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01 January 2019, Volume 37 Issue 3 Previous Issue    Next Issue

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Hydrocarbon Distribution and Accumulation Mechanism of Dibei Tight Sandstone Gas Reservoir in Kuqa Depression, Tarim Basin LIU Liwei, SUN Xiongwei, ZHAO Yingjie, JIN Jiangning 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160302 Abstract ( 106 )   PDF (300KB) ( 208 )   Save Based on the data from formation testing, fracture development degree and natural gas component analysis in Dibei gas reservoir in Kuqa depression of Tarim basin, the hydrocarbon distribution and accumulation mechanism are re?recognized. The results show that Dibei gas reservoir is a transitional one between trap?type and continuous tight sandstone gas reservoirs. Natural gas is mainly discontinuously distributed in and around the traps. Diffusion is not the dominant mechanism of gas transport. Gas generated from source rocks flows into reservoirs selectively and continuously fills the neighboring reservoirs in free state along charging points which may be related to fracture development degree in the reservoir. Dibei gas reservoir is classified as a kind of composite tight sandstone gas reservoir according to its special accumulation features. The similar method for exploration of trap?type tight sandstone gas reservoir can be adopted for Dibei gas reservoir Related Articles | Metrics

Heterogeneity and Main Controlling Factors of Hydrocarbon Distribution in Weibei Sag,Bohai Bay Basin LIU Hua1, LI Zhensheng1, JIANG Youlu1, XU Haoqing2, CHEN Ketong1, WANG Xin1 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160303 Abstract ( 66 )   PDF (300KB) ( 207 )   Save In order to correctly understand the features of extremely heterogeneous hydrocarbon distribution and rich in the east and poor in the west and the controlling factors in Weibei sag of the Bohai Bay basin, this paper analyzes the hydrocarbon migration process and accumulation pattern on the basis of source rock and accumulation period analysis and oil?source rock correlation. The result shows that the oil and gas mainly accumulate in the Eocence Kongdian formation in this sag, and there are significant differences on hydrocarbon accumulation and main controlling factors in the east and in the west: the oil and gas in the east mainly came from the sources rocks of the middle and upper sub?member of Ek developed in nearly eastern part of the northern sub?sag belt, and accumulated during Es4 to Ed depositional period. Tectonic movements resulted in the steplike, uplifting migration of hydrocarbons from the north to the south. Microstructural ridges acted as the predominant pathways for oil and gas migration with a migration and accumulation mode of“bidirection conduction?lateral migration”. The key to good hydrocarbon accumulation is moderate structural movement during entrapment and good preservation; the oil and gas in the west mainly came from the sources rocks of the middle and lower sub?member of Ek in this sub?sag which suffered from 2 times of hydrocarbon generation during Es4 to Ed depositional period and late depositional period of Minghuazhen formation, respectively. Its accumulation is featured with the“entrapped during 2 different periods?the accumulated near source rocks”, large burial depth and tight reservoir. Deep?burial near?source gas reservoirs around the secondary hydrocarbon?generation center are the targets for oil and gas exploration in the western areas Related Articles | Metrics

Accumulation Pattern of Shale Oil in Dongying Sag and Zhanhua Sag, Bohai Bay Basin ZHU Deshun 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160304 Abstract ( 81 )   PDF (300KB) ( 163 )   Save Taking the shale of Lower Sha?3 member and Upper Sha?4 member of Oligocene Shahejie formation in Dongying sag and Zhanhua sag of Baohai Bay basin as a case, this paper systematically studies the enrichment elements of high?yielding shale oil from the perspective of oil and gas generation, migration and accumulation. Integrated with the characteristics of oil and gas productivity, hydrocarbon component, stratigraphic contact relationship, oil saturation and pressure coefficient, the accumulation patterns in Dongying sag and Zhanhua sag can be divided into such 3 types as self?generation and self?preservation, fault connection and interlayer enrichment. Shale oil of selfgeneration and self?preservation widely exists in the shales of the 2 sags, but since it is influenced by the conditions of hydrocarbon generation and accumulation, the oil well productivity of this type is relatively low. Constrained by structure and lithology, the other 2 types are distributed in some local areas but have high productivity. After the identification of shale oil accumulation patterns, more targeted plans can be made for oil exploration and development, thus enhancing efficiency of exploration and development of the shale oils Related Articles | Metrics

