The Upper Permian Changxing Formation reef-shoal carbonates in the Huanglongchang Structure, eastern Sichuan Basin, are important gas reservoirs, yet their characteristics and controlling mechanisms remain poorly understood. We integrated 481 core samples and 126 cast thin sections from 8 wells with logging, petrophysical, and structural data to characterize reservoir properties and controls. The results show that: (1) Reservoirs are dominated by oolitic, reef breccia, and rudstone dolomites, with secondary dissolution pores as the main storage space. They exhibit low porosity, low permeability, and strong heterogeneity, with porosity of 4%-12% and permeability of 0.1-10 mD. (2) The thermoge... More >

Injected water quality critically determines waterflooding effectiveness. The southern area of Gaoshen, a major deep reservoir block of the Gaoshangpu Oilfield (Jidong Oilfield), faces severe injection-well plugging, increased injection pressure, failing injection rates, and rapid production decline—necessitating urgent water-quality optimization. This study conducts reservoir sensitivity evaluation, injected water–reservoir compatibility analysis, and single-factor experiments on the effects of solid particles, suspended oil, and bacteria on permeability. Results show: (1) The reservoir exhibits moderately strong water sensitivity (critical salinity: 6000--10000~mg/L); current injected-... More >