RMR技术在海域天然气水合物钻探中的适应性分析

Adaptability of RMR for marine gas hydrate drilling

深水表层天然气水合物沉积体埋藏浅、地层软、未固结,泥浆密度窗口窄,使用常规隔水管泥浆循环钻进钻遇水合物分解会引起井周孔隙压力及储层水合物饱和度发生变化,导致水合物储层泥浆密度窗口更窄,引发井壁以及井口失稳等问题,并且时间长、成本高。文章介绍了无隔水管泥浆回收(RMR)技术原理,对该技术在深水表层海域天然气水合物钻探中的适应性进行了分析。结果表明,RMR技术利用双梯度原理,能有效解决目前深水表层钻井窄密度窗口难题;实时监控系统提高遇险机动性,严防硫化氢等气体发生泄漏;能够简化井身结构,缩短建井周期,降低建井成本;同时对海洋零排放,安全环保。

Natural gas hydrate(NGH)sedimentary bodies are shallow,soft and unconsolidated,where the mud window is narrow.It is time-consuming and expensive to drilling NGH with conventional riser drilling;meanwhile,NGH dissociation leads to changes in NGH saturation and wellbore pore pressure,causing the mud window to narrow down and the borehole be instability.This paper introduces the principle of deep water riserless mud recovery drilling(RMR)and analyzes its adaptability in marine NGH drilling.The results indicate that RMR can solve the problem of the narrow mud window.The real-time monitoring system can improve the maneuverability and completely eradicate the hydrothion leakage.It simplifies the wellbore configuration and reduces the well construction cost.It is safe and environment friendly without any discharge into the ocean.