Storage Space Types and Controlling Factors of Mesoproterozoic Carbonate Rocks in Jibei and Xuanlong Depressions in Yanshan Area SUN Yuxuan1a, LUO Shunshe1a,1b, L? Qiqi1a,1b, LIU Zhanghao2, XIANG Ji1a, LI Yudong1a 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160305 Abstract ( 65 )   PDF (300KB) ( 172 )   Save On the basis of field measurement and core observation of Mesoproterozoic outcrops in Jibei depression and Xuanlong depression in Yanshan area, through integrated analysis on common thin sections, cast thin sections and SEM data, it is found that the reservoir rocks in the study area are mostly composed of dolomite, secondly of limestone and partially of siliceous rock, sandstone and breccia. The storage spaces of the reservoir are mainly composed of 2 storage systems that are micro?storage spaces in the matrix and macro?storage spaces of fissures and caves, in which the macro?storage spaces include 6 types such as tectonic fissures, interlayer fissures, dissolution fissures, dissolved caves (pores), constricted fissures and pressolution fissures, and the matrix pores are composed of intercrystalline pores, intergranular pores, alga?window pores, slightly dissolved pores (fissures), micro?tectonic fissures and micro?pressolution fissures. The sedimentary environment, lithology, diagenesis and tectonism are the main 4 factors influencing the storage spaces in the study area, among which tectonism and palaeo?karstification are the key factors to improve the storage conditions in the study area Related Articles | Metrics

Structure and Geological Significance of Pishan Caldera in Tarim Basin ZHANG Changjian, LIU Shaojie, LUO Shaohui, WANG Ming 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160306 Abstract ( 126 )   PDF (300KB) ( 510 )   Save On the basis of caldera theory integrated with seismic?lithofacies interpretation and tectonic evolution, the paper investigates the structures of Pishan caldera and describes its impact on the Cretaceous reservoirs. It is considered that the large?scaled composite caldera in Pishan formed in the late Hercynian movement, which is a circle with the diameter of 25 km and the maximum subsidence depth of 1.5 km. Volcanic materials erupted in central and fissure mode along the ring fault and the evacuation of magma chamber resulted in sharply subsidence. Volcanic eruption facies, lacustrine facies and Cretaceous breccia facies assume the circular symmetric distribution; innerdipping circular normal faults and outer?dipping circular inverse faults are developed in collapse structure area and high-steep divergent inverse faults occur in central dome structure area, which indicates the complete process of caldera from its first eruption, subsidence to reactivation. Pishan caldera structure controls the development and distribution of the Cretaceous reservoirs Related Articles | Metrics

Dark Laminae of Bashijiqike Formation and Well Logging Response in Bozi Area of Kuqa Depression, Tarim Basin ZHOU Peng, XIE Yani, NENG Yuan, SUN Di, WANG Bin, ZHANG Xing 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160307 Abstract ( 52 )   PDF (300KB) ( 173 )   Save Large numbers of dark laminae occur in the core samples of Bashijiqike formation in Bozi area of Kuqa depression in Tarim basin. Taking Well Bz102 as an example, this paper studies the development characteristics of the dark laminae and the impacts on the reservoir by using core samples, thin sections, heavy minerals and imaging logging data, and develops the high?resolution imaging logging model for recognizing the dark laminae. Study shows that the dak laminar in Bozi area are mainly resulted from magnetite enrichment due to nearby provenance. The existence of dark laminae decreases the porosity and permeability of the reservoir. In Well Bz102, 169 dark laminated layers have been recognized, and 75% of perforated intervals in test located in the intensive sections of dark laminae. So, the decrease of vertically connecting ability of the reservoir could be an important factor of low productivity in this well Related Articles | Metrics

