CO Storage Capacity Estimation in Tertiary and Depleted Oil Reservoirs

Ding, Shuaiwei (National & Local Joint Engineering Research Center for Carbon Capture and Sequestration Technology, State Key Laboratory for Continental Dynamics, Northwest University) | Liu, Guangwei (CNOOC Research Institute) | Li, Peng (National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields) | Xi, Yi (Exploration and Development Research Institute, Petro-China Changqing Oil Field Company Ltd) | Ma, Jinfeng (National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields)



Oil reservoirs are considered good storage structures for CO2 geological storage. With the right selection of candidate reservoir, injection of CO2 into tertiary and depleted oil reservoirs can result in enhanced oil recovery (EOR) and permanent sequestration of CO2 underground. The selection of candidate reservoirs for future CO2-EOR and storage projects mainly depends on storage potential evaluation. The aim of this work is to estimate the storage potential of CO2 stored in tertiary (CO2-EOR) and depleted oil reservoirs. In tertiary oil reservoirs, a method to estimate the geological CO2 storage capacity (CO2SC) in the reservoir during well open operations (EOR operations), which is a function of reservoir parameters, original geological reserves and oil volume factor is first built. In depleted oil reservoirs, a method to calculate the CO2SC in the reservoir during well shut down operations, which is based on the material balance method is proposed. In both cases, the methodology of storage capacity of CO2 dissolved in remaining oil, formation water and by mineral trapping is presented based on the model established by Ding et al. (2018). At last, Field-scale case study shows that the change rules are all accord with the laws published previously. For the EOR operations, the EOR was 5.11% OOIP and CO2SC was 23.84 Mt at CO2 breakthrough, while 14.76% and 18.19 % OOIP can be achieved at 50% and 100% HCPV injection. Also, the total CO2 sequestration capacity can reach 24.2 and 24.33 Mt, respectively. For the well shut down operations, the total theory storage capacity by dissloved in remaining oil, formation water, mineral matrix and free gas trapping was approximately 21.61 Mt. The proposed method can be used to estimate the CO2 storage capacity qucikly and it is reliable to be promoted in the area of CO2 geological sequestration.