特低渗油藏碳驱油埋存规律三维物理模拟表征

Three-Dimensional Physical Simulation Characterization of Carbon-Driven Oil Storage Patterns in Ultra-Low-Permeability Reservoirs

  • 摘要: 【目的】CO2驱油-埋存是碳捕集利用与埋存(Carbon Capture, Utilization and Storage, CCUS)的重要内容。辽河油田在深层特低渗透油藏S229块开展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,亟需开展特低渗透油藏CO2驱油-埋存生产动态特征及规律研究。【方法】采用三维物理模拟法,其模型制作难度大,但更能反应油藏真实条件,得到实验结果更有指导意义和参考价值。以辽河油田S229试验区现场典型井网为模板,设计制作出人造三维物理模型,基于模型搭建出三维物理模拟实验平台,依据前期研究已初步优选出的注入速度、封窜体系(适合特低渗透油藏的气溶型起泡剂)、注采调控方式(连续注气、异步注采)等,设计出了3组不同封窜手段下的三维平板物理模型实验,最终进行不同封窜手段下的累计产油量与埋存量对比。【结果】实验结果方面,3组实验累计产油量从大到小排序依次为: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);埋存量从大到小排序依次为: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)。发现连续注气累计产油量低,油井见气后气油比迅速上升,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】通过特低渗透油藏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,优选出了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 enhanced oil recovery (EOR)-sequestration is a key component of carbon capture, utilization, and storage (CCUS). Pilot tests of carbon-driven oil recovery and sequestration in the deep, ultra-low permeability S229 block of the Liaohe Oilfield have shown initial success. However, gas migration has occurred in some frontline wells, and the patterns of CO2 miscible drive propagation and well performance characteristics remain unclear. Therefore, urgent research is needed on the production dynamics and patterns of CO2 enhanced oil recovery and storage in ultra-low permeability reservoirs. 【Methods】This study employs a three-dimensional physical simulation method. Although model construction is challenging, it better reflects actual reservoir conditions, yielding more instructive and valuable experimental results. Using a typical well network from the S229 test area in the Liaoning Oilfield as a template, an artificial three-dimensional physical model was designed and constructed. Based on this model, a three-dimensional physical simulation experimental platform was established. Drawing upon preliminary research that had already optimized injection rates, gas-bubble-type foaming agents suitable for ultra-low permeability reservoirs, and injection-production control methods (continuous gas injection, asynchronous injection-production). Three sets of three-dimensional flat-plate physical model experiments were designed under different sealing methods, ultimately comparing cumulative oil production and recoverable reserves under various sealing approaches. 【Results】Experimental cumulative oil production ranked as follows: Asynchronous injection-production transition to foam sealing (2.37×10-4 t) > Continuous gas injection transition to foam sealing (2.2×10-4 t) > Continuous gas injection transition to asynchronous injection-production (2.01×10-4 t) ; Residual oil content ranking: Asynchronous injection-production followed by foam sealing (0.728 g/ml) > Continuous gas injection followed by foam sealing (0.703 g/ml) > Continuous gas injection followed by asynchronous injection-production (0.684 g/ml). Continuous gas injection yields low cumulative oil production. Upon gas detection in oil wells, the gas-oil ratio rapidly increases. Once flow pathways form, ineffective CO2 circulation occurs, severely impacting production in other wells. Asynchronous injection-production transitioning to foam-sealed flow control effectively manages flow and seals, achieving high cumulative oil production and substantial reservoir storage. 【Conclusion】 This study established a three-dimensional physical simulation technology for CO2 flooding and sequestration in ultra-low permeability reservoirs. This technology confirms that asynchronous injection-production effectively controls flow migration, enabling thorough CO2 diffusion within formations. Earlier implementation further delays gas migration, mitigates inter-well interference, and expands CO2 coverage. Gas-soluble foam demonstrates high-efficiency flow control by effectively sealing gas migration pathways, promoting CO2 mobilization in low-permeability zones, significantly enhancing recovery rates and CO2 storage efficiency. The integrated application of flow control and flow sealing techniques can effectively mitigate inter-well interference, improve development outcomes in target blocks, and increase storage capacity.

     

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