This study investigates how to determine the optimal supercritical CO2 foam injection strategies, in terms of total injection rate (or injection pressure, equivalently) and injection foam quality, to place injected foams deep and far into the reservoir. Two different mechanisms that limit field foam propagation, such as “conversion from strong foam to weak foam” and “gravity segregation,” are examined separately, and the results are combined together. The first is performed by using a mechanistic foam model based on bubble population balance, while the second is conducted by an analytical model (called Stone and Jenkins model) and reservoir simulations with a commercial software (CMG-STARS). Note that the gas-phase mobility, required as a key input parameter for gravity segregation simulations, is calibrated by the mechanistic model, which is a significant advance in this study.The results from both mechanisms show in general that foam propagation distance increases with increasing injection pressure or rate (which is often limited by the formation fracturing pressure) and increases with decreasing foam quality down to a certain threshold foam quality below which the distance is not sensitive to foam quality any longer. It is found that the mobilization pressure gradient (i.e., the pressure gradient above which foam films are mobilized to create a population of bubbles) plays a key role to determine the distance. Therefore, the injection of supercritical CO2 foams with lower mobilization pressure gradient should be more favored in field applications. As a step prior to real-world reservoir applications, this study deals with a relatively ideal reservoir (i.e., large homogeneous cylindrical reservoir) focusing on the steady state after foam treatment in the absence of oil.

中文翻译：

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研究超临界 CO2 泡沫传播距离：从强泡沫到弱泡沫的转换与重力分离

本研究调查了如何根据总注入速率（或注入压力，等效地）和注入泡沫质量确定最佳超临界 CO2 泡沫注入策略，以将注入的泡沫深入到储层深处。限制现场泡沫传播的两种不同机制，例如“从强泡沫到弱泡沫的转化”和“重力分离”，分别进行了研究，并将结果结合在一起。第一个是通过使用基于气泡数量平衡的机械泡沫模型进行的，而第二个是通过分析模型（称为 Stone 和 Jenkins 模型）和使用商业软件 (CMG-STARS) 进行的储层模拟进行的。请注意，气相迁移率是重力偏析模拟的关键输入参数，由机械模型校准，这是本研究的重大进展。 两种机制的结果总体上表明，泡沫传播距离随着注入压力或注入速度的增加（通常受地层压裂压力的限制）而增加，并随着泡沫质量下降到某个阈值而增加泡沫质量低于该距离不再对泡沫质量敏感。发现流动压力梯度（即，压力梯度高于该压力梯度，泡沫膜被动员以产生气泡群）对确定距离起关键作用。因此，在现场应用中更倾向于注入流动压力梯度较低的超临界二氧化碳泡沫。作为实际油藏应用之前的一步，本研究涉及一个相对理想的油藏（即，