KCl聚磺钻井液体系在延长气田水平井的应用

Application of KCl Polysulfonate Drilling-Fluid System to Horizontal Wells, Yanchang Gasfield

鄂尔多斯盆地气藏类型多为低孔低渗砂岩气藏,通过水平井技术扩大泄流面积,充分挖掘储层潜力,提高单井产量,达到提高气田开发效益的目的。延长气田自2011年开始水平井钻探,但是钻井过程中经常钻遇井漏、井塌等复杂事故,钻井周期长、成本高,水平井开发效益不明显。通过对水平井的地质、工程概况和钻井液技术难点进行分析,针对气田水平井井壁失稳和井漏等两大突出问题,结合地层对钻井液抑制性和封堵性的要求,对比聚磺钻井液和KCl聚磺钻井液的抑制性和封堵性,KCl聚磺钻井液体系具有强的抑制性和封堵性。现场两口井应用证实,KCl聚磺钻井液具有预防垮塌与漏失的优点,钻井周期短,无复杂事故发生,经济效益明显。

Most gas reservoirs in Ordos Basin are mainly sandstone ones with low porosity and permeability. Horizontal-well technology is usually adopted to enlarge drainage area, explore full potential of reservoir, increase single-well production, and further improve development benefits. Horizontal-well drilling for Yanchang gasfield began in 2011. But, many complicated accidents such as lost circulation and borehole collapse often occurred. Along with the long period and high cost of drilling, the development benefits were not obvious. According to the analysis on geology, engineering condition, and drilling-fluid technical difficulties, aiming at the problems of borehole instability and lost circulation, we compared the inhibition and plugging property of polysulfonate drilling fluid with those of KCl polysulfonate drilling fluid. Results show that the latter possesses the better inhibition and plugging property. Field application to two wells also indicates that the KCl polysulfonate drilling-fluid system has the advantages of prevention of collapse and lost circulation. This system may shorten drilling period, avoid complicated accidents,and bring about obvious economical benefits.