致密砂岩储层微观气水滞留机理及注CO提高采收率研究

Microscopic analysis of gas and water retention mechanisms and CO injection for enhanced gas recovery of tight sandstones： A case study of the Daniudi gas field， Ordos Basin

刘忠群 贾英 梁彬 陈冲 牛骏 郭亚兵 于清艳 李倩

Zhongqun LIU Ying JIA Bin LIANG Chong CHEN Jun NIU Yabing GUO Qingyan YU Qian LI

微观气、水滞留机理不明确严重制约了致密低渗储层中油气采收率的提高。通过新的微观实验方法和数值模拟技术，研究了致密砂岩储层中气、水滞留的微观机制，评估了注入CO提高采收率的可行性。研究表明：① 克服实验压力过低（<0.20 MPa）等实验方法的局限性和实验流程与实际生产条件不匹配的问题，建立全新的微观滞留实验流程和方法，通过微观数值模拟技术，揭示了致密储层中具有盲端-角隅处滞留、绕流形成滞留、卡断形成滞留和“H型”孔道处滞留等4种主要气、水滞留类型。② 注入CO提高致密低渗气藏采收率的机理是CO的注入能够剥离水膜、促进甲烷传质扩散置换以及有效地进行驱替，可以显著提高致密孔喉中的天然气采收率。③ 注入CO能够提高采收率10 % ~ 19 %，这是致密低渗气藏高效开发的新技术途径。

The microscopic gas and water retention mechanisms in tight， low-permeability reservoirs are yet to be clarified， severely limiting the enhancement of oil and gas recovery of these reservoirs. The study delves into the microscopic mechanisms of gas and water retention in tight sandstone reservoirs and evaluates the feasibility of CO injection for enhancing recovery rates via innovative microscopic experimental methods and numerical simulations. Specifically， we establish an entirely new microscopic retention experimental process， while overcoming the limitations of traditional experimental methods， such as ultra-low experimental pressures （less than 0.20 MPa）， and the mismatch between experimental processes and actual production conditions. Combined with the microscopic numerical simulation technique， we identify four primary gas and water retention types in tight sandstone reservoirs， i.e.， blind end-corner retention， bypassing retention， cut-off retention， and “H-shaped” pore retention. On this basis， the mechanisms behind CO injection for enhancing gas recovery of tight， low-permeability reservoirs can be concluded. That is， the CO injection serves to strip water film， facilitate the mass transfer and diffusion replacement of methane， as well as effectively displace gas， significantly increasing natural gas recovery from tight pore throats. The results reveal that CO injection can enhance natural gas recovery rate by 10 % to 19 %， representing an innovative technological approach for the efficient exploitation of tight， low-permeability gas reservoirs.

10.11743/ogg20250118