近井储层改造对天然气水合物藏降压开采特性影响的数值模拟研究

Numerical simulation of the influence of reservoir stimulation in the near wellbore area on the depressurization production characteristics of natural gas hydrate reservoir

本文基于我国第一轮海域天然气水合物试采地质模型,利用Tough+Hydrate对近井储层改造后的水合物藏进行降压开采模拟研究。探究了多孔骨架渗流通道对气/水输送、压降传播、水合物分解等的影响机制,评估了近井储层改造在不同开采层位和整个开采过程中对产能提高的贡献大小。模拟结果表明:多孔骨架渗流通道内气/水流速高,可以起到导流、防砂的作用;近井储层改造可促进压降传播,加快水合物分解,但骨架通道的增产作用随开采时间增加逐渐减弱;近井储层改造在不同开采层位起到的增产效果不同,三相层中的增产效果最明显,但由于模拟改造范围较小、形成的多孔骨架渗流通道渗透性较低,增产效果不明显,多孔骨架渗流通道高度为50 cm时,2年产气量仅提高11.7%。

In this paper,based on the geological model of the first offshore natural gas hydrate production test of China,the production of nature gas hydrate reservoir after reservoir stimulation in the near wellbore area using depressurization was numerically studied through Tough+Hydrate.The influence mechanism of porous skeleton channel on gas/water transport,pressure drop propagation,hydrate decomposition was investigated,and the contribution of reservoir stimulation in the near wellbore area in different layers and in whole production process to productivity improvement was evaluated.The following simulated results were obtained.First,the gas/water velocity in the porous skeleton channel is high,which is helpful to diversion and sand control.Second,reservoir stimulation in the near wellbore area can promote the pressure drop propagation,and increase the decomposition rate of hydrate.However,the favorable effect of porous skeleton channel gradually decreases with the development of production.Third,the stimulation effect of reservoir stimulation in the near wellbore area in different layers is different,the result of three‑phase layer is the most obvious.In this simulation,due to the small reservoir stimulation range and low permeability of the fracture,the increase in gas production is not obvious,the maximum increase was only 11.7 percent in two years when the height of porous skeleton channel is 50cm.