塔河油田TK431井钻井液技术

塔河油田三叠系、石炭系井眼失稳问题一直是该油田勘探与开发的技术难点。TK431井是在该地区实施的一口解决该井段井眼失稳问题的试验井。分析地层坍塌原因后提出，TK431井钻井液密度设计值为1．42g／cm^3，选择抑制封堵固壁型钻井液体系，二开采用PF-PLUS钻井液，三开采用PEM钻井液，四开采用PF-VIS钻井液。选择抑制型钻井液，可提高钻井液滤液的抑制性，减小泥页岩的水化膨胀作用；采用封堵固壁技术，可封固地层微裂隙，提高地层整体强度，形成薄而韧的泥饼，减少滤失量，达到稳定井壁的目的。该井钻井液润滑性能良好；包被抑制性良好，钻屑成形度高、棱角分明；防塌效果好，井径规则，没有明显的大肚子井段；性能稳定、维护处理简单；机械钻速快，辅助时间短，钻井周期较短。现场应用表明，该井实际最高使用钻井液密度为1．37g／cm^3，通过采用高包被、强抑制和综合防塌相结合的方法，有效地稳定了井壁，成功地解决了三开井径扩大问题；存在问题是设计和实际应用费用较高，尤其是三开费用是其它井的2～4倍，全井钻井液费用也是同一区块其它井费用的1．5～2．0倍多。

Drilling fluid technology for Well TK431 in Tahe Oilfieid

The problem of borehole instability in the Triassic system and the Carboniferous system has been kept as a major difficulty in the exploration and development of this oilfield. Well TK431 was a test well drilled in this area trying to solve the problem of borehole instability. By analyzing the causes of formation collapse, it was suggested to design the drilling fluid density at 1. 42 g/cm3, and select the inhibiting plugging drilling fluid system. PF-PLUS drilling fluid was used in the second section, PEM drilling fluid was selected in the third section and PF-VIS drilling fluid was used in the fourth section. By selecting the inhibiting drilling fluid, the inhibition of drilling fluid filtrate could be improved, and the hydration of shale could be minimized; by adopting the plugging and consolidating technology, the micro fractures could be plugged thus improve the integrity of the formation, while thin and firm mud cakes could be formed and minimize the filtrate, so as to stabilize the borehole. The drilling fluid system exhibited good lubricity and cuttings encapsulation, and the cuttings were in good shape; it also had good sloughing control, regular borehole was drilled and no remarkable washout sections; furthermore, it was stable and easy for mainte-nance; ROP was remarkably improved and the drilling period also shortened. Field using showed that the highest drilling fluid density was 1. 37 g/cm3 , and by applying the comprehensive sloughing control measures, the hole was effectively stabilized and the hole enlargement in the third section was successfully solved. However, the drilling cost was relatively high, as the cost for the third section was 2 to 4 times that of other wells, and the overall drilling fluid cost was 1. 5 to 2 times that of other wells in the same block.