川藏铁路复杂地层水平孔钻探护壁堵漏研究与应用

Wellbore protection and sealing for directional drillingin complicated formation at the SichuanTibet Railway

摘要:

川藏铁路地处青藏高原东南部，由于构造活动发育，岩体松散破碎，裂隙及承压水发育，勘察这些地层过程中时常发生塌孔、掉块卡钻、冲洗液漏失等复杂情况。本文针对隧道出口段地层设计的定向水平孔，在钻进过程中出现孔壁失稳和冲洗液漏失等问题，通过分析孔内地层特征、漏失情况，提出了适宜的冲洗液体系。随后，进行正交实验快速得到护壁堵漏材料掺量的最优组合，并通过后续的工程实践结果验证并改进，使得冲洗液工艺效果明显。优化配方后的冲洗液，能够大幅度减少孔内事故，有效地促进勘探进度，取得了显著的经济效益和社会效益。

Abstract:

The SichuanTibet Railway is located in the southeast of the QinghaiTibet Plateau. Due to the development of tectonic activities, the rock mass is loose and broken with well developed fractures and confined water; thus, complex situations such as hole collapse, falling stones, stuck drilling, and lost circulation often occur during the exploration of these formations. In view of the problems of hole wall instability and lost circulation during the drilling of the directional horizontal holes designed for the formation along the tunnel exit section, a suitable drilling fluid system for the hole was proposed through analyzing the formation characteristics and leakage in the hole. Then, orthogonal experiments were carried out to quickly obtain the optimal combination of the adding content of the sealing materials. The follow up field application results verified that the improved drilling fluid worked well. Therefore, the drilling fluid with the optimized formulation can greatly reduce the incidents in the holes, effectively promote the exploration progress, and obtain significant economic and social benefits.