, Volume 30 Issue 6
    

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  • Discussions on exploration strategy in the Bohai Bay Basin
    ZHAI Guangming and HE Wenyuan
    , 2003, 30(6): 705-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Bohai Bay Basin is a matured basin for petroleum exploration, however，its petroleum geological condition is complex and a big complicated oil and gas gathering area. Now， exploration is mainly focused on Shahejie Formation in age of Paleogene. There are some new strata left for exploiting. The exploration strategy in the Bohai Bay Basin should be a play of detail checking up the upper layer (Neogene), progressive exploration and development of middle layer (Paleogene) and exploring the deep layer (Paleozoic). With many large area and low magnitude structures. The neogene has practical potential for finding large petroleum fields. The progressive exploration and development of Paleogene should increase the reserves continuously. The exploration has potential for finding more reserves.
  • A primary discussion on the “low grade resource”
    ZHA Quanheng and HE Wenyuan
    , 2003, 30(6): 706-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Compared with resource of oil and gas field with large-scale, higher abundance, better quality, and higher production, as well as taking technology and economy into consideration, the word “low grade resource” is a relative concept. There is a lot of “low grade resource”in nature. In some basins, the quantity of low grade resource can amount to or even surpass that of high grade resource. Therefore, its importance can't be ignored. The developed countries have attached great importance to low grade resource. There is much low grada resource in China. With the development of exploration,the low grade resource plays more and more important role.
    • 石油地质研究
  • Huanghua superimposed basin evolution and oil & gas accumulation in buried hill
    YANG Chiyin and ZHANG Yiwei
    , 2003, 30(6): 707-0.
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    Huanghua Area, a typical superimposed basin with multiple cycles, is developed with multiple sets of hydrocarbon source and various sets of reservoir and cap. So far various buried hill reservoirs have been discovered in the multi-stages residual basins of Mesozoic, Early and Late Paleozoic. The study shows that the structural reversion evolution pattern of Indosinian-Himalayan Epoch is favorable to form the buried hill reservoirs originated from Cenozoic and got stored in Paleozoic, while the superimposed depression evolution pattern of Indosinian-Himalayan Epoch is favorable to form the buried hill reservoirs both originated from and got stored in Paleozoic, and the textural reversion evolution pattern of Yanshan-Himalayan Epoch is favorable to form the buried hill reservoirs originated from Cenozoic and got stored in Mesozoic. With regard to reservoir forming the study concludes that the discovered Ordovician buried hill reservoirs are all formed through multi-stages of accumulation by the tectonic movements of multiple stages.
  • 银根盆地下白垩统石油地质特征及含油气远景评价
    JIANG Xinyi; SU Chuanguo and JI Wei-hua
    , 2003, 30(6): 708-0.
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    The Permian and the Paleogene sediments are major source rocks in the Dongting Basin which is located in the middle of the Yangzi Sub-plate in South Central China, prior to becoming an inland depression during the Cretaceous Paleogene. The Permian and Paleogene sediments are rich in organic material， which have reached mature or over mature stage, and are prolific source rocks. Permian and Paleogene fractures mudstone and Cretaceous sandstone are major reservoir types in the basin. Three source-reservoir-trap combinations in the basin are: ①Permian reservoir with Permian source; ②Cretaceous reservoir with Permian source; and ③Paleogene reservoir with Paleogene source. Therefore, the Permian should be the primary exploration target because it has by far the most hydrocarbons in the basin.
  • Petroleum geological features and hydrocarbon prospect evaluation of the Lower Cretaceous in the Yingen Basin
    WU Shaobo and BAI Yubao
    , 2003, 30(6): 709-0.
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    Yingen basin, located at the convergent point of four plates, is an intermontane basin within the Inner Mongolia-Tianshan folded belt. Its basement is the metamorphic rock of the Upper Palaeozoic Era. The basin consists of four secondary tectonic units: Chagandelesu Depression, Shangdan Depression, Suhongtu Depression and Zong-Sha Uplift. The Bayingebi Formation, Lower Cretaceous, with the sedimentary thickness of 3000~4000m, is the main source rock and reservoir rock sequence in the basin. The source rock, mainly formed at the middle to upper segment of the Formation, has higher organic matter abundance. The source rock has mainly type Ⅱ and type Ⅲ kerogen that has reached low mature to mature stage. The reservoir, includeing clastic rock, carbonate rock and volcanic rock, presents a characteristic of low porosity and low permeability, but some medium porosity and permeability reservoir also developed. Regionally there are three sets of cap rock with good oil and gas conservation condition. Based on the comprehensive analysis of source rock-reservoir-cap assemblage, Chagandelesu Depression is the most favorable hydrocarbon prospect region, and that Suhongtu Depression and Shangdan Depression are relatively favorable hydrocarbon prospect regions.
