一种海洋水合物地层钻井用新型钻井液

随着全球对天然气水合物勘探与开发的关注越来越多, 水合物地层钻井技术的研究也得到了日益重视.但是, 水合物地层钻井存在井内水合物分解与重新生成从而影响井内安全的严重问题.为了解决这一问题, 针对水合物地层的钻井特点, 结合现有的纳米材料, 通过大量实验优选出一种适合海洋天然气水合物地层钻井用的纳米SiO₂钻井液: 海水+2%纳米SiO₂+3%膨润土+1%Na-CMC+3%SMP-2+1%PVP(K90)+2%KCl, 并对其低温常规性能和水合物生成抑制性能进行了实验评价.实验结果表明, 该钻井液具有适中的密度、良好的低温流变性和泥页岩水化抑制性, 并能够长时间有效抑制近井壁地层中的水合物分解气在钻井液循环系统中重新生成水合物, 有利于保障井内安全和钻井作业的顺利实施. 

A New Drilling Fluid for Drilling in Marine Gas Hydrate Bearing Sediments

With increasing global concern of nature gas hydrate exploration and development, more and more attention has been paid to drilling technology in gas hydrate bearing sediment (GHBS). However, the dissociation and reformation of gas hydrates in borehole will affect the stability of wellbore during drilling. Based on the drilling characteristics in hydrate formation, existing nano-materials, and a large number of experiments, a kind of new nano-SiO₂ drilling fluid for drilling in GHBS is introduced: seawater+2% nano-SiO₂+3% bentonite+1%Na-CMC+3%SMP-2+1%PVP(K90)+2%KCl, subsequently low-temperature traditional performance and hydrate formation inhibition of the drilling fluid were evaluated. Experimental results show that the drilling fluid is featured with optimum density, good low-temperature rheology and shale hydration inhibition, and it can effectively inhibit free gas from hydrate dissociation near borehole reformat hydrate in drilling fluid circulation system for a long time. Therefore, the drilling fluid is beneficial to keep borehole safety and to ensure successful drilling operation while drilling in GHBS.