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Table of Content

    25 September 1995, Volume 16 Issue 3
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    PORE TYPES AND ORIGIN OF SECONDARY PORES OF TRIASSIC AND JURASSIC IN NORTH TARIM
    Wang Zhengyun, Wang Fangping, Lin Xiaoyun, Wu Dongsheng
    1995, 16(3):  203-210.  doi:10.11743/ogg19950301
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    Intergranular pores, intragranular pores, micropores in interstitial material and crevicesare developed in Triassic and Jurassic reservoirs in North Tarim region, and the secondaryporosity of mixed intergranular pores, amounting to 43%-51% of total pore amount, is themain part of resrevoir spaces. Organic acids released by kerogen and clay mineral transformation affected the alumosilicate component and quartz anions in reservoirs. This is the principle cause for the formation of secondary porosity' The increased secondary porosity is up toabout 51.9% of the total porosity. Besides, the reservoir property is also controlled by burialdepth, unconformity and the passage formed of "Y"-type faults.

    REDEFINITION OF UPPER PERMIAN SHAJINGZI FORMATION IN KEPING, XINGJIANG
    Liu Bingli, Li Luozhao, Jiang Yanwen, Li Yibin, Xiao Chuantao, Zhou Shuyuan
    1995, 16(3):  211-215.  doi:10.11743/ogg19950302
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    According to the great amounts of fossils includingostracodes, bivalvies and gastropodsdiscovered in the Shajingzi Formation in the west of Yingan Village, Keping County and therestudy on profile sequences, the authors have redefinited the bottom and top boundaries ofthe formation: the bottom boundary is the uppermost basalt or the top of vocaniclastic rockof the Kaipaizileik Formation which is in conformable contact with the Shajingzi Formation3the top boundary is grey-green mudstone and siltstone that is in disconformable contact withthe overlying Paleogene red coarse elastic rock and Neogene grey conglomerate.

    EARLY PERMIAN DELTAIC FACIES AND ITS ASSOCIATED SEDIMENTS IN KUQA DEPRESSION
    Li Weifeng, Gao Zhenzhong, Peng Detang, Wang Zhengyun
    1995, 16(3):  216-221.  doi:10.11743/ogg19950303
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    Kuqa Depression is a "dustpan" shape depression with steep slope in the north side andgentle slope in the south side.Fan-deltas and braid river deltas are developed on its northmargin while shore deposit, shallow lake deposit and meandering river deltas are developedon the south margin. The fan-deltas are characterized by gravity flow deposit associated withtractive current deposit, Both of the deposits were resulted by sudden catastrophic event. Theformer is primarily massive conglomerate; the later is mainly lenticular channel sand bodiesdistributed within the gravity flow deposit, The normal tractive current deposit of the braidriver deltas is primarily bedded channel sand bodies in which lateral aggradation and crossbedding are well developed, The fan deltas and braid river deltas are independant but closelyconnected to each other,their evolution is controlled by the intensity and range of faulting activity in depression margins.

    ANALYSIS OF CRUDE OIL COMPOSITION BY TLC-FID CHROMATOBAR AND ITS APPLICATION
    Wang Zhansheng, Sun Weilin, Wang Shuangqing, Hu Boliang, Wang Peirong
    1995, 16(3):  222-226.  doi:10.11743/ogg19950304
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    Hydrogen flow rate, scan speed and chromatobar activity have influence on repeatabilityof sample analysis results. When hydrogen flow rate (L) is 180ml per min, scan speed is 30s each time, then control humidity and temperature to certain condition, and keep the activityof the chromatobar, choose different correction factor values according to different crudeoils. The analysis results show that relative deviation is less than 10%. This has proved thefeasibility of TLC-FID chromatobar analysis. The authors applide this technique in describing the geochemistry of Tazhong-4 structural oil reservoir, discovered a bitumne-rich layer inthe reservoir, and determined the present oil-water boundary of the reservoir.

    MICROFACIES OF WAVE-CONTROLLED SHELF AND DELTA IN DEVONIAN OF KOKEYA, SOUTHWEST TARIM
    Luo Shunshe, Gao Zhenzhong
    1995, 16(3):  227-233.  doi:10.11743/ogg19950305
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    The Devonian in Kokuya is a distinct coarsing-upward wave-controlled continental shelfto wave-controlled delta sequence. The wave-controlled continental shelf factes includes 9 microfacies as Streaky mud, lenticular allochemical rock, laminated and cross bedding sandstone, large cross bedding sandsone, shell debris oolitic sparite, bioclastic limestone micro facies. The wave-controlled delta factes include prodelta mud, sheet sandstone, current laminated siltstone, subaqueous distributary channel, littoral bar, beach dum, distributary channel, fload plain and branch-channel inlet micro factes. The characteristics of the above mentioned micro factes are described in this paper.

