延长油田水平井钻井液优化与应用

延长油田水平井现用KPAM聚合物钻井液体系存在着抑制性能不足、流变性能不佳等问题，导致现场卡钻、托压等问题频繁发生。提出用阳离子乳液聚合物DS-301与RHJ-1乳化石蜡取代原体系中的KPAM和水基润滑剂，以改善钻井液性能。DS-301为大分子阳离子聚合物抑制剂，带有大量的阳离子基团，其分子量可以达到600万以上，能够有效提高连续相的黏度；RHJ-1具有优良的润滑防塌性能，能辅助提高DS-301的化学抑制效果。通过室内实验优选，0.3% DS-301与2.0% RHJ-1复配的阳离子乳液聚合物钻井液体系在100℃老化16 h后塑性黏度为25 mPa·s，动切力为12.5 Pa，润滑系数为0.233，高温高压泥饼黏滞系数为0.052 4，滚动回收率高达92.8%，对比KPAM聚合物体系在流变性能和抑制性能上有了明显的提高，有利于大幅度减少了卡钻问题的发生；通过配合加入1%极压减摩剂JM-1，润滑系数进一步降低到了0.137，有效地提高了钻井液的润滑性能，解决了水平段出现的托压问题。现场试验3口井，在水平钻进井段控制钻井液滤失量在5 mL以下，保持动塑比在0.48 Pa/（mPa·s）左右，提高钻井液携岩性能，保持井壁的稳定，现场施工作业顺利。 

Optimization and Application of Horizontal Drilling Fluid in Yanchang Oilfield

The KPAM polymer drilling fluid presently used in horizontal drilling in Yanchang Oilfield has low inhibitive capacity and poor rheology, resulting in frequent pipe sticking and inability to exert weight on bit during drilling. To improve the performance of the KPAM polymer drilling fluid, a cationic emulsion polymer DS-301 and a emulsified paraffin RHJ-1 have been used to replace the main polymers used. DS-301 is a high molecular weight (more than 6,000,000) cationic polymer inhibitor with multiple cationic groups, and is thus able to effectively viscosify the continuous phase of the drilling fluid. RHJ-1 has superior lubricating and inhibitive capacities, synergistically working with DS-301 to enhance the chemical inhibitive capacity of the drilling fluid. Based on laboratory experiments, a drilling fluid formulation containing 0.3% DS-301 and 2.0% RHJ-1 was selected. The new drilling fluid formulation, after hot rolling for 16 h at 100℃, had plastic viscosity (PV) of 25 mPa·s, yield point (YP) of 12.5 Pa, coefficient of friction of 0.233, and percent recovery of shale cuttings of 92.8%, better than KPAM polymer drilling fluid in rheology and inhibitive capacity. Pipe sticking has been greatly mitigated since the use of this new drilling fluid. 1% extreme pressure lubricant JM-1 was added in the drilling fluid to improve its lubricating performance and solve the problem of being unable to exert weight on bit in horizontal drilling, and the coefficient of friction was further reduced to 0.137. In field application, the filtration rates of the drilling fluid in three wells were controlled below 5 mL, and the ratios of YP/PV at about 0.48 Pa/(mPa·s). Cuttings carrying capacity of the drilling fluid was improved, and borehole wall stabilized. No downhole troubles have ever been encountered during drilling, and higher ROP was achieved.