Main Controlling Factors and Characteristics of Cambrian Dolomite Reservoirs Related to Evaporite in Tarim Basin

Massive dolomites are widely distributed in the Cambrian System of Tarim basin,and in Middle Cambrian with thick evaporite,evaporite and dolomite can be good reservoir-seal assemblage,so the dolomite strata is a new exploration field of Tarim Basin in the future.Sabkha dolomite and seepage reflux dolomite are the two kinds of dolomite related to evaporite,and the main controlling factors of reservoir are also associated with evaporite directly or indirectly.This article summarized the petrologic and geochemical characteristics of sabkha dolomite and seepage reflux dolomite by analyzing a lot of cores,thin sections,major element,REE and stable isotope(carbon,oxygen and strontium) data.The lithology of sabkha dolomite reservoir characterized by the deposits of gypsodolomicrite,gypsum mould pores and inter-gravel pores of solution-collapse breccia are the two kinds of porosity,sabkha dolomitization,gypsum precipitation and dissolution of meteoric fresh-water are the main controlling factors of this reservoir;The lithology of seepage reflux dolomite reservoir featured by crystal powder dolomite which has reserved the original grainstone or algae mound structure,intergranular pores,mould pore,framework pores and organism pores are the main kinds of porosity,seepage reflux dolomitization and meteoric fresh-water dissolution are the main controlling factors of this reservoir;The distribution law of these tow dolomite reservoirs are controlled by sedimentary facies,and chiefly developed in arid climate background of middle Cambrian,Tarim basin.