昭通页岩气示范区井漏防治技术与实践

昭通页岩气示范区是我国页岩气勘探开发的重要有利区。受地面和地下条件的综合影响，作业区施工过程中存在着较为普遍的井漏情况，总体呈现了浅表层漏失、中深部直井段漏失和水平段漏失的“三段式”井漏特征。针对井漏风险预测难度大、高密度钻井液漏失严重等问题，浙江油田公司开展了孔隙压力和天然裂缝稳定性预测、水平段低密度钻井液防漏、可变形凝胶复合堵漏等技术措施的攻关。通过不同平台实钻情况的观察，验证了三维地质力学模型对于中深部裂缝性地层可能发生的井漏风险具有良好的预测能力。低密度防漏措施和可变形凝胶复合堵漏技术在YS112、YS131等多个井区进行了试验，通过合理降低钻井液密度、提升堵漏材料对微裂缝的可变形封堵能力，对水平段井漏起到了良好的预防和堵漏效果。结合昭通页岩气示范区地质条件特征，在井漏情况统计分析的基础上，对当前主要的井漏防治技术措施及相关工程实践进行了梳理和分析讨论，为示范区井漏防治技术的一体化发展提供了参考借鉴。

Drilling Fluid Technology of Preventing PDC Bit Balling

The Zhaotong Demonstration Zone of shale gas drilling is an important area favorable to shale gas exploration and development. Affected by the surface and underground conditions, mud losses have generally been encountered during drilling operations. Mud losses generally occurred in the shallow section, the medium-deep (vertical)section and the horizontal section. The mud losses were difficult to predict and become more severe with mud density. PetroChina Zhejiang Oilfield Company started studies on several topics such as predict of pore pressure and stability of natural fractures, prevention of low-density mud losses in horizontal section and mud loss control with deformable gel lost circulation materials (LCM). It was found through observation of drilling practice on several drilling platforms that a 3D geo-mechanical model can be used to predict the potential mud losses in medium-deep fractured formations. Technologies for preventing low-density mud losses and the deformable LCM have been tried on the well YS112 and the well YS131. By reducing the mud density to a reasonable level and enhancing the capacity of controlling mud losses with the deformable LCM, mud losses in horizontal drilling were successfully prevented from occurring. This paper, based on the statistical analyses of the mud looses encountered in previous drilling operations, discusses the current technologies for and practice of mud losses control, taking into account the geological characteristics of the Zhaotong demonstration zone of shale gas drilling. The technologies discussed in this paper can be used as references to the prevention of mud loss control in the demonstration zone.