中秋区块ZQ2井盐膏层水基钻井液技术

中秋区块为塔里木油田3000万吨产能建设重点区块。塔里木油田山前井盐膏地层因地质条件复杂，普遍使用油基钻井液钻井。ZQ1井盐膏地层亦使用油基钻井液，因新近系苏维依组存在低压层，在钻进过程中发生井漏，使用油基钻井液堵漏成功率低，耗时达60多天。为有效解决油基钻井液盐膏层阻卡、堵漏成功率低、钻井液成本高等问题，决定在ZQ2井吉迪克组高压盐膏层和苏维依组低压易漏层采用水基钻井液套打技术。ZQ2井盐膏层水基钻井液技术有效解决了吉迪克组“盐、膏、泥”污染导致的钻井液流变性和失水造壁性控制难的问题，采取主动防漏技术顺利钻穿苏维依组低压易漏层，未出现盐间“软泥岩”堵地面管汇的问题，钻井液性能稳定，井眼畅通。该技术为加快塔里木油田3000万吨产能建设提供了新的可行的钻井液技术思路。

Water based drilling fluid technology developed for the salt-gypsum bed in Well ZQ2 of the Zhongqiu Block

The Zhongqiu Block is the key block for the productivity construction of 30 million tons in the Tarim Oilfield. The salt-gypsum beds in the piedmont wells of the Tarim Oilfield are geologically complex and oil based drilling fluid is mostly used there. And oil based drilling fluid is also used in the salt-gypsum bed of Well ZQ1. There are low-pressure layers in the Neogene Suweiyi Formation, so circulation loss happens in the process of drilling. As a result, the success rate of circulation loss control by oil based drilling fluid is low and it takes over 60 days. In order to effectively solve the problems of oil based drilling fluid, e.g. blocking and sticking in salt-gypsum beds, low success rate of circulation loss control and high cost, it is determined to apply a set of water based drilling fluid technology to the high-pressure salt-gypsum beds of Jidike Formation and the low-pressure thief zones of Suweiyi Formation in Well ZQ2. By applying the water based drilling fluid technology to the salt-gypsum beds in Well ZQ2, the hard control of the rheological property of drilling fluid and the fluid-loss well building property caused by the salt, gypsum and mud contamination in the Jidike Formation is solved effectively. By virtue of the active circulation loss control technology, it drills through the low-pressure thief zones of Suweiyi Formation smoothly. And the phenomenon of inter-salt “soft mudstone” blocking the choke line doesn’t occur, the performance of the drilling fluid is steady and the borehole is unrestricted. This technology provides a new and feasible idea of drilling fluid technology for speeding up the productivity construction of 30 million tons in the Tarim Oilfield.