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01 January 2019, Volume 35 Issue 1 Previous Issue    Next Issue

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Hydrocarbon Resources Potential in Carboniferous Igneous Inner Reservoirs in Ludong Area of Junggar Basin YANG Haibo1a, XIANG Baoli1b, BAO Haijuan1a, PANG Hong2 2014, 35 (1):  1-1.  Abstract ( 150 )   PDF (300KB) ( 279 )   Save In recent years, a lot of hydrocarbons have been discovered in the Carboniferous igneous rocks of Ludong area in Junggar basin, which shows great hydrocarbon exploration potentials. However, the proved or discovered commercial oil?gas flow is distributed in the weathering crust reservoir in the top of the Carboniferous, only hydrocarbon shows are found in the inner reservoirs without oil?gas flow. The comparative analysis of the characteristics of weathering crust and inner reservoirs as well as hydrocarbon exploration potential shows that the porosity of the igneous reservoir appears two peaks with increasing distance from the Carboniferous top unconformity surface, which are corresponding to two secondary karst zones. The first one means the weathering crust reservoir, the second one means the inner reservoir; It is found that the amount of gas resource is about 1 750×108 m3 in the inner reservoir, and the slope zone will be the favorable gas exploration area for the inner reservoir of Carboniferous igneous rocks in Ludong area Related Articles | Metrics

Evaluation of Shawan Reservoir in Sikeshu Sag in Junggar Basin WANG Zhenqi, YANG Fan, JIANG Xue, ZHAO Liang, CHENG Xin 2014, 35 (1):  1-1.  Abstract ( 53 )   PDF (300KB) ( 185 )   Save The lithology of Shawan reservoir in Sikeshu sag in Junggar basin is mostly medium?fine sandstone, conglomerate in some areas. The reservoir space is dominated by primary porosity, with secondary pores in local areas. The pore throat types of Shawan formation were mainly classified as Type Ⅲ and Type Ⅳ by the characteristics of mercury injection curves and the appraisal of thin?sections. The porosity model is established by geophysical well logging and mathematical methods. Compared with the model developed by single well logging parameters, the correlation coefficient of the new model can be improved by 20%, based on which the study of relation between the petrophysical properties and sedimentary microfacies indicates that both do have certain relationship. The branch channel of braided river delta and fan delta are advantageous facies with good physical properties of the sands. According to the physical property, pore structure and sedimentary facies, the reservoir type in the study area is classified as Type Ⅱ and Type Ⅲ, and evaluated that Shawan reservoir is of good petrophysical property at the whole Related Articles | Metrics

Hydrocarbon Accumulation Mechanisms Controlled by Yanshanian Faults in Eastern Junggar Basin LIU Junbang1, LI Peijun2a, HU Zhi2b, LIU Zhen3 2014, 35 (1):  1-1.  Abstract ( 58 )   PDF (300KB) ( 235 )   Save The Zhundong area is one of major hydrcarbon enrichment belts in eastern Junggar basin. It experienced several intense transformations of multistage tectonic movements in the process of the basin formation and evolution, and resulted in complex fracture system. In order to find out the internal relationship between the faults and the hydrocarbon accumulation in this area and get insight into the formation mechanisms of the fault?controlled hydrocarbon distribution pattern, this paper started from the analysis of known hydrocarbon pools and studied the faults characteristics that controlled the distribution of the hydrocarbon pools. It is shown that the pools in Zhundong area have a close relationship to the faults in the formation process; of the numerous faults in the study area, the Yanshanian faults are of significant control effects on the pool distribution; the matching relationship between the spatial allocation and pool?forming period and the stru?ctural evolution determines the availability of the Yanshanian faults as oil?gas transporting channels, by which the formation and distribution of the hydrocarbon pools are controlled eventually; compared to the Yanshanian faults, the faults shaped in the early periods such as Hercynian and Indosinian movements are formed too early, at which the source rocks are not matured, while late faults formed in the Himalayan movement mostly serve as the adjustment and even destruction of the primary hydrocarbon accumulations, hence, both of them show little relationship to the distribution pattern of the current hydrocarbon pools. It is suggested that the hydrocarbon accumulation and distribution in the study area are obviously controlled by the Yanshanian faults, so the further exploration should focus on the traps adjacent to the Yanshanian faults Related Articles | Metrics

