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Table of Content

    25 December 2003, Volume 24 Issue 4
    Previous Issue    Next Issue
    PROSPECT OF BURIED HILL RESERVOIRS IN SINOPEC EASTERN EXPLORATION REGION
    Zheng Herong, Hu Zongquan, Zhang Zhongmin, Liu Cuirong
    2003, 24(4):  313-316,321.  doi:10.11743/ogg20030401
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    The buried hill reservoir is the important type of oil and gas pools in SINOPEC eastern exploration region.Formtion of buried hill reservoir is controlled by several factors.In view of the formation of buried hill,the early-formed buried hills were subjected to a stronger dissolution than did late-formed buried hills,with better reservoir condition.In view of the reservoir lithology of buried hill,carbonate reservoir is easier to undergo dissolution than does clastic reservoir,with a relatively better preserving condition of reservoir space.Tectonic stress can reform the buried hill reservoir to some extent, as fault and fold are advantageous to the development of fracture and underground dissolution.The near disposition of source rock,reservoir rock and cap rock is favorable for oil and gas accumulation in buried hill traps. The future exploration of buried hill in SINOPEC eastern exploration region is (1) to conduct the further detailed prospecting in Jiyang sag in order to ensure stable reserve additions;(2)to drill the favorable traps in Dongpu and Subei sags for finding major discoveries in buried hill reservoirs;(3)to evaluate the exploration prospect of buried hill reservoirs in Nanxiang and Jianghan basins.

    DISCUSSION ON DISCOVERY DEGREE OF PETROLEUM RESOURCES
    Zhou Qingfan
    2003, 24(4):  317-321.  doi:10.11743/ogg20030402
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    A discovery degree of petroleum resources is one of important factors that indicate petroleum exploration maturity.Because of the concepts of resources and reserve used in China and other countries are different,the terms of the discovery degrees used by them have also not same meaning.A misunderstanding might be made when the magnitude of the discovery degrees with different meanings are directly compared. According to the different meanings of resources and reserve concepts used at home and abroad,the discovery degrees of petroleum resources in place and recoverable resources have been introduced in this paper.The discovery degree of petroleum resources in place is the percentage of cumulative proven reserves in place with respect of total resources in place;the discovery degree of recoverable petroleum resources refers to the percentage of cumulative proven recoverable reserves with respect of total recoverable resources.By the end of 2000,the discovery degree of oil and gas resources in place in China is 20.5% and 7.7%, respectively,the discovery degree of recoverable oil and gas resources in China is 52.5% and 17.4% respectively;the discovery degree of recoverable oil and gas resources in the world is 57.3% and 50.3% respectively; the discovery degree of recoverable oil and gas resources in the U.S. is 56.4% and 57.6% respectively.Hence,the difference between the discovery degrees of recoverable oil resources in China and the world (or in the U.S.) is not too large,but the discovery degree of gas recoverable resources in China is much lower than that in the world and the U.S.

    STATUS OF OIL & GAS RESOURCES AND PROSPECTING POTENTIAL IN WESTERN IN SICHUAN DEPRESSION
    Yang Keming
    2003, 24(4):  322-326,331.  doi:10.11743/ogg20030403
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    The western Sichuan depression has experienced very complicated evolution.As a result,it is characterized by vertically stacking of various basin types,multiple styles of trap strucuture,multiple source and resevoir rocks, and multiple superimpositions and reconstructions.Although abundant petroleum resources have been generated, the special distribution of oil and gas is under-concentrated.Systematic study of dynamics of hydrocarbon reservoiring indicates that there might have been late reservoiring condition in this area, and major migration and accumulation of oil & gas might have occurred before the reservoirs to be tightened.Forming phase of trap is crucial to trap validity,and the features of composite petroleum system control the distribution pattern of gas reservoirs to be three-dimensionally in groups.According to the characteristics of hydrocarbon resources in western Sichuan depression and aiming at the large prospecting targets,main objects of near and medium term exploration plans should be focused on deep gas reservoirs,expanding exploration of moderate deep gas reservoirs and extending the periphery shallow gas reservoirs.

