Preliminary Numerical Modeling of CO₂ Geological Storage in the Huangcaoxia Gas Reservoir in the Eastern Sichuan Basin, China

Abstract

Depleted gas reservoirs are important potential sites for CO 2 geological sequestration due to their proven integrity and safety, wellknown geological characteristics, and existing infrastructures and wells built for natural gas production. The Sichuan Basin has a large number of gas fields in which approximately 5:89 × 10 9 tons of CO 2 can be stored. The Huangcaoxia gas field has the best opportunity in the eastern Sichuan Basin for a pilot project of CO 2 sequestration due to its relatively large storage capacity and the nearly depleted state. A coupled thermal-hydrodynamic model including faults is built based on the geological and hydrogeological conditions in the Huangcaoxia gas field. The results of the numerical simulations show that the downhole temperature is above 80°C at a downhole pressure of 14 MPa under the constraint of temperature drop in the reservoir due to the strong Joule-Thomson effect. The corresponding injection pressure and temperature at the wellhead are 10.5 MPa and 60°C, respectively. The sizes of the pressure and CO 2 plumes after an injection of 10 years are 18 km and 5 km, respectively. The zone affected by temperature change is very small, being about 1-2 km away from the injection well. The injection rate in the injection well Cao 31 averages 6.89 kg/s (21:73 × 10 4 tons/a). For a commercial-scale injection, another four wells (Cao 9, Cao 30, Cao 6, and Cao 22) can be combined with the Cao 31 well for injection, approaching an injection rate of 35 kg/s (1:10 × 10 6 tons/a). Both the pressure and temperature of CO 2 injection decrease with the increasing depleted pressure in the gas reservoir when the latter is below 6 MPa. With the technique of CO 2 -enhanced gas recovery (CO 2 -EGR), the CO 2 injection rate is improved and approximately 1:58 × 10 7 kg of gas can be produced during a studied time period of 10 years.

Field‐scale reactive transport assessment of CO2 storage in the Farnsworth unit through enhanced oil recovery practices

“…7,8 Once CO 2 is injected into these environments, its fate is controlled by various processes, including partial dissolution into the existing pore fluids, transport by advection of the existing pore fluids and a separate immiscible CO 2 gas phase, and chemical reactions with other solutes in the pore fluids and with minerals in the host rock [9][10][11] -. These processes in saline aquifers and petroleum reservoirs have been evaluated in numerous studies, 6,10,[12][13][14][15][16][17][18][19] -and their general characteristics are now well understood. However, individual field sites have their own unique characteristics that can lead to significant variances in the fate of injected CO 2 , thus necessitating ongoing studies of individual field sites like the present study of the Farnsworth unit (FWU).…”