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    2012, Volume 19 Issue 2
    25 March 2012
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     Existing problems and sedimentogenesisbased methods of reservoir characterization during the middle and later periods of oilfield development.
    XU Xin-He
    2012, 19(2): 1-14. 
    Abstract ( 2069 )   PDF (3544KB) ( 2777 )  

    During the high watercut stage of proven old oil fields in China, reservoir study has changed from the evaluation of highquality reservoirs to interlayer and plane reservoir heterogeneity which affects the conflict between oil reservoir injection and production. The key issue for interlayer heterogeneity study has transferred from evaluation of traditional heterogeneity parameters to reservoir architecture, where the core of reservoir architecture research is to figure out the geometric shape of sandbodies with different genies and different directions and the distribution characteristics of interbeds; while the core of planar heterogeneity research is to choose scientific and reasonable parameters for accurate calculation and quantitative mapping according to reservoir scale, depositional genesis and characteristics, especially the differences between lithologic characteristics and thickness. All the above formed a new method for reservoir characterization, which can be summarized as “led by microfacies, guided by facies sequence, genesis quantification and integration of plane and profile”. It can better reflect the function and effect of reservoir characterization, which was to identify the genetic characteristics and distribution rules of different reservoirs (sublayers or sandbodies in development) to figure out the problems in oilfield development. The function of reservoir characterization is to approach the geological reality in maximum scale by scientific genesis classification, while the effect of reservoir characterization is to predict the distribution rules of subsurface oil/gas and to provide reliable and synthetic guidance for effective development.

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    Subsurface reservoir architecture characterization: Current status and prospects.
    TUN Qing-He, DI Rui, LI Yu-Feng
    2012, 19(2): 15-23. 
    Abstract ( 2040 )   PDF (1888KB) ( 1675 )  

    Subsurface reservoir architecture analysis has gradually become the important developing direction of hydrocarbon reservoir geology research in the past 10 years. Compared with outcrop architecture analysis, subsurface reservoir architecture characterization depends primarily on seismic and multiwell information, accordingly  two methods are developed: (1) Seismic Sedimentology (or Seismic Geomorphology), study the distribution of deposit units utilizing seismic imaging feature that was acquired by means of 3D seismic stratal slicing and other ways; (2) Multiwell pattern forecast, match various order quantitative architecture mode with well information (well log, core, test and dynamics) to infer interwell architecture unit distribution that restricted in different architecture order. This paper provides an overview of the origin, basic principle, application and problem of these two methods. According to actual production demand and technological development, further research trends are propounded:  (1) indeep research on 3D quantitative architecture mode; (2) recognition of seismic response of reservoir architecture units and seismic interpretation methods for reservoir architecture characterization; (3) improvement and innovation of multiwell pattern matching method.

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    Research on the channel pattern of present subaqueous distributary channel by remote sensing image.
    MA Shi-Zhong, ZHANG Yong-Qing
    2012, 19(2): 24-31. 
    Abstract ( 1930 )   PDF (3440KB) ( 907 )  

    Subaqueous distributary channel is one of the most important microfacies types and highquality reservoirs in deltafront subfacies, but little research of subaqueous distributary channel pattern has been carried out. Whether there is meandering or braided pattern or any other subaqueous channels and whether there is high angle turning is not clear, which directly affect the research of fine characterization, architecture, threedimensional heterogeneous model of subaqueous channel monosandbody in high watercut stage and tertiary phase. Therefore, it is of great theoretic significance and badly needed to ravel the subaqueous channel pattern. Focused on this problem, our study used the remote sensing method (satellite image) which can integrally and finely reveal the plane configuration and the character of subaqueous channel to thoroughly dissect 41 present subaqueous channels and determine subaqueous channel patterns, to classify subaqueous channel region into 4 zones, 3 types and 8 subtypes of channel pattern and discuss  their characteristics and formation condition. Based on the statistics of the channel pattern of 41 present subaqueous channels, it is concluded that  straight channel pattern is common, while lowsinuosity, highsinuosity, braided and anastomosed channel patterns are rare and are normally developed in the  nearshore subaqueous environment in different geological settings.

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    Formation mechanism and pattern of deepwater fan with channel and lobe: A case study of the Zhujiang Formation in Liwan31 area, Baiyun Depression.
    LI Qing-Li, XU Xin-He, LIU Yu-Mei, SHU Guo-Jin, HU Guang-Xi, GAO Bo-Yu, CHENG Yue-Hong, JIN Jian-Li
    2012, 19(2): 32-40. 
    Abstract ( 1820 )   PDF (4256KB) ( 1066 )  

    The depositional characteristics of deepwater fan reservoir are a hot topic in petroleum exploration and development. With the analysis of the depositional characteristics of deepwater fan of the Lower Miocene Zhujiang Formation in the Liwan 31 Area, Baiyun Sag, Pearl River Mouth Basin, some suitable conditions for the deposition of deepwater fan are discussed. Sand enriched deepwater fan controlled by the tectonicsedimentary background were well developed in this area. The deepwater fan was the result of several kinds of hydrodynamic mechanisms which include debris flow, turbidity flow and bottom current that build gravity flow channels with complex lobes on the plane. On the basis of the deepwater fan pattern, a set of sedimentary microfacies classification scheme of deepwater fan (mainly consists of channels and lobes) is presented. Gravity channel, natural levee and slumping lobe are the primary reservoirs in the study area. The wideshallow incision gravity channels become narrowdeep, with the increase of the distance from sedimentary source. And the correlation of the depth of gravity channel is direct proportion to the width of natural levee.

