the total reserves. Reserves of free gas, adsorbed gas and total gas will be overestimated if dissolved gas is not taken into consideration. Therefore, in order to ensure the accuracy of reserves calculation, dissolved gas must be taken into account in the reserves calculation Related Articles | Metrics

Litho-Facies Classification of Baikouquan Formation in Mahu Sag, Junggar Basin ZHANG Changmin1WANG Xulong2ZHU Rui1QU Jianhua2 PAN Jin1AN Zhiyuan2 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160521 Abstract ( 67 )   PDF (300KB) ( 204 )   Save A set of multi-lithological coarse-grained sediments dominated by conglomerate are developed in the Lower Triassic Baikouquan formation in Mahu sag, Junggar basin. Researchers conducted in-depth studies on litho-facies types, but some problems still exist in lithofacies classification and relationship between lithofacies and sedimentary microfacies. The reason is that it is difficult to express the lithofacies associations in different microfacies and to differentiate the characteristics and association differences among similar microfacies by means of small amount of lithofacies types. Based on the systematic descriptions of lithology, color, sedimentary structure, sorting, roundness, orientation, fabric support, cementation type, cement composition, the max. grain size, average grain size, oil-bearing property and gravel component from 77 cored wells in Mahu sag, the paper proposes a new lithofacies classification method, which can be used to classify and denominate lithofacies mainly according to 4 properties such as sedimentary structure, color, grain size and fabric support. 227 lithofacies types have been identified from the cores of Baikouquan formation in Mahu sag, including 153 for conglomerate, 58 for sandstone and 16 for mudstone. The results well reflect the diversity of lithofacies of Baikouquan formation in Mahu sag, lay a foundation for accurate description of sedimentary characteristics of different sedimentary microfacies and provide basis for detailed sedimentary facies identification Related Articles | Metrics

Characteristics of Reef-Flat Reservoirs of Callovian-Oxfordian Stage in Right Bank Area, Amu-Darya Basin NIE Minglong1,2, ZHAO Xinglin1, CHENG Muwei3, CHEN Xiaoshuai1 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160522 Abstract ( 79 )   PDF (300KB) ( 262 )   Save Reef-flat body is the dominant reservoir type in the Middle-Upper Jurassic Callovian-Oxfordian carbonate rocks in Amu-Darya basin. Based on seismic facies analysis, rock thin section identification and reservoir physical property test in Amu-Darya right bank, and combined with paleogeomorphology and stratigraphic correlation, the article demonstrates the types of reef-flat bodies in Callovian-Oxfordian carbonate rocks in Amu-Darya basin, and analyzes the genesis of the reef-flat reservoirs. 2 types of reef-flat bodies such as platform-margin reef-flat body and gentle-slope reef-flat body are found in Callovian-Oxfordian strata in Amu-Darya basin. The development of the reef-flat bodies is controlled by paleogeomorphology and sedimentary environment is the main controlling factor of the development of the reef-flat reservoirs. Selective dissolution of biological components is the reason causing the differences of the 2 types of reef-flat reservoirs. All the characteristics of developed primary framework pores and intergranular pores in the platform-margin reef-flat body, high cotent of the easily dissolved components of reef-building organism and bioclastics, and easy to form diagenetic fluid infiltration and disolved pores indicate that the physical properties of the reservoirs are pretty good and the high positions of the paleogeomorphology are the favorable zones for reef-flat reservoir development Related Articles | Metrics

Genesis of Inclined Water Oil Contact in Nahr Umr Reservoir, Rumaila Oilfield ZHOU Jiasheng1,2XIE Jingbin2LIN Jian3 2016, 37 (5):  1-1.  doi: 10.7657/XJPG20160523 Abstract ( 120 )   PDF (300KB) ( 450 )   Save To understand the genesis of inclined water oil contact in Nahr Umr clastic reservoir of Albian stage in Rumaila oilfield and improve the accuracy of oil and gas reserves estimation and rationality of development plan and adjustment, four aspects are discussed including formation water discharge, inclination degree of water oil contact (WOC) , characteristics of oil and water pressure gradient response and regional pressure variation by analyzing the data of well logging, wireline formation pressure and regional geology, based on the summaries of the different causes of inclined WOC. It is considered that hydrodynamism is the main reason to result in the inclination of WOC in clastic reservoir of Albian Nahr Umr formation and the hydrodynamic force is sourced from the surface water supply in Teros-Zagros thrust-fault fold belt in the northeastern part of the oilfield Related Articles | Metrics