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Strategic concepts of accelerating the survey,exploration and exploitation of shale gas resources in China ZHANG Da-Wei- Oil & Gas Geology    2010, 31 (2): 135-139+150.   DOI: 10.11743/ogg20100201 Abstract （3962）      PDF（pc） （3454KB）（1279）       Knowledge map    Save This paper introduces the world's shale gas resource potential and the trend of its exploration and exploitation.The author also discusses China's shale gas resource potential and current status of exploration and exploitation.Based on this information,this paper puts forward some strategic concepts of accelerating the survey,exploration and exploitation of shale gas resources in China: 1) to conduct a nationwide survey on shale gas geology and potential,to recognize favorable plays and E&P areas,and to establish pilot areas for shale gas exploration and exploitation;2) to do research on the accumulation and pooling patterns of shale gas,to advance innovation of shale gas exploration and exploitation techniques and to set up a technical system which could support shale gas exploration and exploitation;3) to build talent teams for shale gas survey,exploration and exploitation and to develop a geological data sharing system and a social service system;4) to draw up a plan for shale gas survey,exploration and exploitation,to establish an incentive system for shale gas exploration and production,to perfect the mining rights management system,to reinforce international cooperation and exchange and to establish standards and specifications of shale gas technologies. Related Articles | Metrics | Comments（0） Cited: Baidu(92)

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Key challenges and research m ethods of petroleum exploration in the deep of superimposed basins in western Oil & Gas Geology    2010, 31 (5): 517-534.   DOI: 10.11743/ogg20100501 Abstract （3883）      PDF（pc） （55791KB）（812）       Knowledge map    Save Based on comprehensive knowledge of deep reservoirs all over the world and petroleum geological features of superimposed basins in western China，this paper recognizes three key challenges of petroleum exploration in the deep of superimposed basins in western China.The first challenge is thathydrocarbons generated inmulti-phasesm ix together and their origins are not clear，making ithard to select leads.The second challenge is that fractures and dissolved pores/cavities m ix together in reservoirs and their origins are unclear，making ithard to predict favorable plays.The third challenge is thatphases ofhydrocarbon vary greatly and the distribution of hydrocarbon is influenced by high pressure and temperature，low porosity and permeability and several driving forces ofm igration，making it difficult to predict exploration targets using existing pool-form ing theories.Therefore，to accelerate hydrocarbon exploration in the deep of superimposed basins in western China，we have to find answers to three key issues:（i）multistage tectonic overprinting and deep hydrocarbon  generation and evolution;（ii）developmentmechanism and pattern of deep effective reservoirs;（iii）composite pool-form ingmechanism and accumulation pattern ofhydrocarbons in deep strata.It is suggested to adopt a research method that integrates forward modeling with inversion analysis of hydrocarbon accumulation process and a technical route of“geological condition-mechanism pattern of hydrocarbon accumulation”.Tarim Basin and Junggar Basin can be choosen as the focus of study as they have the greatest deep petroleum resource potential.It is expected to develop theories on composite hydrocarbon accumulation in the deep of superimposed basins in western China and supporting techniques to predicthydrocarbon distribution.These new theorieswill promote hydrocarbon exploration and fast reserve growth in the deep ofwestern China basins. Keywords:hydrocarbon distribution pattern，hydrocarbon accumulation，deep hydrocarbon exploration，superimposed basin in China Related Articles | Metrics | Comments（0）

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Gas accumulation patterns and key exploration techniques of deep gas reservoirs in tight sandstone:an example from gas exploration in the Xujiahe Form ation of the western Sichuan Depression，the Sichuan Basin CaiXiyuan Oil & Gas Geology    2010, 31 (6): 707-714.   DOI: 10.11743/ogg20100603 Abstract （3582）      PDF（pc） （7184KB）（778）       Knowledge map    Save Deep tight gas reservoirs are characterized by deep burial depth，poor reservoir quality and low production rate，but large exploration potentials.Distribution of favorable source rocks controls the planar distribution of gas reservoirs，and“effective reservoirs”in deep tight sands are the key to gas accumulation and production.Their development is under the control of structure，sedimentary facies and diagenetic facies.Effective porosity controls gas distribution，while fracture controls gas production rate.The gas reservoirs in the Xujiahe Formation in thewestern Sichuan depression feature in ultra-deep，superpressure and extra-tight，challenging prediction of reservoirs and sweetpoints.The3D-3C seism ic exploration technology is capable of solving such problems as quality reservoir prediction，fracture detection and gas potential identification.Ithas been successfully applied to exploration of the deep tight gas reservoirs in the western Sichuan depression.The success rate of exploratory drilling in the secondmember of the Xujiahe Formation is raised from15%to89%，and high yield well ratio increases from9% to 67%，and the discovered gas in place is121.1BCM.H igh efficiency exploration of tight sand gas is realized in the western Sichuan depression. Related Articles | Metrics | Comments（0）

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Studies of depositional system s and sequence stratigraphy: the present and the future Oil & Gas Geology    2010, 31 (5): 535-541.   DOI: 10.11743/ogg20100502 Abstract （3575）      PDF（pc） （1286KB）（1421）       Knowledge map    Save This paper discusses the present status and the trend ofdomestic and international studies of sequence stratigraphy and depositional systems and presents relevant theories and basic concepts.The trend of sequence stratigraphywill be standardization of research approaches and specification of studied areas for application.In particular，the studies of deepwater sequences and carbonate sequences and sequence simulation should be strengthened.Studies of depositional systems should shift from static description to dynam ic simulation and from macroscopic analysis to m icroscopic characterization.Reconstruction of depositional processes will be strengthened，and depositional systemswill bemapped in amore standard and fine synchronic sequence framework，so as to provide more reliable foundations for petroleum exploration. Related Articles | Metrics | Comments（0） Cited: Baidu(41)

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Distribution of diagenetic facies and prediction of high-quality reservoirs in the Lower C retaceous of the Tanzhuang Sag，the southern North China Basin ZhangQi，Zhu Xiaom in,Chen Xiang,Zhu Shifa，JiHancheng and JiangYongfu Oil & Gas Geology    2010, 31 (4): 472-480.   DOI: 10.11743/ogg20100411 Abstract （3524）      PDF（pc） （11928KB）（481）       Knowledge map    Save Using data such as ordinary thin sections，casting thin sections，scanning electronm icroscope observaˉtions and testing，we quantitatively calculate the diagenesis intensity parameters such as compaction，cementation and dissolution，which influence physical properties of the Lower Cretaceous reservoirs in the Tanzhuang sag，southern North China Basin.The apparent rates of compaction，cementation and dissolution porosity in different wells and intervals are obtained and the division standards of diagenesis intensity are determ ined.The Lower Cretaceous reservoirs are divided into five types of diagenetic facies.The typeˉⅠand typeˉⅡare good reservoir facies belts，the typeⅢis fair reservoir facies belt，while the typeⅣand typeˉⅤare poor reservoir facies belts.By predicting distribution ofdiagenetic facies and in combinationwith study ofdepositional systems and distribuˉtion pattern of secondary pores，we believe that the northern part of the southern fan delta and the southern part of the northern delta in the Tanzhuang sag，with moderate toˉrelatively high compaction，high cementation and moderate dissolution，are favorable reservoir facies belts for each interval. Related Articles | Metrics | Comments（0）

