The Formation Characteristics And Damage Evaluation Of Penglaizhen Shallow Gas Reservoir In Western Sichuan Basin Baima-songhua Area

As the deep advancing of natural gas industry, development of shallow gas reservoirs has become more and more significant to enhance natural gas production. Shallow gas reservoirs in western Sichuan basin are shallowly buried and abundant in resource and its exploitation has a bright prospect. Penglaizhen sandstone gas reservoir in Baima-songhua area is of shallow low-permeability. The unique gee-engineering characteristics make its damage mechanisms differ from conventional oil/gas reservoirs and be of significance in pilot and demonstration in China. Out of this point, through comprehensive studies of multi-subjects and varied methods, the damage mechanisms and characteristics of Penglaizhen formation are systematically discussed and relevant protection advice is provided in this paper. The study results can also be taken as reference to other similar shallow low-permeability sandstone gas reservoirs.Data from thorough and systematic modern core analysis reveal the engineering and geologic characteristics of Penglaizhen formation. It is noted that the characteristics of clay minerals and pore-throat structures lead to complex and unique formation damages. Thus, protection route and strategic emphasis are presented. Aimed at low permeability and near tight gas reservoir, new experimental evaluations of sensitivities, water blocking damages and damages caused by drilling and completing fluids have been carried out. Comprehensive analyses show that water-blocking induces the most serious damage to Penglaizhen formation. At the same time, alkali sensitivity, water sensitivity and stress sensitivity are relative serious. While solid phases invasion and aqueous trap are the dominant damage types during well drilling and completion. Finally, corresponding protection measures and advice are presented in this paper.