Two dedicated field experiments have been carried out at the Heletz, Israel pilot CO₂ injection site. The objective has been to quantify the CO₂ residual trapping in-situ, based on two distinctly different methods. Both experiments are based on the principle of a combination of hydraulic, thermal and/or tracer tests before and after creating the residually trapped zone of CO₂ and using the difference in the responses of these tests to estimate the in-situ residual trapping.

In Residual Trapping Experiment I (RTE I), carried out in autumn 2016, the main characterization test before and after the creation of the residually trapped zone were hydraulic withdrawal tests. In this experiment, the residually trapped zone was also created by fluid withdrawal, by first injecting CO₂, then withdrawing fluids until CO₂ was at residual saturation. The second experiment, Residual Trapping Experiment II (RTE II), was carried out autumn 2017. In this experiment, the residually trapped CO₂ zone was created by CO₂ injection, followed by the injection of CO₂-saturated water, to push away the mobile CO₂ and leave the residually trapped CO₂ behind. In this test, the main reference test carried out before and after creating the residually trapped zone was injection and recovery of gas partitioning tracer Krypton. This paper presents the experimental procedures and results of these experiments. A hydraulic withdrawal test as a characterization method was robust and gave a clear signal. Given the difficulties in injecting water optimally saturated with CO₂, in order not to dissolve the residually trapped CO₂ or to create situations with excess mobile gas, withdrawal test may also be a generally preferable hydraulic testing method, in comparison to injection. The limitation of any hydraulic test is that it only gives an averaged value over the test section. At Heletz additional information about CO₂ distribution was obtained based on thermal measurements and by monitoring the pressure difference between the two sensors in the bolehole. The latter could be used to estimate the amount of mobile CO₂ in the well test section.

Tracer experiments with gas partitioning tracers can in principle give more detailed information of CO₂ residual distribution in the reservoir than hydraulic tests can, but are also far more complicated to carry out, involving sophisticated and sensitive equipment. In the Heletz case the optimal injection of CO₂-saturated water turned out to be difficult to achieve. Creating the zone of residual saturation by means of fluid withdrawal rather than by injecting CO₂-saturated water seemed a more robust approach. Monitoring the gas contents in the test interval gave good guidance on the state of the system. Model interpretations of the two experiments to obtain values for CO2 residual saturation are presented in companion papers in this same Special Edition.

在以色列Heletz的CO ₂试点注入场已进行了两个专门的现场实验。目的是基于两种截然不同的方法对原位捕获CO ₂残留进行量化。这两个实验均基于在创建CO ₂的残留捕集区之前和之后进行水力，热和/或示踪剂测试的组合原理，并利用这些测试的响应差异来估计原位残留捕集。

在2016年秋季进行的残留捕集实验I（RTE I）中，在创建残留捕集区之前和之后的主要表征测试是水力撤除测试。在该实验中，通过首先抽出CO ₂，然后抽出流体直到CO ₂达到残余饱和度，也通过抽出流体来产生残留的捕获带。第二个实验中，残余陷印实验II（RTE II），进行了2017年秋季在该实验中，残余捕集CO ₂区是由CO创建₂注射，接着CO的注射₂ -饱和水，推开移动的CO ₂并留下残留的CO ₂背后。在该测试中，在创建残留捕获区之前和之后进行的主要参考测试是注入和回收气体分配示踪剂K。本文介绍了实验步骤和这些实验的结果。液压退出试验作为一种表征方法是可靠的，并给出了清晰的信号。鉴于注入最佳饱和CO _2的水有困难，为了不溶解残留的CO ₂或造成流动气体过多，抽水试验与注入相比，通常也是优选的水力试验方法。任何液压测试的局限性在于，它仅给出测试部分的平均值。在Heletz，有关CO _2的其他信息分布是基于热测量并通过监测井眼中两个传感器之间的压力差而获得的。后者可用于估算试井段中的移动CO ₂量。

使用气体分配示踪剂进行的示踪剂实验原则上可以比水力测试提供更详细的CO ₂残留分布信息，但是操作复杂得多，涉及复杂而敏感的设备。在Heletz的情况下，很难实现CO ₂饱和水的最佳注入。通过抽水而不是注入CO ₂饱和的水来创建残留饱和区似乎是更可靠的方法。监视测试间隔中的气体含量可以为系统状态提供良好的指导。在同一特别版的配套文件中介绍了两个实验的模型解释，以获取CO2残留饱和度的值。