  • Sequence stratigraphic characteristic of Palaeozoic in Tazhong area, Tarim Basin
    JIAO Cunli; Lü Yancang; ZHU Junling and FAN Tailiang
    , 2003, 30(6): 710-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Stratigraphic sediment in the Tazhong area was of polycycle, which was controlled by previous structure movements. Four grades of unconformities had been developed in Palaeozoic in situ. According to the development feature of unconformity surface,the Palaeozoic has been divided into 3 megasequences, 8 supersequences and 19 tertiary sequences. Different kinds of non-structural traps were relevant to large unconformities developed in multiple periods (stratigraphic trunction, overlap, and lacuna surface, etc.) Three types and 10 subtypes can be divided, which are widely distributed and developed in the top sequences of I degree megasequence as Sinian-Ordovician (MS1) and Middle to Upper Ordovician and Devonian megasequence (MS2), and that should be the important domain for exploration.
  • Petroleum reservoir filling history and oil-source correlation in the Lishui Sag, East China Sea Basin
    SUN Yumei and XI Xiaoying
    , 2003, 30(6): 711-0.
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    Depending to the synthetic studies of petrography, homogenization temperature and biomarker of fluid inclusion, it is shown that there are three times petroleum migrations in the Lishui Sag. The earlier petroleum migrating occurred at the end of Paleocene. The hydrocarbon fluid has maturity equivalent to lower Ro,0.7%. It is generated from Yueguifeng Formation and mixed hydrothermal up, the hydrocarbon inclusions are trapped in the first filling stage occurs widely in the Lishui Sag. The second migration happened during the middle-upper Eocene. The maturity of hydrocarbon fluid is equivalent to higher Ro,1.0%, which is generated from the Yueguifeng Formation and accumulated nearly the Yueguifeng Formation. The third one charged during the later Oligocene to Miocene. As the crust uplift, some of the oil/gas within the reservoir in deeper layer had been re-migrated upward by the fault, and mixed petroleum generated from upper Paleocene up into the shallow layer. The CO2-bearing fluid charged into the reservoir is later than the third stage.
  • Formation of the LS36-1 oil and gas structure in the Lishui Sag, East China Sea Basin
    GUO Yonghua; YU Shui and GE Ling
    , 2003, 30(6): 712-0.
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    Three sets of Paleocene source rocks are recognized in the Lishui 36-1 structure in the Lishui Sag,East China Sea. Biomarker suggests that oil and gas in the structure are from multiple sources and they accumulated during separate geological times. The biomarker series distinguish three Paleocene sources for the Lishui Sag: ①The ancient oil and gas pools are predominantly from the Yueguifeng Formation; ②The present pools are primarily from the Lingfeng Formation, with minor components from the Yueguifeng and the Mingyuefeng Formation; ③The hydrocarbon gas in the present pools are mostly from Yueguifeng and Mingyuefeng Formation, and the CO2 gas is of mantle source. The Yuquan-Qiantang tectonics had unfavorable impact on the preservation of the early oil and gas pools. The large structures close to the source rocks should be more prolific targets for future exploration.
  • Three oil-reservoir combinations in south marginal of Jungar Basin, Northwest China
    LI Xueyi; SHAO Yu and LI Tianming
    , 2003, 30(6): 713-0.
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    According to target layer and structure characteristic of exploration, the Mesozoic-Cenozoic stratum are divided into three oil-reservoir combinations in south marginal of Jungar Basin. On the oil-gas geologic conditions, controlling factors of oils and cause of mechanism, midst and below oil-reservoir combinations should absorb more oil and gas from the major source rocks distributed within the south marginal of the Jungar Basin, in age of Jurassic. The reasons for that are much oil and gas channels have been generated and developed during the forming of structures, and the reservoirs have benefit conditions for constructing with the main generation of oil and gas. The anticlines of Hutubi and Kayindike have been cited to verify the importance of oil-reservoir combinations. The further survey suggestions should be to explorate the midst oil-reservoir combinations, to sconte below oil-reservoir combinations,and to try explore upper oil-reservoir combinations.
  • Forming process of Denglouku Formation as a gas reservoir in the east of Daqing placanticline
    XUE Yongchao; FU Guang and PENG Shimi
    , 2003, 30(6): 714-0.