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A numerical simulation of volcanic gas reservoirs under consideration of start-up pressure gradient XU Jin-Jin, XU Xu-Hui, FAN Zhe-Yuan, HU Jian-Guo, SONG Yan-Bo, GUO Ming-Li, WANG Shu-Ping Oil & Gas Geology    2010, 31 (2): 240-243+259.   DOI: 10.11743/ogg20100216 Abstract （3516）      PDF（pc） （1772KB）（905）       Knowledge map    Save The Darcy flow theory suitble to conventional sandstone gas reservoirs with a single medium can not be applied to volcanic gas reservoirs,because they are characterized by the dual media of matrix and fracture and the higher original water saturation,resulting in an impact of star-up pressure gradient on a percolation process.According to the theory of mass conservation,a mathematical model of two-phase(gas and water) flow in dual media was built under consideration of start-up pressure gradient,for which the finite difference approch was used to obtain numerical solution and a calculation program of numerical simulation was compiled.In combination with laboratory experiment results,the values of this model parameters are determined,and it is shown that the impact of start-up pressure gradient has to be considered when permeability is lower than 0.1×10-3 μm2 and irreducible water saturation is over 20%.The numerical simulation results of a single well in XS gas field are consistent with the actual situation,and several indices of production and development,such as production plateau time,gas output during production plateau,recovery degree of production plateau and final recovery efficiency,are lower when the impact of start-up pressure gradient is considered than not.It is obvious that the impact of start-up pressure gradient has to be considered during the production of volcanic gas reservoirs. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(10)

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Genesis and reservoir features of tuffaceous rocks in Wuerhe oilfield of the Junggar Basin GongQingshun，NiGuohui，Lu Shuping，Ding Liangbo and Xin Yongguang Oil & Gas Geology    2010, 31 (4): 481-485.   DOI: 10.11743/ogg20100412 Abstract （3411）      PDF（pc） （5834KB）（830）       Knowledge map    Save Based on analyses of thin section，core observation，logging and seism ic data，we studied the genesis of tuffaceous rocks and their reservoir features in the Permian Wuerhe Formation in Wuerhe Oilfield，Junggar Basin. The rocks can be classified into tuff，tuffites and tuffaceous sandstone and conglomerate and show high resistivity and low interval transit time in logging curves. The study shows that the sedimentary environment of the Formation is enclosed or semi-enclosed lake bay，and the sediments are composed mainly of volcanic ash and terrigenous clastics. Syngenetic high-salinity and alkaline water body provided favorable conditions for hydrolysis and alteration of the deposited volcanic ash. During the process，dolomitic tuffites were formed and analcite was precipitated. These rocks have different reservoir space（dual porosity media），including dissolved vugs，sluiceˉway and fractures. The dual porosity feature of the rocks improves the poroperm characteristics and controls the accumulation and distribution of hydrocarbons inWuerhe oilfied. Related Articles | Metrics | Comments（0） Cited: Baidu(3)

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Definition and application of tight oil and shale oil terms Zhou Qingfan, Yang Guofeng Oil & Gas Geology    2012, 33 (4): 541-544,570.   DOI: 10.11743/ogg20120407 Abstract （3375）      PDF（pc） （435KB）（2531）       Knowledge map    Save Based on a thorough literature investigation and a detailed analysis of the meanings and applications of the tight oil and shale oil terms,this paper compares their similarities and differences,and presents suggestions for a better understanding and application of the two terms.Though shale oil also refers to the crude generated through processing kerogen from shale rocks,both terms bear broad and narrow senses when used to indicate the oil from shale or shale-like formations.The current usage of the two terms can be summarized and described in the following three scenarios:(1)They refer to different kinds of unconventional resources,therefore are regarded as totally different from each other;(2)They are thought to be identical and are used alternatively;(3)They are different but also inherently connected.It is suggested that when using the terms,we shall follow the rule of "showing respect to customs and facilitating communications" and try to understand fully their connotations and extensions instead of only reading the lines.To tackle problems encountered during using or understanding the terms,we also shall adapt the policy of "continuous perfecting and timely modification" so as to achieve a more objective definition of the terms.Meanwhile,their international applicability shall also be taken into consideration. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(68)

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Application of particle swarm optim ization-based BP neural network to multiˉattribute fusion techniques Oil & Gas Geology    2010, 31 (5): 685-688.   DOI: 10.11743/ogg20100519 Abstract （3348）      PDF（pc） （2470KB）（619）       Knowledge map    Save Constrained by factors such as quality of seism ic data，lithology and structures，single seism ic attribute can only be used to predict reservoirs to a certain extent and there aremultiple possibilities.Through calibrating seism ic attributeswith well data，seism ic attribute fusion techniques can correlate oil/gas potentialwith seism ic attributes.For oil/gas potential prediction of reservoirs，mathematics-based multi-attribute fusion can avoid the ambiguity of single attribute reservoir interpretation.Back propagation（BP）neural network is very good at nonlinear fitting，but it is easy to get a localm inimum without convergence，influencing the accuracy of prediction.To solve this problem，particle swarm is adopted first to optim ize the network weight and threshold，and BP neural network is then used to differentiate reservoirs and nonreservoirs.The results are satisfactory. Related Articles | Metrics | Comments（0）

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Laws of mudstone compaction on the west slope of the Songliao Basin Oil & Gas Geology    2010, 31 (4): 486-492.   DOI: 10.11743/ogg20100413 Abstract （3344）      PDF（pc） （4668KB）（802）       Knowledge map    Save Based on the basic law of mudstone compaction，this paper does a systematic research on the mudstone compaction characteristics in the west slope of Songliao Basin by using various logging data. The overpressure is quantitatively calculated and analyzed. The results show that the strata in the western uplift zone of the study area are basically in normal compaction state，while the Qingshankou and Nenjiang Formations in the Longhupao terrace and QijiaˉGulongkou sag show under compaction. The causes of difference in compaction in different areas are analyzed through comparison of the key parameters of compaction curves and in combination with real geoˉlogic data. On the basis of this，we quantitatively calculate the overpressure in the study area，analyze the structural features and plannar distribution of formation pressures，and predict the features of subsurface fluid migration and accumulation. Related Articles | Metrics | Comments（0） Cited: Baidu(14)

