The development of a performance assessment methodology for CO2 storage sites using dynamic pressure and surface deformation data

Abstract

A basic requirement for safe geological storage of CO2 is the ability and integrity of the storage complex to contain the CO2. However, the storage formation and the caprock may contain fractures and/or faults that could provide a permeable conduit for CO2 migration out of the prime storage formation. Furthermore, CO2 injection may induce or reactivate fracture networks and faults providing a pathway for CO2 leakage. Recent experience from large scale industrial CO2 storage projects have shown that the geomechanical response of structural features to CO2 injection is a critical parameter controlling the injection performance. The monitoring of the geomechanical response using InSAR surface deformation, injection pressure data and seismic data have provided valuable insight into CO2 injection and storage performance. There is, however, a need for greater integration between monitored data and numerical modelling techniques used to assess performance in order to establish the conformity of the actual behaviour of the injected CO2 with the modelled behaviour. Research presented in this thesis developed an integrated performance assessment methodology for CO2 storage sites, which incorporates satellite (InSAR) monitoring data, time-lapse seismic monitoring data, bottom hole pressure (BHP) data, inverse modelling, and coupled flow-geomechanical simulations using the ensemble Kalman filter (EnKF). The developed methodology has been applied to the In Salah CO2 storage field dataset in order to demonstrate its application and usefulness for the performance assessment of CO2 storage sites. First, an inversion scheme using Weiner filters based on a numerical geomechanical model was developed and used to invert InSAR surface deformation for reservoir pressure change. A forward coupled flow-geomechanical modelling study in conjunction with an InSAR and time-lapse seismic analysis was then performed. This lead to an improved understanding of the flow and pressure behaviour at one of the injection wells. Finally, an integrated approach combining inverse and forward modelling using the EnKF was developed and applied. The EnKF tool developed provides a framework for the updating of flow and geomechanical model parameters through the joint assimilation of bottom hole pressure and InSAR data.