Performance Evaluation of Meota East CO2 Storage Reservoir

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 discusses the reservoir engineering 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 and the regulatory approval was granted.

A regional mapping study was conducted using existing well penetrations tying into a network of 2D and 3D seismic data and a number of injection well locations were identified followed by a site screening study. Consequently, the most suitable storage site was selected, two appraisal wells were drilled and fully cored including caprocks. 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.

A detailed geological model of the reservoirs 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 compositional 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 then conducted to understand the potential range of the size of the CO2 plume and the pressure response of the reservoir. This work has shown that the likely performance of the geological storage of CO2 can be predicted with good accuracy in the deep saline aquifers of Meota East near our thermal operations.