深水窄密度窗口钻井液技术改进及现场应用

Technology Improvement and Field Application of Deep Water Drilling Fluid for Narrow Drilling Window

与常规井相比,深水、超深水井钻井液安全密度窗口变窄,给钻井液提出了更为严格的技术要求。针对这一问题,研究了低密度处理剂LDA60和水溶性承压封堵剂PF-STRH对钻井液密度、流变性和承压能力的影响,比较了水合物抑制全防和半防方案的优缺点,介绍了PF-STRH和水合物抑制控制技术在南海深水高温高压井LS25-1-S1井和超深水井LS18-1-1井的现场应用。结果表明,LDA60可有效降低钻井液比重,对钻井液流变性的影响较小;PF-STRH提高钻井液承压能力效果较好,3%PF-STRH可使HEM钻井液承压能力提高2倍。从成本和环保角度考虑,深水井作业钻进期间水合物抑制方案推荐采用半防方案。在现场实施承压封堵作业和水合物抑制措施后,钻井液比重降低、承压能力提高、流变性不受影响。PF-STRH和水合物抑制控制技术可用于水基钻井液深水、超深水井窄密度窗口钻探。

Compared with conventional well, deepwater and ultra-deepwater well had narrower safety density window of drilling fluid, which gave stringent technical requirements for drilling fluids. Aiming at this problem, the effects of low density agent LDA60 and water-soluble pressure plugging agent PF-STRH on the density, rheology and pressure beating of drilling fluid were studied, the advantage and disadvantage of full-hydrate scheme and half-hydrate scheme inhibition were compared. Finally, PF-STRH and hydrate control technology were applied on deepwater well LS25-1-$1 with high temperature and pressure and ultra-deep well LS18-1-1 in South China Sea. The results showed that LDA60 could effectively reduce the density and had little effect on the rheology of drilling fluid. The pressure bearing capacity of HEM drilling fluid could be improved by 2 times after adding 3% PF-STRH, indicating good effect. Half-hydrate scheme was recommended during deepwater drilling operation considering the cost and environment. After pressure plugging and hydrate inhibition operation, the density of drilling fluid reduced and pressure bearing improved with no influence on theology. PF-STRH and hydrate control technology could be used in the drilling of deep water and ultra-deep water wells with narrow density window.