    OVERPRESSURE AND ITS RELATION TO PETROLEUM ACCUMULATION IN SOUTHERN EDGE OF JUNGGAR BASIN
    Zhao Guiping
    2003, 24(4):  327-331.  doi:10.11743/ogg20030404
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    Measured formation pressure,well-log and mud weight data show that there are overpressures in the southern edge of Junggar basin.Vertically,overpressure distribution is not directly related to the burial depth,it is mainly controlled by stratigraphic horizons,especially the lower Tertiary Anjihaihe Formation has the most evident control over the overpressures.Horizontally, overpressure occur in the 3 structural belts in southern edge of the basin,but there are differences in the east and in the west:in the eastern part overpressures occur in the Anjihaihe Formation only,while in the western part,they occur not only in the Anjihaihe Formation,but also in the Shawan and Ziniguanzi Formation.Analysing the relationship between the well test data and overpressures in the southern edge of Junggar basin,it can be found that the distribution of oil and gas reservoirs are closely related to the overpressures.Being affected by faulting,and due to the differences in mechanism of relationaship between overpressures and preservation of oil and gas reservoirs,the distribution of overpressures and oil and gas reservoirs cannot be corresponding to one anther.As a whole,however,oil and gas would be ready to be reservoired in the normally pressured zone below the moderately abnormal pressured or overpressures zone,which would,therefore,be the favorable target of petroleum exploration;while the overpressured zone with relatively high formation pressure coefficient is unfavorable for oil/gas reservoiring.

    DISTRIBUTION PATTERNS OF NORMAL ALKANE AND THEIR SIGNIFICANCE IN CONTINENTAL FAULT-BLOCK OILFIELD
    Liu Zhongyun, Lin Yuxiang, Zeng Qinghui, Chen Qingchun
    2003, 24(4):  332-334,350.  doi:10.11743/ogg20030405
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    Gas chromatograph of saturated hydrocarbon is generally used in the study of single pay contribution in commingled producing wells both at home and aborad,because it is believed that the composition and distribution of normal alkane in the oil reservoirs are basically similar,and are very difficult to be used to solve the above problem; while the application of isoalkane,proves to be very effective.Through the research work made in Linan area, Shengli oilfield,it is found that the isoalkanes are very similar, since the reservoiring time is not long and the oil source is unitary, but the normal alkanes with moderate to high carbon numbers have apparent differences and can be used in establishing single pay's standard pattern of gas chromatogram,and in calculating the single pay's oil contribution in commingled producing well. There are several reasons that cause the different patterns of normal alkanes with moderate to high carbon numbers, for example, the large changes of continental sandstones and their different mineral compositions would have different absorbability and possible chemical reactions between oil and mineral. This phenomenon has important application value in calculation of oil contribution of single sandstone layer in commingled producing well in non-marine fault-block oilfield.

    CHARACTERISTICS OF RESERVOIRING DYNAMIC ON THE SAND-CONGLOMERATE FANBODIES IN THE STEEP-SLOPE BELT OF CONTINENTAL FAULT BASIN:A CASE STUDY ON DONGYING DEPRESSION
    Sui Fenggui
    2003, 24(4):  335-340.  doi:10.11743/ogg20030406
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    Five types of sand-conglomerate fanbodies,including alluvial fan, fandelta, coastal submerged fan, steep-slope deep water turbidite fan and slump turbidite fan,are developed on the northern steep-slope belt of Dongying depression. From the marginal salient to the basin's hydrocarbon-generating center, the oil reservoirs in these sand-conglomerate fanbodies are successively the stratigraphic-lithologic reservoirs,structural-lithologic reservoirs and lithologic reservoirs.In the steep-slope belt,the 4th member and 3rd member of Shahejie Formation are excellent source rocks,with a maximum thickness of 4000m, where the type I-Ⅱ kerogen are present.The organic-carbon content for both source rocks ranges from 0.5 to 3.5 percent.Oil and gas were moved into the fanbodies,developed on the middle-upper parts of steep-slope belt,through the composite conduit system consisting of faults,sand layers and sequence boundaries,which is characterized by stepped migration in vertical and lateral transformation.The oil reservoirs in the fanbodies experienced the hydrocarbon-charging stages corresponding to the deposition periods of Dongying,Guantao and Minghuazhen Formations.The reservoiring process,however,occurred mainly during the deposition of Guantao and Minghuazhen Formations.The dynamic process of oil and gas accumulation can be summarized as the reservoiring model of the fault terrace type of the sand-conglomerate fanbodies in steep-slope belt.

