复合钾盐生物聚磺钻井液在长庆水平气井的应用

Application of biological polysulfonate potassium drilling fluid in the horizontal gas wells in Changqing Gasfield

为解决长庆气田天然气水平井施工中位于斜井段位置的井壁失稳和钻头泥包技术难题，室内研究了复合钾盐生物聚磺钻井液体系，并在长庆地区15口水平井应用．结果表明，该体系表现出防塌能力强，页岩回收率达到78％以上，易塌层平均井径扩大率低于20％；性能易调控，具有良好的井眼净化能力，泥饼薄、坚韧、致密光滑，摩阻系数控制在0．0262～0．0349．与同区块非试验井相比，不仅井下安全，井壁稳定，井眼畅通，而且钻井平均机械钻速都提高了40％以上．该体系成功解决了因泥页岩水化膨胀而引起的缩径扩径、掉块坍塌、高摩阻大扭矩、钻头泥包等技术难题．

To solve the problems of borehole wall instability and bit balling in the deviated section of horizontal gas wells,a biological polysulfonate potassium drilling fluid is developed and applied to 15 horizontal gas wells in Changqing Gasfield.It is shown that this drilling fluid has good collapse prevention capability,shale recovery rate is more than 78% and the average enlargement rate of borehole diameter is less than 20% when it is used.The propertyof the drilling fluid is easy to control.It can make borehole well clean and mud cake thin,tough and dense,and the friction coefficient of the mud cake is in the range of 0.026 2~0.034 9.Compared with the wells in which the drilling fluid is not applied,the tested wells have safer downhole condition,more stable and smooth well wall.Average rate of drilling can be increased by more than 40%.This drilling fluid system successfulliy solves many downhole problems,including hole shrinkage,hole enlargement,sloughing and caving,high drag and torque and bit balling which are caused by the hydrous disintegration in shale and claystone.