Technical Requirements for Regulatory Application of Meota East CO2 Storage Project

Safe storage of CO2 in deep saline aquifers requires that the injected CO2 is contained within the geological formation and its conformance is predictable. This paper explains the technical analysis conducted in order to be able to submit a 1.1 million tonne/year CO2 Storage Project Application to the Saskatchewan Ministry of Energy and Resources. The application was for safe storage of CO2 in the Basal Cambrian Sandstone and Deadwood Sandstone deep saline aquifers in the Meota East area near Lloydminster. The stored amount is equivalent to Strathcona’s CO2 emissions from its SAGD operations in Saskatchewan and from the capture process itself assuming a 90% capture efficiency. A regional mapping study was conducted using existing well penetrations tying into a network of 2D and 3D seismic data. As well, large scale regional aero-magnetic surveys were referenced for basement structural features and trends. A number of injection well locations were identified and a site screening study conducted. Finally, the most suitable storage site was selected and two appraisal wells were drilled and fully cored including caprocks. A complete suite of well logs including image log and dipole sonic log were acquired, pressurized brine samples were taken, and in-situ pressure and temperature profiles were measured. Diagnostic Fracture Injection Tests (Mini-Fracs), injectivity, pressure fall off and, horizontal and vertical pressure interference tests were conducted by individually isolating each zone. Well tests were used to determine among other things the injectivity, reservoir properties, existence of no flow boundaries and fracture gradients. This additional well data was utilized to improve seismic mapping and provide inputs for pre-stack density inversion. The pre-stack density inversion assisted in refinement of 3D spatial reservoir and caprock variability. A detailed geological model of the reservoirs and caprocks was constructed based on data obtained from the well tests, core data, petrographic analysis, petrophysical analysis as well as 2D and 3D seismic data. Facies and the associated properties were distributed using geostatistical techniques. This model was then upscaled and used to predict the behaviour of the CO2 plume, pressure response and storage capacity with a dynamic reservoir simulator. The uncertainty in the input parameters were estimated through the accuracy of laboratory and field measurements, calculation methodology and literature reported values. A risk analysis was conducted to understand the potential range of the size of the CO2 plume and the pressure response of the reservoir. The insight gained during the risk analysis was also used to inform the Measurement, Monitoring and Verification (MMV) plan. Chemical compatibility between the injected liquid CO2 and in-situ reservoir brine was investigated experimentally under reservoir conditions to assess any potential precipitation and scaling tendency. Geochemical compatibility at reservoir conditions between the injected liquid CO2, reservoir rock and in-situ brine was evaluated both experimentally and numerically to understand the changes that may happen in the reservoir due to CO2/mineral/brine interaction over long time frames. Furthermore, a geomechanical model of the reservoir, overburden and underburden coupled to dynamic reservoir simulation model was constructed to evaluate the caprock integrity, fault reactivation potential and surface heave. Finally, a qualitative CO2 containment risk analysis was conducted using the bow tie analysis methodology to identify the threats and consequences of potential CO2 and/or brine leakage from the storage complex. Preventive and mitigative safeguards were identified for each threat pathway. The bow tie method provided a clear and visual approach to key risks and barriers to CO2/Brine migration out of the storage complex. The results of risk analysis were used as a guide to develop an MMV strategy. As a part of the risk analysis and MMV design an area of study was determined that is a 3D cube around the injection site which will be the subject of monitoring. Necessary baseline measurements were identified and are currently being acquired. The aforementioned analyses have shown that safe and low risk geological storage of CO2 is possible in the deep saline aquifers of Meota East near our thermal operations. Thus, Strathcona Resources used this information to apply to the Ministry of Energy and Resources for a New CO2 Storage Project. The regulatory approval was recently granted.