    QUATERNARY HYDROGEOLOGY CONDITION AND RESERVOIRING OF BIOGENIC GAS IN EASTERN QAIDAM BASIN
    Wang Mingming, Li Benliang, Wei Guoqi, Li Jingming
    2003, 24(4):  341-345.  doi:10.11743/ogg20030407
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    Narengele drainage system,originated from Kunlun mountains in eastern Qaidam basin,has formed Na-Tuo groundwater circulation system in Pliocene and Pleistocene periods in Wutumeiren,east to Tainan,Sebei and Tuofengshan areas;and on its both sides,Dabuxun Lake subsag and Yiliping subsag are catchment basins characterized by stagnant hydrogeology.The formation water within the control area of Na-Tuo grounderwater circulation system to the south of Tainan structure,was distinctly salinized in the later period of late Pleistocene (about 30ka).The formation water was basically saturated with dissolved gas at that time.The reservoiring mechanism of biogenic includes two models:(1)during the distinct salinization of formation water,dissolved gas was released from the water,and then migrated, accumulated and finally became gas reservoirs;(2)the Na-Tuo groundwater circulation system,carrying the biogenic gas dissolved in the formation water with relatively low salinity in the south,migrated northward to the saline water area where the gas was then released,accumulated and became gas reservoirs.According to the characteristics of hydrogeology and petroleum system, the most favorable area for the enrichment of the Quaternary biogenic gas has been determined to be in eastern Chuanxingqiu structure-Yanan-Tainan-Sebei area,the relatively favorable area occur on both sides,north and south of the above-mentioned area and Tuofeng mountains-Yanhu and on the slope of Biele lake;the favorable belt for the enrichment of the Tertiary biogenic gas would occur in Chuanxingqiu-Yanan-Nanlingqiu-Yanhu structural belt.

    PATHWAY SYSTEM OF OIL AND GAS MIGRATION IN BACHU-MAIGAITI AREA
    She Xiaoyu, Shi Zejin, Liu Gaobo
    2003, 24(4):  346-350.  doi:10.11743/ogg20030408
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    The pathways of oil and gas migration in Bachu-Maigaiti areas might consist mainly of faults, unconformity surfaces,as well as vugs,fissures and pores in reservoirs,which might have been connected with each other and constitute the delivery network of oil and gas.Among the 8 major unconformities, the T60 and T55 unconformity surfaces have been open in the whole area,the T70 and T54 unconformity surfaces have been open in the southern structural belt of Bachu uplift.Multiple tectonic movements have resulted in the opening of faults, pores,vugs and fissures,and became effective migration pathways of oil & gas.According to the dynamic theory of hydrocarbon migration and accumulation in late Caledonian-early Hercynian,the major pathway would be the pore-vug-fissure system in lower Cambrian dolomite that occurred in Awati sag and northeastern area of Bachu uplift; in late to last stage of Hercynian,the major pathway would include the boundary faults in the northeastern of Bachu uplift, T60 unconformity surface and pore-vug-fissure system in lower Cambrian;in Himalayan period, the major pathway would be the T60,T55 and T54 unconformity surfaces and the fault belt on the southern boundary of Bachu uplift that occurred mainly in the area including the Maigaiti slope and southern boundary of Bachu uplift.

