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Modelling and Improvement of Transient Operations in CO2 Injection Wells
Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, Department of Energy and Process Engineering.
2014 (English)MasteroppgaveStudent thesis
Abstract [en]

Transient well operations such as shut-in, leak-off and step-rate tests are well known in the oil and gas industry, and considered to be useful in deducing reservoir and well properties by studying pressure and temperature behavior over time. Although these tests are routinely used in conventional oil and gas wells, little research on their behavior or possible application to CO2 storage operations has been performed. The primary aim of this work has been to study shut-in and step-rate tests in CO2 injection wells. This has been done through collecting and comparing published data and experiences, and by performing simulations. The multiphase flow simulator OLGA was used to build a saline aquifer injection well model, in which shut-in and step-rate tests were simulated. In addition, the OLGA model was used to simulate water alternating CO2 (WAG) injection, which is used in enhanced oil recovery (EOR). The aim of the WAG simulations was to investigate what pressure and temperature responses can be expected in the well during WAG injection. The published data found on shut-in and step-rate tests showed the importance of the well being thermally stable before the tests are commenced, and enough fluid having been injected before test start to mitigate any near well skin effects. The OLGA model was used to successfully history match the bottom hole data from one step rate test, with partial success in matching wellhead data. It was not found possible to match the bottom hole data of a shut-in test performed on the same well, casting doubt on OLGA's ability to simulation injection well shut-ins. In addition to being a first published attempt of WAG simulations with OLGA, the simulation results highlighted the differences in time scales on which pressure and temperature operates in an injection well. While pressure effects were found to stabilize quickly, temperature effects were found to work on a substantially longer time scale. The literature study and simulations have together resulted in a set of recommendations for obtaining most usefull knowledge from shut-in and step-rate tests.

Place, publisher, year, edition, pages
Institutt for energi- og prosessteknikk , 2014. , 119 p.
URN: urn:nbn:no:ntnu:diva-25825Local ID: ntnudaim:12221OAI: diva2:741378
Available from: 2014-08-27 Created: 2014-08-27 Last updated: 2014-08-27Bibliographically approved

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