A New Reservoir Protection Technology for Offshore Condensate Gas Wells during Shut-in

Abstract

Wells in tight sandstone condensate gas reservoirs of East China Sea often suffer from dramatic production declines after being closed for several days. The closure can be caused by typhoon. For example, the gas production of target well B1, studied in this paper plummeted from 50,000 to 0 m3/d after the typhoon. This study aims to propose a reservoir protection technology preventing the offshore condensate gas wells from production decline caused by emergent shut-in operations. Firstly, based on comprehensive analysis of the production parameters, experimental data, and process mechanism, it was shown that the sudden drop in gas production of well B1, is attributed to wellbore liquid loading and reservoir liquid locking damage and is not caused by the insufficient recoverable reserves and solid plugging damage. Secondly, a liquid locking removal technology combining wettability alteration treatment with coiled tubing gas technique was proposed and applied on the well B1. The result showed that the gas production increased dramatically from 0 to 40,000 m3/d. However, even though the liquid locking removal technology proved to be efficient, it is also time-consuming and costly. Therefore, in order to optimize the construction time and costs for the conditions of the actual offshore production, an improved innovative two-step reservoir protection technology was suggested, combining foam drainage gas recovery and wettability alteration treatment.