    SEQUENCE MODELING AND SEDIMENTARY FACIES EVOLUTION OF JURASSIC IN NORTHWESTERN EDGE OF JUNGGAR BASIN
    Hu Zongquan, Li Mingjuan
    2003, 24(4):  351-355,361.  doi:10.11743/ogg20030409
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    Factors controlling sequence development include topography of lake basin, basement subsidence, lake lev- el fluctuation and supply of sediments. Analyzing synthetically the changing characteristics of these factors with time and space, the sequence stratigraphy in the terrestrial lake basin with slope-break belt has been simulated numerically. Setting an altimetric point to be the sedimentary base level, those located higher than the base level would be apt to be eroded away, while those lower than the base level would be apt to be filled with sediments. Grain sizes of sediments would depend on the distance from the sedimentary base level, the larger the distance,and the finer grain size would be. Simulation results indicate that within a complete sequence cycle,lowstand system tract would mainly distribute below the slope-break belt with filling up characteristics. Accompanying the rising of lake level, transgressive system tract would onlap the salient located above the slope-break belt.Because the increase of accommodation space became slower, high stand system tract would prograde into the basin and deposit mainly coarse sediments, but erosion occurred on the salient above the slope-break belt. Junggar basin is a downwarped basin with foreland characteristics,which has been controlled by extrusion stress in Jurassic, and the differential elevation and subsidence of the basement would result in the formation of slope-break belt at the margin of the basin. The whole Jurrasic is a second-order sequence which can be subdivided into four third-order sequences, namely A,B,C and D sequences,respectively. The second-order sequence is lithologically characterized by coarse-fine-coarse,and constitute an integral episode of tectonic subsidence, which coincides very well with the computer modeling results. The coincidences of the third-order sequences are also relatively well, but the symmetry and integrity are not as good as those of the second-order sequence. The four third-order sequences consist,vertically,of coarse-fine-coarse cycles,or retrograding first and then prograding,and are,horizontally,characterized by decreasing propertion of sand-prone facies first and then increasing.

    A RECOGNITION OF HYDROCARBON POTENTIAL IN WESTERN HUNAN AND HUBEI AREA
    Xu Yangang, He Ziai, Wang Jinyi
    2003, 24(4):  356-361.  doi:10.11743/ogg20030410
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    The western Hunan and Hubei area have been considered to have nice prospects due to its lower Paleozoic is similar to that in Weiyuan gasfield,and has also experienced similar geologic process of early subsidence and intensive late uplifting in later stage. However,the overpressure system is no longer present in western Hunan and Hubei area,because the uplifting amplitude has been too large and the lack of favorable paleostructure controlling early hydrocarbon accumulation.Therefore,the hydrocarbon exploration in this region should be cautious,but a further exploration is required in Zigui synclinore.

