川藏铁路DZ-深02-1钻孔高密度冲洗液的研究与应用

High density drilling fluid research and applicationin Borehole DZShen021 at SichuanTibet Railway

摘要:

川藏铁路林康段DZ深021孔系构造勘察孔，地层非常复杂。钻探施工中出现了涌水、涌砂，掉块、缩径等复杂孔内情况。涌水携带破碎颗粒极容易造成孔内卡钻。同时孔内涌水稀释冲洗液，造成孔内压力失衡，加大了孔内垮塌事故，提高了钻孔的施工难度。通过研究和应用高密度冲洗液，平衡孔内压力，防止泥砂涌入钻具，使内管能顺利到位钻进。通过强抑制性低失水冲洗液的选择与配置，减少了泥岩的垮塌与缩径现象。通过采用加大钻头，增大环空间隙，使孔内岩粉能顺利排出，减低循环泵压，有利于断层泥段孔壁稳定。通过下入花管隔离等方法，分离出部分涌水量，减少了对冲洗液性能的破坏。通过强化钻进参数控制，减少了钻进中对孔壁的扰动，尽可能维持了孔壁稳定。最终钻进至设计孔深，达到了工程勘察的目的。

Abstract:

Borehole DZShen021 at SichuanTibet Railway is a tectonics investigation hole where the stratum is very complex. During drilling, water gushing, sand gushing, falling stones and borehole shrinkage occurred. The high density drilling fluid was researched and used to balance downhole pressure to prevent mud and sand from flowing into the drilling string, so that the inner tube of the core barrel can be landed in place smoothly. Through selection and concoction of the strong inhibitive and low water loss drilling fluid, borehole collapse and shrinkage in mudstone were reduced. The drill bit diameter was also increased, hence the annulus to allow drilling cuttings to be discharged smoothly; thus the circulating pump pressure can be reduced, which was conducive to the stability of the hole wall in the fault gouge section. The screen pipe was used over the broken section to divert some water inflow so as to reduce the damage to drilling fluid performance. By strengthening the control of drilling parameters, disturbance to the borehole wall was reduced and the borehole wall was maintained as stable as possible. Finally, the borehole was drilled to the designed depth, achieving the purpose of engineering investigation.