EXPERIMENTAL EVALUATION OF DAMAGE FAC TORS OF TIGHT SANDSTONE GAS RESERVOIRS IN SHENFU BLOCK, CHINA

摘要

Natural gas has been widely used as a clean energy source. In recent years, the development of unconventional natural gas reservoirs has entered a boom, including shale gas and tight gas reservoirs, but the development of unconventional gas reservoirs is more difficult. Tight sandstone gas reservoirs have been hot spots for exploration in recent years. The tight sandstone gas reservoirs in the Shenfu Block in the eastern Ordos Basin have low permeability and small core pore size distribution, which makes the reservoirs have serious water locking damage. The drilling fluid could intrude into the formation during drilling, causing Blockage of the reservoir. When the external fluid surface tension value is large, the water lock damage of the reservoir core is serious, and the invading fluid cannot be easily displaced. Through the analysis of core self-absorption experiments, we found because the waterproof lock PF-FC has a lower surface tension, it can effectively reduce the capillary force, thereby reducing the self-absorption of water in the core. Based on the Shenfu Block drilling fluid, adding the waterproof locker PF-FC enables the drilling fluid has a low surface tension value of the filtrate and can increase the core contact angle to 81.3 0, turning the core surface to neutral wetting. It can effectively reduce the self-absorbed liquid volume of the core, so that the invading fluid is more easily discharged back at a lower pressure, thereby reducing the liquid lock effect. The recovery value of permeability after core pollution can reach 91.2%, showing good reservoir protection effect.