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    The analyses of fluid inclusions in the reservoirs composed by the Denglouku Formation in east Daqing placanticline, and gas and oil generation from source rocks and the history of fracturing reflect the filling history and process of the gas. Two major gas filling process had happened in the Denglouku Formation, as the later period of Quantou Formation and the later period of Nenjiang Formation, in which the later Quantou Formation is the key accumulation period and the later Nenjiang Formation is the secondary rank accumulation period. The exploration in this area practically proved the inferring and analysis.
  • Sealing factors of faults and their sealing effects
    CHEN Yongqiao; ZHOU Xingui; YU Xinghe and TONG Weishao
    , 2003, 30(6): 715-0.
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    Present research situation, including relationships between the capacity of fault sealing and some main control factors (present ground stress, fault type, fault intensity, contact probability between reservoirs on fractured surface and geometric characteristics of faults) on this capacity, is analyzed and discussed. It is pointed out that if the angle between the maximum axis of principle stress and fault strike is closer to 90° and the combination between maximum principal stress and gravity of overlaying formation is larger than or closer to the compression stress of the formation, the sealing of fault is better; if it is a wrench fault, the sealing of fault is the best, abnormal fault, better, normal fault, worse; if the fault does not break the sealing, its fault displacement is longer, the capacity of fault is better, and if its recent activity is lower, capacity of fault is better.
  • Oil-source correlation of mixed oils derived from multiple source rocks in the Cainan Oilfield, Junggar Basin, Northwest China. Part III: Geological and geochemical analysis of possible oil sources in the Cainan Oilfield
    CHEN Jianping; LIANG Digang; WANG Xulong; DENG Chunping; XUE Xinke; JIN Tao; SONG Fuqing and ZHONG Ningning
    , 2003, 30(6): 716-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    he crude oils in the Cainan Oilfield are mixtures of hydrocarbons from Permian, Triassic and Jurassic source rocks, based on their distribution in the reservoirs, and their carbon isotopic and biomarker compositions. A calculation using whole-oil stable carbon isotope ratios of typical end-member crude oils suggests that the contribution of Jurassic source rocks to the Cainan crude oils averages 50%~65%. A matching calculation with absolute concentrations of biomarkers indicates that the Jurassic contribution averages 62%, while those of the Triassic and Permian source rocks average 15% and 23%, respectively. The oils with similar features to the Cainan oils, occur only above the Jurassic Sangonghe Formation around the Fukang sag. Hence they are derived from the Fukang sag.
  • The structure of source rocks and characteristics of hydrocarbon expulsion—An example from Paleogene system in Jiyang Depression
    CHEN Zhonghong and ZHA Ming
    , 2003, 30(6): 717-0.
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    There are macroscopic and microscopic heterogeneities in the distribution of organic matter in the JiYang Depression and many forms of lithologic structure of the source rocks, showing an inhomogeneity of hydrocarbon expulsion from source rocks. In the formation the state of pressure and characteristics of hydrocarbon expulsion are different from each other. The phenomena of stagnant expulsion and abrupt expulsion suggest that there are two extreme states for hydrocarbon expulsion. The inhomogeneity of hydrocarbon expulsion is guidance for resource evaluation and prediction, which will be able to provide the ways for simulation of hydrocarbon expulsion.
  • A new understanding on the Putaohua reservoirs of Xingshan synclinal zone of Sanzhao Sag in Songliao Basin, East China
    WANG Shouqing; XU Xian-hua; HE Zurong; ZHANG Yumin; LIANG Sujuan; HAN Xiaoqiang and YAO Yaming
    , 2003, 30(6): 718-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    In the oil exploration of Yaojia Formation (in age of Cretaceous) Putaohua oil reservoir of Xingshan synclinal zone of Sanzhao Sag in Songliao basin, no big achievement has been gotten depending on the lithological model as usually did. Based on the combination of the key bed and morphological feature of logging curve and formation thickness, a new understanding suggests that the Putaohua oil reservoir changed thinner from west to east and from north to south generally. The posthumous fault-anticline zones mainly control the formation of the reservoir and the horizontal distribution of oil and water are easily affected by the faults. The reservoir belongs to a structure-lithologic type and the effects of lithological factor made the reservoir more complex. According to this new understanding, the oil-bearing area is expanded into 102km2 and the reserve of oil will be added up to 1800×104t.