     

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    A study of braided river sand deposit in Changyuan, Daqing through physical simulation experiments.
    HE Yu-Hang, SONG Bao-Quan, ZHANG Chun-Sheng
    2012, 19(2): 41-48. 
    Abstract ( 2371 )   PDF (3420KB) ( 826 )  

    Abstract: Physical simulation experiments were conducted based on the braided river sand deposit of the Daqing Oilfield unit PI23 as the background. Through six rounds of experiments, the five main microfacies types, i.e. the braided channel, the heart beach, the abandoned channel, the embankment deposit and the overbank deposit, and their distribution patterns were identified and analyzed. Among them, the braid channel and the heart beach deposits are widely developed, accounting for about 90% of the braided river deposits. Heart beach bar more developed in the middle and lower reaches of the river; the connectivity between the heart beach bars is of a higher degree and the mutually connected heart beach bars may account for 60 to 80 percent of the beach thickness. The connectivity in the lower part of the heart beach is good and in the upper part is poorer. At the same time, the correlation between the configuration parameters of sedimentary microfacies sand body and the model of physical parameters were established. The preliminary view is that the width to thickness ratio of the channel sand body is between 70 and 120, and the aspect ratio is between 3 and 5. The width to thickness ratio of heart beach bar sand body is between 80 and 100, and the aspect ratio is between 1 and 3. The distribution range of river face rate is 10%-11% with the trend of being gradually smaller upward. The distribution range of heart beach bar face rate is 9%-10% without obvious variation in the profile. The sandwich of the heart beach bar in the center part is approximately horizontal and in most cases the inclined angle is less than 3°. In the long axis direction, the sandwich on the meeting water side is little steep (<5°) while on the back water side is relatively flat. In the short axis direction, the sandwich is slightly inclined in two wings of the heart beach (<8°). The study is of great significance for forecasting the internal configuration parameters of the main sedimentary microfacies of braided river deposit in Daqing Oilfield.

     

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     Characteristics and genesis of reservoir spaces in Neocene reef reservoir of Liuhua Oilfield, Pearl River Mouth Basin.
    GU Chi, HU Guang-Xi, LUO Wen-Sheng, NI Jun-E, LIANG Wei, TUN E-Sheng, MEI Mian-Xiang, LIU Yan
    2012, 19(2): 49-58. 
    Abstract ( 3331 )   PDF (2177KB) ( 1282 )  

    The reservoir of Liuhua oilfield, which belongs to Zhujiang Formation, is a typical Neocene platformrim reef located on the margin of carbonate platform of Dongsha Massif in Pearl River Mouth Basin, South China Sea. There are 7 types of rocks, including crusty algal boundstone, twined algalcoral framestone, foraminifer and algal grainstone and rhodolite reef limestone. The reservoir spaces include 7 types of pores and 4 types of fractures. The main pores include primary intergranular pores, pores in algal frames, intragranular dissolved pores, cavity pores and intercrystalline micropores. The main fractures include dissolution fractures, interlayer fractures in crusty algal boundstone, and stylolite dissolved fractures. The reservoirs are classified into four types, including porecavernfracture type, pore type, fractureporecavern type and fracture type. Crusty algal boundstone belongs to porefracture type reservoir. Mieritic grainstone and rhodolite reef limestone are pore type. Coral framestone belongs to fractureporecavern type. Fracture type includes sparry grainstone and relatively heavily cemented algal boundstone. Sedimentary microfacies and diagenesis control the distribution of different types of reservoir. Multiple exposures during the formation of reef have great influence on the reservoir. The sedimentarydiagenetic evolution of reef reservoir can be divided into four periods, including early reef formation and early exposure period, late reef formation and minor exposure period, reformation period during the early burial, two stages of reservoiring and groundwater dissolution periods. The spatial distribution of reservoir types are predicted according to the sedimentarydiagenetic evolution.

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    Modelling of carbonate fracturevuggy reservoir: A case study of Ordovician reservoir of 4th block in Tahe Oilfield.
    HOU Jia-Gen, MA Xiao-Jiang, LIU Yu-Ming, DIAO Ban
    2012, 19(2): 59-66. 
    Abstract ( 2536 )   PDF (1630KB) ( 1309 )  

    The carbonate fracturecavity reservoirs have experienced multiple tectonic movements, strong weathering, denudation and eluviations and the storage space has various types, irregular geometrical shape and stochastic spatial distribution, resulting in the difficulties in 3D description of the reservoirs and direct application of the existing modeling method of clastic rock reservoir. This paper proposed the research idea of classification modeling of large cave, solution pores, large scale fractures and small scale fractures about carbonate fracturevuggy reservoir. Taking drilling and seismic interpretation as deterministic data of large cave, restrained by large cave development probability cube from seismic wave impedance interwell, under the frame of vertical karst zoning and planar paleogeomorphy division, we use the sequential indicator simulation with a trend to establish the discrete distribution model of large cave; using large cave discrete distribution as the facies controlling condition, taking the solution pores interpretation from borehole as hard data, making use of the sequential indicator simulation algorithm, we establish the stochastic distribution model of solution pores; according to the fault information automatically extracted from seismic ant cube, revising seismic interpretation fault data by manmachine interactive, we build the deterministic discrete distribution model of large scale fractures; obtaining the interwell development probability body of small scale fractures based on discrete distribution model of large scale fractures, integrating the fracture density and attitude of borehole, we set up the discrete distribution model of small scale fractures by combination of the annealing simulation and the objectbased marked point processes simulation. Finally we use the above modelling methods, taking the Ordovician carbonate reservoirs in Tahe oilfield 4th block as an example, to set up the geometrical spatial model of fracturevuggy reservoir. The model can display 3D structure shape of the reservoir.