    CHARACTERISTICS OF CENOZOIC STRUCTURAL DEFORMATION IN NORTH MARGIN OF SOUTHWEST DEPRESSION, TARIM
    Liu Xuefeng, Chen Yushui, Xiao Ancheng, Hu Wangshui, Liu Shengguo
    1995, 16(3):  233-239.  doi:10.11743/ogg19950306
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    The structural deformation during Cenozoic along north margin of southwest-depressionin Tarim Basin is controlled by about S-N direction compressive stress field. It can be dividedinto two segments in terms of the deformational styles. The west segment is called frontalsouth Tianshan Moutains structural deformation region which is related to the southwardpush-compression of south Tianshan Mountains thrust -fold belt. and the.superimposion ofwest Kunlun mountains fault-fold belt. Its deformational styles include: lubricate fault assemblage, fault-bent anticlille, structural delta belt and baffle fold. The east one is callednorth Maigaiti slope structural deformation region which is controlled by Selibuya fault andMazatage fault. Its deformation styles include a fault-anticline belt along the main fault and acomplex wrench fault belt.

    DETERMINATION AND APPLICATION OF VERTICAL AND SPHERICAL VADOS FLOWS
    Chen Pingzhong, Xia Weirong, Wang Xinhai
    1995, 16(3):  240-245.  doi:10.11743/ogg19950307
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    The result of vertical interference test shows that vados flow exists in Donghe sandstonereservoir. In incompletely opened oil wells with vertical vados flow, the flowing shape of fluidappears to be spherical vados flow, and it is the sum of planar and vertical vados flow. In formation test interpretation, plane radial flow method would result in serious deviation of permeability interpretation. But horizontal well and deflecting well could effeciently improve theproductivity of this kind of reservoir. The amount of improved productivity would increasewith the increasing of Kv/Kh; deflecting well could improve the productivity at any permeability ratia, and the result would be more favourable when inclination is greater than 40?. Incomparason, the horizontal well is much better than the deflecting well.

    NONSTRUCTURAL TRAPS IN GUCHENG NOSEUPLIFT AREA, TARIM BASIN
    Guo Jianhua, Zhai Yonghong, Liu Shengguo, Luo Chuanrong
    1995, 16(3):  246-251.  doi:10.11743/ogg19950308
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    The Carboniferous basement of Gucheng nose-uplift area is a regional unconformity.The extensively developed overlying stratigraphic traps include: 1. Erosion-surface formedchannel-valley system stratigraphic traps. The trap properties depend on basements. It isconsidered that the basement of the Middle-Upper Ordovician is the best while that of theSilurian is secondarys 2. The fringe marginal overlap traps of the nose uplift. Different degrees of erosion result in sandstone overlap and gravel overlap. The former prevails over the later.

    DIAGENESIS AND PORE EVOLUTION OF CARBONIFEROUS CLASTIC ROCKS IN CENTRAL TARIM
    Zhai Yonghong, Liu Shengguo, Guo Jianhua, Xiao Chuantao, Luo Chuanrong
    1995, 16(3):  252-258.  doi:10.11743/ogg19950309
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    Carboniferous elastic rocks in Central Tarim Basin are characterized by clay mineraltransformation, well-developed dissolution, weak compaction and quartz secondary enlargement, lacking of carbonate cementation in early stage and local carbonate filling in late stage.Primary porosity was preserved to the maximum value of about 15%. The Carboniferoussequences drilled in Central Tarim are now in the late diagenetic stage (containing A1 and A2 stages). This stage is considered to be the peak period of organic acid production, and dissolution is intensive. This could considerably improve the primary porosity (increasing to 20%-23% ), thus forming high porosity and high permeability reservoirs.

    DIAGENETIC REACTION OF JURASSIC-TRIASSIC SYSTEM IN NORTH TARIM
    Cai Chunfang, Mei Bowen, Ma Ting, Liu Changqing
    1995, 16(3):  259-264.  doi:10.11743/ogg19950310
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    The diagenetic reactions of Jurassic-Triassic successively deposited sandstone-mudstonesystem in North Tarim Basin were mainly controlled by temperature intervals. The concentration of organic acid in oilfield water reached the peak value when temperature was 90135C, and this resulted in the dissolution of aluminosilicate and carbonate minerals. Extensive dissolution of plagioclase is the main cause of abundant authigenic kaolinate and highsecondary porosity. The improvement of porosity was closely related to the physical properties of original reservoir.

