海底天然气水合物地层钻探甲酸盐钻井液实验

Experiment of Formate Drilling Fluid for Drilling in Marine Gas Hydrate Bearing Sediments

在海底含天然气水合物地层钻进时,水合物的分解和进入泥浆循环系统的天然气重新生成水合物是影响钻井安全的主要因素.为获得确保在水合物地层安全钻进的钻井液,利用"天然气水合物模拟实验系统"研究评价:粘土对甲酸盐钻井液低温流变性的影响、甲酸盐无土钻井液的低温流变性和动力学抑制剂PVPK-30、PVPK-90的水合物抑制效果.表明:加入粘土的甲酸盐钻井液在低温条件下粘、切增长较快;甲酸盐无土钻井液在低温条件下,流变参数变化不大;在-4℃和18MPa附近压力的实验条件下,PVPK-90抑制性能优于PVPK-30;加入1%PVPK-90的甲酸盐无土钻井液抑制效果良好.

When drilling in marine gas hydrate bearing sediments, the decomposition of gas hydrate and the entering of the released gas into the mud circulating system and reforming gas hydrate are key factors that affect the safety of drilling operation. In order to develop a drilling fluid that can ensure safe drilling, the authors utilized the natural gas hydrate simulation experimental system, and evaluated the effect of bentonite on the rheologieal property of formate drilling fluid at low temperature, the rheological property of formate drilling fluid without bentonite at low temperature, and the performance of kinetic hydrate inhibitor PVPK-30 and PVPK-90. The experiment indicates that with the addition of bentonite, the viscosity and shearing force of formate drilling fluid increase rapidly at low temperature while the formulation without bentonite has a steady rheological parameter at the same circumstances. At the temperature of -4 ℃ and pressure of 18 MPa, PVPK-90 has better performance than PVPK-30, and an addition of 1% wt of PVPK-90 in formate drilling fluid can effectively inhibit the formation of gas hydrate.