    FORMING FACTORS OF LARGE AND MEDIUM LITHOLOGIC FIELDS IN THE SLOPE AREA OF CONTINENTAL PETROLIFEROUS BASINS IN CHINA
    Zhou Liqing
    2003, 24(4):  362-366,379.  doi:10.11743/ogg20030411
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    A lot of large and medium lithologic-type fields have successively been found in the slope areas of Ordos,Songliao,Bohai Bay and Junggar basins in last ten-old years.Their formation need some essential conditions,including:1) development of high-quality source rocks, with moderate to high abundance of oil & gas resources(0.1～0.6 million t/km2); 2) development of relatively large hydrocarbon-gathering units to ensure large amount of oil and gas could fully migrate toward the same structural,stratigraphic and lithlogic belts;moreover, the structures developed on the gentle slopes of large basins would relatively be uneasy to be cut off,and sandbodies would be able to distribute evenly in large area;3)sandbodies deposited in the fandelta front would not only provide huge reservoir spaces;since they are unevenly-roughly envenly interbedded with high-quality souce rocks,they and source rocks together would also constitute high-efficient fluid-discharge units increasing the abundance of oil and gas resources in various blocks;4) because lithologic wedging-out belts are characterized by repeated swinging and migrating, lithologic traps would not be able to stack vertically one upon another,and would be difficult to become high-abundance fields;however,in the area characterized by abrupt change in occurrences,such as in regional fault zone, uplifted area at depth or stratigraphic overlapping wedging-out belt, there would be good stacking lithologic reservoirs; 5)reversed tilting would often reform the frontal zone of sandbodies from downdip pinchout to upwarp pinchout,while uplifted tilting would result in the lateral blocking of sandbodies,which would be favorable to the development of large and medium lithologic-structural composite traps;6)the strikes of fan delta sandbodies would often be perpendicular or obliquely cross the course of strata at large angles;as a result,it would not only ensure the opening of delivery system,but would also be favorable to the formation of numerous lithologic traps on the upwarping sandbodies;7)the reservoir with low and moderate porosity and permeability would be the most favorable to the formation of lithologic oil and gas reservoirs,because the reservoirs in the fan delta front have generally experienced relatively strong diagenesis and catagenesis,i.e.the thin siltstones and fine sandstones in the interdistributary bay would have seriously been tightened,which would block the further migration of oil and gas;8)the timely matching of trap formation and hydrocarbon migration would be favorable to the formation of large and medium lithologic oil and gas fields.

    TECTONIC THERMAL REGIME AND MULTIPLE TRANSPORTING CHARACTERISTICS OF FAULTED BASINS IN EASTERN CHINA
    Zhu Jianhui
    2003, 24(4):  367-370,400.  doi:10.11743/ogg20030412
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    The Cenozoic faulted basins in eastern China are located in the relatively thinning area of platform lithosphere,where the regional uplifting of upper mantle and the present depression just like the inverted reflection in water. The thermal energy at depth can be transmitted upward to the upper crust through changes of crust and mantle properties and magmatic intrusion,which would resulted in a relatively high geothermal field during the fault-subsidence period.The high geothermal field during fault-subsidence and further deeply buried in depression stage would cause the source rocks to be in their hydrocarbon-generating stage.The changes of major fault system's active center and intensity would directly affect the variations of sag's subsidence and depocenter,which would also result in the variations of hydrocarbon generation.As for Subei basin,the relatively high resources abundance in the basin has resulted from the high sedimentation and subsidence rates of Bohai Bay basin in post-Oligocene.

    CLASSIFICATION OF FAULT-BLOCK TRAPS AND CHARACTERISTICS OF PETROLEUM RESERVOIRING IN SUBEI BASIN
    Qiu Xuming
    2003, 24(4):  371-374.  doi:10.11743/ogg20030413
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    Structural traps in Subei basin consist mainly of faulted noses and blocks. According to their origin or having resulted from extension and wrench movements, the structural traps in the basin can be divided into four types,including: typeⅠ,group of faulted noses and blocks that occur in the sag and on its slope one; typeⅡ,faulted blocks developed on both sides of major faults; type Ⅲ, faulted noses and blocks developed on the shearing and transforming position of major faults;and type Ⅳ, complicated faulted blocks that occur between fault-terrace belts. By analyzing the genetic types of structural traps and characteristics of oil sources and pathways of oil migration and accumulation, the reservoiring patterns can be divided into three major types and six subtypes,,i.e (1) primary and secondary reservoirs (subtype a and b) formed mainly typeⅠtraps;(2) subtypes c,d and e reservoirs formed in typeⅡand type Ⅲ traps and migrated either through faults or reservoir rocks;(3) subtype f reservoirs formed in type Ⅳtraps.Presently,the gas and oil reservoirs found in Gaoyou and Jinhu sags in Subei basin are mainly of subtype a and b, which distributed on the slope areas of the sags;secondly are subtype c reservoirs that distributed on both sides of major faults.Besides,there are also some subtype f reservoirs developed within the fault terrace belt in Gaoyou sag.

