Prediction and Detection of Land Surface Deformation Associated with CO2 Injection at the FutureGen 2.0 Carbon Capture and Storage Project Site

Abstract:

The FutureGen 2.0 Project will inject 22 MMT of supercritical CO₂ into the Mt Simon sandstone reservoir utilizing four deep-injection wells and a comprehensive monitoring program, which includes surface deformation monitoring. Analytical and numerical modeling analysis were both performed to predict potential vertical elevation changes based on simulated pressure changes and geomechanical properties for the targeted injection zone. Pressure changes due to continuous CO₂ injection of 1.1 MMT of CO₂/year over 20 years were obtained using the STOMP-CO₂ numerical simulator. Injection zone elastic properties were calculated primarily from wireline geomechanical survey results that were obtained from the initial FutureGen 2.0 stratigraphic borehole. The continuous wireline geomechanical log elastic property results were utilized to estimate model layer thickness and rock compressibility for the various injection zone/model layers and were compared with hydrologic characterization results.  Compressibility estimates obtained both from hydrologically based, in-situ tests, together with limited laboratory core samples provided similarly low compressibility results (1.0510^-7 to 4.9210^-7 psi^-1) to those derived from the geomechanical wireline surveys.  

The predicted surface deformation was then estimated using two parallel modelling approaches. First, an analytical Biot-based, poro-elastic model was used to calculate an equivalent vertical displacement at land surface from the expected pore pressure increase and predicted injection zone model layer rock compressibility. The second method utilized a fully 3-D geomechanical modelling analysis to calculate the expected deformation at the surface using a STOMP-CO₂/ABAQUS® sequentially coupled simulator. The predicted surface uplift after 20-years of continuous injection for both methods indicated a maximum deformation of approximately 20-25 mm, with most of the deformation occurring during the first 2 years. Surface deformation monitoring will be performed using interferometric synthetic aperture radar (InSAR) along with ground-based data from permanent tilt and GPS stations and annual DGPS surveys. These methods have sub-centimeter accuracies and will be able to detect the expected deformation.