Oil and Gas

Biography

Biography: Wenzheng Li

Abstract

In recent years, the largest integral single gas field of the lower Cambrian Longwangmiao formation with proved reserves of 4403×108 m3 was found in Sichuan basin, China and the main production is from Longwangmiao formation grain dolomite. Based on observation of outcrops, cores and thin sections and analysis of logging data and experiment, the features, main controlling factors, evolution and distribution of the Longwangmiao formation reservoirs in the lower Cambrian, Sichuan basin are examined carefully and the distribution of favorable reservoirs is predicted. The Longwangmiao formation reservoirs are grain shoal-dolostone fracture–vug type made up of residual dolarenite, oolitic dolomite and crystal dolomite with vugs and dissolution pores as the main storage space, residual inter-granular pores, inter-crystalline pores and fractures as the secondary storage space, these reservoirs have a porosity of 2% to ~8%, 4.28% on average and a thickness of 20m to ~60 m, 36 m on average. Shoal facies and penecontemporaneous dissolution are the main factors controlling the reservoir occurrence. Grain shoal, the basis of reservoir development controls the phases and distribution of reservoir. Penecontemporaneous dissolution is the key factor affecting the formation of the main reservoir space. In addition, penecontemporaneous dolomitization plays a constructive role in the preservation of the pores formed earlier and generation of micro-fractures in late stage. The reservoirs experienced four evolution stages. The sedimentation and penecontemporaneous dissolution in pore-forming period laid the material basis for reservoir space types and physical property conditions. Supergene karstification and burial dissolution made some contributions to the improvement of reservoir physical properties. Hydrothermal mineral filling and asphalt filling are the main factors making reservoir quality worse. Based on the main controlling factors of the Longwangmiao reservoir, the favorable reservoir zones are ancient high topography areas between Huayingshan Fault and Longquanshan Fault and breakthroughs are expected to make in the Guangan-Nanchong-Jiange area.