    CHARACTERISTICS AND THEIR SIGNIFICANCE OF MUDSTONE SOURCE AND RESERVOIR ROCKS IN THE 3rd MEMBER OF SHAHEJIE FORMATION IN GUO 7 WELL,JIYANG DEPRESSION
    He Weigang, Jin Kuili, Hao Duohu
    2003, 24(4):  375-379.  doi:10.11743/ogg20030414
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    The analyses of data from organic petrologic and organic geochemical experiments and testings indicate that the fissured mudstone in the 3rd member of Shahejie Formation encountered in Guo 7well drilled in Jiyang depression was deposited on the lakeshore environment during local transgression.The mudstone is composed of both the harder and the softer components.It has the lithologic composition and textural characteristics of rare reservoirs reported in Santa Maria basin in the U.S.There are two occurrence types of organic matters in the mudstone: one is the dispersed organic matters (mineral-bitumen matrix) that occur in the softer components of mudstone; another are those occur in the harder components of mudstone,including bitumenites in the micropores and microclearances of minerals and free hydrocarbons in the interfissures. Both of them might have come from the same source rock,but the amount of free hydrocarbons that mater occur in the harder components,fissures and pores would apparently be higher than the bitumen in the softer components of mudstone.

    HIGH-RESOLUTION SEQUENCE STRATIGRAPHIC FRAMEWORK OF DOLOMITE ROCKS IN BIYANG SAG:A CASE STUDY OF THE APPLICATION OF BASE LEVEL CYCLE THEORY
    Cheng Zhe, Sun Fenghua, Lü Mingjiu, Qin Weijun, Wang Zhong
    2003, 24(4):  380-384.  doi:10.11743/ogg20030415
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    Based on the base level cycle theory, two long-term base level cycles,i.e.C1(the 1st sub-member of 3rd member of Eogene Hetaoyuan Formation(Eh31)—the 3rd sub-member of 2nd member of Eogene Hetaoyuan Formation(Eh23)) and C2(Eh22-Eh23),have been built up through the sequence stratigraphy analysis of 4 well-to-well correlation sections in the study area.Their boundaries might be a breakpoint where base level rises and falls. C1 cycle is vertically a sequence which water body shallows upwardly,and it can further be divided into two medium-term base level cycles,i.e.MSC1 and MSC2,corresponding to the Eh31 and Eh23 deposition. Each medium-term cycles are subdivided into smaller short-term cycles. C2 cycle is vertically not complete and is only composed of one half cycle with a fall in base level (equivalent to Eh22 and Eh21 depositional stages), which can further be divided into four medium-term base level cycles, i.e.MSC3, MSC4, MSC5 and MSC6. On the basis of the established sequence stratigraphic framework, a more detailed sequence classification will be helpful to study the microfacies of dolomite area in Biyang sag, and to predict the facies belts favorable for development of fractures and dissolved pores closely related to oil and gas accumulation.

    GEOTHERMAL HISTORY OF SHIWANSHAN BASIN AND ITS NEIGHBOURING REGION USING APATITE FISSION-TRACK ANALYSIS
    Wang Xinwei, Wang Xinwen, Han Xiaozhong
    2003, 24(4):  385-390,412.  doi:10.11743/ogg20030416
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    The geothermal history of strata or rocks has been qualitatively and semi-quantitatively in Shiwanshan basin and its neighbouring region, based on analyses of fission-track apparent age and modelling of confined track lengths distribution of apatite samples.The results show that all samples have experienced paleogeotemperatures of over 60～70℃;the basement strata(T1b) on the northwestern side of Shiwanshan basin have been uplifted and denuded to the near-surface (with a paleogeotemperature of below 70℃) much more earlier than the basement rocks(γ51)on the southeastern side of the basin and the paleogeothermal history of samples from the basin can be divided into six stages,they are the fast burial and increasing temperature(T3-J3)stage,transient decreasing temperature(latest J3-early K1)stage,burial and increasing temperature(K)stage,rapid decreasing temperature(last K2-E1)stage,relatively stable (E2-E3)stage and another rapid decreasing temperature (since N1)stage.

