Accurate Monitoring of an Electrically Energized Casing Source using Fiber Optic Sensing

The Department of Energy’s (DOE’s) Carbon Storage program is focused on ramping up commercial scale carbon capture and geologic storage (CCUS) operations across the US to combat the release of CO2, a potent greenhouse gas responsible for global warming, into the atmosphere. Each one of these commercial scale operations will sequester greater than one metric megaton per year of CO2 in geologic reservoirs, with an initial focus on storage in brine filled aquifers. To ensure safe storage with the injected CO2 behaving as predicted, and that there is not a risk of induced seismicity that develops due to over-pressuring of the reservoir and surrounding strata, the Department of Energy’s (DOE’s) Small Business Innovative Research (SBIR) program recently has funded efforts to develop Novel Sensors or System Components for Subsurface Electromagnetic Monitoring, specifically in applications concerning metallic casings. Old Oil & Gas reservoirs are our best in-place candidates for CO2 sequestration sites; monitoring systems that can exploit the already in-place casing systems are ideal candidates.General statement of how this problem or situation is being addressed.In this proposal we will demonstrate the feasibility of fiber optic, electrical, and electromagnetic sensors which may be deployed to secure carbon storage sites by developing a fiber optic sensor that monitors the casing current. The measurement of the casing current will improve the accuracy of the processing results by providing a direct measurement of the casing source function. By using sensors to map the electrical resistivity of the reservoir along with the improved casing function, the CO2 can be more accurately mapped.What is to be done in Phase IPaulsson, Inc. (PI) is partnering with LBNL to develop a fiber optic sensing capability for monitoring the current distribution along a metallic wellbore casing for the purpose of creating a more accurate source function during electromagnetic geophysical monitoring applications. Currently, source functions are determined by a ‘best guess’ methodology, and although these are educated guesses, they are guesses. LBNL will provide modeling to determine which fiber coatings are best suited for detecting the fields created when current flows through metallic casings. Based on the modeling, PI will build a prototype of the sensor utilizing the coatings that were simulated and test them in a laboratory setting. The testing results will be compared to the modeling results and any discrepancies addressed. The testing will be conducted is a custom designed apparatus that will simulate field-like conditions.Commercial Applications and Other Benefits.The sensor developed in this project will allow for higher resolution subsurface mapping, which will benefit the CO2 Sequestration, Enhanced Geothermal Systems (EGS), Underground Gas Storage (UGS), and Unconventional Oil & Gas Markets. Initially the CO2 sequestration market will be small, but these sensors can also be deployed in the UGS market to help alleviate regulator concerns of another blowout such as the one that occurred in Aliso Canyon, California. Reservoir characterization and integrity monitoring will be key factors for America’s transition to clean energy.