深水高温高压井钻井液技术

Drilling Fluid Technology for Deepwater HTHP Well

LS25-1S-1深水高温高压井实钻井深为4 448 m,完钻层位为梅山组,采用六开井身结构,φ212.7 mm井段为目的层段,压力系数预测为1.70~1.84,安全密度窗口窄,需重点关注井控、防漏和水合物生成的预防;同时由于井底温度约为147℃,而出口温度只有17℃,保持钻井液在高密度下的高、低温稳定性、防重晶石沉降、良好流变性和储层保护是该井段技术重点。以LS区块气源为研究对象,通过利用水合物抑制软件Hydra FLASH绘制不同抑制剂浓度下水合物P-T相图,优选出钻进及静止期间水合物抑制配方:(9%~15%)Na Cl+5%KCl+10%KCOOH+(0~45%)乙二醇。选用了抗高温降滤失剂HTFL,其加量为0.8%时体系高温高压滤失量小于10 m L,泥饼质量好。研发了一种新型的封堵剂PFFPA,PF-FPA较FLC2000具有更好的封堵降滤失效果。性能评价结果表明,该体系抗温达170℃,高低温流变性平稳,能抗10%的钙土污染,而且沉降稳定性好,封堵能力强,渗透率恢复值在80%以上,储层保护效果好。在现场应用中,通过Drill Bench软件模拟,将排量降至1 400 L/min,此时ECD为1.94 g/cm3,小于漏失压力当量密度(1.96 g/cm3),ROP为10 m/h,岩屑传输效率仍在85%以上,满足携岩要求。该井顺利完钻,表明该套钻井液技术解决了现场作业难题。

Well LS25-1S-1 is a deep water HTHP well drilled to 4 448 m, completed at the Meishan Formation. A six-interval well profile was adopted during drilling. The predicted pressure coefficient of the Ф 212.7 mm target section was 1.70-1.84. Narrow safe drilling window, blowout, lost circulation and the formation of gas hydrate were all problems that needed to be addressed. Meanwhile, the bottom hole temperature and the wellhead temperature are 147 ℃ and 17 ℃, respectively, requiring the high density drilling fluid to have good high temperature and low temperature stability, good performance in preventing barite settlement, and good rheology. Gas samples from the block LS were used in studying the formation of gas hydrate. HydraFLASH, a computer software, was used to draw the P-T phase diagram of gas hydrates at different concentrations of gas hydrate inhibitors. From the P-T phase diagram, a gas hydrate inhibition formulation used during drilling and non-drilling processes was formulated： （9%-15%） NaCl＋5%KCl＋10% KCOOH＋ （0-45%） MEG. A high temperature filter loss reducer, HTFL was selected to control fluid loss. At a concentration of 0.8% HTFL, the HTHP filter loss of the formulated drilling fluid was less than 10 mL, and quality of the mud cake was satisfactory. PF-FPA, a newly developed plugging agent, was used in the drilling fluid, and it had better plugging performance than another plugging agent FLC2000. In laboratory evaluation, the drilling fluid formulated showed high temperature stability （170 ℃）, stable rheology at both high temperature and low temperature, resistance to 10% calcium bentonite contamination, good settlement stability and plugging performance, and recovery of permeability higher than 80%. In filed application, through simulation with computer software Drill Bench, the flow rate was reduced to 1 400 L/min, and the corresponding ECD was 1.94 g/cm3, lower than the equivalent density of 1.96 g/cm3, at which lost circulation would occur. At ROP of 10 m/h, the efficiency of carrying drill cuttings out of hole was still higher than 85%, satisfying the need for hole cleaning. The success in completing the well indicted that the formulated drilling fluid had solved the problems previously existing in the area.