Natural Gas Genetic Type and Accumulation Characteristics in Erboliang III Structure in North Margin of Qaidam Basin TANG Guomin1a,1b, LUO Qun1c, PANG Xiongqi1a,1b, ZHANG Yongshu2, GUO Jigang1a,1b, SHEN Weibing1a,1b, GUO Yingchun1a,1b 2014, 35 (1):  1-1.  Abstract ( 72 )   PDF (300KB) ( 289 )   Save Use the existing wells data, this paper systematically analyzed the natural gas genetic type and accumulation characteristics in the Erboliang III structure based on the analysis of the characteristics of Ca, He and Ar isotopes analysis, integrated with the hydrocarbon source rock evolution, structural development and natural gas accumulation history. The results show that the nature gas in Erboliang III structure is typically coal?related gas. The reverse sequence phenomenon of methane and ethane in the gas reservoir is resulted from mixed natural gas with different maturity in the process of gas accumulation. The natural gas mainly came from the deep over?matured Jurassic hydrocarbon source rocks. The faulting activities play an important role in controlling the formation and evolution of the nature gas reservoir. The natural gas accumulation model could be described as the up?source accumulation model for the fault?Transport layer type Related Articles | Metrics

Diagenesis in Tight Sandstone Reservoir of the Chang9 Interval in Ansai Area in Ordos Basin BAI Yubin1, SUN Huaizhi2, HAO Xiaorong3, CHEN Dong3, LIU Peng4 2014, 35 (1):  1-1.  Abstract ( 50 )   PDF (300KB) ( 202 )   Save According to the analysis and testing data from sandstone thin?section, cast thin?sections, cathodoluminescence, scanning electron microscope, X?ray diffraction, the diagenesis of Chang?9 tight sandstone reservoir in Ansai area in Ordos basin is studied. The results show that Chang?9 sandstone reservoir went mainly through compaction, cementation and dissolution, of which the compaction and cementation are the main factors for reducing reservoir porosity, the dissolution is the main factor for increasing reservoir porosity, while the microfractures serve as improving the reservoir permeability and increasing the fluid percolation ability in a certain extent. The Chang?9 sandstone reservoir’s diagenesis belongs to the“A”phase of medium diagenesis, with close relations between porosity evolution and diagenesis. The compaction made the porosity loss of 15.64%, the cementation made the porosity loss of 11.32%, the dissolution and micro?fractures increased porosity of 4.04%, hence the calculated porosity in the study area is determined as 7.48%, which is relatively consistentwith the average value of the measured porosity of 7.20%. The favorable diagenetic facies of Chang?9 reservoir is the feldspar corrosion facies and the chlorite film?feldspar corrosion facies developed in the underwater distributary channel sedimentary microfacies, and the most unfavorable diagenetic facies are the carbonate cementation facies and the strong compaction facies Related Articles | Metrics

Paleostructural Evolution and Relationship with Hydrocarbon of Permian in Yining Sag ZHONG Hongli1, PU Renhai2, GAO Shanlin3, QIU Fangqiang3 2014, 35 (1):  1-1.  Abstract ( 77 )   PDF (300KB) ( 215 )   Save The tectonic deformation in Yining sag is so strong that leads to unclear understandings of the tectonic evolution up to now. This paper restored the paleotectonic features of Permian-Paleogene in Yining sag by means of the seismic and drilling data, including the denudation thickness, by which predicted the probable hydrocarbon migration and accumulation for the Permian source rocks. The result shows that Yining sag was converted from fault depression into sag in Triassic; the sag’s shape appears low in north and west and high in south and east in general from Permian to Paleogene; in the Permian, the northern part of the sag was a deep rifted belt, the south and east parts were in slope area that looks like steeper in the south than in the east; in the Triassic, the sag structure became lower, the sub?swell zone in the central sag occurred some small swells extending along NWW; in the Jurassic, the subduction center of the sag transferred toward NW, appearing flat in the south slope and steep in the east one. It is concluded that the fault swell near Well Ning?4 and fault nose at the west of Well Yi?2 in center of the sag and fault nose in the south of Yingtamu could be the favorable hydrocarbon accumulation areas of Tiemulike formation in Yining sag Related Articles | Metrics