  • Origin of secondary porosity of Paleogene sandstone in the Dongying Sag
    HU Xiao-min; HU Xiao-min; HU Xiao-min and HU Xiao-min
    , 2003, 30(6): 719-0.
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    The secondary porosity of Paleogene sandstone in the Dongying Sag mainly originated from the dissolutions of different stages carbonate cements, secondarily, from the feldspar dissolution. The secondary porosity from calcite dissolution is distributed in the shallow section, which is generated by the organic acids during organic mater maturation and the later secondary porosity from Fe calcite and Fe dolomite dissolution is distributed below 2500m,which related to the CO2 from the decarboxylation of organic acids and the thermal cracking of organic mater. The secondary porosity is mainly distributed in the interval below 2500m.
  • Ordovician carbonate reservoirs in the Suqiao buried hills zone of Jizhong Depression
    SU Li-ping; LUO Ping and HU Sherong
    , 2003, 30(6): 720-0.
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    The Ordovician carbonate reservoirs in the Suqiao buried hills zone of Jizhong Depression mainly consist of crack and secondary pore spaces, which are formed by paleo-karst and tectonic splits. Dissolved pores developed in micrite-powder dolomite or fine-sparry dolomite. The fresh water karst during Yanshanian-Himalayan tectonic movement occurred near the fault, which developed in dolomite and cracked limestone, is one of the contributors for the Ordovician' reservoirs. The cracks developed in 5 episodes and they are basement for forming the reservoirs and the reservoir development has a positive relationship with the development of cracks.
  • Hydrocarbon generation of Ordovician carbonate source rocks in Huanghua Depression
    YUE Yun-fu; YU Xuemin; HE Yongmei; SU Jun-qing and WANG Li
    , 2003, 30(6): 721-0.
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    The carbonate is thickly developed within the Huanghua Depression. The kereogen typing, organic abundance and thermal evolution analyses suggest that the organic matter is good, however, its thermal evolution reaches a higher rank and the samples that residue organic carbon is more than 0.3% are amount to 49%, and more than 0.4% are amount to 32%. If the original organic carbon abundance could be recovered, the abundance would be much higher, so some good Ordovician carbonate source rocks should be developed the Huanghua Depression.
  • Dominate factors and distribution of low resistivity reservoir in southern Songliao Basin
    LIU Hongyou and LIANG Chunxiu
    , 2003, 30(6): 722-0.
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    The low resistivity oil beds in the south Songliao Basin are caused and formed by mud invasion, low height structure and additional shaliness conductivity, etc. However, under different geological conditions, only one or two of which are the dominant factors. In ten oilfields of southern Songliao Basin, the main controlling factors of the low resistivity reservoir formation are analyzed in detail on the basis of core analysis. In deferent formation and deferent zone, genetic
    • 综合勘探开发技术
  • Analysis and countermeasurement of seismic prediction in the Sulige Gas Field
    ZENG Zhong; YAN Shixin; WEI Xiucheng and LIU Yang
    , 2003, 30(6): 723-0.
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    Sulige Gas Field is a large but low pressure and low saturation gas field located in the Ordos Basin. The main reservoirs are of Late Paleozoic amalgamated fluvial channel sands. High-resolution 2-D seismic played a critical role in reservoir prediction and the discovery of gas fields. Data acquisition, quality, processing and interpretation in recent years are reanalyzed to improve the predictability of future work. To meet the ever increasing gas field development demand, it is suggested here to apply 3-D pre-stack seismic attributes analysis, well-logging, strata time-frame constraint, reservoir inversion and elastic wave inversion technology, 3-D VSP and 3-C seismic techniques in future work.
  • Distinguishing of sequence interface of carbonate rock in the covered field:an example for Feixianguan Formation，Lower Triassic in Northern Sichuan Basin
    WEI Guoqi; CHEN Gengsheng; YANG Wei; YANG Yu; HU Mingyi; ZHANG Lin; WU Shixiang; JIN Hui and SHEN Jiehong
    , 2003, 30(6): 724-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    It is very difficult to distinguish sequence interface of carbonate rock in the covered field. By comprehensive application of seismic, well logging, rock core and field outcrop etc., distinguishing of sequence interface can be achieved. When distinguishing interface, field outcrop must be considered at first, comprehensively applying seismic data, base on research of sedimentary facies, by applying data of diagenesis, well logging etc, It is very important for exploration of oil and gas to make off the sequence interface, so the distribution of platform margin oolitic beach reservoirs of Feixianguan Formation， Lower Triassic can be predicted by the method in the northern Sichuan basin
  • Reservoir types and prediction of Majiagou Formation in the Ordos Basin
    ZHOU Jingao; DENG Hongying and ZHENG Xingping
    , 2003, 30(6): 725-0.