Characteristis and Prediction of Natural Fractures in Triassic Chang8 Member, Jinghe Oilfield LI Lingchuan1, XU Wenxi2, DENG Hucheng3, LIU Yanjun1, LIANG Chen1, HAN Jielin1 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160308 Abstract ( 90 )   PDF (300KB) ( 327 )   Save Through analyses of outcrop, core and FMI logging data, it is considered that vertical fractures and high?angle oblique fractures are the dominant natural fracture types in Triassic Chang?8 member of Jinghe oilfield in Ordos basin. These fractures are mainly NE-SW trending, which are mainly developed in sandstone reservoirs with a few strata?penetrating fractures and relatively low filling. Most fractures are open with relatively good validity. The development of natural fractures is mainly controlled by lithology, structural deformation and fault, and the fault is the main factor. The prediction result of natural fracture distribution shows that the fractures are best developed in Wellblock Jinghe?17 in eastern Jinghe oilfield and Wellblock Jinghe?2 in western Jinghe oilfield, and the sandbodies in the reservoir are thick with relatively good development potential; fractures in the middle and northern parts of the region are relatively developed with secondary development potential. The prediction results are well matched with the actual production data Related Articles | Metrics

Simulation Experiment Study on Dynamic Hydrocarbon Accumulation of FaultBlock Sandstone Reservoirs WU Ping 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160309 Abstract ( 62 )   PDF (300KB) ( 119 )   Save In order to study dynamic hydrocarbon accumulation in fault?block sandstone reservoirs, related simulation experiments are carried out on the differences of filtration capacities between oil and water and the impact of hydrodynamic conditions on oil enrichment during the dynamic oil accumulation. The result shows that significant difference exists in oil and water filtration capacities, oil filtration capacity is lower than that of water, which results in the oil accumulation in cores and then the dynamic oil enrichment in permeable media; oil enrichment is constrained by hydrodynamic conditions during hydrocarbon charging, and the stronger the hydrodynamic force is, the easier the oil enrichment will be, and the higher the enrichment degree will be, too. It is assumed that appropriate?open reservoirs sheltered by normal faults are in accordance with the dynamic reservoir accumulation patterns and the application of the dynamic model could macroscopically explain the relationships among the effectiveness of fault sheltering, complicated physical property distribution of fault block reservoirs, accumulation of fault?sheltered reservoirs and hydrocarbon generation setting in the basin and so on Related Articles | Metrics

Study on Karst Development Pattern Based on FMI Logging Facies:A Case Study of Paleozoic Strata in Nanpu Sag of Huanghua Depression, Bohai Bay Basin WANG Yelei1QIU Longwei1SHI Zheng1, CAO Zhonghong2, ZHANG Hongchen2 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160310 Abstract ( 66 )   PDF (300KB) ( 133 )   Save Carbonate buried?hill reservoir is the most important reservoir type in the Nanpu sag with controlling effect of karstification on it. In order to further understand the pattern of karst development in Nanpu sag, based on formation microlog imaging (FMI) logging data integrated with geological data such as conventional logging data, log data and thin section analysis of rocks, this paper summarizes the characteristics of FMI logging response controlled by karst development, and establishes 5 logging facies such as high?resistance fracture facies,high?conductivity fracture facies, enlarged dissolution fracture facies, dissolved pore facies and cave collapse facies. A relationship between karst development characteristics and FMI logging facies is established on the basis of data statistics. The result shows that epigenetic karst belt is developed in the upper part of Nanpu sag and the buried karst belt in the lower part, and high?conductivity fracture facies,dissolved pore facies and cave collapsse facies are mainly found in the epigenetic karst belt, and the cave collapse facies is a unique feature for this belt; while high?resistivity fracture facies, enlarged dissolution fracture facies and dissolved pore facies are mainly found in the burial karst belt. Lithology and fault are the dominant controlling factors for karst development Related Articles | Metrics

Quantitative Analysis on Minimum Lateral Resolution Range of FractureCave Bodies in Carbonate Rocks LI Fanyi1, DI Bangrang2, WEI Jianxin2, XU Jianyong1, WU Aijun1, YIN Binhao1 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160311 Abstract ( 56 )   PDF (300KB) ( 171 )   Save Quantitative analysis on fracture?cave bodies’lateral minimum resolution range is a practical problem for the prospecting and development of fracture?cave carbonate reservoirs. This paper derives a spatial wavelet function using the double?focusing theory, analyzes the minimum lateral resolution range based on criteria of Rayleigh and Rickers theoretically. It is considered that the minimum lateral resolution range of point scatterer could be 1/2 of the main lobe width of the spatial wavelets approximately, whose value is proportional to seismic wave length and shows an inverse correlation with the sine value of the maximum emergence angle. Seismic forward modeling is performed from the perspective of practical application, which provides a precision basis of the minimum lateral resolution range of fracturecave bodies for actual production Related Articles | Metrics