Reservoir Controlling Factors of Toutunhe No.2 Member in Fudong Slope Zone in Eastern Junggar Basin YU Jingwei1, LI Lulu2a, QI Liqi2a, WEI Fen2b, WEN Huaguo1, LI Yun1 2014, 35 (1):  1-1.  Abstract ( 90 )   PDF (300KB) ( 268 )   Save The Toutunhe formation of Middle Jurassic is the main sequence for oil exploration in Fudong (eastern Fukang) slope zone in eastern Junggar basin. By means of many analyses and testing methods, this paper studies the characteristics of lithology, reservoir space and physical property of the second member of Toutunhe formation in the Fudong slope zone, including the reservoir controlling factor analysis in detail. The results show that the lithology in this member is dominated by fine arenstritic sandstone, the reservoir space is dominantby primary intergranular pores, belonging to medium?porosity and medium?low?permeability reservoir. The reservoir physical property is controlled by the provenance and abnormal pressure zone, the reservoir distribution is controlled by the sedimentary facies and paleo?geomorphology, and the reservoir quality is controlled by the clay minerals types and contents in this area Related Articles | Metrics

Depositional Facies and Favorable Reservoir Distribution of Sha4 Upper Member of Shahejie Formation in Bonan SubSag LIU Yali1,3, LIU Peng2, YI Wei4 2014, 35 (1):  1-1.  Abstract ( 65 )   PDF (300KB) ( 269 )   Save Based on the core, logging, lab testing and seismic data, by means of theory of sedimentology and reservoir geology, four sedimentary facies are classified in the upper part of fourth member of Shahejie formation in Bonan sag as fan delta facies, near?shore subaqueous fan facies, beach bar facies and lake facies, their distributions of each system tract are discussed, and eight favorable reservoir bodies are ascertained, such as sandstone beach bar in Luojia nose?like structural belt, fan delta front in the ramp belt, reef in Yidong fault belt, sandy limestone beach bar in the ramp belt, limestone beach bar in the ramp belt, fan delta front in the steep slope belt, fan delta plain in the ramp belt and fan prodelta in the ramp belt. Based on these, four favorable areas are predicted, they are the fan delta front area in the steep slope belt, the reef area in Yidong fault belt, the sandstone beach bar area in Luojia nose?like structrual belt, and the mixing areas of fan delta-limestone beach bar-sandy limestone beach bar in the ramp belt Related Articles | Metrics

Depositional System and Development Model for Bashijiqike Formation in Northeastern Tarim Basin MENG Xiangjie, GAO Zhiqian, FAN Tailiang, HU Xiaolan, LUO Jing, HE Wei, QIAO Bo 2014, 35 (1):  1-1.  Abstract ( 66 )   PDF (300KB) ( 274 )   Save The Cretaceous Bashijiqike formation in northeastern Tarim basin was the product of lacustrine basin margin alluvial fan deposition involving two major sedimentary systems: an alluvial fan?braided fluvial delta depositional system and a fan delta depositional system. The alluvial fan?braided fluvial delta depositional system is composed of an alluvial fan facies, a braided fluvial delta plain facies and a delta front facies from the foothill belt in S?N direction to the basin center. The fan delta depositional system is mainly composed of fan delta front subfacies, which developed near Kuqa depression in the northwest of the study area. When Bashijiqike formation was deposited, the lake was shallow and the climate was arid, which led to deposits with a high sand ratio. During transgression strata deposited in the lake basin margin is thicker than that in the basin center. During regression, in contrast, the basin center experienced more deposition than the margins. Drilling and seismic data show that the northeast of the study area was controlled by single terrigenous depositional source from the paleo?Tianshan mountains in north. Deposition in the southern part of the basin was controlled by the East Kunlun?Altun mountains during transgression and regression. Deposition in central area was controlled by a single sediment source which was gradually supplanted by multiple sources. Therefore, the strata deposited during regressive phase in lake basin center are of good reservoir quality Related Articles | Metrics

