10:00 AM - 10:15 AM
[STT36-05] Continuous- spatiotemporal strain measurement for geomechanical modeling using Distributed Fiber Optic Strain Sensing at geologic CO2 storage sites
Keywords:DFOSS, Co2 injection safety, Continuous- spatiotemporal monotoring , geomechanical modeling
Introduction: Geomechanical monitoring could play a critical role in large-scale geological CO2 storage to ensure injection safety, as the injection operation may cause pore pressure build-up and deformation of the reservoir-caprock system. The deformation (strain) may migrate more rapidly (spatially) than the actual pressure change caused by the CO2 plume; imaging geomechanical changes of the target reservoir and investigating the surface deformation have been conducted via numerous studies using geophysical and geodetic observations. However, only a few studies have continuously measured the vertical strain migration from the subsurface to the surface. In addition, rock property information remains a concern in geomechanical modeling. Recent studies suggested deploying a fiber-optic cable behind a well casing as an effective technique for subsurface geomechanical monitoring, offering the opportunity to continuously track the deformation (strain) along the fiber-optic cable. These features of DFOSS could be ideal for application in geological CO2 storage sites for wellbore and caprock integrity monitoring in real-time and as a permanent post-injection tool. In this study, we installed DSS in a shallow well to monitor the deformation water injection field tests and measure the strain profiles to demonstrate the high potential of using Distributed Fiber Optic Strain Sensing DFOSS for caprock and wellbore integrity, leakage monitoring, and geomechanical modeling at geological CO2 storage sites.
Method: DFOSS-based Rayleigh scattering (TW-COTDR) was used to measure the strain profile in three shallow wells during water injection tests. Two different fiber cables were installed behind the casing in the three wells at different distances from the injection well. The combined strain profile, pressure, and lithological heterogeneity analysis were conducted.
Result and Discussion: By combining strain profile, pressure, and lithological heterogeneity analysis, the strain responses under, within, and upper the injection zone have been successfully interpreted, and the delayed strain response that appeared upper the injection zone owing to water leakage resulted from the pressure breakdown. The distributed strain fiber successfully detected the deformation at the mud-sand alternation in high spatial resolution. Our results proved that strain measurements could indicate lithology and rock physical properties, assisting the geomechanical modeling. The strain data could be used to estimate distributions of elastic modulus, permeability, and related properties important to geomechanical modeling.
Method: DFOSS-based Rayleigh scattering (TW-COTDR) was used to measure the strain profile in three shallow wells during water injection tests. Two different fiber cables were installed behind the casing in the three wells at different distances from the injection well. The combined strain profile, pressure, and lithological heterogeneity analysis were conducted.
Result and Discussion: By combining strain profile, pressure, and lithological heterogeneity analysis, the strain responses under, within, and upper the injection zone have been successfully interpreted, and the delayed strain response that appeared upper the injection zone owing to water leakage resulted from the pressure breakdown. The distributed strain fiber successfully detected the deformation at the mud-sand alternation in high spatial resolution. Our results proved that strain measurements could indicate lithology and rock physical properties, assisting the geomechanical modeling. The strain data could be used to estimate distributions of elastic modulus, permeability, and related properties important to geomechanical modeling.