Estimation of trapped CO₂ is essential for assessing the potential of a site for geological carbon storage. In situ residual trapping can be obtained through Residual Trapping Experiments (RTE). RTE experiments consist in performing characterization tests e.g. hydraulic, thermal and tracer tests before and after creating the residually trapped zone of CO₂ and estimating residual saturation from the differences between the two tests. We introduce a methodology for interpreting residual drawdowns from hydraulic tests, and specifically those performed before and after the creation of the residually trapped zone. Martinez-Landa et al. (2013) demonstrated that the reduction of hydraulic conductivity and the increase in storativity within the trapped CO₂ zone can produce early time differences that are significant. However, our interpretation is hindered by the fact that accurate measurement of early time (a few minutes) response is difficult because the large inertia of the system prevents us from rapidly establishing a controlled constant flow-rate. This is particularly true for the RTE test at Heletz, where water withdrawal during the hydraulic tests had to be performed by air-lift. To resolve this difficulty, we use the proposed methodology which avoids instabilities derived from changes in flow rates. Our approach consists of four steps: (1) filtering of natural trends in heads to ensure good definition of drawdowns; (2) transformation of residual drawdowns into constant pumping test drawdowns, by using the Agarwal or other methods, while accounting for flow rate variations during the pumping phase; (3) computation of smooth log-derivatives to prepare diagnostic plots to aid in conceptual model identification; and (4) quantitative interpretation. The application of our approach to the Heletz RTE experiment gave rise to diagnostic plots consistent with theoretical expectations and a residual CO₂ saturation of about 10%.

估计捕获的 CO ₂对评估地质碳储存地点的潜力至关重要。可以通过残留捕获实验 (RTE) 获得原位残留捕获。RTE 实验包括在创建 CO ₂残留捕集区之前和之后进行表征测试，例如水力、热力和示踪剂测试，并根据两个测试之间的差异估计残余饱和度。我们介绍了一种解释来自水力测试的残余压降的方法，特别是在创建残余圈闭区之前和之后进行的那些。马丁内斯-兰达等人。(2013) 证明了水力传导率的降低和捕获的 CO 内的储存能力的增加₂zone 可以产生显着的早期时间差异。然而，我们的解释受到以下事实的阻碍：准确测量早期（几分钟）响应是困难的，因为系统的大惯性阻止我们快速建立受控的恒定流速。这对于 Heletz 的 RTE 测试尤其如此，在该测试中，水力测试期间的取水必须通过气升进行。为了解决这个困难，我们使用所提出的方法来避免因流速变化而导致的不稳定性。我们的方法包括四个步骤：（1）过滤正面的自然趋势以确保回撤的良好定义；(2) 使用 Agarwal 或其他方法将残余压降转化为恒定抽水试验压降，同时考虑泵送阶段的流量变化；(3) 计算平滑对数导数以准备诊断图以帮助概念模型识别；(4) 定量解释。我们的方法在 Heletz RTE 实验中的应用产生了与理论预期一致的诊断图和残留的 CO₂饱和度约10%。