Use of Fiber Optic Distributed Temperature Sensing to Detect Injection Well Leakage for Geologic Carbon Sequestration

The protection of Underground Sources of Drinking Water (USDWs) is of primary concern for the safe and permanent sequestration of CO2 within geologic formations. A method is required to improve current capabilities for identifying potential wellbore leakage pathways for Carbon Capture and Sequestration (CCS). All injection wells and offset wellbores within the identified AoR should be tested to verify against casing, cement, cement-casing, and/or cement-formation bond leaks prior to the commencement and routinely during CO2 injection operations. GeoMechanics Technologies proposes the use of Fiber Optic Distributed Temperature Sensing (FODTS) technology to detect such leakage in existing wellbores. This technique will lead to better identification and quantification of leakage characteristics (such as location, possible leak flux, and dimensions of leakage pathway), which will greatly assist mitigation measures if leaks do occur. The technical objectives of this project are to further develop and demonstrate a combined monitoring and analysis system to detect CO2 leakage and migration through weak points in casing or between casing and cement or casing and formation at offset wells. GeoMechanics Technologies plans to perform a comprehensive review on CO2 plume migration modeling in the subsurface for CO2 field-scale experiments. Special focus shall be on the latest advancements on relative permeability and capillary pressure information available for modeling multi-component systems consisting of CO2, water, and salt in porous media. Numerical modeling techniques will be applied to simulate temperature changes and heat transfer through casing and cement to determine temperature of the supercritical CO2 at the injection depth. Identifying the temperature of the downhole flowing fluid will provide more accurate input for reservoir numerical modeling to determine if a leak within the casing and/or cement-casing bond of an offset well can be detected by the FODTS system. Sensitivity to rates and volumes will be investigated and documented, taking into account variability and uncertainty in model parameters (lithology properties, cement quality, thermal properties). All critical parameters will be identified and summarized in a final report. Key Words: Fiber optic, temperature sensing, FODTS, well integrity, wellbore leak