塔里木山前盐底恶性漏失沉降堵漏技术

Settling Plugging Technology for Severe Lost Circulation at the Salt Bottom of Tarim Piedmont Zone

塔里木盆地山前普遍发育高压盐膏层和低压碎屑岩目的层,两套地层系统压差高于20 MPa,钻井过程中由于地质卡层不准极易造成钻穿盐膏层、进入目的层后发生恶性井漏事故。为解决塔里木山前盐底恶性井漏问题,在已知塔里木山前盐底恶性漏失机理为高低压差地层钻穿连通造成的恶性漏失和“瓶塞”堵漏原理的基础上,通过评价堵漏材料的承压强度和高温下的沉降速度等性能参数,分别筛选出油基钻井液和水基钻井液沉降堵漏塞形成(速度和质量)的最佳条件,并最终形成一套高密度、大压差油基和水基钻井液专用的沉降堵漏技术。其中,当油基钻井液油水比50∶50、破乳电压(ES)在200~300V范围内,水基钻井液添加了0.2%XC、0.2%破胶剂和堵漏剂时,沉降塞形成效果最好。该沉降堵漏技术在塔里木山前成功试验3口井,其中在DB1302井上堵漏塞承压能力达30 MPa,说明盐底恶性漏失堵漏技术取得了显著的应用效果。

High-pressure gypsum salt beds and low-pressure clastic rock target beds are commonly developed in the piedmont zone of Tarim Basin,and the pressure difference between these two stratigraphic systems generally exceeds 20 MPa.Because of the inaccuracy of geological stratigraphic determination during drilling,it is highly likely to drill through the gypsum salt bed into the target bed and then trigger severe lost circulation.To solve the problem of severe lost circulation at the salt bottom of Tarim piedmont zone,this paper evaluates the performance parameters of plugging materials such as pressure-bearing capacity and settling velocity,identifies the opti-mal conditions(velocity and mass)of oil-and water-based drilling fluid(OBM and WBM)settling plugging pills respectively,and finally develops the high density large pressure difference settling plugging technology specialized for OBM and WBM,based on the known mechanism of the severe lost circulation problem(drilling induced communication between high and low pressure formations)and the principle of the"bottle plug"plugging practice.Specifically,optimal plugging pills are expected to form in the case of OBM with a oil-water ratio of 50:50 and ES of 200-300 V or WBM with 0.2%XC+0.2%demulsifier+plugging agents.The developed set-tling plugging technology has been successfully tested in three wells in Tarim piedmont zone,and Well DB1302 was found with a pres-sure bearing capacity of 30 MPa,demonstrating excellent application performance.