逆断层中天然气运移特征的物理模拟

逆断层在活动期时易形成断层空腔,该空腔为天然气的穿层运移提供了畅通的通道,天然气在其中运移具涌流特征。如果断层空腔连通地表,天然气则大部分沿其逸出地表,仅有少量的天然气能注入断层两侧的相邻储层中。进入储层的天然气具有明显的选择性,气体首先向物性好、倾角陡和埋藏浅的储层中注入。如果没有其它动力,仅靠天然气自身浮力作用,断层下盘储层不能或很少能有天然气的注入。当断层处于静止期时,断层空腔消亡,天然气穿塑性层段的运移通道是破碎带中的岩石孔隙,天然气在其中的运移遵循达西渗流规律。天然气在断层带中的运移速度随断层充填物颗粒粒度的增加而呈指数关系增大,随断层倾角的增大呈指数关系增大,随断层充填物中泥质含量的增加呈幂函数关系减小。

PHYSICAL EXPERIMENT OF GAS MIGRATION ALONG REVERSE FAULT

Generally, reverse fault would create some fault caves during its active stage, by these caves (channel-ways) gas migrated through the strata quickly, and gas migrated through the caves by the form of surge flow. In case of the caves reaching to the grownd surface, much gas would emit through the caves, and only a little gas inject the neighboring reservoirs in both sides of the fault. The gas which could inject neighboring reservoirs possessed a clear selectivity. First of all, the gas injected reservoir with good permeability, sharp dip-angle and more shallow burial. Without other power except buoyancy, only little gas could inject reservoir in the lower block of fault. When fault was in a static stage, fault caves would be disappeared, the channel-ways which gas migrated through strata were rock pores in crushed zone, and the rule of gas migration followed the Darcys Law. Migration velocity of gas in fault zone increased, exponentially, with grain size of filling matter becoming coarser and fault dip angle becoming larger, and the velocity decreased, exponentially, with the argillaceous content increased in fault filling.