伊朗TABNAK气田低压裂缝性地层泡沫钻井液技术

伊朗TABNAK气田地层岩性以灰岩和白云岩为主，石膏夹层较多；碳酸盐岩地层裂缝发育，连通性好，漏失严重；海平面以上是干层，无孔隙压力，海平面以下至井深2450m是盐水层。长城钻井公司采用了空气—泡沫钻井流体，即：空气粉尘、雾化空气、稳定泡沫钻井液和硬胶泡沫钻井液。通过实验，优选出发泡体积大、稳定时间长、抗盐抗钙能力强和耐温性能好的发泡剂和稳定泡沫液及硬胶泡沫液配方。现场应用表明，空气—泡沫钻井流体密度低；钻速快，平均机械钻速是常规钻井液的3—5倍；携砂性好，井眼清洁；能顺利穿过严重漏失地层。其中，空气粉尘用于干层钻进，速度快，无钻井液材料消耗，但必须有足够的空气排量；雾化空气适用于出水量较小的水层，但需要的空气排量更大，而且对钻井腐蚀太严重；泡沫钻井液适用于低压干层和水层，需要的空气排量较小，钻速快，抗盐钙和携砂能力强。

Foam drilling fluid technology in TABNAK gas field,Iran

Air/foam drilling fluid systems have been used in TABNAK gas field of Iran to solve the problems of fracture developing, formation communication and lost circulation during drilling in low pressure fractured carbonate formation. The drilling fluid systems include dust, mist, stable foam and foam drilling fluids. The air/foam drilling fluid has such properties as low air/fluid column pressure, high ROP, lost circulation prevention, etc. , and gypsum and high concentration saline contamination resistance. Foaming agent and foam formulation of large foaming volume, long stabilization period, salt and calcium resistance, high temperature tolerance have been optimized based on experiments, and field using showed that the air/foam drilling fluid systems are suitable for using in the low pressured dry formation and water zone, it needs low air pumping rate and higher salt and calcium resistance; it has low density, good cuttings transportation and suitable for fast drilling through the thief formation. By using the air/foam drilling fluid, ROP of 25 m/h was achieved, and the average ROP is 3-5 times of the conventional drilling.