Effect of Fractures on Forming Dibei Tight Sandstone Gas Reservoir of Ahe Formation in Yangxia Sag of Tarim Basin YI Shiwei1, LI Dejiang1, YANG Haijun2, LI Yong2, LIN Tong1, YE Maolin2 2014, 35 (1):  1-1.  Abstract ( 71 )   PDF (300KB) ( 207 )   Save Ahe formation of Jurassic is a large braided river delta deposit in Yangxia sag in Tarim basin. The thick sand bodies of braided river channel occur in shape of longitudinal overlapping and lateral cross connecting, and the low?porosity and low?permeability reservoir is extensively distributed in this area. The field survey, core observation, microscopic identification and imaging logging show that the fractures in the Ahe sandstone are well?developed. Dibei gas reservoir in this sag has the characteristics of a typical fractured tight sandstone gas reservoir. The fracture development has very important controlling effect on such a gas accumulation, including reducing initial charging pressure, forming advantageous charging, shaping network charging channels, improving the efficiency of gas charging, enhancing tight sandstone permeability, increasing gas saturation and pore space as well as enlarging the size of the reserves Related Articles | Metrics

The Mechanism of HighTemperature and Overpressure Sandstone Reservoir Development of Huangliu Formation in Dongfang Area of Yinggehai Basin L? Xiaowei1, ZHANG Shaonan1a,2, FU Meiyan1, LIU Jinghuan3, ZHANG Ya2, ZHOU Yong4 2014, 35 (1):  1-1.  Abstract ( 62 )   PDF (300KB) ( 282 )   Save The sandstone of Huangliu formation in Dongfang area of Yinggehai basin is characterized by obvious high?temperature and overpressure diagenetic environment. By means of thin section, cathodeluminescence, SEM, enclosure, X?ray, etc, this paper studied the diagenetic characteristic of Huangliu sand under high?temperature and overpressure and its effect on the reservoir quality. This sandstone with poor compaction and strong corrosion has crystallized with such authigenic minerals of hydrothermal origin as siderite, barite and rutile, etc. Under the high?temperature and overpressure, the primary porosity was not only preserved mostly, but also favorable to forming a great amount of secondary pores for dissolution of the high temperature hydrothermal fluid on feldspathic mineral. The cementing of siderite, ferrocalcite and ferrodolomite and the filling of authigenic kaolinite were resulted in lower porosity of the reservoir, while the rapid smectite?illite conversion could be the main reason for quick decline of the reservoir permeability. The studied result shows that the hightemperature and overpressure could not only preserve the primary porosity in this reservoir, but also result in a great amount of corrosion of unstable minerals. Conducting research of the reservoir development mechanism under high?temperature and overpressure is of great significance for prediction of“dessert”in the sandstone reservoir Related Articles | Metrics

Technological Policy Research of Cyclic Waterflooding in FractureCavity Carbonate Reservoir in Tahe Oilfield HU Guangjie 2014, 35 (1):  1-1.  Abstract ( 69 )   PDF (300KB) ( 231 )   Save The Ordovician carbonate reservoir in Tahe oilfield is characterized by strong heterogeneity, developed cavity and fractures as well as complicated distribution influenced by tectonic activity and karstification, which gives rise to big difference between carbonate reservoir and sandstone reservoir development by waterflooding process. This carbonate reservoir is usually developed by such waterflooding process as injecting water into lower reservoir intervals and oil production from higher reservoir intervals, or injecting water into fractured intervals and production from cavernous intervals. However, with the deepening of waterflood development, part of fracture?cavity intervals have occurred poor responses in effectiveness. This paper presents the cyclic waterflooding process using numerical simulation method, and demonstrates the injection?production parameters such as water injection timing, cycle and volume, etc. It is suggested that the water injection timing could be at water cut of 80%, the cyclic injection amounts to 5.1×104 m3, the time of each cyclic injection is 50 d, and intermittent injection process should be used by 30 d for water injection and 20 d for shut?in phase Related Articles | Metrics