A Comprehensive Production Formula for Horizontal Wells LI Chuanliang1, ZHU Suyang1, DONG Fengling2 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160312 Abstract ( 87 )   PDF (300KB) ( 69 )   Save Conventional production formulas for horizontal wells only consider the outer planar radial flow and the inner vertical radial flow, and ignore the intermediate planar linear flow. So the flow resistance is underestimated and oil production is overestimated with these formulas. This paper presents a comprehensive production formula for horizontal wells, which covers all the three flows. In comparison with the conventional production formulas, this new formula can get a higher flow resistance and a lower production rate for horizontal wells. Calculations show that the longer the horizontal section is, the higher the ratio of the intermediate planar linear flow to the total flow of wells will be, and the larger the drop of the production rate from the conventional production rate formulae will be. As the horizontal section length is close to the length of oil drainage zone, the new formula tends to be the production rate formula for wells with relatively long horizontal section. Therefore, horizontal wells with long and short horizontal section lengths can be unified by this new formula Related Articles | Metrics

Application of GasDrive Type Curves to FireFlooding Development of Heavy Oil Reservoirs YUAN Shibao1, YANG Fengxiang2, SHI Yaoli2, DIAO Changjun2, SHI Xiaorong2, JIANG Haiyan1 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160314 Abstract ( 64 )   PDF (300KB) ( 191 )   Save Fire?flooding or in?situ combustion is an effective process for primary and secondary development of heavy oil reservoirs. Compared with water drive, this process is more complex, and few engineering methods can be used for studying production performance in fireflooding reservoirs. The paper proposes a new method to study fire?flooding reservoir’s productoin performance with gas?drive type curves,by which the problems in dynamic analysis during production can be well solved. This new method has been proved by production performance data obtained from Wellblock Hongqian?1 in Karamay oilfield and Suplacu oilfield in Rumania. Relations among cumulative oil production, cumulative gas production and produced GOR can be established on the basis of the gas?drive type curve. Finally, recoverable reserves by fire?flooding process can be determined with the relations as the fire?flooding reaches the economic limits Related Articles | Metrics

Escaping Loss of CoalBed Methane during Production ZHU Suyang,LI Chuanliang,DU Zhimin,LI Zepei,PENG Xiaolong 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160315 Abstract ( 108 )   PDF (300KB) ( 160 )   Save This paper analyzes coal?bed methane (CBM) preservation, accumulation and the escaping loss during production, presents several factors to identify coalbed methane escaping loss by defining 2 parameters?escaping velocity ratio and escaping distance ratio. Then the escaping loss volume and distribution of CBM escaping are calculated by simulation. Meanwhile, the impact of surrounding rock permeability, initial entrapped gas volume in coal beds and gas production on CBM escaping loss volume are studied. If CBM escaping distance ratio is larger than the maximum CBM escaping velocity ratio, it is considered that CBM will not escape from coal beds. Case calculation shows that the escaping loss is likely to occur in the areas far from wellbores and 10%~15% of CBM reserves will be lost during production, and more than 10% of CBM reserves escapes during the early production stage. Relative low loss commonly occurs in the coal?beds with high and low CBM content, however, the coal?beds with intermediate CBM content may suffer relative high losses. Therefore, the key to reducing CBM escaping loss is to establish producing pressure?drop quickly in coal beds to realize rapid production at the early stage Related Articles | Metrics

