狮子沟构造带裂缝储层保护钻井液配方

针对青海油田英西裂缝性碳酸盐岩储层在钻井过程中存在的储层损害问题,开展了储层裂缝特征、储层岩石成分、储层岩石的分散性和膨胀性能分析,完成了储层固相颗粒损害、水锁损害以及敏感性损害的评价,明确了储层受到损害的主要因素.评价7种现场储层保护剂的酸溶率、油溶率、粒径范围,其中XY-2和NFA-25的可溶解性(酸溶率和油溶率)大于90％,NFA-25的粒径较大且分布范围最广,可作为储层保护剂.评价了3套钻井液体系的动态渗透率恢复值,复合有机盐钻井液污染岩心后,渗透率恢复值为85.52％,储层保护效果最佳.在复合有机盐钻井液配方下,通过加入可酸溶纤维屏蔽暂堵剂,提高钻井液对裂缝的屏蔽暂堵率以及加入低聚有机硅防水锁剂减少钻井液对储层微裂缝造成的水锁伤害,将钻井液的渗透率恢复值从85.2％提高至92.24％,复合有机盐钻井液储层保护效果显著提高.

Study the Formulation of Drilling Fluid to Protect the Fracture Reservoir of the Shizigou Structural Belt

The fracture was developed in the Shizigou structural belt of the Qaidam Basin, which causing the reservoir to be seriously damaged by the drilling fluid. The main factors of reservoir damage were identified by analysis of reservoir fracture characteristics, reservoir rock composition, dispersion and expansion performance of reservoir rock, and evaluation of solid particle damage, water lock damage and sensitive damage. In order to reduce the reservoir damage problem, the particle size range, solubility of seven on-site reservoir protection agents were evaluated. The experimental results showed that the solubility of XY-2 and NFA-25 (acid-soluble, oil-soluble) was above 90%, and NFA-25 had a large particle size and a wide distribution, which could be used as reservoir protection agents. The dynamic permeability recovery values of three drilling fluid systems were evaluated. The organic salt drilling fluid reservoir has the best protection effect, and the permeability recovery value is 85.82%. The composite organic salt formulation was optimized using acid soluble fiber and oligomeric silicone waterproofing locker to increase the drilling fluid permeability recovery value from 85.2% to 92.24%.