It is well-known that the CO2 dissolved into water will increase the water density, thereby introduce convective flow which again accelerate the CO2 mixing at the CO2-water interface. This process will contribute to CO2 storage by accelerated CO2 dissolution. The project "Understanding of CO2 dissolution in oil by convection-driven mixing and wettability alteration (UNCOVER)" will contribute to further understanding of the physical process of the convectional flow in an OIL reservoir when using CO2 for enhanced oil recovery (EOR). The project includes a series of laboratory experiments where CO2 will mix with both oil (or residual oil) and water in the reservoir rock through convectional flow. One important effect to be included in the experiments are the rock wettability alteration by CO2 which is occurring along with the convectional flow. The project has developed a large 2D transparent circular shaped model of 15 cm in diameter which can be operated at supercritical CO2 conditions (30C, 70 bars). The initial experiments have been performed to test the experimental procedure and data acquisition methods. A number of porous media with various permeabilities have been tested, using both oil and water. These experiments have resulted in new visual observations at these challenging conditions and have been presented in a number of conference papers and posters with well received feedbacks. The experimental data will be used to improve the existing and new mathematical models and simulation tools which are used for large scale prediction of the EOR effect, this work is now completed. The latest functionalities for CO2 dissolution in OPM has been used to capture the CO2 convection. Also, the WP3 for core flooding to collect complementary data from flow in real rock has been completed in 2020 with good results supplying another important data set for description of the convectional flow. Both gravity override and convective mixing during miscible displacement of CO2 and oil has been studied using the simulation framework developed within the Open Porous Media (OPM) initiative.
Our PhD candidate Widuramina had a visiting stay at HWU for the planned laboratory experiments with Professor Mehran Sohrabi December 2019 to January 2021. He is now finishing his PhD thesis and is planning the defence early 2021. He has now got a permanent job at Noah for a CCS related position from January 2021.
The PhD defence was successfully completed 25 June 2021 with the title 'Visual Investigation of CO2 Mixing in Water and Oil at Realistic Reservoir Conditions'.
The primary objective of the proposed project is to establish a set of quality experimental data set to understand and describe the convection-driven dissolution of CO2 in a porous medium containing liv-oil and water. A practical outcome of the project will be quantification of field scale impacts and assessment of reservoir conditions under which oil and gas recovery can be improved while simultaneously increasing the long-term CO2 storage potential.
This set goal has been successfully achieved by the experimental data sets obtained using the unique laboratory set up. The results complement to the earlier observations of similar phenomenon but with either synthetic fluids or much smaller scale. Therefore, the new data set from the UNCOVER project provides both more realistic visual demonstration of the convectional flow processes at relevant subsurface conditions and have been used to improve numerical modelling input and upscaling methodology.
The UNCOVER project is a supporting and collaborating project with the ongoing 3-year research project 'Fundamentals of CO2-Hydrocarbon Interactions for CO2 storage with enhanced recovery (EOR/EGR) in offshore reservoirs: modelling, numerical methods and upscaling (CHI)', funded by CLIMIT for 2016-2019 (CLIMIT project number 255510). Both projects are dedicated to basic research on CO2-EOR/EGR which is one of the most important parts of the CCUS value chain. In order to maximize the CO2 storage and at same time optimise the enhance oil and gas recovery by CO2, it is critical understand the fundamental recovery processes to be able to arrive to the accurate economic value. While the scope of CHI is focusing on the mathematical formulation and numerical modelling of the fundamental processes occurring during CO2-EOR/EGR and storage processes, UNCOVER is designed to support and validate the mathematical formulations by performing lab experiments to uncover the physical processes and to obtain a consistent experimental data set of a wide scope. The main scientific advance of the proposed experimental work is to improve the understanding of the physical phenomena of CO2 behaviour with BOTH oil and water present in the porous media, and with the experimental scale to capture multiple effects contributing to EOR/EGR.
In order to obtain a complete data set, we plan to use visual observation for process understanding, combined with core flooding experiments to cover the sufficient scope and scale for the numerical modelling. The acquired data set should support the small-scale phenomenological study and the field scale simulation with realistic reservoir data.
Collaboration with the international groups with long experiences and laboratory capabilities is planned to share the experimental experiences and potentially also data.