    FRACTURE PREDICTION OF E32 RESERVOIR IN YUEHUI 1 WELL BLOCK, GASIKULE OILFIELD
    Peng Licai, Shao Wenbin, Zhang Lin, Song Wei
    2003, 24(4):  391-395.  doi:10.11743/ogg20030417
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    According to the geological features of studied area, geologic model, inverse model and dynamic model have been established. Numerical simulation of paleotectonic stress field and fracture prediction of the E32 reservoir in Yuehui 1 well block of Gasikule oilfield in Qaidaim basin have then been made by using finite element method. The paleotectonic stress field, fracture direction and density in the main oil-bearing layers are mapped out. The results got from numerical simulation are consistent with the measured data. Fracture directions are somewhat different in various tectonic position and burial depth. Shear fractures are mainly in NEE and NWW directions. Tension fissures are mainly in near E-W and near S-N directions. Axes and higher parts of structures generally have higher fracture density than the limbs have, and the density would increase with increasing of burial depth.

    DAMAGE FACTOR AND PROTECTION AND STIMULATION TECHNIQUES OF DEEP RESERVOIRS IN BIYANG SAG
    Wang Min, Qin Weijun
    2003, 24(4):  396-400.  doi:10.11743/ogg20030418
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    The deep reservoirs are mainly referred to as the 5th sand layer in the lower part of the 3rd member of Hetaoyuan Formation and Dacangfang Formation in Biyang sag,they are characterized by their low porosity and low permeability.These oil/gas reservoirs have been damaged heavily in the course of drilling,well completion, perforation and testing.As a result,the oil/gas reservoirs would often be difficult to be found,and the productivity of those reservoirs with low porosity and permeability would be relatively low.Well productivity can only be increased by stimulation treatment.Through various studies, reservoir protection and stimulation techniques, such as formula of high quality drilling fluid, temporary plugging method and advanced reservoir protection technique with polymeric alcohol,high quality perforation fluid and underbalanced perforation,have been applied,and significant results have been obtained in Zhaowa-Anpeng area.As for stimulation, optmimization of high quality fracturing fluid has also been made,which are characterized by its heat-resisting quality,good compatibility, low friction resistance,and high proppant-carrying capacity.Besides,application and dissemination of large-scale fracturing technology have also been made in Zhaowa-Anpeng area,which prove to be highly effective.

    QUANTITATIVE DESCRIPTION OF REMAINING GAS DISTRIBUTION IN LOW AND EXTREMELY-LOW PERMEABILITY GAS RESERVOIRS
    Wang Xibin
    2003, 24(4):  401-403,416.  doi:10.11743/ogg20030419
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    After the dry gas reservoir with low and extremely-low permeability,but without identified edged and bottom water has been produced for a period,the formation pressure of different areas decreases inhomogeneously,while the gas saturation (Sg) changes slightly,which can not be used to describe accurately the distribution of remaining gas.Therefore,the formation pressure in production process is usually used to describe qualitatively the distribution of remaining gas.According to the state equation of real gas and the definition of recoverable gas reserve,the functional relation between produced degree of recoverable gas reserve (K) and formation pressure (P) has been established,by which the formation pressure distribution during production process can be transformed to the distribution of produced degree of recoverable gas reserve, realizing the quantitative description of remaining gas distribution.