     

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    Methods and practices of reservoir geologic modelling constrained by seismic impedance.
    CHEN Gong-Xiang, HU Yong, ZHOU Yan-Li, LUO Dong-Gong, LIANG Wei, ZHANG Wei
    2012, 19(2): 67-73. 
    Abstract ( 2084 )   PDF (2336KB) ( 974 )  

     Threedimensional geological modelling technology based on geostatistics has become a key technology for the fine reservoir description, however, practically a restriction  exists on the density of hard data. The technology tends to be most used for the fine reservoir description in the zone with great  well density. In the exploration block, seismic attribute data are most applied as soft constraints to make up the deficiencies of insufficient information. Based on the research of an offshore oilfield in China, this paper discusses the application of 3D seismic inversion constrained reservoir model in several ways, and provides modeling strategies of “multicondition, multilevel constraint”. Our results demonstrate that the application of multisubject information  including seismic information can efficiently make up the shortcoming of lacking of information between wells, and decreases the uncertainty of geologic models. The established models can integrate the vertical high resolution of wells and horizontal high resolution of seismic data, hence, with this method, 3D stochastic modeling technology can be applied successfully to solve any problems of fine reservoir description during exploration and development.

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    Method for seismic sedimentology interpretation of reservoir architectures on development scale in meandering river.
    ZHANG Chao, LIN Cheng-Yan, ZHANG Xian-Guo, DONG Chun-Mei, CENG Hong-Liu
    2012, 19(2): 74-80. 
    Abstract ( 2325 )   PDF (1196KB) ( 1310 )  

    Reservoir architectures of meandering river are complex and the lithologic surfaces cross the isochronic ones. Traditional seismic facies analytical method can not satisfy seismic interpretation of reservoir architectures on reservoir development scale. Outcrop detection with ground penetrating radar (GPR), 3D seismic forward modeling and real seismic data are employed in this study. The influences of seismic frequency and strata thickness on seismic reflection of meandering rivers are analyzed. Principle and method of meandering fluvial interpretation with stratal slices are studied. Seismic sedimentology interpretation workflow for meandering rivers is created. It is found that (1) seismic events in high frequency seismic data are reflection of isochronic surfaces formed by point bar complexes, while those in low frequency data are reflection of lithologic surfaces; (2) seismic reflection characters of bars vary with thickness, this causes the ambiguity in its seismic interpretation. Three key points of this method were proposed: (1) making full use of geologic information from vertical and horizontal dimensions of 3D seismic data; (2) taking fluvial sandbody as an integrated genetic body in 3D space; (3) using hierarchic interpretation method and interpreting sandbodies of different hierarchy with particular technologies. This method and workflow are used in seismic sedimentologic interpretation in the Gulf of Mexico, and architecture of point bar complexes are characterized in 3D space.

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    Preliminary application of the seismic sedimentology to reservoir refined description under the condition of high density wellpattern in Daqing placanticline.
    HAO Lan-Yang, GUO E-Jie, LI Jie, JI Jin-Cheng, JIAO Yan-Li
    2012, 19(2): 81-86. 
    Abstract ( 7359 )   PDF (1572KB) ( 10220 )  

    According to the demand of accurate reservoir description for intense adjustment and potential tapping in ultrahigh water cut stage of Daqing Oilfield and directed by fine reservoir characterization and highdensity 3D seismic data of Daqing placanticline under the condition of dense well pattern, the methods of the high fidelity seismic processing by the integration of seismic date processing and interpretation, the method of highdensity fine synthetic calibration and the method of strata slice optimization have been established. Aiming at distribution of different types of sand bodies, the identification method of single channel with the feature of “looking for shale in sand” and “looking for sand in shale” has been given by using strata slices.The accurate reservoir description method using logging and seismic data and “directed by seismic attribution and controlled by single well facies” has been formed. The results show that the methods are much more appropriate for analyzing remaining oil. Horizontal well scheme design in D area has been guided by the results of identifying point bar, and the effects of drilling sand bodies are good.

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    Application of reservoir characterization techniques in DF11 Gas Field.
    JIANG Beng, XU Xin-He, HUANG Ru-Yin, CHENG Chao, LI Mao, LIU Li-Hui
    2012, 19(2): 87-94. 
    Abstract ( 1722 )   PDF (3699KB) ( 2669 )  

    With the high heterogeneity, welldeveloped mudflowgully and complicated distribution of the gas composition in DF11 Gas Field, the development effect was affected. Based on the study of sedimentary microfacies, this paper describes the reservoir heterogeneity and its cause. With the new geophysical techniques, data resolution can be improved greatly and the single sandbody can be characterized. Finally, a 3D fine geologic model is built. Based on precise reservoir description, we know the sedimentary microfacies, the origin and distribution of sandbodies and all kind of reservoir heterogeneity that influence the gas distribution. We also describe the single sandbody, the interlayer, and the boundary of mudflow gully. We build a 3D heterogeneity parameter model, describing reservoir geometry and the distribution of rock property in the space. Then, based on the results above, we optimize the type, location and trajectory of development well to balance reserveproduction of DF11 Gas Field and enhance gas recovery, meanwhile satisfying the market demand. The results of this research provide references to reasonable development for similar offshore gas field.

