大古1井多压力系统钻井液技术

Drilling Fluid Technology for Multi-pressure Systems in Well Dagu-1

大古1井是位于天山南大涝坝二号构造上的1口重点预探井。该井二开吉迪克组高压盐水层极为发育，富含石膏，存在大段的水敏性泥岩和膏质泥岩，因此使用了阳离子钾基聚合物（聚磺）钻井液。由于该钻井液抗污染能力和包被抑制性强，有效解决了起下钻的阻卡问题。三开存在上涌下漏和压差卡钻的极大风险，但由于为探井，多种防塌剂、润滑剂的使用受到了限制。优选出了阳离子超低渗透聚磺防塌钻井液。在应用中，该钻井液泥饼摩阻系数一直保持为0．04～O．05，并有良好封堵能力，有效降低了压差卡钻的风险。四开形成了欠平衡钻进，通过使用加有乳化石蜡的超低渗透成膜封堵钻井液对油气层进行保护，共发现了5套油气显示层。

Well Dagu-1 is a key exploration well located in the 2nd structure in Dalaoba to the south of Tianshan Mountain.The Jidike Formation in the second interval had high-pressure saltwater zones,gypsum layers,and thick water-sensitive shales.Cationic polymer mud was used in this interval,and was successful.In the 3rd interval,there were water kick zones in the upper portion and mud loss zones in the lower portion,and the risks of pipe sticking.The use of drilling lubricants with fluorescence was not allowed in this exploration well.A cationic polymer mud treated with sulfonates and ultra-low filtration rate additives was used in this interval.Fourty-five tons of a selected drilling lubricant with no fluorescence was used,and the friction coefficient of the mud cakes was maintained at 0.04-0.05,minimizing the risk of pipe sticking.Under balanced drilling was applied in the fourth interval,in which filming drilling fluid treated with emulsified wax and ultra-low filtration rate additives,and five pay zones were pinpointed.