OffCenter Well Test Analysis for Composite DualPorosity Reservoirs JIANG Ruizhong1, GAO Yihua1, SUN Zhaobo2, HE Jixiang1, LI Zhitao1 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160316 Abstract ( 58 )   PDF (300KB) ( 208 )   Save The basic assumption of formation test in composite dual?porosity reservoirs in vertical wells is that wells should be located in the center of the inner region of the reservoir. However, this assumption is hard to be realized during the actual well test. Eccentricity is used to describe well locations in the inner region of composite reservoirs, then an off?center well test model considering skin effect and wellbore storage is established for composite dual?porosity reservoirs. The line?source solution of the model is obtained on the basis of pointsource theory, superposition principles and Laplace transform, and the solution in the real space is acquired by Stehfest numerical inversion, based on which the typical pressure curves are further plotted and the influence of eccentricity on typical pressure curves is analyzed.The results show that the influence of eccentricity on the pressure performance of composite reservoirs is mainly embodied in the transition stage of radial flows between that in the inner region and the fracture system in the outer region. And a bigger eccentricity will lead to an earlier end of the inner?region radial flow of the whole system, the transition stage of radial flows will occur earlier, and the pressure derivative curve in the transition flow stage will change more slowly Related Articles | Metrics

Determination of the Minimum Displacement of Staged AcidFracturing BallOff in Horizontal Wells ZHOU Jianping1,2, GUO Jianchun1, JI Xiaohong2, YUAN Xuefang2 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160317 Abstract ( 55 )   PDF (300KB) ( 166 )   Save There are several shortcomings of conventional staged acid?fracturing technology in horizontal wells drilled in carbonate rocks:The fracturing stage is limited, full?bore of the strings can’t be realized and water searching and plugging can’t be implemented at the late stge of the production. The paper introduces the main tools and its technical principles of staged acid?fracturing in full?bore horizontal wells and gives the detailed demonstration to the key technology of ball?off plugging. A force model has been established for ball sealer where the ball?sealer can be seated and maintained under the forces of the eyehole, and an equation controlling ball?sealer displacement is obtained.Thus a technique is developed for the minimum displacement control. The field application shows that the staged acid?fracturing technology in full?bore of horizontal wells is matured, and the open rate of staged tools is higher, which can well solved the problems of acid?fracturing in multi?layers and the impact of hole shrinkage inside tubing on the follow?up production Related Articles | Metrics

Hydraulic Fracture Geometry of Shale Gas Reservoirs with Strong Tectonic Stress and Large Dip Angle in Northeastern Margin of Sichuan Basin ZHOU Tong1, ZHANG Shicheng1, ZOU Yushi1LI Ning1, ZHENG Yonghua2 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160318 Abstract ( 73 )   PDF (300KB) ( 202 )   Save Hydraulic fractures are distributed irregularly due to strong tectonic stress, large dip angle formation, highly developed bedding and natural fissures of shale gas reservoirs in northeastern margin of Sichuan basin. Based on finite?element and discrete?element combined method, the transverse isotropic constitutive relations are introduced to represent lamellar shale and a 3D complex fracture propagation model has been established. Then the model is used to analyze several important parameters which could influence the fractures after stimulation, such as in?site stress difference, fracturing fluid viscosity, injection rate and natural fracture, etc. The modeling result shows that the larger the difference between vertical stress and the minimum horizontal principle stress is, the easier the vertical fractures will occur. Under the condition of the low differential stress (5 MPa), increasing fracturing fluid viscosity and injection rate is more likely to decrease the limit of bedding to fracture propagation, increase vertical fractures and improve vertical stimulation effect. The more developed the natural fractures without advantageous strikes in shale, the more the shear fractures will be under strong tectonic stress differences Related Articles | Metrics

Numerical Simulation Method and Its Application when Considering TimeDependent Effect of Reservoir Parameters JIN Zhongkang1, FANG Quantang2, WANG Lei1, ZHAO Long3 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160319 Abstract ( 68 )   PDF (300KB) ( 72 )   Save Due to the influence of long?term scouring of injected?water, the physical properties and characteristic percolation parameters of reservoirs tend to change greatly in water?injection oilfields, which will result in large variations of relative permeability of rocks and more complexity of relative permeability curves after the changes. Conventional numerical modeling software never considers the variations of physical properties and relative permeabilities of reservoirs, so that the modeling results can’t match with the actual situation completely.A percolation mechanism model has been established for low?permeability Sha?20 fault block in eastern Subei basin to evaluate the changes of typical characteristic reservoir parameters during long?term water injection, by which the characterization of time?dependent numerical simulation method can be realized for physical properties and relative permeability of reservoirs. The result shows that long?term scouring of injected water will result in poorer physical properties and enlargement of the calculated average remaining oil saturation regarding medium and low permeability reservoirs, especially in the surroundings of injectors. But the remaining oil distribution patterns are basically the same before and after considering the time?depending effect Related Articles | Metrics

