| The exploration of Cambrian dolomite is still in its preliminary stage in Tarim Basin.In 2012 and 2013,the Gucheng-6 well and Zhongshen-1 well have a great breakthrough,it confirms that this domain has the potential of forming large oil and gas fields.The previous study has been considered the Middle Cambrian evaporate rock and the Lower Cambrian dolomite as the main accumulation associations,but the fundamental research of the sedimentary facies is weak in Middle and Lower Cambrian.This study aims to restore the sedimentary evolution in Middle and Lower Cambrian,and provides a basis for the combination of cap rock and reservoir,the research of the favorable exploration zone.Using the data of drilling lithology,electrical property and isotope test,combined with the research of stratigraphic classification with the geologic and seismic integration method,the paper finishes stratigraphic division and correlation in Middle and Lower Cambrian in the study area,and compiles the strata thickness of maps.The formation feature is “western-thick-eastern-thin,and northern-thick-southern-thin” in Middle and Lower Cambrian.Based on the comprehensive research of lithology,lithofacies,sedimentary environment and sedimentary facies maps,there are 6 types of sedimentary facies and subfacies,8 kinds of microfacies in Middle and Lower Cambrian.The sedimentary pattern features presented “western platform and eastern basin”.The sedimentary pattern was “mixed tidal flat-evaporative dolomite tidal flat-open platform-platform edge and slope-basin” at early Cambrian.The sedimentary pattern was “mud dolomite tidal flat-gypsum dolomite tidal flat – lagoon-mud dolomite tidal flat-platform edge – deep water basin” at middle Cambrian.The favorable zones of the dolomite reservoir was in banks in Lower Cambrian,where was located in inter-platform mound and bank and platform edge.It was mainly distributed in Tabei,Tazhong and the north-west of Bachu. |
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