Research On Reservoir Characterization And Key Controlling Factors Of Xiaohaizi Formation In Bamai Region Of Tarim Basin

This paper studies the lithological characteristic, sedimentary facies, diagenesisand the reservoir characteristic, reservoir evolution, property characteristicsas well asthe key controlling factors in Xiaohaizi Formation of Bamai area through thecomprehensive utilization of well drilling and logging, seismic interpretation, rareearth elements, SEM and geochemistry analysis. According tothe analysis of all theinfluencing factors, finally predicts the better reservoir distribution.Based on the theories of carbonate sedimentology, the material ofsedimentologyrocks and by utilization of well logging and seismic interpretation,Xiaohaizi formation of carboniferous in Bamai has restricted shelffacies-slope-platform marginal facies-open platform facies-platform facies from westto east. Also sedimentary facies and microfacies of xiaohaizi formation have beendividedand show in the plane pictures. Among this the most important is clear themarginal-platform shoal and intra-platform shoal microfacies distribution.By utilization the data on core observation, cast thin section scanning electronmicroscope and a series of geochemical testing means. Considering each diagenesistype has its own effect on reservoir body. Dolomitization and corrosion are the mostadvantageous diagenesis types. And the dolomitization is more common inBashituo-Yasongdi area, but fewer dolomite in Bachu uplift. The dolostoneis formedby seepage-reflux dolomitization, shallow burial dolomitization and moderate-deepburial dolomitization. Compared with the shallow burial dolomitization, the deepburial dolomitization does not develop widely in the study area. Reservoir spacemostly results from burial dissolution, while the syndepositional dissolution areoften been transformed in the latter part of the burial process so have little effent forthe transformation of reservoir property. Combined with the basis of well logging, bore core and thin sectionobservation,it is considered that the reservoir space of xiaohaizi group are mainlyprimary intergranular dissolved pores, intragranular dissolved pores,intercrystalpores, intercrystal solute on pores, dissolved fractures. and the solution pores andcaves are the most important reservoir space. Among this the main reservoir typesare porous(pore-cavity) and pore-cavity-fracture types which have good reservoirqualities. After analyzed the dolomitization is helpful for the reservoir’s developmentwhich mainly consist of residual granular dolomite and powderfine crystallinedolomite.Finally through sedimentary facies, diagenesis and reservoir characteristics thatthe dolomitization is the most important factor in quality reservoir development inXiaohaizi group and dolomite reservoir permeability properties are generally to befar better than the imestone classes. The grain beaches in platform margins andplatform shoal of open platform are all shallow water and highenergy depositionalbody, due to the larger original porosity and also easy to the exposed surface of thewater suffered freshwater dissolution, provided theconditions for the occurrence ofdolomition, these two functions superimposed will enable reservoir properties mostdevelopment. Then hydrothermal dissolutionhas a certain improvement to thereservoir in deep burial stage, Especially for dolomite which have more developedoriginally pores, hydrothermal fluidcirculation quickly in it, can bring precipitate outof diagenetic system, therefore, the process of dissolution is mainly to increase theporosity.