Characteristics and controlling factors of Jurassic limestone reservoir in the piedmont of Kisar Mountain in Amu Darya Basin

Abstract

The characteristics of Jurassic carbonate reservoirs in various structural belts in the piedmont of Kisar Mountain east of Amu Darya Basin or different well areas of the same structure are quite different. Due to complicated controlling factors, the reservoir development and distribution law are not clear, and the deployment of high-yield wells is difficult. Through the comprehensive analysis of cores, thin sections, well logging and geochemical data of 17 exploration wells in this area, the research shows that in the Jurassic limestone of the front belt of Kisar Mountain east of Amu Darya Basin, micritic granular limestone and granular micritic limestone are good reservoir rocks and that the granular micritic limestone and micritic limestone can still be used as good reservoir rocks after structural fracture and dissolution transformation. Fractures and corrosion holes developed along fractures are the main reservoir space. The physical properties of the matrix reservoir are poor. The matrix reservoir space is only a small number of biological mold holes, body cavity holes and occasional intergranular solution holes. Jurassic limestone in the Kisar Piedmont belt in the east of Amu Darya Basin is developed in the lower-gentle slope facies belt, which does not have the diagenetic environment for reservoir development in the quasi-syngenetic early diagenetic stage. However, affected by the tectonic activities of Early Cretaceous strong tension and Paleogene quaternary strong tectonic compression and uplift, faults/fractures are relatively developed, providing a channel for the dissolution transformation of surrounding rock by later diagenetic fluid and an important prerequisite for the development of reservoir in the study area. The key to developing and forming reservoirs in the study area is the dissolution of hydrothermal fluid and hydrocarbon emplacement organic acid. Along the large fault zone or fracture intensive development zone, the reservoir development is better.