CO2 sequestration using carbonated water injection in depleted naturally fractured reservoirs: A simulation study

Abstract

In this work, the focus is given to the study of sequestration potential and recovery improvement in depleted NFRs using CWI. Initially a number of CWI experiments on reservoir cores with different wettabilities were modeled to verify physical aspect of the suggested simulation approach. Afterward, a modeling procedure was suggested to make an insight into the engineering parts of this process. In summary, it defined a 3 × 3×3[m3] reservoir rock matrix (a single matrix block, SMB) surrounded by carbonated water in fractures. The numerical aspects of the model were verified by a mesh independent study, in addition. The effects of several key parameters such as anisotropy, permeability, CO2 fraction in water, wettability alteration and block height were studied and compared for matrix blocks with different wettabilities. These effects were studied by incremental oil recovery and the amount of trapped CO2 in the matrix block. As indicated in this study, by implementing CWI, 10.6% incremental oil recovery can be achieved for a water-wet sample and 4.7% for an oil-wet sample during a period of 10 years. Moreover, about 3000[mol] CO2 were trapped in oil and water of the matrix after 10 years and this was increased to more than 8000[mol] after 100 years for the water-wet matrix block with a volume of 27[m3]. During the same period, by increasing the CO2 concentration from 1% to 2% in CW, oil recovery factor increased by 8.4% in water-wet sample. Subsequently, the amount of trapped CO2 grew from 850 to 3000[mol] in 10 years.