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    Genetic analysis on Neogene multiple oil & water system faultblock reservoirs in the sea area of Yellow River Mouth Sag.
    HU Guang-Xi, YANG Xi-Pu, GU Chi, FAN Ting-En, WANG Hui, HONG Zhen-Yu, GAO Yun-Feng
    2012, 19(2): 95-101. 
    Abstract ( 2406 )   PDF (5646KB) ( 924 )  

    To clarify the development orientation and potential target in the similar fields, taking A oilfield located at the northern end of the central structural ridge of Yellow River Mouth Sag as an example, genesis of Neogene multiple oil & water system faultblock reservoirs is systematically researched. The effective matching of sand reservoir and fault connecting source rocks is a key factor that controls hydrocarbon accumulation.The reservoir distribution of A oilfield is studied on the basis of fine stratigraphic classification and reservoir characterization by the integration of well logs and seismic data. Reservoir characterization combined with the analysis of sourceconnected faults, the controlling effect of reservoirfault coupling on oil and gas distribution is systematically studied. Firstly, the vertical distribution of hydrocarbon accumulation may be controlled by a “coupling” between the differences of vertical fault activity and relevant sand reservoir distribution. Secondly, the horizontal distribution of hydrocarbon may be controlled by the “coupling” between the differences in horizontal fault activity and the abundance of sand reservoir. Finally, the contact patterns of sand reservoir and fault affect the oil and gas accumulation.

     

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    The physical property lower limit of mediumdeep effective clastic reservoirs in Liushagang Formation, 117 district of Weixinan Depression.
    TAO Guang-Qiang-1, ZHANG Jian-Guang, JIANG Beng, LI Mao
    2012, 19(2): 102-109. 
    Abstract ( 2146 )   PDF (5920KB) ( 750 )  

    On the basis of the comprehensive application of physical properties, production test, oil testing data, mercury injection data and well log geological interpretation, and by applying distribution function curve method, production test method, oil testing method, irreducible water saturation method, and the lowest effective pore throat radius method, we define the physical property lower limit. Also, we analyzed the controlling factors of the effective reservoir from sedimentary facies, sand thickness, diagenetic evolution, rock components and formation pressure. Our results demonstrate that the main controlling factors are sedimentary facies and sand thickness. Distributary channel facies of braided delta are most effective reservoir development areas, while the least effective reservoir development area is gravity flow environment. Porosity and permeability difference increased with the increasing of particle size in the same diagenetic stage. Also, the higher content of quartz and feldspar, the higher porosity and permeability difference and higher feldspar content, the higher porosity and permeability difference in secondary pore belt. There was positive correlation between overpressure and reservoir effectiveness, but overpressure phenomenon is not developed in the Liushagang Formation and the overall impact is less important.

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    Fluid dynamic connectivity of karst carbonate reservoir with fracture & cave system in Tahe Oilfield.
    KANG Zhi-Hong, CHEN Lin, LU Xin-Bian, YANG Min
    2012, 19(2): 110-120. 
    Abstract ( 2365 )   PDF (2351KB) ( 1597 )  

    The Lower Ordovician carbonate reservoir in Tahe Oilfield is a large fracture & cave system formed by supergene karstification. The reservoir pore space of Tahe Oilfield mainly consisted of touchingvugs such as fractures related with karst cavities and pores. The exploration and production of oilfield proved that reservoirs have different connectivity and multipressure system. Based on the characteristics that the carbonate reservoir connected with fracturecavity system, this article analyzed the features different from discrete carbonate reservoir. Approach on the complicated features of the fracture & cave reservoir which are different from sand reservoir, the authors pointed out emphatically that variable dynamic data are very significant for the research on the connectivity of fracture & cave reservoir. By the study on dynamic data the author inferred the “fracture & cave unit” in the karst reservoir, and put forward the research ideas and methods that how to use dynamic data to study on the connectivity of the reservoir. Then the author concluded: (1)in the same fracture & cave system, every well is similar in pressure drop; (2)interwell interference analysis can make sure the connectivity immediately; (3)the changes of development well lead to dynamic changes of other wells in the same flowage unit; (4)connectivity grade can be divided by testing the tracer material in the wells which nearby the tracer injector and making sure how long the wells are affected; and (5) the fluid in different fracture & cave system is variable in composition, density and viscosity. In the end, according to the factual data of Tahe Oilfield, 42 fracture & cave units are recognized, and the author considered that the distribution of the reservoir is in accordance to karst palaeogeomorphology, palaeodrainage pattern and fault zone.

     

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    The reservoir characteristics and their controls on development in extralow permeable fracture conglomerate reservoir: A case study from the P2w1 reservoir of Karamay Oilfield.
    XU Fu-Min, LIN Guo-Feng
    2012, 19(2): 121-125. 
    Abstract ( 2302 )   PDF (784KB) ( 988 )  

    On the basis of reservoir cores research and log interpretation, the research established criteria for reservoir classification of the Lower Urho of Region Eight both statically and dynamically. Using comprehensive evaluation method, reservoirs in the entire region were divided into four categories. The best was class I, the worst was class IV. Good results have been achieved when this method was used in the four encryption tests. Prediction error of reservoir thickness was within 5%, and matching rate of reservoir types was 80%. According to the regional tectonic evolution and various characteristics of the stress field, geological background of crack formation in Lower Urho of Region Eight was analyzed. With the statistical data of cores and logging imaging, natural fractures of the Lower Urho of Region Eight are dominated by highangle joints. Artificial joints are dominated by fracturing pinnate joints and all kinds of cracks are mostly close cracks. Combined with the dynamic data of development, our study concludes that reservoir welldeveloped area controlled the distribution area of oil fields with high production. The better the oil reservoir conditions, the higher the initial production. The existence of cracks results in the prior onrush of the injected water along the crack causing fracture water breakthrough and the presence of water but no effect. Comprehensive analysis concludes that different oilwater displacement channels (reservoir matrix and fracture) and different development of reservoir and cracks lead to different effects on oil wells. On the basis of the mentioned static and dynamic study, the oilfield implemented four encryption test wells and more than 90% wells achieved the designed capacity.