Tubing Pressure Characteristics and Fracturing Response Analysis of Horizontal Well in Tight Reservoir An example from three horizontal wells in Changji oilfield of eastern Junggar basin LIANG Chenggang, TANG Fuping, XIE Jianyong, SHI Yan, LIU Jinjun, WU Chengmei, GUO Zhineng 2014, 35 (1):  1-1.  Abstract ( 77 )   PDF (300KB) ( 271 )   Save Tight oil reservoir development requires large?scale volume fracturing for effectively producing, so the evaluation of the fracturing response is particularly important. The tubing pressure change characteristics after fracturing have a closely relationship with the fracture network system volume (FNSV) or stimulated reservoir volume (SRV) and the size of the single broken pieces or blocks, which is a practical parameter for the evaluation of fracturing effect. If the reservoir pressure converted from the tubing pressure is close to the equilibrium pressure, the radius of the broken pieces in the SRV is relatively small. Similarly, the less pressure change percentage under the cumulative percentage of produced fluid, the bigger SRV shaped under the same fracturing fluid volume, and the better the fracturing effect is Related Articles | Metrics

An Unstable Productivity Prediction Model for Fractured Horizontal Well in Tight Oil Reservoirs WEI Yi, SONG Xinmin, RAN Qiquan, TONG Min 2014, 35 (1):  1-1.  Abstract ( 65 )   PDF (300KB) ( 232 )   Save In consideration of the matrix?crack and crack wellbore coupling flow under the threshold pressure gradient and the pressuresensitive effect, on the basis of elliptic seepage theory, superposition principle and equivalent wellbore radius model, an unsteady productivity prediction model for fractured horizontal well with arbitrary numbers of transverse fractures was developed considering mutual interference among fractures. Then the oil production decline rules of fractured horizontal well and the effects of various factors on its productivity were analyzed. The computational results from a case study show that such a well in tight oil reservoir is characterized by high initial production, rapid decline, short high?yield stage, low production in later stage followed by gradually steady state and keeping a long period of stabilized production. The threshold pressure gradient and the deformation coefficient have a great effect on production, the greater the gradient and coefficient, the lower the production of such a well will be. And the longer the horizontal wellbore length, the more the fracture number, the longer the fracture length and the bigger the flow conductivity, then the higher the production will be, but these values have their own optimum ranges Related Articles | Metrics

Effect of Emulation on Displacement of Residual Oil Film Following Waterflooding: Experiment and Evaluation SUN Yingying1, YUE Xiangan2, ZHANG Lijuan2, GUO Zhi3, WANG Ping3, LIU Wanlu1 2014, 35 (1):  1-1.  Abstract ( 87 )   PDF (300KB) ( 464 )   Save Emulsion ability between oil displacement agent and crude oil has a great influence on oil displacement efficiency of chemical flooding. This paper presents an artificial residual oil film model for screening activity of oil displacement agent and testing the effect on the oil film displacement, makes a quantitative of the emulsifying effect and provides the reasonable index for evaluating the emulsion displacement ability of surfactant. The experimental results show that the the emulsion process between oil displacement agent and crude oil can strip oil film effctivelly, suitable for further enhance of sweep efficiency at stage of high water cut. There exists very good positive correlation between the emulsion ability and oil film sweep efficiency. It is indicated that interfacial tension is not the only key influencing factor for evaluating the emulsion ability, which provides a further improvement for the mechanism of emulsion to enhance the microscopic oil displacement efficiency Related Articles | Metrics

Prediction of Water Breakthrough Time in Fractured Gas Well in LowPermeability Gas Reservoir with Bottom Water ZHANG Qinghui, QU Xinzhong, LIU Jincheng, CHEN Xiaodong, SHI Zhenghao 2014, 35 (1):  1-1.  Abstract ( 71 )   PDF (300KB) ( 317 )   Save This paper developed the water conning computational model for fractured gas well in consideration of both horizontal radial flow and semi?spherical flow, derived the water breakthrough time formulae for post?fracture gas well in low permeability gas reservoir with bottom water. The numerical simulation analysis shows that partial penetration of this fractured gas well could delay the conning of bottom water and the time of water breakthrough due to existence of fractures, and the longer the fracture semi?length, the better the response is. Applying these formulae into the case study of Well YS1 in such a reservoir given by Sinopec indicates that a post-fracture gas well can get delay of water breakthrough time obviously, and enhance its water?free recovery factor Related Articles | Metrics

