特低渗油藏CO2驱油-埋存规律三维物理模拟表征

Three-dimensional physical simulation and characterization of CO2 flooding and storage patterns in ultra-low permeability reservoirs

  • 摘要:
    目的 CO2驱油-埋存是碳捕集利用与封存(Carbon Capture, Utilization and Storage, CCUS)的重要内容。辽河油田深层特低渗油藏S229块开展的CO2驱油-埋存先导试验已初见成效,但部分一线油井发生气窜,CO2混相驱波及规律与油井见效特征尚不明确。因此,亟需开展特低渗油藏CO2驱油-埋存生产动态特征及规律研究。
    方法 采用三维物理模拟方法,以辽河油田S229试验区现场典型井网为模板设计制作三维物理模型,基于模型搭建三维物理模拟实验平台,依据前期初步优选出的注入速度、封窜体系(适合特低渗油藏的气溶性起泡剂)、注采调控方式(连续注气、异步注采),设计3组不同封窜手段下的三维平板物理模型实验,对比不同封窜手段下的累计产油量、累计气油比、埋存效率及单位体积孔隙埋存量。
    结果 3组实验累计产油量从大到小依次为:异步注采转泡沫封窜(2.37×10−4 t)、连续注气转泡沫封窜(2.20×10−4 t)、连续注气转异步注采(2.01×10−4 t);单位体积孔隙埋存量从大到小依次为:异步注采转泡沫封窜(0.728 g/mL)、连续注气转泡沫封窜(0.703 g/mL)、连续注气转异步注采(0.684 g/mL)。连续注气累计产油量低,油井见气后累计气油比迅速上升,窜流通道形成后,会导致CO2无效循环,严重影响其余油井产油。异步注采转泡沫封窜开发可以有效控窜封窜,累计产油量高,埋存量大。
    结论 通过特低渗油藏CO2驱油-埋存三维物理模拟技术,明确了异步注采可以有效控窜,气溶性泡沫可以高效封窜,优选得出异步注采转泡沫封窜是高效合理的开发方案。形成了控窜封窜综合调控技术,能够针对性解决CO2驱油-埋存过程中气窜问题,其核心作用是精准抑制CO2沿高渗通道的无效窜流,最终实现驱油效率与埋存效果的双重提升。

     

    Abstract:
    Objective CO2 flooding and storage are integral components of Carbon Capture, Utilization and Storage (CCUS). While pilot tests in Liaohe Oilfield’s deep, ultra-low permeability Reservoir Block S229 have shown initial success, gas channeling in several production wells remains a challenge. Currently, the CO2 miscible flooding sweep patterns and corresponding oil well response characteristics are poorly understood. Consequently, targeted research into the production performance and dynamic laws of CO2 flooding and storage in ultra-low permeability reservoirs is essential.
    Methods A three-dimensional physical simulation method was employed for this research. Based on the typical well pattern of the Liaohe Oilfield S229 test area, a three-dimensional physical model was designed and established, and a corresponding experimental platform was constructed. Using optimized injection rates, a gas-soluble foaming agent for channeling control, and specific injection-production regulation modes (continuous gas injection and asynchronous injection-production), three groups of three-dimensional plate physical model experiments were designed under varying channeling control measures. Cumulative oil production, cumulative gas-oil ratio, storage efficiency, and storage volume were comprehensively compared across the different measures.
    Results Both the cumulative oil production and CO2 storage capacity followed the same descending order across the three groups of experiments: asynchronous injection-production followed by foam blocking (cumulative oil production: 2.37×10−4 t; CO2 storage capacity: 0.728 g/mL), continuous gas injection followed by foam blocking (cumulative oil production: 2.20×10−4 t; CO2 storage capacity: 0.703 g/mL), and continuous gas injection followed by asynchronous injection-production (cumulative oil production: 2.01×10−4 t; CO2 storage capacity: 0.684 g/mL). Continuous gas injection yielded low cumulative oil production, as rapid gas breakthrough triggered a sharp increase in the cumulative gas-oil ratio. The formation of dominant channeling pathways led to ineffective CO2 circulation, severely compromising the productivity of adjacent wells. The development mode of asynchronous injection-production followed by foam blocking could effectively control and block gas channeling, featuring high cumulative oil production and large CO2 storage capacity.
    Conclusion Three-dimensional physical simulation of CO2 flooding and storage in ultra-low permeability reservoirs demonstrates that asynchronous injection-production effectively mitigates gas channeling, while gas-soluble foam provides efficient blocking. Consequently, asynchronous injection-production followed by foam blocking is identified as the most effective and viable development strategy. A comprehensive regulation technology for channeling control has been developed to address gas channeling during CO2 flooding and storage. Its primary function is the precise inhibition of ineffective CO2 cross-flow through high-permeability channels, ultimately enhancing both oil displacement efficiency and CO2 storage capacity.

     

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