Sedimentary Facies and Favorable Rock Assemblages of Jurassic Da'anzhai Member, Central Sichuan.

In view of the imprecise sedimentary facies division, unclear favorable rock assemblage and undefined favorable exploration area of Jurassic Da'anzhai Member in Central Sichuan, a study was conducted on the rock type, sedimentary facies type, sedimentary facies distribution, sedimentary model, rock assemblage and favorable exploration area in the study area by the core description of three fully cored wells and the observation results of six field profiles in combination with thin slice identification, logging interpretation and organic geochemical analysis methods. The study results show that Rock was divided into 10 types. The sedimentary facies was divided into 3 subfacies (shore lake, shallow lake and fairly deep lake) and 10 microfacies (including fairly deep lake mud, organic bank and gravity flow). Gongshanmio-Lianchi-Yingshan line is the sedimentary center developed in a fairly deep lake environment, and three rock assemblage types (C, D and E) were identified. Nanchong-Quxian-Yilong line was circularly developed in a shallow lake environment, and three rock assemblage types (A, B and F) were identified. The study results were applied from conventional tight oil to shale oil exploration. According to the TOC, porosity, permeability, fracturing effect and other evaluation indicators, it was considered that Type A rock assemblage was a favorable combination for tight oil carbonate rock exploration under the matching of fractures and cracks, and Type F was the most favorable combination for shale oil exploration, which was mainly distributed in the shallow lake facies at Sub-member 1 to Sub-member 2a of Da'anzhai Member. The study results are of great significance for shale oil exploration in the future. [ABSTRACT FROM AUTHOR]