| dc.description.abstract | Transient well operations such as shut-in, leak-off and step-rate tests are wellknown in the oil and gas industry, and considered to be useful in deducingreservoir and well properties by studying pressure and temperature behaviorover time. Although these tests are routinely used in conventional oil and gaswells, little research on their behavior or possible application to CO2 storageoperations has been performed. The primary aim of this work has beento study shut-in and step-rate tests in CO2 injection wells. This has beendone through collecting and comparing published data and experiences, andby performing simulations. The multiphase flow simulator OLGA was usedto build a saline aquifer injection well model, in which shut-in and step-ratetests were simulated. In addition, the OLGA model was used to simulate wateralternating CO2 (WAG) injection, which is used in enhanced oil recovery(EOR). The aim of the WAG simulations was to investigate what pressureand temperature responses can be expected in the well during WAG injection.The published data found on shut-in and step-rate tests showed the importanceof the well being thermally stable before the tests are commenced, andenough fluid having been injected before test start to mitigate any near wellskin effects. The OLGA model was used to successfully history match thebottom hole data from one step rate test, with partial success in matchingwellhead data. It was not found possible to match the bottom hole data ofa shut-in test performed on the same well, casting doubt on OLGA's abilityto simulation injection well shut-ins. In addition to being a first publishedattempt of WAG simulations with OLGA, the simulation results highlightedthe differences in time scales on which pressure and temperature operates inan injection well. While pressure effects were found to stabilize quickly, temperature effects were found to work on a substantially longer time scale. Theliterature study and simulations have together resulted in a set of recommendationsfor obtaining most usefull knowledge from shut-in and step-rate tests. | nb_NO |