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Status，trend and outlook of organic geochem istry research in China —a summary of the Twelfth National Conference on Organic Geochem istry ZHANG Shui-Chang Oil & Gas Geology    2010, 31 (3): 265-270,276.   DOI: 10.11743/ogg20100301 Abstract （3343）      PDF（pc） （707KB）（1328）       Knowledge map    Save Nearly30years ofdevelopmenthas expanded the research scope of the organic geochem istry in China from the petroleum exploration to key research domains such as coal，biology，environment and climate.Its great contribution to the econom ic growth and social advancement of the country has showed its strong vitality.In the Twelfth National Conference on Organic Geochem istry，breakthrough has been made in the researches of deep hydrocarbon fluid properties，tight sand gas and shale gas reservoiring，biochem ical characters of permanent organic pollutes，etc.The direction for the discipline is therefore further clarified.At present and for a period of time to come，the research of the disciplinewould be focused on①technologies for analyzing and predicting the formation and distribution of organicˉrich sediments;②the development ofmodels that integrate geochem istry with geology;③the interaction of nonorganic and organic matters aswell as the secondary alteration and transˉformation of hydrocarbonˉbearing deposits;④the mechanism，potential，and distribution of natural gas with difˉferent origins;and⑤the geochem istry of environment，coal，and biology.The conference proposes that①stress should be put on the repeatability of experimental data，the reliability of experimentalmethods and the comparaˉbility of experimental results;and②that the geochem istry research in China should follow closely the internaˉtional lead，bemore creative，blaze a trail for a integrated research of organic geochem istry and geology，and play 266 Related Articles | Metrics | Comments（0）

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Quantitative identification of waterˉflooded zones in conglomerate reservoirs —an example from the Kexia Formation in the Liuzhong block of Karamay oilfield TAN Feng-Qi, LI Hong-Qi, WU Xin, FAN Xiao-Qin, YU Hong-Yan- Oil & Gas Geology    2010, 31 (2): 232-239.   DOI: 10.11743/ogg20100215 Abstract （3320）      PDF（pc） （4240KB）（11728）       Knowledge map    Save The conglomerate reservoirs inKaramay Oilfield have entered the development phase of high waterˉcut after forty years of water flooding. An accurate identification of waterˉflooded zones as well as a quantitative classification of wateringˉout level is the key and difficult issue to be considered in the adjustment of development strategy in this maturing oilfield. This paper documents a study that takes the conglomerate reservoirs in the Kexia Formation of the Liuzhong block as an example. It analyzes factors that affect the reservoir parameters by using the pressure coring data of three wells that were the focus of development adjustment in 2006 and by combining the actual geological characteristics of conglomerate reservoirs. It also selects logs that match well with the geoˉlogical characteristics and production pattern of the conglomerate reservoirs. Models for the interpretation of physical properties，lithology，water production rate，and water drive index of the Kexia Formation are established based on methods like cross plotting and multivariate linear regression. Three parameters，namely the water production rate，the oil saturation，and the water drive index，are chosen to be the main factors for aquantitative determination of wateringˉout level. Combining these factors with qualitative resistivityˉidentification chart for wateredˉout zones，the study offers rules and methods for qualitative identification of wateredˉout zones in this kind of reservoirs. The application of the method to the Kexia Formation yielded a coincidence rate of as high as 84.36%，well beyond the required accuracy. A set of technologies for quantitative identification of wateredˉout zones in conglomerate reservoirs is finally developed to improve the accuracy of wateredˉout zone identification. Reference | Related Articles | Metrics | Comments（0）

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Reservoir modeling of tight gas sands in the Upper Palaeozoic of the northern Ordos Basin Oil & Gas Geology    2011, 32 (4): 560-567.   DOI: 10.11743/ogg20110409 Abstract （3309）      PDF（pc） （3366KB）（1150）       Knowledge map    Save Abstract: The tight gas sands in the Upper Palaeozoic in northern Ordos Basin feature in tightness, low porosity and low permeability. Their geophysical anomalies are often insignificant, characteristics of priori geological models are ambiguous, and constraints on corresponding geophysical data volume are poor. For these reasons, the final reservoir model can not reflect exactly the heterogeneity of the tight gas sands. In order to solve these problems in modeling of the tight gas sands in the study area, geologic research results and seismic information are fully integrated in reservoir modeling. A reservoir geology database is first created based on geologic research results and is used to quantify the priori geologic knowledge. Then, a database of seismic constraints which are sensitive to reservoir parameters is created through seismic attribute optimization and seismic inversion. Next, information of time and depth domains is matched by building a fine velocity model. Finally, an integrated geologic model of the tight gas sands is established based on structure modeling, sedimentary facies/ lithofacies modeling and continuous reservoir parameter modeling under the control sedimentary facies. Application to reservoir modeling of the tight gas sands in the Daniudi gas field verifies its effectiveness. Related Articles | Metrics | Comments（0） Cited: Baidu(11)

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Distribution of gypsum-salt cap rocks and near-term hydrocarbon exploration targets in the m arine sequences of China Oil & Gas Geology    2010, 31 (6): 715-724.   DOI: 10.11743/ogg20100604 Abstract （3271）      PDF（pc） （7967KB）（673）       Knowledge map    Save Through reverse thinking，we summarize the status of research in the field of subsalt hydrocarbon exploration，analyze the distribution characteristics for gypsumˉsalt cap rocks，and discuss the potentiality and targets of subsalthydrocarbon explorationwithinmarine seuences in china.Gypsum and salt are excellent cap rocks whichwidely occur in themarine sequences ofTarim and Sichuan basins.Subsalt reservoirs are large in resource volume and are the main targets of future exploration.In southern China，gypsum-salt cap rocksmainly occur in the Lower-Middle Cambrian and Lower-Middle Triassic，in addition to the Cretaceous and Paleogene.The gypsum-salt cap rocks are extensive in lateral distribution but large in differences in different areas.For example，the Lower-Middle Triassic gypsum-salt cap rocks are closely related to hydrocarbon distribution in Sichuan Basin.The Cambrian and Lower-Middle Triassic gypsum-salt cap rocks are relatively thick and are the best seals for the marine reservoirs.The Carboniferous gypsum-salt cap rocks also occur in centralHunan province.Moreover，several gypsum-salt cap rocks also exist in Tarim Basin.For the Tarim platform-basin area，there are two sets of major cap rocks，i.e.the Cambrian and the m iddle-upper Carboniferous gypsum-salt cap rocks，especially the former is the major regional seal.The Cambrian gypsum-salt cap rocks in Bachu-Maigaiti area are large in both areal distribution and continuous thickness.Taking the overall geologic conditions for hydrocarbon accumulation in subsalt area into account，especially the controlling factors of slope and hinge zone for hydrocarbon accumulaˉtion，the paper suggest five plays or fields as themajor targets of near-term exploration in southern China and Tarim Basin. Related Articles | Metrics | Comments（0） Cited: Baidu(38)

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Significant advancem ent in natural gas exploration and developm ent in China during the past sixty years Oil & Gas Geology    2010, 31 (6): 689-698.   DOI: 10.11743/ogg20100601 Abstract （3267）      PDF（pc） （4573KB）（1031）       Knowledge map    Save :Based on analyzing the reserve and production growth of natural gas in China from1949to2009，we summarize theoretical and practical significances of the coal-derived gas theory and sum up the achievements in exploration and development of giant gas fields and their significances.Over the past sixty years，significant advancement has been made in gas exploration and production in China.First，China has become one of the world’s top players in natural gas reserves.In1949，China’s proved geological reserves was only0.385BCM，but in2009，this number exceeded7000BCM.Second，with a annual production of85.2BCM in2009，China is theworld’s7th biggestgas producer now，while itonly produced11.17MCM ofgas in1949.Third，the theory on coalˉderived gas has promoted the rapid advancement of gas exploration and production.In1979，the theory on coal-derived gas emerged as a new theory to lead the exploration and production of natural gas.Fourth，it is an importantway to rapidly developmentChina’s natural gas industry by exploring and developing giantgas fields.By2009，44large and giant gas fields have been discovered in China.They account for80.5%of the total reserves and66.4%of total gas production in China.Significantprogress has beenmade in natural gas exploration and development in China during the past sixty years. Related Articles | Metrics | Comments（0） Cited: Baidu(23)

