| In recent years,the theory of dolomite-evaporite paragenesis system(DEPS)and diagenetic system has been improved,which has enriched the research and exploration application of Cambrian reservoirs in Sichuan Basin.In this paper,based on the reference of previous related research results,the stratigraphic characteristics,planar distribution,and basic characteristics of reservoirs of the Cambrian dolomite-evaporite development system in east Sichuan Basin and the peripheral area are studied by combining the actual drilling and seismic data and field section data in the area,analyzing the sequence characteristics of the rock assemblage of the DEPS,clarifying the genesis mode,and summarizing the main controlling factors and evolution mode.Combining the isotope,inclusions and cathodoluminescence characteristics of the DEPS,the diagenetic system of the DEPS,and the reservoir characteristics of the Cambrian DEPS were analyzed and the favorable reservoir distribution was predicted on the basis of some petrophysical analysis data,and the following results and understanding were achieved:(1)Four rock combination sequences are developed in the Cambrian dolomiteevaporite syngenetic system in east Sichuan and the peripheral area,including:dolomite interbedded with evaporite,dolomite overlying evaporite,dolomite interbedded with evaporite and evaporite interbedded with dolomite.The Shuangxiangchi Group develops dolomite interbedded with evaporite,and all four dolomite-evaporite rock assemblage sequences are developed in the Gaotai and Longwangmiao Formations.In plan,dolomite and evaporite interbedded are most widely distributed in the study area;dolomite overlying evaporite is mainly distributed in the western part of the study area;dolomite intercalated evaporite and evaporite intercalated dolomite are mainly distributed in the eastern part of the study area.(2)The diagenetic modes of the dolomite in east Sichuan Basin and its peripheral areas mainly include the "Sabkha mode" and the "reflux-permeability mode".The sedimentation mode of evaporites mainly includes "bull’s-eye" and "water-drop".The development of the DEPS in eastern Sichuan Basin and its peripheral areas is mainly controlled by three factors:(1)continuous sea retreat;(2)confined and closed paleoenvironment;(3)hot and arid paleoclimate.Based on the analysis of the main controlling factors,the developmental evolution model of the symbiotic system was established.(3)The evolutionary history of the DEPS is divided into four diagenetic systems:pore water,confined brine,compacted hot brine,and tectonic hot brine.(4)On the basis of the study of the reservoir space and reservoir properties of the DEPS,the relationship between the sequence of the DEPS rock assemblage,planar distribution and the reservoir is analyzed,and the relationship between the diagenetic system and the reservoir development is discussed,and the diagenetic system closely related to the reservoir development is considered to include: the closed brine diagenetic system in the early diagenetic stage and the tectonic hydrothermal brine diagenetic system in the tectonic diagenetic stage.From the basin scale,a series of fractures caused by the Cambrian slip in east Sichuan Basin are the dominant factors controlling the spatio-temporal coupling relationship between the diagenetic system and the reservoir of the DEPS.The granular beach microphase and early diagenetic stage buried dolomite petrogenesis are the basic elements of reservoir development,and the tectonic diagenetic stage for TSR and recrystallization improves the reservoir quality and further improves the reservoir pore permeability. |