Heat Transfer Calculation and Influence Factors Analysis for SAGD Circulation Phase in Dual Horizontal Wells LI Jingling1, ZHU Zhihong2, DOU Shengjun2, CHEN Sen2 2014, 35 (1):  1-1.  Abstract ( 76 )   PDF (300KB) ( 254 )   Save Before bringing into production of dual horizontal wells by steam assisted gravity drainage (SAGD) process, the reservoir preheating between up an down parallel injection?production well pair is required. The preheating effectiveness is very important to the successful development by the SAGD process. In this paper, the calculation models for circulation preheating of dual horizontal wells by SAGD are developed. Taking one SAGD well pair in Fengcheng oilfield as an example, the relevant parameters during the preheating phase are simulated and calculated, including studies of the effects of distance between the two wells, the speed of steam circulation and the steam quality on the preheating effectiveness. The analysis indicates that when the steam quality in the phase of circulation preheating is 0.8, the speed of steam circulation should not be less than 30 t/d; while the speed reaches 60 t/d, the steam quality should not be less than 0.4; the distancebetween the horizontal well pair is about 5 m, the time of circulation preheating is about 93 days Related Articles | Metrics

Sand Plug Mechanism and Productivity Formula for Horizontal Well Development of Heavy Oil Reservoir by Steam Stimulation TIAN Kezhong1a,2, MIN Chao1b,2, SUN Yanbin1b, CHEN Hongling3 2014, 35 (1):  1-1.  Abstract ( 76 )   PDF (300KB) ( 232 )   Save In the process of an oilfield production, sand production issue tends to extensive existence and be an inevitable. So it is important to predict the sand plug status of bottom hole, draw up rational sand washing measures, avoid sand plugging of oil layers due to too frequent operation and/or operation measures nor in time. Based on the horizontal interval sand plugging mechanism by horizontal well development of heavy oil reservoir with steam stimulation, this paper analyzed the regularity of continuous sand production, and proposed the productivity formula considering the sand plug factor. The case study indicates the rationality of the formula, which provides preliminary theoretical basis for prognosis of the sand plug situation in a sand producing well and implementing in?time sand washing. It is believed that this study will be helpful to prolong the production period length of each round of steam stimulation for heavy oil recovery by horizontal well process and increase the production of a heavy oil reservoir. Related Articles | Metrics

Determination of Hydration Damage Instability Cycle of Shale Borehole Wall in Sulige Gas Field SHE Haicheng1, QU Zhan2, CHEN Junbin2 2014, 35 (1):  1-1.  Abstract ( 52 )   PDF (300KB) ( 181 )   Save The complex stress and solid?liquid interaction in drilling cause hydration diffusion and swelling in surrounding rocks, which changes the stress field and mechanics parameters of the rocks and leads to the borehole instability of shale. Based on experiments, the hydration changing law of surrounding shale with time and space as well as the damage weakening rule of elastic modulus and compressive strength of the rocks with water content are discussed in this paper. Then with the consideration of strength?deformation and damage theory, the damage?evolution equation and limit equation after the invasion of water into shale are deduced, and accordingly the collapse cycle of borehole wall is determined. Applying this method to Sulige gas field shows that its shale borehole wall collapse cycle is about 6.8 days Related Articles | Metrics

Blocking Agent for High Temperature and High Salinity Reservoir: Development and Evaluation DAI Caili1, FU Yang1, YOU Qing2, ZHAO Mingwei1, ZHAO Fulin1,WANG Kai1 2014, 35 (1):  1-1.  Abstract ( 68 )   PDF (300KB) ( 296 )   Save In high temperature and high salinity reservoir, the polymer gel blocking agent has the problems of low strength, poor stability, short gelation time, etc. This paper presents a new blocking agent suitable for this reservoir, which is composed of such a formula as sulfonated tannin (4%~7% in mass fraction), ZY?1 crosslinking agent (1.8%~2.2%), ZY?2 crosslinking agent (1.8%~2.2%), FY?1 stabilizer (1.5%~3.0%) and FY?2 stabilizer (0.04%~0.08%), at 130℃. The gelation time of it is 9~14 h, the gel strength is 0.06~0.08 MPa. The lab experiment indicates that this gel system has better heat resistance, salt tolerance and continuous plugging performances for its volume and strength retention reach over 90%, the plugging rate is still higher than 92%, after 60 days of ageing time in the condition of high temperature (130℃) and high salinity (over 2.0×105 mg/L) Related Articles | Metrics