    SEQUENCE STRATIGRAPHY AND SEDIMENTARY FACIES OF KARASHAYI-XIAOHAIZI FORMATIONS, CENTRAL TARIM
    Guojianhua, Liu Shengguo, Xiao Chuantao, Zhai Yonghong
    1995, 16(3):  265-271.  doi:10.11743/ogg19950311
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    In accordance with the division and correlation of sequence stratigraphy, the Karashayiand Xiaohaizi Formations can be classified into two sedimetary sequences which reflect twoeustatic changes of sea level. The isochronal deposit surface between two sequences is theboundary between Karashayi and Xiaohaizi Formations. Karashayi Formation consists alternately of coastal plain factes and fan-delta factes, whereas the Xiaohaizi Formation consistsmainly of shelf factes and fan-delta factes. However, the fan-deltas in the two sequences arerespectively deposited in high-stand rapidrise of sea level, and they both have wet fan-deltafeature.

    KEZILIQIMAN REEF IN PISHAN, XINJIANG
    Peng Detang, Gong Wenping, Guo Chengxian, Gao Zhenzhong, Li Weifeng
    1995, 16(3):  272-276.  doi:10.11743/ogg19950312
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    A reef situated 500m southesast of Keziliqiman, Pishal County, Xinjiang belongs to theKeziliqiman Formation of the Lower Permian. The reef core is 57.6m thick and its maximumexposure is up to 300m across. The reef flank, consisting of grain limestone, middle to thinbedded marly limestbne and bioclactic limestone, is connected with the reef core by interfingering.Reef-building organisms consist chiefly of colonial tetracorals, Sphinctozoas, blue-greenalgae and Tubiphytes and then bryozoans, Inozoas and hydrozoans. Most of the organismshave kept their original growth patterns. The orgamisms could be divided into 4 micro-factessuch as baffle limestone, baffle-skeletal limestone, bound limestone and reef debris limestoneand 4 stages of reef evolution correspondingly based on the vertical zonation.

    CHARACTERS OF TRIASSIC-JURASSIC RESERVOIRS IN NORTHERN TARIM UPLIFT
    Wang Fangping, Wang Zhengyun, Lin Xiaoyun, Wu Dongsheng
    1995, 16(3):  277-284.  doi:10.11743/ogg19950313
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    The Triassic and Jurassic reservoirs in the northern uplift of Tarim Basin are mainly distributed in three exploring regions, i. e. Lunnan, Donghetang and Yingmaili.regions. The variation of the reservoiring spaces follow a certain rule, and the reservoirs' quality is closely related to the pore structure. The reservoirs can be classfied into four grades according to theirphysical properties and capillary pressure. The main factors that control the reservoir properties are the buried depth, the development of faults and unconformity planes.

    DESCRIPTION OF RESERVOIR HETEROGENEITY USING WELL-TEST PRESSURE
    Chen Shiqing, Chen Pingzhong
    1995, 16(3):  285-289.  doi:10.11743/ogg19950314
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    The data of well-test pressure could be used to describe reservoir heterogeneity. Whenderivative curves bend downward in middle stage, the storage coefficient of the reservoir increases; on the contrary, the storage coefficient decreases. When the derivative curves stepup or step down from horizon, the flow coeficient of the reservoir also decreases or increases,and the obliqueness of the straight part of radial flow on Horner on.rve would become biggeror smaller accordingly. Several examples in Tarim basin have proved this.

    PREDICTION OF SANDSTONE POROSITY BY APPLYING SEISMIC WAVE VELOCITY
    Wu Dongsheng, Wang Zhengyun, Wang Fangping, Lin Xiaoyun
    1995, 16(3):  290-293.  doi:10.11743/ogg19950315
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    The factqrs including lithologic characteristics, geophysical signature, hydrocarbonbearing and formation pressure have effects on seismic wave velocity. According to nonconstrain least-square fit of drilling and well-logging data,V=AΦ+BΨ+Ch1/n would be anideal mathematical model in expressing the relation between velocity and porosity. On the basis of the above mentioned model, the combined model of three-element medium is proposedin this paper. The prediction of mudstone distribution in reservoirs and then the prediction ofporosity were' made by applying the response of interval velocity to the content of mud. Thismethod is used to predict the porosity distribution of T-J sandstone reservoirs in TarimBasin, and the result is good.

    INTERPRETATION OF UNSTABLE WELL TEST FOR CONDENSATE GAS WELLS
    Wang Xinhai, Xia Weirong, Guo Kangliang, Chen Pingzhong
    1995, 16(3):  294-297.  doi:10.11743/ogg19950316
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    Complicated phas variation and phase state redistribution exist in condensate gas wells.This may result in considerable effect on derivative curves of well test pressure. To choosethe straight section of well test analysis accurately is the key factor in successfully interpreting well test. The effect of condensate oil must be considered in calculating the parameters ofhigh-pressure physical property. In order to avoid interpretation error,the productivities usedin well test analysis should also include condensate oil productivity. This has been proved bywell-test information of a condensate gas well in Tarim Basin.