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    Reservoir types and prediction of Majiagou Formation in the Ordos Basin
  • Reservoir evaluation and prediction with log data under domination of lithologial character
    TIAN Bo; CHEN Fanghong and HU Zongquan
    , 2003, 30(6): 726-0.
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    Under strong compaction and cementation, the clastic reservoir of Upper Paleozoic becomes very tight in south Ordos Basin, the correlation between log data and reservoir parameters could hardly be done. The research reveals that lithological character of reservoir has apparent controlling effect on porosity and permeability, by adding quantified lithological parameter into neural network as an input parameter. Cumulative productivity factor is used to define the permeability inferior boundary of effective reservoir, with the relation between permeability with porosity, which is used to sort reservoir into five categories. The distribution of reservoir parameters is predicted under domination of even porosity and permeability of each segment of the key wells.
  • Method and application of facies controlling isochrone oil-layer
    WANG Xiwen; SU Mingjun; WANG Daxing; ZHU Wenchun; LIU Chunhui and TANG Yuehong
    , 2003, 30(6): 727-0.
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    Precision and correct of log layer interpretation is related for looking for new oil layer which were found before. Therefore, method of facies controlling-isochrone oil-layer interpretation, which include: results of precision interpretation by 3-D seismic facies are calibrated; logs are interpreted according to depositional cycle; single sand layer is interpreted by log facies, is put forward. The method is testified to be correct and efficient in times of the application of Madong-Tangnan Oilfield.
  • Application of multi-binary sequential indicator algorithm to simulate lithofacies in Huoshaoshan Oilfield
    ZHANG Xiangzhong; XIONG Qihua and CAI Yi
    , 2003, 30(6): 728-0.
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    The kernel basis of a 3-D reservoir model is the simulation of sedimentary microfacies and lithofacies, which controls the distribution of reservoir parameters at a great degree. Multi-binary Sequential Indicator Simulation Algorithm, an improvement of the sequential indicator simulation algorithm, is used to the simulation of lithofacies at the H1-13 layer in the Huo Shaoshan Oilfield. In addition to the advantages of the sequential indicator simulation algorithm, such as easy to use, honoring original data, and fast, multisis has the advantages of easy controlling the simulation sequence and post processing of the simulation results. The final simulation results are more continuous, reasonable and consistent with the real geological scenarios.
  • A new approach for predicting fractures using principal curvature
    LI Zhiyong; ZENG Zuoxun and LUO Wenqiang
    , 2003, 30(6): 729-0.
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    The density, direction, width, and depth of fracture development are controlled by the principal curvatures of structural surfaces. To certain extent, therefore, the thickness of the oil-bearing interval as well as the volume and permeability of the fracture porosity are also influenced by principal curvatures. The general equations of principal curvature derived from differential geometry overcame the limitations of previous equations derived from the theory of elastic thin plate with small deflection. By combining the analyses of trend surface and difference method, the scattered structural surface data are dealt with and the principal curvatures are calculated. The spatial distribution of fractures predicted using this method has been shown to have a generally good match with the field observations in the Wangchang area of the Jianghan Basin.
  • Application of windowing technique in reservoir simulation
    LI Jianfang; HAN Dakuang; DENG Baorong and ZHANG Hansong
    , 2003, 30(6): 730-0.
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    The fast adaptive composite (FAC) grid technology can be applied in fully implicit black oil simulator MURS to open and close the LGR (local grid refinement regions, i.e. windows). Size of the LGR, when necessary, can be adjusted anywhere between on and off position during the entire simulation process. The numerical experiments demonstrate that results from this windowing technique are approximate to the global fine grid, but it saves 8% CPU time compared with the fixed local grid refinement method, and 37% CPU time when it compared with the global fine grid, respectively.
  • Determination of minimum in-situ stress from normalized Mohr-Coulomb failure criteria
    ZHANG Baoping; FANG Jing; DING Yunhong; TIAN Guorong; SHEN Weibing and WANG Yongli
    , 2003, 30(6): 731-0.
