海洋天然气水合物分解过程中其上部地层稳定性分析

在有覆盖层的海洋天然气水合物开采过程中,由于水合物分解引起上部地层应力重新分布可能导致上部地层蠕变、坍塌、滑坡、套管变形及井口安全等事故。以海洋天然气水合物沉积层具有覆盖地层为例,利用静力学理论建立了采用控压法开采海洋天然气水合物时上部地层物性参数、井筒压力及天然气水合物分解后地层剩余支撑力之间的力学稳定性模型。从理论上讲:当K>1时,上部地层稳定;当K<1时,上部地层失稳。该力学模型可对海洋天然气水合物开采井设计及安全开采具有一定的借鉴意义。

MECHANICAL STABILITY OF STRATA ABOVE A GAS HYDRATE EXPLOITATION WELL

The pressure change caused by marine gas hydrate decomposition during exploitation will result in stress redistribution, sediment creeping and collapse and/or landslides of the upper strata, in addition to casing deformation and wellhead incidents. Taking a well covered marine gas hydrate deposit as an example, we established in this research a mechanical stability model for the upper strata based on the parameters of the upper strata, wellbore pressure and residual formation support force of the gas hydrate deposits when gas hydrate is decomposed, as wellbore pressure change was adopted to exploit gas from the deposits.