Quantitative Prediction of Mineral Component Content and Brittleness Index in Tight Rocks Based on Multivariate Regression Analysis HUANG Junping1a,1b, ZHANG Zhisheng2, YANG Zhanlong1a,1b, HUANG Yunfeng1a,1b, DI Jun1a, ZHANG Liping1a 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160320 Abstract ( 72 )   PDF (300KB) ( 296 )   Save Quantitative prediction of mineral component content and brittleness in tight rocks can provide a basis for optimization of exploration targets and fracturing intervals in unconventional reservoirs. Taking Jurassic coal?bearing strata in ZKZ basin and Jurassic non?coal strata in YBL basin in western China as examples, conventional logging curves sensitive to mineral components are selected based on conventional logging and core analysis data. Standardized processing is performed for sensitive logging curves related to modeling. Based on multivariate regression analysis, a quantitative model is established with multivariate regression analysis to predict mineral component content and brittleness in tight rocks in coal?bearing and non?coal strata, and the features and geneses of tight rock brittleness are demonstrated.The prediction results highly correspond to the actual measured values Related Articles | Metrics

Application of Annulus Fracturing Technology with Coiled Tubing in Deep Igneous Reservoirs:A Case Study of Well Mahu5 in Wellblock K81, Karamay Oilfield PANG Dexin, GUO Xinwei, ZHAO Qian, HUANG Ronghui, JIAO Wenfu 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160321 Abstract ( 61 )   PDF (300KB) ( 171 )   Save The igneous reservoir of Wellblock Ke?81 in Karamay oilfield is characterized by deep burial, no natural productivity in oil wells, so there is generally no effect to increase oil production without fracturing and/or acidizing. On the basis of analyses of the rock mechanics, fracture characteristics and the impact of fracturing fluid systems on fractures, the fracturing scheme is optimized, and coiled tubing bottom sealing annulus fracturing process is used to perform fracture network fracturing. Such a large displacement and high pump pressure fracturing can form fracture networks connecting natural fracures and improve flow conductivity in the reservoir for obtaining high oil production. The successful application of this technology in Well Mahu?5 will provide practical guidance for future development of Wellblock Ke?81 and similar wells Related Articles | Metrics

A New Method to Calculate Dynamic Reserves in FracturedVuggy Reservoirs: A Case from Halahatang Oilfield, Tarim Basin CHEN Lixin1, WANG Lianshan2, GAO Chunhai1, SUN Yinhang2, WANG Xia1, ZHANG Mao2 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160322 Abstract ( 92 )   PDF (300KB) ( 235 )   Save It is difficult for conventional methods to evaluate dynamic reserves in fractured?vuggy carbonate reservoirs due to great differences in well performances. Accurate results cann’t be obtained with material balance method because more parameters are needed for calculation,which tends to bring some errors of them. After the driving stage is defined for reservoirs, the difference value of bottom?hole crude oil density obtained from two pressure tests and the cumulative production during the stage can be used to calculate the dynamic reserves more accurately. Compared with material balance equation and other methods, the method of bottom?hole crude oil density difference can avoid impacts of crude oil volume factor, crude oil compressibility coefficient and rock compressibility coefficient on calculation results,and the accuracy of calculated dynamic reserves can be further improved Related Articles | Metrics