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    Minimum in-situ stress could be obtained from normalized Mohr-Coulomb failure criteria through rock mechanical property testing. These properties include cohesion, frictional angle and uniaxial strength along failure plane. Tested samples were taken from different sandstone formations of Changqing, Erlian, Jilin Oilfield, Sichuan and Tarim Basin and Venezuela and hydraulic fracturing treatments would be performed in these formations. By comparing experimental results with those obtained from long distance sonic logging and mini-frac, it showed that the differences were within 2-3MPa. So it is an economic and reliable method to determine minimum in-situ stress from normalized Mohr-Coulomb failure criteria.
    • 油田开发与油藏工程
  • Pressure transient analysis of two layers cross-flow reservoir perforated partially with constant pressure outer boundary
    SUN Hedong and ZHOU Fangde
    , 2003, 30(6): 732-0.
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    Based on the semi-permeable model, the effective hole-diameter mathematical model of a two-layer cross-flow reservoir perforated partially is solved rigorously. The exact solutions obtained are expressed in terms of ordinary Bessel functions by using the Laplace transform. The numerical computation of these solutions is made by Crump numerical inversion method. Pressure behavior of a two-layer cross-flow reservoir perforated partially is the same as that of a two-layer cross-flow reservoir. There are three stages. At the early time, pressure behavior is homogenenous. At the intermediate time, curve of pressure derivative is sunken. At the late time, the system reaches a homogenous behavior characterizing the total producing system. The value pressure derivative is close to 0.5 with the increasing of outer boundary. The larger the semi-permeability is, the earlier the transition occurs and the flatter the curve of pressure derivative is. The larger the storability is, the smaller the peak value of pressure derivative is. As the heterogeneity in permeability becomes smaller, the transition becomes shorter.
  • Pulse water injection technique in interval wells to increase reservoir recovery
    ZENG Xiangping and YANG Huiyan
    , 2003, 30(6): 733-0.
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    The distribution of remaining oil is highly dispersive at the late stage of water injection, and obvious differences of remaining oil saturation between the individual streamline and the main exist. The high ratio of stop-injection to water injection may cause the great decrease of formation energy, leading to the decreasing of water cut and fluid, but no increasing of oil production, so the predicated objects can not be achieved. Based on the above conditions, a new method of pulse water injection in interval well to increase the reservoir recovery is presented. During shutting down in the interval wells, the adjoining well's water volume is enhanced to ensure the formation energy for stabilizing; the reservoir recovery is increased by adjustment of streamline distribution. After the trial to the Block No. 19, in the south of Gudao Oilfield for two years, the ratio of water-bearing is 1.3% lower than that of before the progress and the accumulated oil production is 1.9×104t, and the water injection recovery is increased up to 5.8%.
  • The residual oil in Es2 reservoir, south area of Pucheng Oilfield
    LI Jian and LI Hongnan
    , 2003, 30(6): 734-0.
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    Production of the reservoir in Es2, south area of Pucheng Oilfield in Dongpu Sag began in 1981.The water cut is up to 96% in 2001 and the recovery factor was 26.94% only. Most intervals with a So higher than 35% were water flooded. According to the analysis of oil-bearing slice in high or very high water cut, the distribution of residual oil is mainly in the little pore throat. The forming mechanism of residual oil is that the speed of waterflood is more than which irreducible water peels from oil membrane and detour of cusping injection water makes the oil left in the little pore throat. The oil saturation is high in the reservoir where the average radius of pore throat is little. Main productive formation with a great quantity of recoverable reserves should be the main target of development of residual oil.
  • The remaining oil distribution of high water-content reservoir in Wendong Oilfield
    XU Shouyu; LIU Jiguo and LI Cungui
    , 2003, 30(6): 735-0.
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    The middle part of the Member 3 in the Shahejie Formation in the Wendong Oilfield is a low permeability reservoir with a high inter-bed heterogeneity, strong inter-bed interference, and asymmetrical vertical water-flow. Such properties unfavorably affect production. The current study concentrates on reservoir characters such as lithofacies, depositional environment, pore structure and clay minerals to better understand the impact of reservoir heterogeneity on distribution of remaining oil. The remaining oil is mostly in minor reservoirs and traps associated with faults, or isolated spots.
  • Optimization of the pressure inspection system
    WU Hongbiao; WANG Qiwen; LIU Liming and CHEN Qinlei
    , 2003, 30(6): 736-0.
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    An optimized pressure inspection system is always desired for reservoir dynamics analysis and development. With flow rate, stratum coefficient, and relative position as constraints, and with the value of variance as optimized objective function, simulated annealing method is applied to test an optimum theoretic model for pressure inspection system. A practical method was then tested for determination of the optimum pressure inspection system. The results indicate that the spatial distribution unbalance problem of the original inspection system is minimized. Applying this method, two adjacent wells will no longer serve as each other's reference well. Meanwhile, any well has a reference well nearby.