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    Architectural analysis of meandering river reservoirs in Fuyu oil layer, C107 block, Changchunling oil field.
    SUN Tian-Jian, LI Qing-Li-*, HU Lei, LI Shun-Li
    2012, 19(2): 126-132. 
    Abstract ( 1664 )   PDF (2443KB) ( 858 )  

    This is a case study of Fuyu oil layer in C107 block, Changchunling oil field, which analyzed the architecture of meandering river reservoirs by hierarchy method with the data of lithology, logging, dynamics and testing etc. Based on the identification of single channel sandbodies and modern meandering river pattern, interwell correlations of these sandbodies were conducted by faciesdominated principle and four association models of point bars have been developed such as sigmoid, orthokinetic, antitropic, and dissected. In the study area, eight point bars with areas ranging from 0.02 km2 to 0.16 km2 were identified according to the thickness of point bars and characteristics of adjacent abandoned channels. Integrating the data of logging, core and wireline well log, identification of lateral accretions, and analysis of analogous wells, dip angle of lateral accretions was calculated to be about 5° and the width of lateral accretions was expected to range from 25 m to 70 m. Therefore, quantitative model for architecture of point bars was established by these parameters. The results of meandering river’s architectural analysis provide an insight into thermal production dynamics.

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    Characteristics of pore structure and reservoir evaluation of low permeability reservoir in Sulige gas field.
    LI Hai-Yan, YUE Da-Li, ZHANG Xiu-Juan
    2012, 19(2): 133-140. 
    Abstract ( 2755 )   PDF (3929KB) ( 1112 )  

    Taking the Shan1 and He8 segments in Sulige gas field as an example, this study focused on the micro pore structures of low permeability reservoir. Based on the study of mercury injection test, scanning electron microscope, and casting slice of core wells, micro pore structure was classified into four types through analysis of reservoir pore types and structures. Characteristics of each micropore structure was analyzed in detail. Dual influence of sedimentary environment and diagenesis resulted in the complexity of the micro pore structures. It is indicated that the genetic mechanism of the low permeability in Sulige gas field is the strong compaction, filling and cementation of autogenetic minerals during diagenesis. Reservoir space was dominated by secondary pores, and the pore throat assemblage was mainly low poresmall throat. With the cluster and Bayes discriminant analyses, combined with seven macro and micro heterogeneity parameters, discriminant function of four pore structure types was established, pore structure types for Sulige gas field were recognized, and the universal evaluation maps of main mini layers were drawn. Further analysis indicates that type Ⅰ and type Ⅱ reservoirs are of highquality, and considered as the further targets for exploration and development of low permeability Shan1 and He8 segments.

     

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    Reservoir heterogeneity characteristics in the framework of multigrade base level cycle of the oil layers of Tongbomiao and Nantun Formations in the Sudeerte Oil Field.
    WANG Jian-Beng, FAN Ta-Liang, WANG Hong-Yu, LIU Zhen-Xin, LI Yi-Fan- , HU Xiao-Lan
    2012, 19(2): 141-150. 
    Abstract ( 2342 )   PDF (6717KB) ( 682 )  

    According to the characteristics of the unconformity and depositional conversion surface, the oil layers of Tongbomiao and Nantun Formations in the Sudeerte Oil Field are divided into three longterm base level cycles and thirteen mediumterm base level cycles, and the main oil formationsⅠand Ⅱ are further divided into twenty six shortterm base level cycles (layers). The oil formations are well corresponding to the mediumterm cycles. In the framework of the multigrade base level cycles, the reservoir heterogeneity characteristics show obvious regularity: the structural patterns of different shortterm cycles determine the four modes of intralayer physical property changes; the medium cycles and their positions control the interlayer reservoir heterogeneity and the plane reservoir heterogeneity; and in the early period of the base level rise, in the late period of the base level fall and in the lowest position of the base level, the sandstone monolayer has large thickness, good continuity and good reservoir physical properties; in the period of high base level, the sandstone reservoir condition is poor.

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    Mineral morphology and composition characteristics of the plugging materials in polymer flooding.
    ZHOU Feng-Shan, CUI Fu-Xi, FANG Ying, LI Ji-Yong, TIAN Yu-Qin, SU Li
    2012, 19(2): 151-156. 
    Abstract ( 2244 )   PDF (1801KB) ( 850 )  

    By the comprehensive analysis of the cases of polymer flooding and profile control in the Block B19 in Shengli Oilfield, it is suggested that the main factor causing plugging in B19 was the injecting water that did not meet the standards of water flooding, which caused the excessive crosslinks of the injecting polymer and the formation of strong gelatinous material. The chemical analysis, the energy spectroscopy and the IR spectroscopy were used to investigate the mineral morphology and main compositions of gel scales. It was shown that the gel scales are composed of crosslinked polyacrylamide (PAM),in which a mass of water have been absorbed. The chloride mineral crystals as the inorganic scale material were gradually enriched and formed the inorganic scale structures in vivo environment of crosslinked polymeric inclusions. Moreover, some clay minerals from the formation were wrapped into the polymeric inclusions, eventually leading to the formation of the strong gelatinous materials with the complex polymermineral structural characteristics, which seriously affected and even obstructed the flow path of the polymer solution in polymer profile control and polymer flooding.

     

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     Physical simulation experiment of remaining oil distribution controlled by interlayer within braided bar of braided river reservoir.
    YUE Da-Li, DIAO Dun-Wei, WEN Li-Feng
    2012, 19(2): 157-161. 
    Abstract ( 2396 )   PDF (1513KB) ( 1086 )  

    This paper aimed to summarize remaining oil distribution patterns controlled by muddy interlayers within braided bar of sandy braided river reservoir, using the method of waterflooding physical simulation. Our results show that remaining oil distribution is controlled by three factors, i.e.,  extensional length of interlayer, matching relationship between injection & production wells and interlayer, and perforation interval location. The longer the horizontal extension length of interlayer, the more enrichment space of remaining oil. If the perforation condition of injection and production wells is the same, when the production well was drilled into the interlayer, remaining oil will be more enriched. If the entire interval is perforated in the injection well, compared to the entire perforation interval of production well, enrichment space of remaining oil is bigger in the upper perforation interval of production well, and the degree of reserve recovery is smaller.