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Deformation of the Late Palaeozoicaulacogen basin in the Great Nanpanjiang area   Ding Daogui，DengMo and ZhuWenli Oil & Gas Geology    2010, 31 (4): 393-402.   DOI: 10.11743/ogg20100401 Abstract （3257）      PDF       Knowledge map    Save The Late Palaeozoic aulacogen（D-P 1 ）basin and later syneclise depression（P 2 -T 2 ）basin in the Great NanpanjiangˉYoujiang area are located mainly in Guangxi Province and also stretch into parts of Yunan，Guizhou，and Guangdong provinces. They experienced deformation due to the collision and closure of the AilaoshanˉHonghe prototethys ocean during the IndosinianˉEarly Yanshanian period. The over thrusting of three basal detachment bodies（MaguanˉHejiang，Xuefengshan and Yukansan）helped to form progressive tectonic deformation domains with strong to weak thrustingˉfolding in different places. The LiupanshuiˉZiyunˉDuan strikeˉslip belt acted as the deformation transform zone in the depression. These tectonic deformation domains controlled the generation，accumulation and distribution of marine oil/gas in the area. Related Articles | Metrics | Comments（0）

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Sequence stratigraphy and sedim entary evolution of Es 1 in D iannan area of the Jizhong Depression Oil & Gas Geology    2010, 31 (5): 542-551.   DOI: 10.11743/ogg20100503 Abstract （3246）      PDF（pc） （10737KB）（488）       Knowledge map    Save Based on an integration of core，drilling，logging and seism ic data，the paper performs sequence stratigraphic division of the firstmember of the Eogene Shahejie Formation（Es 1 ）in the Diannan area of JizhongDepression and constructs an isochronal sequence stratigraphic correlation framework with one system tract as a unit.One third-order sequence is recognized in Es 1 ，and it can be subdivided into a lowstand，a lake transgression and a highstand systems tractbased on the stratigraphic superimposition patterns aswell as its lithologic and lithofacies changes.The construction of the isochronous stratigraphic framework shed light on the analysis of composition，evolution and distribution pattern of its sedimentary facies.The result indicates that the Es 1 is dom inated by delta and lacustrine facies. Related Articles | Metrics | Comments（0）

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A new approach to the exploration of lithologicstratigraphic reservoirs in the Hong-Che fault belt，the Junggar Basin Chen Xuan,Zhang Changmin,Zhang Shangfeng and Zhang Liping Oil & Gas Geology    2010, 31 (4): 420-427.   DOI: 10.11743/ogg20100404 Abstract （3237）      PDF（pc） （7105KB）（608）       Knowledge map    Save Based on the relationship between sedimentary sequences and reservoir formation，the author puts for-ward a new approach to exploration of lithologic-stratigraphic reservoirs in the fluvial-delta sedimentary systems-“to look for intervals with low net-to-gross ratio outside a facies zone with high net-to-gross ratio，and to look for reservoirs with relatively high net-to-gross ratio within intervals with low net-to-gross ratio”.In combination with sequence stratigraphic theories and relevant target-evaluation techniques，this new approach is used to identify reservoirs in the1stmember of the Triassic Karamay Formation in the HongˉChefaultbelt in JunggarBasin. It is believed that the middle cycle-MSC2is the favorable“low net-to-gross ratio interval”，in which the channel sands with high curvature index are the favorable“exploration targets with relatively high net-to-gross ratio”.The exploration well（Hongshan-4）targeting at these channel sands was drilled and flowed commercial oil. Mean while，for the delta deposits in the Neogene Shawan Formation，it is believed that the transgressive system tracts in the third-order sequence-NSQ2-are the favorable“low net-to-gross ratio interval”，in which the underwater distributary channel sands at delta front are considered to be the“exploration targets with relatively high net-to-gross ratio”.The exploration well（Che-89）targeting at these sand stones was drilled and obtained discoveries. This indicates that，intervals with low net-to-gross ratio also can have well-developed lithologic-stratigraphic reservoirs. This new approach is of significance to exploration of lithologic-stratigraphic reservoirs in the terrestrial strata in China. Related Articles | Metrics | Comments（0）

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G as accumulations and distribution features in the south of the Changling fault depression in the Songliao Basin Xie- Chen, HU Chun-Xin Oil & Gas Geology    2010, 31 (3): 381-385.   DOI: 10.11743/ogg20100317 Abstract （3233）      PDF（pc） （3488KB）（800）       Knowledge map    Save Three sets of source rocks，namely the Yingcheng Formation，Shahezi Formation，and Huoshiling Forˉmation，occur in the south of the Changling faultdepression in the Songliao Basin.Among them，the ShaheziForˉmation shale with high TOC is considered to be themajor source rocks in the area.It ismainly distributed in inˉdependent subˉsag being strongly compartmentalized.The hydrocarbon kitchen controls the distribution of gas reservoirs and the hydrocarbonˉgeneration potential controls the fullness of gas reservoirs.Gas reservoirs in the area feature in multiˉstage hydrocarbon charging and late carbon dioxide charging.It is suggested that the front row structures and lithological traps near the hydrocarbon kitchen are the potential targets for gas exploration. Related Articles | Metrics | Comments（0） Cited: Baidu(10)

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Application of geochemical parameters in hydrocarbon m igration studies: taking Tazhong area of the Tarim Basin as an example Oil & Gas Geology    2010, 31 (6): 838-846.   DOI: 10.11743/ogg20100617 Abstract （3228）      PDF（pc） （7629KB）（646）       Knowledge map    Save Hydrocarbon migration in the Tazhong area of Tarim Basin is studied through geochem ical tracing based on analyses of saturated hydrocarbons，aromatic compounds，nitrogenous compounds and trace elements of fluid inclusions.The result reveals that both vertical and lateral hydrocarbon migration are common in the study area.Faults here are the effective verticalm igration pathways，while unconform ities and connected sand bodies serve as the lateralm igration pathways.The exploration success rate can be improved by studying vertical hydro-carbon migration through integration ofgeochemical datawith geological data and selectingmultiple targets based on an analysis of faulting history.Analysis of lateral carrier systems for lateral hydrocarbon migration indicates that excellent reservoirswith certain tectonic settings are dominant pathways forlateral hydrocarbon migration.Therefore，the relative structural highs of these quality reservoirs are favorable for hydrocarbon accumulation through lateralm igration. Related Articles | Metrics | Comments（0） Cited: Baidu(5)

