253 / 2019-06-30 18:24:06

Reservoir Characteristics and controlling factors of Sinian Dengying Formation in Western Yibin Area, Sichuan Basin, China

Sichuan Basin,Western Yibin Area,Dengying Formation,reservoir,controlling factors

A comprehensive analysis of the cores, casting thin sections, scanning electron microscope, cathodoluminescence, physical paramaters and logging interpretation results of wells has been carried out to study the Dengying Formation reservoirs in western Yibin area. The study suggests that the main reservoir rock types of the Dengying Formation in western Yibin area are algal dolomite and micritic-powder crystalline dolomite. The reservoir space is complex, mainly composed of secondary karst pores and caves, residual pores of botryoidal lace algae dolostone. The former pores are distributed in the top of the 4th member of Dengying Formation, and the latter developes with the characteristics of bedding development and vertical superposition in the 2nd member of Dengying Formation. However, the reservoir storage capability is poor, with low porosity and low permeability. Reservoir controlling factors include sedimentary facies distribution, diagenesis, paleogeomorphology and tectogenesis. Sedimentary facies play a macroscopic control role in reservoir formation, and favorable reservoir developed in mound and shoal facies. Diagenesis affects reservoir improvement decisively, especially epigenetic karstification for the secondary corrosional pores and holes, controlled by paleogeomorphology. High ancient landform and slopes are conducive to karst development reservoir development. Besides, the multi-stage fractures formed by late tectonic movements effectively improve the reservoir performance.