抗高温低密度水包油钻井液在文古2井的应用

Application of high temperature and low density oil-in-water drilling fluid in well Wengu-2

文古2井是位于中原油田文留地区古潜山构造的一口重点探井,是实现东濮潜山突破的首选目标。文古2井井深为4750.18 m,地层孔隙压力系数为0.98-1.0,井底温度为166℃。该井在五开井段欠平衡钻井施工中首次使用了抗高温低密度水包白油钻井液。该体系乳化剂为新研制出的抗高温水包油乳化剂A-1(抗温可达180℃);油为5#白油,体系荧光级别在6级以下,对探井地质录井无影响;油水比为6:4;该钻井液密度在60℃下为0.89 g/cm3,在40MPa、150℃下为0.93 g/cm3,基本满足欠平衡钻井要求。在现场应用过程中,该钻井液遇到了H2S气体侵以及严重的石膏侵和HCO3-、CO32-污染问题,经处理后,保证了钻井液pH值在12-13之间,钻井液整体性能良好,证明该钻井液抗污染能力强。现场用水包白油钻井液在高温高压下有良好的流变性;静、动态渗透率恢复值分别为91.4％和83.1％,保护油气层效果好;具有良好的抑制性和润滑性,携砂效果良好,起下钻畅通无阻;钻井液密度一直稳定在0.88-0.89g/cm3之间,实现了真正的欠平衡钻井;电测一次成功率为100％。

Well Wengu-2 is an important exploratory well drilled in the buried hill structure in the Wenliu area of Zhongyuan oilfield, with its bottom depth at 4750. 18 m. It has a formation pore pressure coefficient of 0. 98 -1. 0, and its downhole temperature is 166℃. In the underbalanced drilling of the bottom 152. 4 mm hole, high temperature tolerant and low density oil-in-water drilling fluid is firstly used. The emulsifying agent for this system A-1 can tolerate a temperature as high as 180℃, and the oil used is 5# white oil. The fluorescence grade of the system is under 6 and this has little influence on mud logging. Oil to water ratio is 6/4. The drilling fluid density is 0. 89 g/cm3 in 60℃and 0. 93 g/cm3 in 150℃ and 40 MPa, which can meet the requirements of underbalanced drilling. In field drilling, H2S and gypsum invasion were encountered, and contamined by such ions as HCO3- and CO32-, however, the pH value maintained at 12-13 after treatment and good drilling fluid performances were achieved. The system kept a good rheological property in HTHP condition, and the static and dynamic return permeability reached 91. 4% and 83. 1% specifically, which showed good formation protection results. It also displayed its good inhibition and lubricity, and good cuttings transportation. Drilling fluid density stabilized at 0. 88-0. 89 g/cm3 during drilling, and a real underbalanced drilling was realized.