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T im ing of hydrocarbon charging in shallow reservoirs by differences of diagenetic characteristics of reservoirs —an example from A oilfield in Kazakhstan LIU Jing-Dong, JIANG You-Lu Oil & Gas Geology    2010, 31 (3): 315-320.   DOI: 10.11743/ogg20100307 Abstract （3226）      PDF（pc） （6443KB）（1188）       Knowledge map    Save For the tim ing of hydrocarbon charging in shallow reservoirs，methods such as traditional geological analysis，fluid inclusions in reservoirs and illite dating have obvious shortages.Based on the interactions between hydrocarbons，water and m inerals，this paper puts forward a newmethod to determ ine hydrocarbon charging time of shallow reservoirs by differences of diagenetic characteristics of reservoir rocks.Taking the A oilfield in Kazakhstan as an example，the hydrocarbon charging time for theMˉⅡoil layer is determ ined in this way.The time of bulk hydrocarbon charging can be determ ined through the analyses of differences of content of certain m inerals and in combination with diagenetic evolutionary sequence and burial thermal history.On the basis of poolˉform ing element analysis，hydrocarbon charging direction can be traced and hydrocarbon charging process can be identified with references to the trend of relative content of diagenetic m inerals. Related Articles | Metrics | Comments（0）

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Provenance system s and their control on the sedim entation of the upper Es 4 in Guangli area of the Dongying Sag，the Bohai Bay Basin Oil & Gas Geology    2010, 31 (5): 583-593.   DOI: 10.11743/ogg20100508 Abstract （3217）      PDF（pc） （18750KB）（496）       Knowledge map    Save According to analyses of rock component，element geochem istry and sandy net-to-gross ratio，two provenance systems，namely the southern one and the northeastern one，are believed to exist during the sedimentaˉtion of the upper4 th member ofEocene Shahejie Formation（Es 4 ）in Guangli area ofDongying Sag，the BohaiBay Basin and they controlled the genetic types and distribution of sandbodies.In the early period of the sedimentation of the upperEs 4 ，the south provenance predom inated，and there developed meander river delta and shallow lake-beach bars.While in the late period the sedimentation of the upperEs 4 ，the northeast provenance predom inated，and there developed braided river delta and fan delta.In the m iddle period of the sedimentation of the upperEs 4 ，the two provenance systems coexisted，and there developed sandbodies ofmultiple genetic typeswith alternating gravity flow deposits and traction currentdeposits.Beach bars resulted from modification of longshore current at the delta front should be important targets for further exploration.Exploration of lithologic structural combination traps of beach bars types should be strengthened. Related Articles | Metrics | Comments（0）

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Diagenetic reaction pattern of the sequence boundary and its impacts on reservoir quality Han Denglin,Zhang Changm in and Yin Taiju Oil & Gas Geology    2010, 31 (4): 449-454.   DOI: 10.11743/ogg20100408 Abstract （3214）      PDF（pc） （3340KB）（1030）       Knowledge map    Save Cluster sampling was performed in the vicinity of the sequence boundary within deltaic sedimentary system and a detailed analysis of lithological and mineral composition was carried out on the samples gathered. The results reveal the diagenetic reaction patterns near the boundary. The constraints of the sequence boundary over diagenetic reaction are reflected in the following aspects.First，sequence boundary indicates a relative fall in lacustrine level，which led to flush and leach of meteoric waters and facilitate the kaolinitization of siliciclastic grains（mainly unstable feldspar），thus causing a higher kaolinite content in the bulk composition of the under-lying formation of the boundary. Secondly，the boundary means a relative longer residence time of the sediments，which increasing the content of carbonate cement in reservoirs under the boundary. Finally，the boundary is usually accompanied by a decrease in accommodation space，causing a large amount of fineˉgrained sediments being flushed and eroded by overlaying coarseˉgrained sediments and then leached into the underlying formation. With the increase of burial depth，these filling materials become pseudo matrix under compaction and reflected as a signal of higher content of claymatrix under the boundary. These diagenetic alterations have an obvious impact on reservoir quality. The kaolinite cement，for instance，has a positive effect upon the porosity of reservoirs; while clay matrix and carbonate cement，on the contrary，exert a negative effect upon reservoir porosity. Related Articles | Metrics | Comments（0） Cited: Baidu(7)

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Reservoir pore structure and micro-flow characteristics of waterflooding: a case study from Chang-6 reservoir of Wangyao block in Ansai oilfield Quan Honghui, Zhu Yushuang, Zhang Hongjun, Li Li, Shao Fei, Zhang Zhang Oil & Gas Geology    2011, 32 (6): 952-960.   DOI: 10.11743/ogg20110620 Abstract （3199）      PDF（pc） （759KB）（1326）       Knowledge map    Save The real sandstone micromodel was used to perform an experiment of microscopic waterflooding in Chang-6 reservoir with low permeability in Ansai oilfield, Ordos Basin. Based on the experiment and the in-depth analysis of thin section observation, physical property,SEM,relative permeability and mercury injection data,we studied the relationship between pore structure and micro-flow characteristics of waterflooding, which provide a scientific basis for effective oil exploitation in the future. The study shows that the lithology of reservoir is mainly fine-grained arkose with low compositional maturity; there are three major pore types including resid- ual intergranular pore, dissolved pore and dual pore+fracture, of which the residual intergranular pore is dom- inant; Dissolved pore and fracture are the key factors influencing the micro-heterogeneity. The experiment results indicate that there are homogeneous, reticular and finger-like micro-flows. Pore structure is closely related with micro-flow features. Reservoirs with different pore types show different micro-flow features. Flow paths of injected water depend on the relative permeability of pores and fractures in zones with well-developed fractures. Pore structure heterogeneity and wettability are the two main factors influencing displacement efficiency. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(30)

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G eochem ical characteristics of light hydrocarbons in natural gas in the TabeiUplift of the Tarim Basin and their implications CHEN Jian-Fa, MIAO Zhong-Ying, ZHANG Chen, CHEN Hong-Yan Oil & Gas Geology    2010, 31 (3): 271-276.   DOI: 10.11743/ogg20100302 Abstract （3191）      PDF（pc） （2027KB）（1008）       Knowledge map    Save Based on the analysis of light hydrocarbons in natural gas in the TabeiUplift of the Tarim Basin，obˉvious differences are found in the distribution characteristics of lighthydrocarbon in3types ofnatural gas:petroliˉferous gas，coalˉrelated gas and m ixed gas.For petroliferous gas，which is distributed in the Yingmaili low uplift and the Halahatang sag，relative contents of nˉalkane and nˉheptane are high;for coalˉrelated gas，which is disˉtributed in the Luntai fault uplift，relative contents of isoparaffin，methylcyclohexane and benzene are high;for m ixed gas，which is distributed in the Donghetang fault belt，relative contents of benzene，methylclohexane and nˉheptane are high.According to gasmaturity estimated using parameters such as carbon isotope ofmethane and the maturity of light hydrocarbon，we believe that（1）there were at least twoˉphases of poolˉform ing for natural gas in the Ti’ergen faultbelt，theYangtake faultbelt and theYingmai32buried hill structural zone;（2）natural gas in the Yingmai7fault belt，the Donghetang fault belt and the Yingmai2buried hill structural zone expeˉrienced oneˉphased poolˉform ing process;（3）parameters of light hydrocarbon reveal that natural gas in the western part of the Luntai fault uplift has features ofm igrating and charging from the Kuqa depression to the Tabei forebulge belt. Related Articles | Metrics | Comments（0） Cited: Baidu(11)