    EVALUATION OF GAONAN(Nm-Ng) SHALLOW RESERVOIRS
    Qiu Liwei, You Xiuling, Ran Qiyou
    2003, 24(4):  404-408.  doi:10.11743/ogg20030420
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    Statistical analysis,probability cumulative curve of sandstone grain size,C-M plot and core observation show that the shallow reservoirs in Gaoshangpu oilfield are of fluvial depositional system.3-D visiualized models have been made for the sedimentary facies in a single well,section and plane,and the fluvial type can further be classified as alluvial fan braided channel.Based on the research of depositional system,3-D quantitative characterization of reservoir's porosity and permeability has been made by using well logging interpretation data(including porosity,permeability,shale content and oil-reservoir groups)and geostatistical modeling technology.Lastly,according to the evaluation parameters,including control factor of oil,facies association,reservoir-cap rock association and faults,3 major reservoir groups have been pointed out,and G75-G94-G29 and G3106-G30-G68-30 well blocks are determined to be the most favourable blocks.There are 14 layers evaluated to be the most favorable pay beds,including the 1st and 2nd layer in the 2nd submember and the 1st layer in the 3rd submember of the lower member of Minghuazhan Formation;and there are 15 layers evaluated to be relatively favorable pay beds,including the 3rd layers in the 2nd and 3rd submembers of the lower member of Minghuazhen Formation;while the other 15 layers are evaluated as unfavorable layers,including the 4th,5th and 6th layers in the 2nd submember of the lower member of Minghuazhen Formation.

    APPLICATION OF MULTI-PARAMETERS, LOGGING DATA AND WAVE IMPEDENCE, TO OIL-GAS PREDICTION
    Wu Xingwei, Yang Yong, Zhu Aili
    2003, 24(4):  409-412.  doi:10.11743/ogg20030421
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    The application of wave impedance inversion data to oil/gas reservoir prediction would generally have multiple solutions,due to the effects of reservoir characteristics,such as the wave impedances of sandstones and mudstones in Pinghu reservoirs would often be similar,the thinly interbedded reservoirs in northern Hubei block are affected by coal seams,the reservoir water salinity in Shiwu fault depression in northeastern China is very low,and karsts and fractures are unevenly distributed in carbonates in northern Tarim basin.Considering these conditions,oil/gas reservoir prediction has been made by using crossplot of multiple logging parameters and wave impedence data.The multiple solutions caused by using wave impedance data only can then be avoided.According to various conditions,logging parameters with relatively high sensitivity should first be carefully selected,then make the crossplots of those logging parameters and wave impedence data.The crossplots must be calibrated against the known oil/gas distribution.The oil/gas reservoirs in a new well can finally be predicted by using the calibrated crossplot.Practical testing has proved the prediction is feasible.

    APPLICATION OF GeoX SOFTWARE TO HYDROCARBON EXPLORATION IN TAIPINGZHUANG STRUCTURE IN SHIWU FAULT DEPRESSION
    Zhu Youhong
    2003, 24(4):  413-416.  doi:10.11743/ogg20030422
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    During the exploration in Taipingzhuang structure,the GeoX software has mainly be applied to make geologic risk analysis,estimation of hydrocarbon resources,and economic evaluation.(1)Through setting valuation on marginal probability,and probabilities of effective reservoir (P1),effective trap(P2),effective source rock and hydrocarbon accumulation (P3) and effective preservation(P4) in both exploration targets,Yingcheng Formation and Quantou Formation,the finding probabilities in the two reservoir sets have been calculated to be 0.192 and 0.201,respectively.It can then be judged that the exploration in Taipingzhuang structure would be in the category of moderate geologic risk.(2)Giving the 12 parameters,including trap area,reservoir thickness,geometric configuration,effective porosity,trap's fillup efficiency,oil/gas saturation,etc,the resources in place and recoverable resources in the target structure can then be estimated to be 2.91million tons and 0.6 million tons,respectively.It should be of small field with rather low abundance.(3)Lastly,economic evaluation of the exploration target has been made.The geologic reserves in Taipingzhuang structure has now been proved to be 0.76million tons of oil,very similar to the estimating result made with GeoX software.