NDW无土相低伤害储层钻井液在CB8-3井的应用

Application of NDW clay-free low damage drilling fluid on Well CB8-3

长北气田属于致密性气藏,钻井过程中工作液的侵入是造成储层伤害的主要因素。为了降低钻井液完井液对气层的伤害,主要从暂堵和改变储层岩石表面的润湿性两方面着手,研制出了暂堵效果显著、抑制性强、润滑防卡性能良好、密度可调、失水低等特点的NDW无土相低伤害钻井液体系。动态伤害模拟实验表明,该体系对气层的平均伤害率为11.25%,暂堵性好,并且易于通过储层自身能量完成解堵,很大程度上简化了完井、投产作业。该体系在CB8-3井完成水平段累计进尺4 388 m,其中240 m泥页岩夹层,在整个施工过程中,井眼始终处于良好净化状态,起下钻无阻卡,井底无沉砂;裸眼完井并直接气举投产,获得无阻流量230万m3/d的高产气流。应用结果表明,该体系能有效地保护油气藏,提高单井产量,值得推广。

Changbei gasfield belongs to tight gas reservoir. In the drilling process, the invasion of drilling fluids is one of the main reservoir damage factors. To reduce the invasion of drilling and completion fluids, studies were mainly focus on temporary plugging and wettability change of reservoir rock surface, and a type of NDW clay-free low damage drilling fluid was developed. The fluid had effective protection for gas reservoir because its average damage ratio to the pay-zone is only 11.25%, tested under reservoir conditions. The fliud had good temporary plugging, excellent inhibitive ability and high lubricity. In the whole drilling of horizontal interval in well CB8-3, the cumulative horizontal interval length using the fluid is 4 388 m, and the borehole is always kept clean, with no blockage and no pipe-sticking during tripping, and no sand setting in downhole. Moreover, more than 240 m shale was stable and the production of 230x 104 ma/d in this well was obtained, which created the new record of highest individual production rate in onshore low permeability gasfield in China.