适合页岩储层的强抑制防塌水基钻井液体系

针对威远地区页岩气井W-X1井长水平段钻进时存在井壁失稳、漏失以及摩阻较大等问题，以多氨基页岩抑制剂HCA-3、复合封堵剂和高效润滑剂RMLUB-1为主要处理剂，研制了一套适合该区块页岩储层的强抑制防塌水基钻井液体系，并对其综合性能进行了评价。结果表明:该钻井液体系具有良好的流变性能、较低的滤失量以及较好的润滑性能，能够满足页岩储层水平井钻井施工对钻井液性能的基本要求；该钻井液体系与其他水基钻井液相比，其能够更好地降低页岩岩样的Zeta电位值，具有更强的抑制能力；该钻井液体系的高温高压PPA滤失量和滤失速率均与油基钻井液相当，并且能够较好地阻缓压力传递，具有较强的封堵能力；此外，该钻井液体系还具有较强的抗污染能力，加入不同的盐、钻屑粉和膨润土后，体系性能变化不大。强抑制防塌水基钻井液体系在威远地区W-X1井三开水平段成功进行了应用，现场各分段钻井液性能稳定，施工过程顺利，未出现井壁失稳、起下钻遇阻等复杂井下情况，井眼稳定，且提高了钻井效率，取得了良好的施工效果。 

A Strongly Inhibitive Anti-Sloughing Water Base Drilling Fluid for Shale Reservoir Drilling

Drilling the long horizontal section of the shale gas well W-X1 in Weiyuan area has encountered downhole problems such as borehole wall instability, mud losses and high friction between the drilling string and the borehole wall. A water base drilling fluid with strong inhibitive capacity and anti-sloughing ability was developed to deal with these problems. The drilling fluid was formulated mainly with a poly amino shale inhibitor HCA-3, a compound plugging agent and a high efficiency lubricant RMLUB-1. Evaluation of the formulated drilling fluid showed that it has good rheology, low filtration rate and good lubricity, and is able to satisfy the basic needs of horizontal drilling of shale gas wells. Compared with other water base drilling fluids, this drilling fluid has better shale inhibitive capacity because it can reduce the Zeta-potential of shales to a much lower level. The PPA filtration rate and API filtration rate are all comparable to those of oil base muds, and this water base drilling fluid is able to prevent pressure transmission across the borehole wall and has high plugging capacity. Furthermore, this drilling fluid has good resistance to contamination; the properties of the drilling fluid do not change a lot when salts, drilled cuttings or bentonite clay is/are added. This drilling fluid has been successfully used in drilling the horizontal section (3rd interval) of the well W-X1 in Weiyuan area. During drilling operation, the properties of the drilling fluid were stable and the operation was done smoothly; no borehole wall instability, drag and resistance during tripping of drill string have ever been encountered, and drilling efficiency was enhanced.