致密储层孔隙介质内石油运移的物理模拟试验

Physical simulation experiment of oil migration in porous media of tight reservoir

关键词:  致密储层  石油运移  真实砂岩微观模型  微观孔隙介质

Key words:  tight reservoir  il migration  uthentic sandstone micro-model  icro porous media

摘要:

通过真实砂岩微观模型油驱水试验,结合铸体薄片、微米CT等图像分析,对不同驱替压力条件下致密油运移过程及其影响因素进行研究。结果表明:低驱替压力下石油在孔隙间的运移呈“跳跃式”,单个跳跃性事件表现为石油突破喉道、充填孔隙和发生卡断,跳跃式事件多次重复发生使油水界面不断向前推移;在运移方向上无统一油水界面,其推进速度存在差异,石油优先选择充填连通大孔隙,发育优势运移路径,石油主要呈孤立状和多孔状分布;高驱替压力下优势运移路径发生分叉与合并,石油主要呈网络状分布;石油运移主要受局部毛细管力(与孔隙结构有关)控制,外界驱替压力为石油运移提供必要的动力。

Abstract:

Experiments of oil displacing water in authentic sandstone micro-models were conducted under various injection pressures, aiming to visualize the process of oil migration in tight reservoirs. Factors controlling the oil migration process in tight reservoirs were elucidated in combination with thin sections and micro-CT image analyses. The results suggest that oil migration in the porous media shows an obvious jump pattern at low injection pressure. The jump event occurs with breaking through throat, filling pore body and occurring snap-off. Multiple and repeated jump events result in the movement of the oil-water interface. However, there is no uniform oil-water interface, and the displacing rate of water by oil varies in the direction of migration. Oil preferentially enters into the connected large pores, forming the dominant migration path. As a result, the majority of oil clusters are isolated in single pores or distribute in several connected pores. The divergence and convergence of these migration paths result in these isolated oil clusters converging slowly into continuous phases under high injection pressure, and oil clusters present as the mesh network. The oil migration pattern in the porous media is dominantly controlled by local capillary pressure, which is associated with the pore structure. Meanwhile, the external driving force provides necessary energy supply for oil migration.