Fracturing Technology Research and Application on Tight Dolomite Reservoir in Mahu Sag in Junggar Basin CUI Yumiaoa, ZHANG Jinga, LI Jiaqib, LI Hongchaoc, GU Yanlinga, CHEN Xianjianga, JIANG Xianzhaoa, JIANG Honga 2014, 35 (1):  1-1.  Abstract ( 63 )   PDF (300KB) ( 228 )   Save The Fengcheng formation in Mahu sag in Junggar basin develops a thick?bedded tight dolomite reservoir, which is a typical oil reservoir with lower generation and upper accumulation. The tight and rigid lithology is sensitive to the fluid in a wellbore and resulted in difficulty for reservoir stimulation. The reservoir is characterized by very high salinity and containing B, Ti and Zr heavy metal ions in the formation water, which lead to the incompletion of gel breaking and the difficulty of fluid returning. Also, the reservoir has the features of “three highs and one deep”, namely, high pressure coefficient (>1.5), high temperature(>100℃), high closure stress (>90 MPa) and large buried depth (>4000 m). The complexity of the stress distribution and the development of natural fractures have caused fracturing filtration, varied fracture shapes, narrow fracture width and easily sand plugging. Aiming at these difficulties, this paper presents a new kind of fracturing fluid with high?temperature resistant and acidic hydrophobic association to solve the post?fracturing gel?returning problem. In addition, by establishing the formula of rock mechanics parameters of static and dynamic conversion and studying screening approach of proppant grain size, this paper establishes the empirical equation for prediction of the formation fracture pressure, thus systematically optimizing the fracturing design program. At present, 23 field tests have been implemented, and the success rate of the projects has increased from 50% to 100%, then the average proppant volume has increased from less than 35 m3 to 42.5 m3 Related Articles | Metrics

Influence of Seismic Coverage Density on Prestack Migration Imaging Effect PENG Xiao, LI Xianmin, XIA Jianjun, WANG Zhengjun, YANG Wanxiang, LI Jian 2014, 35 (1):  1-1.  Abstract ( 67 )   PDF (300KB) ( 201 )   Save In conventional sparse 3D seismic acquisition, the large line interval leads to poor seismic coverage density. The theoretical analysis and seismic acquisition examples demonstrate that when the shooting distance and the trace?to?trace interval basically meet the spatial sampling theorem, we should pay full attention to the spatial sampling density in direction of shooting line spacing and geophone line spacing. Reducing such two spacings to improve the coverage density can expand 3D space bandwidth and achieve the aim of enhancing the prestack migration imaging accuracy, allowing the prestack migration trace gathers and the signal?to?noise ratio of imaging data to be significantly improved Related Articles | Metrics

The Enlightenment from Comparative Studies of the Coalbed Methane (CBM) Development at Home and Abroad CAO Yan, LONG Shengxiang, LI Xinzi, HU Xiaohu, WANG Chuangang, WANG Feng 2014, 35 (1):  1-1.  Abstract ( 92 )   PDF (300KB) ( 572 )   Save The United States, Canada, Australia and other countries have entered the stage of commercial development and utilization of CBM resources. China’s CBM resource amounts with burial depth of less than 2 000 m are basically equal to natural gas resource amount. So fully development and utilization of CBM resources is of great significance to improve the energy structures of China. However, China’s CBM commercial development is still in the initial stage, there exists big gap with the United States, etc. To realize the rapid and sound de? velopment of China’s CBM development, this paper compares the block geological conditions, the development technologies of CBM, preferential support policy and economy at home and abroad, uses the successful experiences of the United States in CBM development and utilization for reference, proposes relevant knowledges and suggestions in geologic understanding, development process and technology, low cost strategy and policy support and so forth, based on the current development status of CBM in China Related Articles | Metrics