  • Pilot-plant of oily wastewater treatment for reinjection of low permeability oilfield
    LEI Lecheng and CHEN Lin
    , 2003, 30(6): 737-0.
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    In order to meet the strict water quality standards, a pilot plant examination of oil wastewater treatment for reinjection to low permeability oil field was carried out in Liaohe Oilfield. Oil remover was added to the wastewater before it went into the precipitation tank. Then, the oil content of oily wastewater dropped from 20g/L to 150mg/L, as well as the suspended solid from 10g/L to 3g/L. EDUR multiphase pump air floatation was applied, which could reduce the contents of oil and suspend solid to 5mg/L and 30mg/L, respectively. Finally, after a novel technology of guhr dynamic membrane ultra filtration, the content of oil and suspended solid in oily wastewater was all lower than 2mg/L, and the average diameter of suspended solid was about 1μm. Guhr filter that has a low operational cost is in possession of the merits of both packed bed and ultra filtration membrane.
  • Application of polesilicon in low permeability oil field
    LU Xianliang; Lü Guangzhong; LUAN Zhian; WU Zenggui and SU Xiantao
    , 2003, 30(6): 738-0.
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    The injected water volume plays an important role in low permeability oil field waterflood development. It universally exists that injected pressure is high in a long time，injected water volume is low，the difference of injected pressure of each well is very large during oilfield development . Nanometer Polesilicon can resolve the question. This paper studies the mechanism that nanometer polesilicon can improve the waterflood response by changing the wettability of rock, enhancing relative permeability of water，and reducing significantly the flow resistant of injection water because of its stronger hydrophobility through core driving experment and micro-driving test . The core driving experment and full size field test prove that it can decompress and augment injection . Its best economic profit can be proved through economic evaluation .
    • 油藏物理
  • Asphaltene structure in reservoir affected by discharge of secondary condensate oil: laboratory simulation
    JIA Wanglu and PENG Pingan
    , 2003, 30(6): 739-0.
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    The oil accumulated probably changed in chemical characters due to discharge of natural gas and condensate oil generated later. This process has been simulated by the adding of petroleum ether to crude oil instead of condensate oil, and the structure of asphaltenes from the Well Lunnan 1, Tarim Basin precipitated under various petroleum ether: crude oil ratio was investigated by flash pyrolysis-GC-MS. It is found that the chemical structure of asphaltene precipitated from oil have not been changed yet when petroleum ether was added continuously. The pyrolysate of asphaltenes can be used as the substituent of low molecular compounds for oil-source rock correlation and also for identification of oil source whatever the oil reservoir in superposition basin was discharged by secondary gas or condensate oil. The major contributors to these alkyl components might be non-saponifiable and aliphatic biopolymers in the cell walls of some algae species. The high abundance of 1,2,3,4-tetramethylbenzene in the pyrolysate of the asphalting may derived from photosynthetic green sulphur bacteria, which indicated the precursor of the oil from the Well Lunnan1 were formed under strongly reducing conditions.
    • 油层保护与改造
  • Water-blocking damage and its solution in low permeability gas reservoirs
    LIN Guangrong; SHAO Chuangguo; XU Zhenfeng; WANG Xiaolin and WANG Li
    , 2003, 30(6): 740-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The gas reservoirs of Upper Paleozoic strata in the Ordos Basin are characterized by low permeability with minute pores and microscopic throats, which results in severe water-blocking damage in the lithologically heterogeneous formations (with an average damage level up to 83.6%). The analysis of drill core suggests that the degree of water-blocking damage is inversely correlated with permeability: the greater the permeability, the lower the level of damage. The correlation between damage and porosity is difficult to define, although a generally inverse relationship exists. Water-blocking damage is also inversely related to the amount of primary pore water, but it is positively proportional to the saturation level of fetter water. The study of 17 core samples using reversed drainage test indicates that water flow is associated with the porosity and permeability of the reservoir rock, draining pressure, and draining time. Improving the flow of formation water can reduce the damage of water blocking.
