| Theme: | Carbon CUS (T02) |
| Status: | Ended |
| Start Date: | 2019-04-01 |
| End Date: | 2020-12-31 |
Project Overview
Our collaboration will focus on technical issues associated with CO2 injection stream impurity and well integrity impacts associated with CO2 storage projects. Our project on CO2 injection stream impurities will require enhancement of the experimental capacity in GeoREF (Geomechanical Reservoir Experimental Facility) in order to compare the results of geophysical testing in core samples, which were either used, or similar to those used, in the testing undertaken at Tsinghua University. In the longer term, experimental studies at both institutions will be conducted on different classes of materials. The potential for cost savings by delivering less pure CO2 streams to a storage reservoir or for enhanced hydrocarbon recovery (CO2-EOR) are substantial if it can be shown that these impurities do not adversely impact injectivity, conformance or containment for storage operations and critical fluid system properties for CO2-EOR such as minimum miscibility pressure. Our second project will build and calibrate a model based on well modeling approach described at Tsinghua Univesrity to try to duplicate temperature data being collected by fibre-optic distributed temperatures system installed on the CO2 injection well within the Aquistore Project. In the longer term, a validated model of the thermal evolution of a CO2-injector borehole system, thermal stresses and their impact on wellbore integrity can be better assessed.
Outputs
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| Salt Precipitation at an Active CO2 Injection SiteThe Aquistore research is part of SaskPower’s Boundary Dam Integrated Carbon Capture and Storage (CCS) Demonstration project. Carbon dioxide, captured from the flue gas of Unit Three of the Boundary Dam coal-fired power generation station, is injected into a 3400 m deep injection well drilled specifically for CO2 injection. The target aquifer is highly saline (TDS 330 g/L) with injection through four distinct perforation zones extending over about 200 m.
Drying-induced salt precipitation within the target reservoir has been identified as having the potential to cause formation damage in CO2 injection operations. Key parameters in assessing the possible severity are the initial salinity of the formation water and the residual water saturation under drainage. However, a second mechanism for reducing CO2 injectivity was observed at the Aquistore site. Downhole images from the injection well, together with recovered samples reveal that scales of simple salts have formed on the inside of a CO2 injection well. These are developed by evaporation of formation water to near complete dryness in the CO2 dominated wellbore fluids. The timing of the water backflow into the well and the mechanism driving it are uncertain, but the very high salinity of the formation water means that the total volume of scale observed could be due to minor volumes of flow back fluid. Since large salt build-ups are associated with what is very likely small volumes of inflow, the salts precipitated in the wellbore may threaten to CO2 injectivity. This observation suggests that an effort should be made prior to the onset of CO2 injection to reduce the likelihood of such a scale development. This requires a better understanding of the conditions responsible for any flow-back of water into the injection well.
Images and other descriptions of the salt deposits will be presented along with an interpretation of their mechanisms of formation and preservation.
| Publication | 2019-09-25 | Stephen James Talman, Alireza Rangriz Shokri, Richard John Chalaturnyk, "Erik Nickel" |