Analysis of Seismic Exploration Cost Change Rules and Influencing Factors in Xinjiang Oilfield Company QIAO Wenlong1, LI Na1, YANG Xinfeng1, LI Jie2, XIONG Weili1, ZHENG Yi1, GONG Hongyan1 2014, 35 (1):  1-1.  Abstract ( 63 )   PDF (300KB) ( 179 )   Save Based on the statistical analysis on the data of seismic exploration investment, workload and achievement of Xinjiang Oilfield Company during 2001-2010, the change rules of seismic exploration cost during 2001-2010 are summarized and all the factors influencing the seismic exploration cost are systematically analyzed. Then basic countermeasures are presented to optimize or reduce seismic exploration cost and the following understandings have been obtained: the seismic exploration cost in Xinjiang oilfields shows a gradually increasing trend from 2001 to 2010. The rise of prices resulted from economic factors is the main objective reason of the cost increase, the update of seismic technology and strengthening of parameters are the most direct reason, the change of seismic and geological targets is the main driving force and the differences in geography and landform are natural reasons. Therefore, the key factor to optimize and reduce the cost lies in the improvement of technology and management in Xinjiang oilfields Related Articles | Metrics

Geological Characteristics and Hydrocarbon Accumulation Model for Cenozoic Play in Persian Gulf Basin JIA Xiaole1, HE Dengfa1TONG Xiaoguang2 2014, 35 (1):  1-1.  Abstract ( 80 )   PDF (300KB) ( 606 )   Save There are five hydrocarbon accumulation plays in Cenozoic in Persian Gulf basin, of which the Asmari?Gachsaran play is the most important one. The paleogeography evolution, hydrocarbon source rocks, reservoir rocks, cap rocks and hydrocarbon accumulation process are studied, showing that the Middle Cretaceous hydrocarbon source rock of Kazhdumi formation was deposited in low energy and euxinit environment, and reached hydrocarbon generating/expulsion peak in Early Pliocene. Oil and gas migrated vertically along fractures and finally accumulated in Oligocene?Lower Miocene Asmari fractured limestone reservoir. The Miocene Gachsaran formation provided an effective regional seal for the Oligocene?Lower Miocene Asmari reservoir. The oil and gas accumulation occurred in structural trap formed by lateral compression. The high quality source rocks, favorable reservoir rocks, fractures connecting the source rocks with reservoirs, effective regional/local seals, and the good matching between hydrocarbon generating peak and tectonic activity, fracture, trap forming time are the key of hydrocarbon enrichment in Asmari?Gachsaran play Related Articles | Metrics

Geometric Analysis and Kinematic Simulation of Abu Ghirab Anticline in Missan Area, Iraq HAN Yaozua, CHEN Weia, OU Chenghuab, ZHOU Xiaojuna, LI Shiqina 2014, 35 (1):  1-1.  Abstract ( 76 )   PDF (300KB) ( 259 )   Save Based on the seismic data of high signal?to?noise ratio, this paper presents the structural analysis of the structural deformation feature in the Abu Ghirab anticline and its corresponding growth strata geometric relationship in the study area by means of fault?related folding theory, the parameters of structural characteristics and the kinematic simulation of the structural geometric deformation of wedge?inner strata confining by thrust F1, back?thrust fault F2 and related growth strata. The simulation results show that this anticline and related structures are influenced by late Himalayan orogeny and started to shape and grow in the Pleistocene and ended in the Holocene, belonging to typical triangular wedge?inner structural strata. The transition folding from complex anticline?type fault formed by control of underlying detachment fault had totally nappe displacement of about 1 100 m during this period, with average nappe rate of 0.45 mm/a. The fault F3 developed in Holocene could transform the forelimb of growth fault?bend folds on the upper wall of back?thrust fault F2, and then suffer ongoing denudation latterly, finally forming the present tectonic framework in Missan area of Iraq Related Articles | Metrics