致密碳酸盐岩气藏钻井液水相圈闭损害与防治

The water phase trapping damage caused by drilling fluid and prevention in tight carbonate gas reservoirs

为了确定钻井液对致密碳酸盐岩气藏的损害程度及钻井液液相侵入深度,以采取适宜的水相圈闭损害防治措施,文中采用现场所用钻井液,开展了毛细管自吸实验、考虑侵入-返排过程的水相圈闭损害程度实验以及钻井液动态滤失量随时间的变化实验,根据动态滤失量实验数据,建立一种更符合现场的钻井液液相侵入深度计算模型,并根据钻井液对致密碳酸盐岩气藏的损害情况,开展了适用于致密碳酸盐岩气藏的水相圈闭损害防治剂筛选及效果评价实验。结果表明:钻井液滤液自吸最终含水饱和度为57.86%~73.57%,不可恢复渗透率损害率为31.57%~65.24%,钻井液液相侵入深度平均为2.528 m;钻井液中加入水相圈闭损害防治剂F后,自吸量减少了0.208 PV,渗透率损害率降低了30.3%。根据研究结果,制定了钻井液水相圈闭损害预防、解除措施。

To determine the damage degree to tight carbonate gas reservoirs and invasion depth of drilling fluid phase,taking appropriate measures to prevent and control water phase trapping damage,water phase trapping damage experiments were carried out,including capillary imbibition experiments and water phase trapping damage degree experiments considering invasion and flowback process,as well as the relationship between dynamic filtration rate and time of drilling fluid,all of which in this paper were carried out with the drilling fluid used in the field.Based on the dynamic filtration experimental data,a calculation model for drilling fluid invasion depth that is more in line with the actual situation on site is established.According to the damage of drilling fluid to tight carbonate gas reservoirs,screening and effectiveness evaluation experiments of water phase trapping damage prevention agents suitable for tight carbonate gas reservoirs are carried out.The results show that the final water saturation of drilling fluid filtrate imbibition ranges from 57.86%to 73.57%,and the damage rate of unrecoverable permeability ranges from 31.57%to 65.24%.The average depth of drilling fluid invasion is 2.528 m,after adding water phase trapping damage prevention agent F into the drilling fluid,the spontaneous imbibition capacity decreased by 0.208 PV and the permeability damage rate decreased by 30.3%.According to the research results,the measures to prevent and relieve the damage of drilling fluid water phase trapping are determined.