| There has turned in proven oil reserves 329×10~4t,natural gas reserves 620×10~8m~3,control natural gas reserves 430×10~8m~3 in Bachu-Markit area of southwestern Tarim Basin.But compared with mature exploration area such as north and central area of Tarim Basin,there has lower exploration level.Multiphase tectonic movement,higher thermal evolution of source rock,strong reservoir heterogeneity,the relatively great buried depth in this area and complex accumulation periods,that's lead to the lower success rate of wells and the difficulty of exploration.On the basis of predecessors'study results,combining with the logging data,seismic data,multiple field geological investigation and laboratory analysis test,this paper analysis and summary the pattern of petroleum accumulation in Bachu-Markit area.Research suggest that the source of reservoir is the high maturity Cambrian hydrocarbon source rock with two types:slope facies and platform facies.TOC is between 1.38%~9.36%,with average 5.08%of slope facies and 0.68%of platform facies.The carbonate reservoir space is main composed of fractures-holes,fractures-pores and pores-holes-fractures in Ordovician,the main reservoir types are distributed in type?to type?.As for weathering crust,the eastern part is more developed than the western part after three-phase weathering effect,and formed good reservoir cap association with upper cover.The complex channel system,the source rock and trap with appropriate time and space are the influence factors of accumulation pattern.There are two main accumulation period,oil generating in late Hercynian and gas generating in Himalayan.The main migration channel is deep fracture connected Cambrian source rock and trap such as Hetianhe-niaoshan gas reservoir.Yubei reservoir lacks dry gas filling and because of the re-charge of hydrocarbon,Bashituopu-Yasongdi reservoir has petroleum migration and accumulation happened in the upper Paleozoic. |
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