Simulations on Carbon Dioxide Sequestration Into Coal Seams Within an Effective Area: A Case Study in the Eastern Section of Songji Uplift, China

This article selects a coal mining field located in the eastern section of Songji Uplift of China as an example, determines favorable areas in the research area, uses numerical simulation method to predict CO2 sequestrations under an imaged well net group, and simulates sequestration performances for all the wells arrayed in a favorable area finally. The following cognitions are achieved. The specific surface area in the research area is 2.90–7.77 m2/g, with an average value of 5.36 m2/g; the average pore volume is about 0.06 mL/g; and the porosity varies from 5.97% to 15.20%, with an average value of 8.43%. Langmuir volume varies from 16.2 to 26.5 m3/t, and Langmuir pressure is from 1.08 to 1.53 MPa. Permeability varies from 0.036 to 1.342 mD, with an average value of 0.378 mD. The compressive strength of the cap rock varies from 18.59 to 121.49 MPa and is generally lower than 100 MPa. Combined with the values of porosity, permeability, Langmuir pressure, compressive strength of cap rock, and others, five effective areas are obtained by overlapping isograms of those parameters. An effective area is selected to conduct CO2 sequestration and CH4 production, and the results indicate that the cumulative CO2 injection and cumulative CH4 production are 11.5 × 108 and 5.7 × 108 m3, respectively. Sensitivity analyses show that the permeability and injection pressure both have a great impact on CO2 sequestration, whereas the porosity has a relatively low impact.