     

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    Waterflooded situation and its key controlling factors in sealed coring of inspection wells at high watercut stage: A case study of Quan4 Formation of Fuyu Oilfield.
    GAO Xin-Jun, SONG Xin-Min, LI Chu-Zhen, SUN Yuan-Hui, DIAO Ying-Cheng, ZHANG Wei-Min, SHI Jing, MA Wen-Long
    2012, 19(2): 162-170. 
    Abstract ( 3078 )   PDF (3405KB) ( 815 )  

    Sealed coring is an important means of understanding the remaining oil distribution in high watercut oil field. Based on the sealed coring data of Quan4 Formation of Fuyu Oilfield at high water cut stage,this paper systematically demonstrates the qualitative and quantitative method to determine the water flooded situation of sealed coring well. The qualitative methods include: (1) observation with naked eyes; (2) microscope observation; (3) dripping test. The quantitative methods include: (1) determination of sealing condition of cores; (2) correction of oil and water saturation from core analysis; (3) calculation of original oil saturation; (4) determination of oil displacement efficiency of cores and its relationship with water production rate; (5) classification and discrimination criteria of water flooded extent. With this method, we analyzed 5 recent sealed coring wells and counted the waterflooded features of single well and all wells. Combined with the intralayer, interlayer and planar heterogeneity and the position relationship of the injection and production wells near the location of the sealed coring wells, key controlling factors of remaining oil distribution and water flooded condition were proposed, which play a fundamental role in the further mining of remaining oil.

     

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    1. School of Geosciences, China University of Petroleum (East China), Dongying 257061, China 2. The Baikouquan Oil Extraction Plant of Karamay Oilfield, Karamay 834000, China 3. Dongxin Oil Extraction Plant in Shengli Oilfield, Dongying 257061, China
    LI Zhi-Feng, LIN Cheng-Yan, DONG Bei, BO Li-Xia, CUI Ling
    2012, 19(2): 171-175. 
    Abstract ( 2259 )   PDF (993KB) ( 1392 )  


    Abstract: On the basis of classification and interarchitecture of monosandbody, studies on the influencing factors of the water flood development of low permeability reservoirs were carried out with the combination of geological factors and productions. There are three major geological factors which affect the water flood effect of low permeability reservoir. The first is pore structure. The more complex the pore structure and the smaller the pore diameter, the worse the development effect of low permeability reservoir. The second is interarchitecture of monosandbody. The more complex, the worse the development effect. The third is the frequency of thin interbeds. Moderate thin interbeds improve production effect, but excessive interbeds will decrease the development effects. At the same time, development factors such as the flow characteristics, the Jamin effect and the pressuresensitive effect are also analyzed to see the the development effect of low permeability reservoir. The greater the initial pressure gradient, the worse the development effect. Jamin effect decreases the development effect. The more serious the pressuresensitive effect, the worse the development effect. In view of the above influencing factors, we propose five measures to improve the development effect including the commingled injection and production by monosandbody in small layer, horizontal well development, moderately enlarging production pressure, narrowing well spacing as far as possible and early water flooding.

     

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    Microflow characteristics and influencing factors of oil displacement efficiency of Chang6 reservoir in Heshui area.
    ZHANG Zhang, SHU Yu-Shuang, CHEN Chao-Bing, NIU Xiao-Bing, XIN Gong-Gang, SHU Jing, QUAN Hong-Hui
    2012, 19(2): 176-183. 
    Abstract ( 2972 )   PDF (2552KB) ( 1374 )  

     The present paper is aim at a deeper study  on  the microseepage flow and the influencing factors of displacement efficiency  of Chang6 reservoir of Triassic Yanchang Formation in the area of Heshui, in the Ordos Basin in order to  provide a scientific basis for increasing the recovery ratio. Take the real sandstone micromodel experiment as the main method in this study, and  combined with  the checkup of slices, SEM, mercury penetration etc.  to study the pore structure, the composition of the rocks. The results show that the waterdrive patterns in the reservoirs of Chang6 in this area are mainly homogeneous seepage and reticular seepage, the finger like seepage is few. The homogeneous seepage gets the highest final oil saturation and final displacement efficiency, the models of reticular seepage are lower, the models of the finger like seepage are the lowest. As to the physical properties, the permeability is the first factor affecting the displacement efficiency, the porosity is the second; the displacement efficiency can be increased effectively by increasing the drive pressure advisably; the displacement efficiency also can be increased by increasing the multiple volume of driving water, finally the  heterogeneity also is one of the affecting factors.

     

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    The method of shale gas assessment: Probability volume method.
    ZHANG Jin-Chuan, LIN La-Mei, LI Yu-Chi, JIANG Sheng-Ling, LIU Jin-Xia, JIANG Wen-Li, TANG Xuan, HAN Shuang-Biao
    2012, 19(2): 184-191. 
    Abstract ( 6913 )   PDF (686KB) ( 11845 )  

    Abstract: The assessment method of shale gas resources can differ completely from that of conventional hydrocarbon. Combined the present exploration and development situation of shale gas in China with the demands of “The national survey and evaluation of shale gas resource and favorable area selection”, a new method and technique for shale gas assessment is proposed, namely the probability volume method, based on the shale gas accumulation mechanism and characteristics. According to the shale gas geological recoverable conditions and statistical analysis, the parameters system for determining shale gas prospect areas, favorable areas and target areas is established. Furthermore, criteria for shale gas targets selection of different types and work flow for shale gas resources evaluation are put forward. Combining domestic and USA shale gas statistics data, this study laid the foundation of evaluation conditions for systematically assessment of the shale gas resources in China. Resource assessment parameters can be classified as discrete and continuous ones, which can be obtained and possibility assigned according to their distribution characteristics. Probability volume method and technique are applied in the Chinas first systematical shale gas resource assessment and work well.

