The origin of heterogeneous sucrosic dolomite reservoir of the lower Permian Qixia Formation, NW Sichuan Basin, China

Sucrosic dolomite, an important hydrocarbon reservoir, has long been the focus of carbonate sedimentological and reservoir geological studies. This study investigated a kind heterogeneous sucrosic dolomite in Lower Permian Qixia Formation NW Sichuan Basin, which recently location giant natural gas discoveries. The is characterized by coexistence porous euhedral tight anhedral it mainly distributed platform-marginal shoal facies with quasi-layered structure. Further geochemical analysis, including C, O, Sr isotopes as well rare earth elements, reveals that have similar properties to matrix limestone representing coeval seawater, they were generated from dolomitization closed marine-related fluid (left-leaning REE δPr < 1) shallow burial. difference crystal morphology, porosity, permeability between related compositional textural heterogeneities host rocks. Due dissolution meteoric water (relatively flat low Y/Ho) early diagenetic stage caused high frequent exposures, vugs caves formed grainstones. In process burial dolomitization, loose-filled sands due sufficient space, while relatively poor porosity permeability. Accordingly, paleogeomorphic highland controlled superimposed main factor for formation reservoirs, manifested inheritance adjustment pre-existing pores rock. Therefore, exploration direction reservoirs Basin should be shifted favorable sedimentary facies-controlled model, can also referential other cases under setting.