  • Quickly evaluating method of selecting hydraulic fracturing wells and pay-zones
    SUN Ping; XU Zejun; JIANG Tingxue and DING Yunhong
    , 2003, 30(6): 741-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    A specified conformal transformation function and Laplace method are utilized jointly to establish a mathematicalmodel of calculating a hydraulic fracturing well's oil rate and accumulative oil at various producing time under the condition of infinite conductivity, which may be used to select fracturing wells and pay-zones so as to maximize economic profits. After that, the influence of effective permeability, net pay-zone thickness, fluid viscosity and the pressure difference of initial pore pressure to the bottom flowing pressure on the fracturing result is calculated according to the model put forward. Consequently, a comprehensive evaluation index which includes above four parameters is put forward to the base of above calculations, and the result indicates that the fracturing well's oil rate is unchanged with the above comprehensive index kept as a constant while the included four parameters mentioned above may be changed greatly, so that the established index may be used to quickly select the fracturing wells and pay-zones. Overall, the study may be used to perform formation evaluation, fracturing effect evaluation and selecting the optimal fracture length as well.
    • 学术讨论
  • The formation of two-sides oblique compression and substrate contraction of Mesozoic Yanqi Basin
    ZHU Zhanjun and ZHOU Jianxun
    , 2003, 30(6): 742-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The Sandbox models were designed from the typical structures of the plane and profile in Yanqi Basin northwest China. The experimental results show that the Yanqi Basin can be interpreted as one caused by the deformation of the two-sides oblique compression in a SW-NE direction and substrate contraction. The faults in different orientations in the basin were caused by the same compression deformation. The basin's boundary direction, the horizontal compression direction and the substrate contraction controlled the direction of the structural zones. It is not certain that the structural patterns in Yanqi Basin were caused by the superposition of the strike-slip of the boundary or pull-apart deformations. The experimental model can provide evidence for interpreting the mechanisms of tectonics in Yanqi Basin.
  • Oil accumulation and water discharge mechanism of lithologic reservoir
    ZHUO Qingong; QIU Yigang; HAO Xuefeng and CHANG Jianfeng
    , 2003, 30(6): 743-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    After oil and gas filling into the sandstone lens that is around by source rocks, the original mixture liquid composite by formation water and latterly filled water will have two types model: ①seal-bounded fluid compartment evolvement, in which after the seal-bounded fluid compartment close down, the pressure of the liquid within the sandstone lens will higher than that of wall rocks, so the mixture liquid will be discharged to the wall rocks where the pressure is relatively lower; ②fault drainage are put forward, when the fault actives the mixture liquid will be discharged along the fault. Owing to multiphase structure of rifted basin, fluid compartment and fault time after time close down or close down, oil and gas will follow the actions and the full degree of oil and gas in the lithologic trap is increased.
    • 国际交流与合作
  • Recovery factor in fractured reservoirs:lessons learned from 100 fractured fields
    Jack Allan and S Qing Sun
    , 2003, 30(6): 744-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    One hundred fractured reservoirs from around the world were evaluated to determine how ultimate recovery was affected by inherent reservoir and fluid properties, such as porosity, permeability, viscosity, mobility ratio, Sw, wet ability, fracture distribution, and drive mechanism vs. the choice of reservoir management strategy, e.g., optimization of production rate and type of EOR technique. Fractured oil reservoirs were divided into four groups. Type Ⅰ reservoirs have little matrix porosity and permeability. Fractures provide both storage capacity and fluid-flow pathways. Type Ⅱ reservoirs have low matrix porosity and permeability. Matrix provides some storage capacity and fractures provide the fluid-flow pathways. Type Ⅲ (microporous) reservoirs have high matrix porosity and low matrix permeability. Matrix provides the storage capacity and fractures provide the fluid-flow pathways. Type Ⅳ (macroporous) reservoirs have high matrix porosity and permeability. Matrix provides both storage capacity and fluid-flow pathways, while fractures merely enhance permeability. Results of studying 26 Type Ⅱ and 20 Type Ⅲ reservoirs demonstrate that recovery factor is controlled by different factors in these two reservoir types. Recovery factor in Type Ⅱ reservoirs is sensitive to aquifer-drive strength and optimization of flow rate. Type Ⅱ reservoirs are easily damaged by excessive production rates, but when managed properly, some achieve good recovery without the need for secondary or enhanced recovery programs. Recovery factor in Type Ⅲ reservoirs is affected by inherent rock and fluid properties, particularly matrix permeability, API gravity, wet ability, and fracture intensity. The choice of proper EOR technique is essential for optimum exploitation. No Type Ⅲ reservoir is produced to final depletion without the aid of some type of secondary or EOR technique. Recognition of the differences between Type Ⅱ and Type Ⅲ fractured reservoirs should lead to better choices of exploitation strategy.
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