水驱断块油藏CO_(2)气顶边水双向驱油封存机理及应用

Mechanisms of CO_(2) gas cap and edge water bidirectional flooding and sequestration in water flooded fault-block reservoir and application

复杂断块油藏水驱后会形成高部位剩余“阁楼油”及井间剩余油,为此建立了人工CO_(2)气顶与人工边水组合的双向驱技术,以实现该类油藏的剩余油动用及CO_(2)封存。首先,建立了模拟水驱“阁楼油”及双向驱过程的物理模型及方法,开展了CO_(2)驱及不同渗透率条件下双向驱对比实验,明确了双向驱提高采收率及碳封存潜力。然后,基于拟合数值模型,对CO_(2)和N2双向驱开展了不同油藏及注入参数的数模研究,分别揭示了双向驱驱油及封存的主要机理,对比了2种气体双向驱的差异。结果表明:双向驱的焖井过程是气顶形成及“阁楼油”置换的必要过程;高含水油藏双向驱可提高采收率20%以上,相比气驱提高8百分点以上,而封存率相比气驱提高15百分点以上;双向驱主要驱油机理为控制油气界面运移,重力分异,气顶膨胀及抽提原油组分,而主要封存机理为控制油气界面运移,重力分异及增压促溶。经矿场试验取得良好效果,研究为水驱断块油藏有效提采提压提供技术手段及参考。

After water flooding in complex fault-block reservoir,"attic oil"and interwell residual oil accumulate in the high position.The proposed artificial CO_(2)gas cap and artificial edge water bidirectional flooding is expected to achieve oil development and CO_(2)sequestration performance.Firstly,the physical model and method are established to simulate"attic oil"and bidirectional flooding process,and a comparative experiment of CO_(2)flooding and bidirectional flooding with different permeability is carried out to identify the enhanced oil recovery and carbon sequestration potential.Then,based on the fitting numerical model,the numerical simulation of different reservoir and injection parameters for CO_(2)and N2 bidirectional flooding is carried out to reveal the main mechanisms of bidirectional flooding for displacement and sequestration,and the differences of two gas bidirectional flooding are compared.The results show that the soaking period of bidirectional flooding is the crucial process for gas cap formation and"attic oil"displacement.In high water cut reservoirs,bidirectional flooding can increase recovery by more than 20%,more than 8%compared with gas flooding,and increase sequestration efficiency by more than 15%compared with gas flooding.The dominant displacement mechanisms of bidirectional flooding are oil and gas interface migration control,gravity differentiation,gas cap expansion and extraction of crude oil components,while the main sequestration mechanisms are oil and gas interface migration control,gravity differentiation and pressure increase and CO_(2)solubilizing.The good effect of oil displacement and CO_(2)sequestration was obtained through pilot test.The study provides technical means and reference for enhancing oil recovery and formation pressure effectively for water flooded fault-block reservoir.