A New Method to Calculate the Lower Limit of Effective Pore Throat Threshold of Tight Sandstone Reservoirs: A Case Study of He8 Gas Reservoir in Sulige Gas Field LIU Xiaopeng, LIU Xinshe, ZHAO Huitao, WANG Huaichang, ZHANG Hui 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160323 Abstract ( 64 )   PDF (300KB) ( 175 )   Save Because the mercury injection process is similar to that of hydrocarbon charging and accumulation, it is considered that the throat radius corresponding to the capillary pressure of mercury injection saturation which equals to hydrocarbon saturation of sealed?coring samples should be the effective pore throat radius threshold on the capillary pressure curves of sealed?coring samples, and the minimum effective pore throat diameter threshold in representative sealed?coring samples is the lower limit of effective pore throat of the reservoir. The paper proposes a new method to calculate the lower limit of the effective pore throat threhold of tight sandstone reservoirs accurately and rapidly. It also discusses and analyzes the advantages and limitations of the current methods. Taking He?8 reservoir of Sulige gas field as an example and based on the method of capillary pressure curve of sealed?coring samples, the obtained effective pore throat threhold of He?8 reservoir is 53.3 nm. Therefore, it is concluded that the pore systems connected by the pore throat with the radius more than 53.3 nm will be the main targets for exploration and development Related Articles | Metrics

Accumulation Features of Sarvak Unsteady State Reservoir in Azadegan Oilfield, Iran DU Yang1,2, HU Yang2, XIONG Shu3, XU Qiancheng2, XIN Jun2, WANG Juan2 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160324 Abstract ( 70 )   PDF (300KB) ( 329 )   Save Base on the understanding that the Upper Cretaceous Sarvak reservoir of Azadegan oilfield in Iran is an unsteady state reservoir with an inclined oil?water contact, this paper studies the accumulation features of the reservoir using the data of 3D seismic, core analysis and actual drilling. The result shows that the reservoir was influenced by Late Cretaceous Alpine tectonic movement and the paleotraps formed with the features of higher in the north and lower in the south. The reservoir received the charging of hydrocarbons generated in Kazhidumi source rocks in the eastern Dezful depression of the oilfield in Miocene, and thus the ancient reservoirs formed. Miocene Zagros orogeny resulted in the structural inversion of the paleotraps that evoluted into the current structural configuration of two highs both in the south and north, and higher in the south and lower in the north. Because this change broke the dynamic balance of the paleotraps and the tectonic movement didn’t impact the overlying cap rocks, the secondary migration from the paleotraps in the north to the secondary traps in the south occured in the blocked accumulates. The reservoirs are still in the unsteady state of the early modulating stage, that means a steady horizontal oil?water contact is noted in the northern paleotraps and a significant incline uplifting oil?water contact exists in the southern secondary traps Related Articles | Metrics

Lithofacies Paleogeography of Cretaceous Bashijiqike Formation in Kuqa Depression,Tarim Basin MA Yujie1, ZHANG Ronghu2, TANG Yangang1, CHEN Ge2, MO Tao1, WANG Junpeng2, XIE Bin1 2016, 37 (3):  1-1.  doi: 10.7657/XJPG20160301 Abstract ( 86 )   PDF (300KB) ( 211 )   Save To identify the characteristics of sedimentary facies and microfacies and their relationships with the paleogeographic setting,based on microfacies observation of outcrops, microfacies description of cores, characterization of imaging?logging facies, restoration of structural evolution and superimposed analysis of sedimentary elements, it is considered that Cretaceous Bashijiqike formation is generally controlled by 3 factors such as southern Tianshan mountain, Wensu swell and Kuruktag mountain in provenance. Bashijiqike formation provenance in the Kelasu thrust belt is mainly originated from southern Tianshan mountain, and that in the western part of Tabei uplift is from Wensu swell, and that in the mid?eastern part of Tabei uplift from Kuruktag mountain. Qiulitag structural belt is the intersection area of these 3 provenances and Wushi sag is controlled by both southern Taishan mountain and Wensu uplift; 2 typical sandstones such as braided delta?front mid?fine sandstone and fan?delta front underwater distributary?channel silt?fine sandstone are mainly developed in the Kelasu thrust belt. Sandbodies are superimposed and distributed continuously with the residual thickness of 150~260 m; Tabei uplift is dominated by mid?fine sandstones of fan?delta front underwater distributary?channel facies and fine?silt sandstones of braided delta?front underwater distributary?channel facies mixed with some silt?fine sanstones of river mouth bar facies. The thick sandbodies are generally distributed continuously in Tabei uplift with the residual thickness of 100~300 m. The understanding as“the sandstones are distributed in the whole depression”in Cretaceous Bashijiqike formation provides a significant theoretical basis for the breakthrough of the oil and gas strategy in Kuqa foreland area Related Articles | Metrics