Shusheng Gao, Liyou Ye, Huaxun Liu, Jianzhong Zhang, Wenqing Zhu, Weiguo An
Research Institute of Petroleum Exploration and Development, Beijing, 100083, China.
University of Chinese Academy of Sciences, Beijing, 101408, China.
Heliyon. 2024 Dec 17;11(1):e41306. doi: 10.1016/j.heliyon.2024.e41306. eCollection 2025 Jan 15.
Tight sandstone gas reservoirs are characterized by high water saturation, significant seepage resistance, low single-well productivity, rapid decline, and low gas recovery. Enhancing the recovery rate of tight sandstone gas reservoirs is a complex engineering challenge that necessitates thorough, refined, and systematic research into its fundamental theories. This study employs a comprehensive approach integrating mercury injection, nuclear magnetic resonance, micro-model visualization, and simulation experiments of displacement and inter-layer seepage flow, alongside foundational seepage theories, to systematically explore the characteristics of tight sandstone gas reservoirs, seepage patterns, and methods for improving gas recovery. Our findings reveal: (1) Detailed characterization of the microscopic pore characteristics in tight sandstone reservoirs helps disclose the status and mechanisms of gas-water occurrence and the principal mechanisms of water production under gas-water co-sealing conditions, such as gas expansion, energy of water-sealed gas, movable water volume, and displacement pressure gradient; (2) Testing single-phase and gas-water two-phase seepage characteristics under bound water saturation identifies permeability and water saturation as critical parameters influencing gas seepage characteristics; (3) Inter-layer gas-water interaction flow experiments demonstrate the interference in multi-layer commingled production and introduce the concept of an interference index, a predictive model for well productivity and dynamic performance in the Sulige tight sandstone gas reservoir; (4) A model correlating reservoir recovery rates with drive indices has been developed, highlighting that increasing production pressure differential and reducing seepage resistance are the primary strategies for enhancing recovery rates in tight sandstone gas reservoirs, supplemented by six technological countermeasures including water-blocking, water control, and densifying well networks. The research outcomes provide effective guidance for practical measures to enhance recovery in tight sandstone gas reservoirs.
致密砂岩气藏具有含水饱和度高、渗流阻力大、单井产能低、产量递减快、气藏采收率低等特点。提高致密砂岩气藏采收率是一项复杂的工程难题，需要对其基础理论进行深入、精细和系统的研究。本研究采用综合方法，将压汞、核磁共振、微观模型可视化以及驱替和层间渗流模拟实验与基础渗流理论相结合，系统地探索致密砂岩气藏的特征、渗流规律以及提高气藏采收率的方法。研究结果表明：（1）详细表征致密砂岩储层微观孔隙特征有助于揭示气水赋存状态和机理以及气水共封条件下产水的主要机理，如气体膨胀、封存气能量、可动水量和驱替压力梯度；（2）在束缚水饱和度下测试单相和气水两相渗流特征，确定渗透率和含水饱和度是影响气体渗流特征的关键参数；（3）层间气水相互作用流动实验证明了多层合采中的干扰，并引入了干扰指数的概念，建立了苏里格致密砂岩气藏单井产能和动态性能的预测模型；（4）建立了气藏采收率与驱动指数的关联模型，强调提高生产压差和降低渗流阻力是提高致密砂岩气藏采收率的主要策略，并辅以堵水、控水和加密井网等六项技术对策。研究成果为致密砂岩气藏提高采收率的实际措施提供了有效指导。
