Genesis of dolomite and main controlling factors of reservoir in Penglaiba Formation of Lower Ordovician,Tarim Basin:A case study of Dabantage outcrop in Bachu area

Dolomite reservoir is a potentially important exploration field in Cambrian-Lower Ordovician of Tarim Basin,but because of deeply buried and low exploration and research degree,the current understanding unable to meet the needs of the exploration,especially the main controlling factors and distribution rules of dolomite reservoir.This paper takes the dolomite reservoir in Penglaiba Formation of Dabantage outcrop in Bachu area as an example,measured 9 section,collected 195 samples and studied the characteristics of thin sections,physical properties and geochemistry systematically,and gets tow new understanding.Firstly,powder dolomite,fine dolomite,medium dolomite and coarse dolomite are the four dolomite types in research area,the dolomitization took place in the shallow-medium burial phase,the dolomitization fluid is mainly sea water,and some dolomites influenced by hydrothermal.The size of crystals is associated with the size of structure and pore space of protolith.Secondly,the distribution of pores has stratification and cyclicity,the pores mainly occur in the top of upward shallowing sequences,and their formation is relate to exposure.The main carrier of pores is fine-coarse dolomite,the pores are mainly from the pores of original rock or their readjustment,and just a few pores are from burial solution.It is different from conventional opinion which is pores are mainly formed by dolomitization,and this opinion is of a great significance for guiding the prediction of dolomite reservoir in Tarim Basin.