Development and Evaluation of Reusable Salt-Resistant Foam Sand Flushing Liquid

Sand out of oil formation is one of the common problems in oilfield exploitation, and foam as a special fluid has been successfully applied in sand flushing operation. The coiled tubing drilling and grinding sand flushing operation of low-pressure wells adopts nitrogen foam system to clean the wellbore, but there are difficulties such as poor performance and high cost of the foam system formulated by the return fluid. Through indoor experiments, a new type of foaming agent, foam stabilizer and defoamer were developed to form a set of reusable salt-resistant foam sand flushing system. The formulations of clear water and return liquid are 0.3% foaming agent +0.3% foam stabilizer + clear water; 1.0% foaming agent +1.0% foam stabilizer + return liquid, respectively. The system foam half-life ≥45 min, foam quality ≥70%, mineralization resistance ≥20000 mg/L, temperature resistance 90 °C, placed at room temperature for 30 min without settling, defoamer has no effect on the performance of repeated dispensing, to meet the needs of low-pressure wells flushing sand.