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    A preliminary discussion on evaluation of continental shale gas resources: A case study of Chang 7 of Mesozoic Yanchang Formation in ZhiluoXiasiwan area of Yanchang.
    WANG Xiang-Ceng, ZHANG Jin-Chuan, CAO Jin-Zhou, ZHANG Li-Xia, TANG Xuan, LIN La-Mei, JIANG Cheng-Bi, YANG Yi-Ting
    2012, 19(2): 192-197. 
    Abstract ( 3730 )   PDF (750KB) ( 1687 )  

     Shale gas is a kind of unconventional natural gas accumulation types; its practice is still in the experimental stage in China. There are no mature methods to evaluate the resources reasonably at present and it lacks reference especially for evaluation of continental shale gas. Based on the analysis of differences and characteristics between marine shale and continental shale, the conditions and standards of terrestrial shale resource evaluation are confirmed. The continental shale gas resources are evaluated preliminarily on the basis of sample tests and gas content assessment of the Mesozoic Triassic Yanchang Formation shale in Yanchang exploration area. For different exploration degree and geological conditions, different assessing methods should be used. By a comprehensive evaluation, it is shown that the Mesozoic continental shale gas resource is of great value for exploration development; its volume is 626.4×108m3 to 6037.2×108m3.

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    The main progress and problems of shale gas study and the potential prediction of shale gas exploration.
    JIANG Fu-Jie, LONG Xiong-Ai, OU Yang-Hua-Cheng, GUO Ji-Gang, JIN Cong, HE Zhi-Feng, WANG Qiang
    2012, 19(2): 198-211. 
    Abstract ( 6795 )   PDF (4978KB) ( 8540 )  

    Shale gas means the internal residual natural gas resource in mudshale, which exists in the form of adsorption, liberation, dissolution, etc., and is generated in diverse geologic settings in mudstone or shale, and has saturated multiform residual requisitions of rocks and entered the threshold of expulsion yet not being completely expulsed. With the increasing of exploration in North America, Europe and Asia, the research in the reserve characteristics and the hydrocarbon accumulation mechanisms of shale gas has achieved extraordinary progress. However, there are still many problems in the research in shale gas, for instance, the concept of “shale gas” does not express the scientific meaning of shale oilgas reservoir; there are not a definite genetic mechanism and an effective judgment of shale gas; the distribution and generation of shale gas are not clear and the united method of prescription does not exist. In view of the current cognition of shale gas, the authors prescribe the shale gas resource in China by the critical saturating capacity of residual hydrocarbon and the ratio of oil and gas expulsed by hydrocarbon due to the decline of temperature and pressure in the process of drilling and extracting.

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    Dominant factor of fracture development in shale and its relationship to gas accumulation.
    DING Wen-Long, LI Chao, LI Chun-Yan, HU Chang-Chun, JIU Kai, CENG Wei-Te
    2012, 19(2): 212-220. 
    Abstract ( 3279 )   PDF (2141KB) ( 2233 )  

    Shale with high quartz, feldspar and carbonate will have low Poisson’s ratio, high Young modulus and high brittleness. As a result, the shale is conducive to produce natural and induced fractures under external forces. In general, there is a good correlation between fracture development in shale and the volume of brittle minerals present. Shale with high TOC or abnormally high pressure has welldeveloped fractures. Shale fracture development also shows a positive correlation with total gas accumulation and free gas volume, i.e., the better shale fractures are developed, the greater the gas accumulation and therefore the higher the gas production. Fractures provide migration conduits and accumulation spaces for natural gas and formation water, which are favorable for the volumetric increase of free natural gas. Wider fractures in shale result in gas loss. In North America, there is a high success ratio of shale gas exploration and high gas production from highangle fracture zones in shale. Good natural gas shows or high yield producers in the Lower Paleozoic marine organic matterrich rocks in the Sichuan Basin are closely related to the degree of fracture development in brittle shales.

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    Reservoirforming conditions and strategic select favorable area of shale gas in the Lower Paleozoic of Chongqing and its adjacent areas.
    LONG Feng-Yu, ZHANG Jin-Chuan, LI Yu-Chi, TANG Xuan, CHENG Li-Jun, LIU Zhu-Jiang, HAN Shuang-Biao
    2012, 19(2): 221-233. 
    Abstract ( 3218 )   PDF (3746KB) ( 2207 )  

    The paper primarily studied geological background of organicrich shale and its distribution characteristics, reservoirforming conditions of shale gas and potential favorable areas of shale gas reservoir development. The study started from basic data such as the field surface outcrops, underground core and typical profile, and by the analysis of the reservoirforming conditions of shale gas in the lower Paleozoic of Chongqing and its adjacent, and using comprehensive information method, the favorable areas for shale gas reservoirs were predicted. The results indicate that the Qiongzhusi Formation of Lower Cambrian system organicrich shale, Wufeng Formation of Upper Ordovician system and Longmaxi Formation of Lower Silurian system organicrich shale in the study area were characterized by wide distribution, great thickness, buried moderately, good organic type, high organic content, high organic thermal evolution degree and high hydrocarbon potentials. The shale is rich in brittle minerals, with great quantity of matrix micropore and cracks, and good reservoir conditions, which offered sufficient accumulated space and migration pathway for shale gas. The result of isothermal adsorption simulate test and well site desorption test showed that the two sets of black shale all have strong ability and high performance of gas adsorption. The widespread multistage gas shows of many wells drilled in the black shale strata in this area indicated the great potential of shale gas. In a word, the tectonic evolution characteristics and geological conditions in this area are similar to the typical shale gas basins in Eastern America, and the study area is a favorable and prospective place for shale gas exploration, having lots of advantages for forming shale gas reservoir.

