冀东NP280 Es_(3)^(1)井壁稳定钻井液技术

Drilling Fluid Technology for Stabilizing the Borehole Penetrating the Shasanyi Sub-member in Block NP-280 in Jidong Oilfield

针对冀东油田南堡280区块多口井钻遇至沙三1亚段(Es_(3)^(1))时发生井壁失稳,研究表明区块内泥岩遇水易产生水化作用,其漏失段间裂缝发育,裂缝多为中高角度裂缝,原裂缝宽度(0.1~100μm)受压力等诱导因素后变大导致成为致漏性裂缝漏失频繁,同时也会诱发大规模的掉块从井壁上剥落进而导致了井下的坍塌卡钻等井下复杂问题。对南堡280区块破碎地层进行井壁稳定机理、评价方法的相关研究,以原三开抗高温抑制钻井液为基础,进行室内优化实验,构建了适合诱导性裂缝地层的强封堵性井壁稳定钻井液,现场应用表明该钻井液体系可有效防止Es_(3)^(1)地层的坍塌失稳问题,具有重大的推广应用意义。

Borehole wall collapse has been encountered when drilling the Shasanyi sub-member in many wells in the NP-280 block in Jidong Oilfield.Study has shown that the shales in the block are easy to hydrate when in contact with water.Microfractures with medium and high angles are developed in the thief zones.These microfractures,with original widths of 0.1μm–100μm,become widened under pressure and hence further become fractures through which drilling fluids are lost.This in turn induces large-scale sloughing of the borehole walls and borehole collapse has thus occurred.In this paper,the studies on the mechanisms of borehole wall stabilization in the broken formations in the NP-280 block and the methods of borehole wall instability evaluation are described.Using the high temperature inhibitive drilling fluid,which was used to drill the third interval of the wells,a new inhibitive drilling fluid with high plugging capacity is developed thorough laboratory optimization.This drilling fluid is suitable for drilling formations with induced microfractures.Field application shows that it can be used to effectively prevent the borehole wall collapse problems encountered in drilling the Shasanyi sub-member,and this technology is worth applying in future drilling operation in this area.