Direct gas thickening is a conventional mobility control method to improve volumetric sweep efficiency for miscible gas injection (MGI) projects. However, the viability of this approach with technically feasible thickeners has not been verified at the field-scale due to a combination of high costs and/or environmental issues. One approach to make this technique economically more attractive is the implementation of an alternating injection scheme (similar to water-alternating-gas (WAG)) that would require less of the thickened gas compared with a continuous injection scheme. In this study, the effectiveness of this approach where a miscible alternating injection of thickened associated gas (TAG) or thickened CO₂ (TCO₂) with unthickened AG is explored in both nonfractured and fractured composite carbonate cores. Twelve core-flooding experiments were conducted using different injection schemes (i.e., continuous unthickened, continuous thickened, and alternating thickened–unthickened). These tests demonstrate that overall the experimental results indicate that the alternating injection of TAG or TCO₂ with unthickened AG mixture as an enhanced recovery technique may produce results similar to those with continuous thickened gas injection. This reduces the consumption of thickening agents noticeably resulting in reduced operational costs and improved economic viability for this method.

中文翻译：

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交替进行增稠和不增稠天然气驱以提高采油率的新方法

直接气体增稠是一种常规的迁移率控制方法，可提高混溶气体注入（MGI）项目的体积吹扫效率。然而，由于高成本和/或环境问题的结合，这种方法在技术上可行的增稠剂的可行性尚未在现场进行验证。使该技术在经济上更具吸引力的一种方法是实施交替注入方案（类似于水交替气体（WAG）），与连续注入方案相比，该注入方案所需的增稠气体更少。在这项研究中，这种方法在交替注入稠密伴生气（TAG）或稠密CO ₂（TCO ₂）在未破裂和破裂的复合碳酸盐岩心中都研究了未增稠的AG。使用不同的注入方案（即连续未增稠，连续增稠和交替增稠-未增稠）进行了十二个岩心驱油实验。这些测试表明，总体而言，实验结果表明，与未增稠的AG混合物交替注入TAG或TCO ₂作为增强的回收技术，可能会产生与连续增稠的气体注入相似的结果。这显着减少了增稠剂的消耗，从而降低了运营成本，并提高了该方法的经济可行性。