天然气水合物降压开采中渗透率对低压传递的影响

Influence of permeability on low pressure transmission in gas hydrate depressurization

用降压法开采天然气水合物时,储层渗透率对井中低压的传递有十分重要的影响。在内边界定压,外边界封闭的情况下,建立一维径向数学模型,模拟不同渗透率对井中低压传递的影响。分析表明:当储层的渗透率较高时,储层的渗透性和流体疏导性较好,井中低压可以有效地向储层深部传递;离开采井越近,储层压力下降速率也越快;开采后期,储层压力的最大值接近开采井处的压力。通过数值分析,提出一种增压降压成对压裂作业的方法。通过该方法能够增大储层渗透率,使天然气水合物分解产生的甲烷气体有效的流向开采井。

When the gas hydrate is extracted by the depressurization method, formation permeability plays a significant role on the penetration process of the low-pressure front. In this paper, a one-dimensional radial model is established, with the pressure fixed at the inner boundary and the outer boundary enclosed. The pressure profiles are simulated with the formation permeability being 50 md, 30 md and 10 md. The permeability dependence of the penetration depth of the lowpressure front with respect to the production days is analyzed. When the permeability is higher, the low-pressure front moves faster. With the same production days, the drainage area is larger. This observation leads to the hydraulic fracturing scheme for the enhancement of the efficiency of gas hydrate production. A "push-pull" paired fracturing method is introduced to protect the covering formation from being damaged in the process of the hydraulic fracturing operation.