Investigation of high temperature, high pressure, scaling and dissolution effects for Carbon Capture and Storage at a high CO2 content carbonate gas field offshore Malaysia

Abstract

Malaysia is considering Carbon Capture and Storage (CCS) as a possible way to reduce its greenhouse gas emission footprint. An offshore carbonate reservoir has been identified in which all aspects of CCS are investigated in detail. There, the CO2 is planned to be re-injected into a saline aquifer. However, formation damage in underground formations linked with permeability reduction can significantly impact oil and gas production and could render CCS infeasible. Thus, in order to manage the injection of CO2 from the subsurface side a study was conducted investigating geomechanical aspects, rock fluid interactions as well as production aspects from the gas field. Only very few studies exist that investigate scaling and dissolution effects at elevated pressures and temperatures. Here, results from 3 high pressure high temperature scaling and dissolution core floods for the scheduled to be developed carbonate field are presented in detail. Core floods were performed under temperatures ranging between 121 °C to 136 °C and CaCO3 scaling tendencies between 0.24 and 1.47. The scaling tendency of each brine was adjusted to represent, baseline, assumed worst case scaling as well as worst case dissolution scenarios identified based on fluid and gas samples and prior geochemical modelling. Bicarbonate, Calcium and pH were analysed from samples taken during the core flood. SEM-EDX analysis was done on core flood effluent particles. A calcite dissolution rate of 0.008 mol/m2/sec was calculated for the core flood with the scaling tendency of 0.24. The specific surface area of the calcite was estimated at 0.17 cm2/mol. Overall the results indicate that only minor dissolution can be anticipated during production from the CO2 rich gas field.