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    Trajectories of radioactive materials after the nuclear leakage in Fukushima Nuclear Power Station in Japan.
    CEN Kuang, CHEN Yuan, LIU Shu-Bei, XU Yang
    2012, 19(2): 234-238. 
    Abstract ( 2124 )   PDF (1549KB) ( 1155 )  

    Magnitude 9.0 earthquake occurred in Coastal waters of northern Japan on March 11, 2011, triggered a succession of disasters and led to nuclear leakage in Fukushima Nuclear Power Station. The level of this nuclear accident raised from 5 to 7 (the highest level of nuclear accidents). The spread and migration of radioactive materials after the nuclear leakage is the focus and a hot spot in nuclear accidents. HYSPLIT model is used to simulate radioactive materials’ trajectories after the nuclear leakage. The results show that atmospheric particulates with radioactive materials mainly move to the east and northeast over the Pacific, and even enter the United States. Sometimes they represent southward and turn to southwest trajectories or movement tendencies making them to move into China. Radioactive materials’ trajectories in the next four months, May to August, are speculated by historical meteorological information, and air dispersion from Fukushima is mainly northward, northeast and west directions. Due to factors such as  atmospheric turbulence, wind direction, rainfall, ocean current and so on, radioactive materials will still have influence in China. Atmospheric particulates with radioactive material into China mostly come from high altitude.

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    A case study of the third member of Mesoproterozoic Gaoyuzhuang Formation in Xuanhua County of Hebei Province.
    MEI Mian-Xiang
    2012, 19(2): 239-247. 
    Abstract ( 2046 )   PDF (2269KB) ( 813 )  

    Earthquakeinduced deformational structures mainly include the smallgrade tensional or compressional fault, the inconsistent fold of soft sediment, which are marked by shock deformation; thus, these structures become the main discerning marks for seismites. Many typical earthquakeinduced deformational structures developed in the third member of Mesoproterozoic Gaoyuzhuang Formation in Xuanhua County of Hebei Province, and these structures include the obvious intrastratal fault, the intrastratal fold and the cataclastic breccia and so on. The earthquakeinduced structure in the third member of Mesoproterozoic Gaoyuzhuang Formation provides an important example for both the study on not only the reconstruction and the destruction of depositional rock beds generated by earthquake but also the distinguishability from other event deposits such as the storm and the tsunami deposits, and also provides an important information for the formation setting of the third member of Gaoyuzhuang Formation that is marked by a nonstromatolitic succession of the Precambrian.

     

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    Flexibility energies of coalbed gas reservoir and the controlling function on coalbed gas reservoir formation: A case study from Qinshui Basin.
    TUN Cai-Fang, QIN Yong
    2012, 19(2): 248-255. 
    Abstract ( 2391 )   PDF (3102KB) ( 1358 )  

    The main controlling factors of coalbed gas reservoir formation include right pressure system, right transit system and corresponding energy mechanism, which is the spacetime configuring relation of effective pressure system and effective transit system of coalbed gas reservoir substantively. Flexibility energies of coalbed gas reservoir are just about ties between the two systems. Different flexibility energy models are put forward in the paper, threeunit differentiate symbols of coalbed gas reservoir formation function including crevice growth degree coefficient ζ1, crevice open and close degree coefficient Δ, and effective pressure system growth degree coefficient ζ2 are established, and their distributing laws in Qinshui Basin are discussed. ζ1 and Δ can show effective transit system quantificationally, while ζ2 can show effective pressure system quantificationally. According to threeunit differentiate symbols, the controlling function of coalbed gas reservoir formation of flexibility energies is analysed, threeunit model on differentiating coalbed gas reservoir formation style was advanced. The research results considered that there are 27 sorts of styles of coalbed gas reservoir formation function, but just 8 sorts are propitious for coalbed gas enrichment and high produce. Actually only 2 favorable styles in Qinshui Basin are effective pressure system and effective transit system distributing in DaningPanzhuangFanzhuang zone of southern basin, and rather effective pressure system and rather effective transit system distributing in QinshuiZhengzhuangFanzhuang zone of southern basin and QinyuanAnze zone of middle basin.

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    ar methods concerning metallogenic element association in Donggapu mining area, Tibet for seeking geochemical anomaly.
    LIU Bing-Li, GUO Ke, WANG Wei, AO Dong, WU Ju
    2012, 19(2): 256-266. 
    Abstract ( 2197 )   PDF (1741KB) ( 823 )  

     Complicated  geological processes and controlling factors always make the distribution of geochemical elements having nonlinear characteristics. Traditional linear model methods are limited due to the character of nonlinear element association. In this paper, we adopted aiNet to preprocess geochemical data in order to study the geochemical metallogenic  element association. Fractal contentarea method was used to determine the anomaly threshold of elements. Fractal contentgradient method was used to determine the zone of element concentration.  Thus a series of nonlinear metallogenic element association method system to seek out geochemical anomaly has been formed.   We applied this nonlinear method for anomaly seeking of geochemical metallogenic element association  to process 1∶10000 soil geochemical survey data from Donggapu mining area of Tibet and had achieved good results.

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