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Great hydrocarbon potential in the Paleozoic m arine sequences in China Oil & Gas Geology    2010, 31 (6): 699-706,752.   DOI: 10.11743/ogg20100602 Abstract （3186）      PDF（pc） （6297KB）（1043）       Knowledge map    Save In1984，China made a breakthrough in petroleum exploration in the Paleozoic marine sequenceswith the discovery of the Shacan-2well in Tarim Basin.Since then China has not only leftbehind thewrong idea that there is no hydrocarbon in the Paleozoic marine sequences in China，but also found tens of oil and gas fields in Tarim Basin，Sichuan Basin，Ordos Basin and JunggarBasin.Theories on hydrocarbon generation and accumulation in the Paleozoic marine sequences in China have been brought forward and corresponding exploration techniques have been developed.According to the study of resource potential in the Paleozoic in China，the Paleozoic source rocks，which have not experienced metamorphism，occur in NortheastChina，southern North China，Qaidam Basin，the Hexi corridor and the Qinghai-Tibet area，further proving the great hydrocarbon potential in the Paleozoic marine sequences in China. Related Articles | Metrics | Comments（0）

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New knowledge of gas source rocks in the m arine sequences of South China and relevant index system for tracing Oil & Gas Geology    2010, 31 (6): 819-825.   DOI: 10.11743/ogg20100615 Abstract （3178）      PDF（pc） （3389KB）（936）       Knowledge map    Save Simulated experiments and geochem ical analyses of different types of hydrocarbon sources（source rocks，solid bitumen，asphaltic sandstone，crude oil/oil seepages）inmarine sequences ofSouth China reveal the coexistence ofmultiple hydrocarbon sources and theirmutual transformation and continuous or overlapping hydrocarbon generation.Marine source rocks in South China commonly feature in a state conversion of gas-generating parentmaterials and a relay of hydrocarbon generation process，presenting a characteristic that can be described as“coexistence ofmultiple sources and continuity ofmultiple gas generating phases”.An index system for tracing is established in accordance with such effects as the parentmaterial inheritance，isotopic fractionation and accumulation.It is based on stable isotopic components and important tracingmeans such as composition，biomarker，light hydrocarbon，nonˉhydrocarbon gases as well as rare gas isotopes and trace elements，and can be used to trace the process of transformation of different sources and hydrocarbon generation.The ternary tracing system of gas generation and accumulation is further improved.This paper presents a gas source rock tim ing model，gasˉsource correlationmethod，identification index of gas origin and their tracing，aswell as a prelim inary model for source identification and quantification ofm ixed gas. Related Articles | Metrics | Comments（0）

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O rigins of natural gas in Tazhong area，the Tarim Basin and their differences WANG Xiang, ZHANG Min, LIU Yu-Hua- Oil & Gas Geology    2010, 31 (3): 335-342.   DOI: 10.11743/ogg20100310 Abstract （3163）      PDF（pc） （4086KB）（1030）       Knowledge map    Save A systematic analysis is conducted on compositions and geochem ical characteristics of carbon isotopes of natural gas in the Tazhong area，Tarim Basin.It is found that the gaseous hydrocarbon compositions of the naˉtural gas from the Tazhong area basically show a pattern ofδ 13 C 1 <δ 13 C 2 <δ 13 C 3 <δ 13 C 4 with their values ofδ 13 C 1 all below-30‰，indicating their organic origin.According to the relationship between ln（C 2 /C 3 ）and ln（C 1 /C 2 ）and that between C 2 /iC 4 and C 2 /C 3 ，natural gas in the Ordovician is believed to originate from pyrolyˉsis of crude oil.While natural gas in the Carboniferous is m ixed gas originating from pyrolysis of both kerogen and crude oil.In the eastern and western parts of the Tazhong area，the source rocks are different in age and thermal history，leading to the significant differences of hydrocarbon compositions and carbon isotopes of natural gas in these areas.In the western part，natural gas mainly originates from the MiddleˉUpper Ordovician source rocks.While in the eastern part，natural gas probably originates from the highˉto overˉmature Cambrian source rocks.Thermochem ical sulfate reduction in the eastern wellblock is stronger than that in the western wellblock. Related Articles | Metrics | Comments（0）

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Heterogeneity of crude oil from W en’an oilfield in Jizhong area and its implications XU Zhen, ZHANG Chun-Ming Oil & Gas Geology    2010, 31 (3): 321-326,334.   DOI: 10.11743/ogg20100308 Abstract （3152）      PDF（pc） （2926KB）（1061）       Knowledge map    Save The whole oilGC/MS analysis shows thatmolecular constituents of oil in theWen’an oilfield in the Jizhong area have certain heterogeneity.According to this study，it is believed that at least two genetic types ofoil（TypeⅠand TypeⅡ）occur in theWen’an oilfield.The TypeⅠoil is characterized by relatively high steˉraneˉhopane ratio，relatively higher content of biomarkers（sterane，gammacerane and4ˉmethyl sterane）and reˉlatively lower content of aromatic compounds（methylphenanthrene，triaromatic sterane and methyldibenzothioˉphene）.In contrast，the TypeⅡoil features in lower steraneˉhopane ratio，relatively lower content ofbiomarkers and relatively higher contentof aromatic compounds.The distribution of these two types ofoil shows certain reguˉlarity，with the typeⅠoil occurring in the Yilunpu structural belt in the southern part and the TypeⅡoil disˉtributed in the Shigezhuang structural belt in the northern part.At least two petroleum systems occur in the Wen’an oilfield. Related Articles | Metrics | Comments（0）

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Petroleum exploration prospect of the Jurassic tight reservoirs in central Sichuan Basin Liao Qunshan, Hu Hua, Lin Jianping, Liu Zhongliang, Mu Xianzhong Oil & Gas Geology    2011, 32 (6): 815-822,838.   DOI: 10.11743/ogg20110602 Abstract （3147）      PDF（pc） （707KB）（1980）       Knowledge map    Save From viewpoint of continuous petroleum accumulation and comparison with Bakken Formation in Willsiton Basin(USA),the paper discussed petroleum exploration prospect of the Jurassic tight reservoirs in central Sichuan Basin.The Jurassic reservoirs in Sichuan Basin are typical tight ones with an average porosity of 1-3.7%,average permeability of 0.35×10-3-0.53×10-3 μm and median pore throat radius of 0.05-0.24 mm.The Jurassic reservoirs contacte closely with source rocks both laterally and vertically in central Sichuan Basin.The hydrocarbons accumulates within source rocks or in reservoirs close to the source rocks.The major reservoirs are continuously distributed in the slope area and sags,have no distinct trap boundaries,and are not controlled by local structures.Multiple reservoirs superimposed vertically and connected laterally,forming a large hydrocarbon-bearing areal extent.Most oil-bearing blocks have an abnormal overpressure system,no water in the reservoir and no uniform oil/water contact.The Jurassic oil accumulation in central Sichuan Basin is a typical continuous one basically similar to the Bakken Formation.In recent years,the Bakken tight oil have been deve- loped in large scale with horizontal well and multi-stage fracturing techniques thanks to the relatively high oil price.In contrast,exploration and development of the Jurassic tight reservoirs in central Sichuan Basin have no breakthrough due to the constraints of understanding,investment and technology.Improving geological understanding,strengthening research of key technologies such as horizontal drilling and multi-stage fracturing and increasing single well production are critical to the successful exploration and development of the Jurassic tight re- servoir in central part of Sichuan Basin. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(29)

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Wavelet effect and recognition methods of thin sand bodies in braided river facies HUANG Jun-Bin, GAO Li-Jun, GAO Yong, WANG De-Fa- Oil & Gas Geology    2010, 31 (2): 225-231.   DOI: 10.11743/ogg20100214 Abstract （3121）      PDF（pc） （9868KB）（507）       Knowledge map    Save Under a fixed seismic frequency，wavelet side lobes may increase the difficulty of interpreting and recognizing thin sand bodies. To investigate the impacts of wavelet side lobe effects，we design a series of forward models and produce synthetic seismic profiles using zero phase Ricker wavelets of different frequencies. The purpose is to identify the relationship of sand body location and frequency with side lobe effects. This study also aims at exploring the relationship between amplitude attributes and the description of thin sand bodies. The results show that，an integrated use of multiˉfrequency profile and amplitude attributes can reliably interpret and describe thin sand bodies of braided river facies which are thicker than1/8wavelength. Related Articles | Metrics | Comments（0） Cited: Baidu(4)

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Characteristics of the complex O rdovician carbonate reservoirs in the Tarim Basin Oil & Gas Geology    2010, 31 (6): 763-769.   DOI: 10.11743/ogg20100609 Abstract （3056）      PDF（pc） （4299KB）（801）       Knowledge map    Save Multidisciplinary analyses of reservoir geology and exploitation geology reveal that the Ordovician carbonate reservoirs in Tarim Basin are differentwith conventional reservoirs.They feature in extensiveness of oil/gas distribution，diversity of oil/gas property，layering and heterogeneity ofhydrocarbon accumulation，and instability of oil/gas production.There are two basic geological conditions controlling the formation of these special reservoirs，namely great reservoirheterogeneity andmultiˉphase hydrocarbon accumulation and latemodification.The special carbonate reservoirs thathave large oil/gas-bearing area，complex oil/gas-water contacts and a small amount ofwellswith high and stable production contributing to bulk of the oil/gas production are common in the Ordovician carbonates in Tarim Basin.Therefore，an integrated exploration and development strategy should be employed. Related Articles | Metrics | Comments（0）

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Resevoir evaluation and development strategies of Daniudi tight sand gas field in the Ordos Basin Hou Ruiyun, Liu Zhongqun Oil & Gas Geology    2012, 33 (1): 118-128.   DOI: 10.11743/ogg20120115 Abstract （3041）      PDF（pc） （1319KB）（1224）       Knowledge map    Save Daniudi gas field in Ordos Basin is typical tight sand gas reservoirs with low permeability,low pressure and low production rate.It has been a challenge to develop this kind of gas field economically.This paper cove- rs lithofacies,lithology,petrophysical property,pore structure and gas bearing potential of different formations.On this basis,four types of reservoirs have been identified.In terms of production rate,TypeⅠis the highest,followed by Type Ⅱand then Type Ⅲ,while Type Ⅳ has no productivity.According to the types and distribution of reservoirs,different development strategies have been adopted.Single layer production through vertical well fits TypeⅠ,whose porosity and permeability are better,net pay is thicker and production rate is higher.Commingled system through vertical well for overlapped layers suits Type Ⅱ,whose porosity and permeability are moderate,net pay is thinner and production rate of single layer is lower.Staged fracturing through horizontal well matches both Type Ⅱand Type Ⅲ with only one widely distributing layer.Applying different development strategies to different types of reservoirs,we has succeeded in improving the individual-well production rate and achieving economical development of this gas field.Annual production capacity of 25×108 m3 has been built up there. Reference | Related Articles | Metrics | Comments（0）

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Diagenetic facies types and logging identification methods for low-permeability tight sandstone reservoirs:a case study on the 8th member of Xiashihezi Formation in Sulige gasfield,Ordos Basin Zhang Haitao, Shi Zhuo, Shi Yujiang, Wang Liangliang, He Lujun Oil & Gas Geology    2012, 33 (2): 256-264.   DOI: 10.11743/ogg20120212 Abstract （3021）      PDF（pc） （9503KB）（1484）       Knowledge map    Save Sulige gasfield in Ordos Basin is a typical tight gas reservoir.According to clastic constituents,diagenetic mineral assemblage,interstitial matter,and diagenesis types,et al,we identified 6 diagenetic faceis types in the 8th member of Xiashihezi Formation(He8)reservoir of Sulige gas field,including intergranular pore+strong solutional phase of volcanic material,intercrystal pore+solutional phase of volcanic material,intercrystal pore+solutional phase of debirs,intercrystal pore+cementation phase of quartz,hydromica cementation+weak solutional phase of debris and compaction+cementation tight phase.In addition,we analyzed the impacts of different digenesis on log responses.On the basis of these studies,a method for continuously and quantitatively identifying diagenetic facies was established by using gamma ray,interval transit time,density and deep lateral resistivity log data.Logging data of Well Z65 were processed with this method,and a comparison with the thin section data and mercury injection data show that the results are accurate.Based on single well diagenetic facies identification,we defined the diagenetic face distribution in He8 reservoirs of Sulige gasfield.The central part of the gas field is dominated by intergranular pore+strong solutional phase of volcanic material and intercrystal pore+solutional phase of volcanic material,which are the favorable diagenetic faces belts. Reference | Related Articles | Metrics | Comments（0）

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Prediction of sublayer sandstones based on wave impedance inversion in the wellblock of the horizontal well Zhou-57 DAN Jing-Fu, WANG Feng, SUN Hai-Lei, SUN Ji-Gang, HAN Xi- Oil & Gas Geology    2010, 31 (2): 212-218.   DOI: 10.11743/ogg20100212 Abstract （3018）      PDF（pc） （7673KB）（504）       Knowledge map    Save During the whole process of petroleum exploration and development,the prediction of sandbodies in any target area,especially those in wellblocks of horizontal wells,is always dependent upon an analysis of reservoir deposition systems.The well Zhou-57 produces from the Putaohua Formation,which was deposited within the transition zone from a large-scale delta front to lake in northern Songliao Basin.The formation features in thin single sand bodies with a thickness of less than 2 m.The spatial distribution of these sandbodies is controlled by the variation and evolution of deposition systems during different geological times.The distribution and strike of sandboies are strictly controlled by lake transgression and regression.Therefore,a fine description of these sandbodies requires firstly a detailed geological study and then a prediction of sandstone sublayers through seismic wave impedance inversion.The prediction results can be used as important reference factors to adjust the injection-production pattern and improve the recovery ratio during the later phase of development. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(13)

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Geological concept，method and application of sequence unit identification through wavelet analysis ZhaoWei,Jiang Zaixing,Qiu Longwei and Chen Yan Oil & Gas Geology    2010, 31 (4): 436-441.   DOI: 10.11743/ogg20100406 Abstract （2982）      PDF（pc） （3352KB）（875）       Knowledge map    Save Wavelet analysis as amathematic method can be used to solve some problems in sequence stratigraphy research. This paper analyzed the concept of this method from a geological standpoint and come to a conclusion that the logs are reflections of certain characteristics of strata that reveal the superposition of the sedimentary cycles in different periods，while these sedimentary cycles can be identified through wavelet analysis and used for division of sequence stratigraphic units. In practice，we realize that choosing the right wavelets are essential to the division of sequence units. We applied the technique to the analysis of different intervals of two wells in Dongying Sag of BohaiBay and found out that the method is not only useful in division of conventional interbedded sandstone and shale stratum，but also capable of identifying subtle changes that tend to be ignored with con-ventional methods. Combined with Fischer Diagram，we can use the techniques to identify the sequence units in a large interval with mono lithology. Related Articles | Metrics | Comments（0）

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Water sensitivity experiment and damage mechanism of sandstone reservoirs with ultra-low permeability:a case study of the eighth oil layer in the Yanchang Formation of Xifeng oilfield,Ordos Basin Liao Jijia, Tang Hongming, Zhu Xiaomin, Ren Mingyue, Sun Zhen, Lin Dan Oil & Gas Geology    2012, 33 (2): 321-328.   DOI: 10.11743/ogg20120220 Abstract （2965）      PDF（pc） （6486KB）（1658）       Knowledge map    Save Taking the eighth oil layer of Yanchang Formation in Xifeng oilfield in Ordos Basin as an example,this paper investigates reservoir characteristics through cast thin section observation,SEM,image analysis and whole rock analysis,and studies water sensitivity through core flow displacement experiment.In addition,the changes of microscopic features within cores before and after water sensitivity experiment such as clay mineral occurrence and pore structure are qualitatively and quantitatively determined by using SEM and capillary flow porometer respectively,so as to investigate the mechanism of water sensitivity.The eighth oil layer of Yanchang Formation in Xifeng oilfield is a sandstone reservoir with ultra-low permeability.Its clay minerals are dominated by kaolinite,chlorite and illite,with no montmorillonite but some mixed-layer illite/smectite(only 11.4%).The degree of water sensitivity damage is moderate to strong.The damage from expanding clays is limited.The mecha-nisms of water sensitivity damage in cores include reduction of effective throat radius caused by secondary amorphous;damage or scattering of the paragenetic structures of clay minerals;dispersion of non-expanding clay mineral assemblage and cracking of their single crystal;collapsing of structure of matrix in pores and throat-plugging caused by migration of fine particles. Reference | Related Articles | Metrics | Comments（0）

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Influences of caprock sealing capacity on natural gas accumulation: an example from D-12 wellblock of Daniudi gas field in Ordos Basin Zhang Wenqi, Wang Zhizhang, Hou Xiulin, Xu Fang, Liu Lang, Li Chunlei Oil & Gas Geology    2011, 32 (6): 882-889.   DOI: 10.11743/ogg20110610 Abstract （2939）      PDF（pc） （750KB）（1171）       Knowledge map    Save In view of the large variations of production capacity both vertically and laterally in Daniudi gas field,this paper analyzed the influences of the caprock sealing mechanism and capability on natural gas accumulation by cores,laboratory test and logging data.The result indicates that the caprocks are overpressure sealing caprocks consisting of interbedded tight mudstone and undercompacted mudstone.The sealing capability is jointly controlled by the normal compacted mudstone and uncompacted mudstone.Thickness,total porosity,gross-to-net ratio and abnormal pore fluid pressure are selected as parameters to assess the sealing capacity of caprocks.The sealing capability is in positive correlation with the tested average open flow capacity and the maximum open flow capacity.The 3rd member of Xiashihezi Formation is the main gas pay zone thanks to the regional caprocks,and the high yield area is located on the western edge of the study area.The other pay zones are controlled by the sealing ability of direct caprocks,their gas are too scattered with low abundance to form large-scale contig- uous gas-bearing areas which is a key factor limiting productivity in the D-12 wellblock. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(9)

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Characteristics of fluid inclusions and reservoiring phases in the Yanchang Formation of Zichang area, the Ordos Basin Oil & Gas Geology    2011, 32 (2): 182-191.   DOI: 10.11743/ogg20110204 Abstract （2897）      PDF（pc） （1126KB）（1027）       Knowledge map    Save Abstract: The main diagenetic types of sandstone reservoirs in the Yanchang Formation of Zichang area, the Ordos Basin, include compaction, cementation, disolution and fracturing. The diagenetic authigenic minerals are dominated by chlorite, authigenetic quartz and calcite. Two different phases of hydrocarbon inclusions have been identified according to the formation time series of the host diagenetic minerals. The hydrocarbon inclusions formed in the first phase mainly occur in the dissolution pores of quartz and feldspar or along earlyhealed fractures, and are coated by quartz or feldspar overgrowth. The hydrocarbon inclusions formed in the second phase are distributed along the lateformed fractures or in sparry calcite cement. The late fractures cut the early fractures or the quartz overgrowth, and go beyond the grain contact. The homogenization temperature of the paragenetic brine inclusions of hydrocarbons has two peaks at 90-105℃ and 105-120℃ respectively. Analysis of salinity and density of the two generations of fluid inclusions reveal that the oil/gas reservoirs in the Yanchang Formation were formed continuously in one stage. The test data of fluid inclusions and illitic K-Ar isotope dating and the thermal history show that late Early Cretaceous (100-120Ma) is the main hydrocarbon accumulation period in Zichang area, the Ordos Basin. Related Articles | Metrics | Comments（0） Cited: Baidu(15)

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Characteristics of marmorized reservoirs in the Tarim Basin Oil & Gas Geology    2011, 32 (4): 506-511，521.   DOI: 10.11743/ogg20110403 Abstract （2893）      PDF（pc） （2471KB）（570）       Knowledge map    Save Abstract: The Lower Paleozoic carbonates of Tarim Basin were marbleized locally due to the thermal effects of magma intrusions. Marmorization is typical on the Tangwangcheng outcrop section in Bachu county at the northwestern margin of Tarim Basin and in cores from Well Zhong-16 in the Tazhong area. The characteristics of marmorization change regularly with the distance from carbonate rocks to intrusions. The degree of marmorization is high in the periphery of igneous intrusions with grains of marble being relatively coarse, but is progressively lowers and eventually disappears away from the intrusions. Grains of carbonate experienced marmorization show pseudo-hexagonal poikilitic structure with poorly developed secondary pores. Compared with the unaltered limestone, the marmorized carbonates have similar strontium isotope composition but slighter oxygen and carbon isotope compositions, indicating that the marmorization is a process dominated by thermal metamorphism. During this process, no extraneous fluids except for a small amount of formation water in the original carbonates are involved. The quality of marmorized reservoirs is basically similar with the unaltered limestone due to the absence of dissolution from extraneous fluids. Related Articles | Metrics | Comments（0） Cited: Baidu(1)