Process Modeling of CO₂ Injection into Natural Gas Reservoirs for Carbon Sequestration and Enhanced Gas Recovery

TLDR

Injection of CO₂ into depleted natural gas reservoirs can sequester carbon while enhancing CH₄ recovery, partially offsetting injection costs. The study aims to assess the feasibility of carbon sequestration with enhanced gas recovery (CSEGR) by examining the physical processes of CO₂ injection into natural gas reservoirs. A TOUGH2‑based reservoir simulator module incorporating water, brine, CO₂, tracer, and CH₄ under nonisothermal conditions was developed and applied to the Rio Vista Gas Field, using CO₂ sourced from flue gas of a 680 MW Antioch power plant. Model results indicate that the reservoir properties and CO₂/CH₄ behavior favor CSEGR, with CO₂ injection enabling additional CH₄ production during and after injection.

Abstract

Injection of CO2 into depleted natural gas reservoirs offers the potential to sequester carbon while simultaneously enhancing CH4 recovery. Enhanced CH4 recovery can partially offset the costs of CO2 injection. With the goal of analyzing the feasibility of carbon sequestration with enhanced gas recovery (CSEGR), we are investigating the physical processes associated with injecting CO2 into natural gas reservoirs. The properties of natural gas reservoirs and CO2 and CH4 appear to favor CSEGR. To simulate the processes of CSEGR, a module for the TOUGH2 reservoir simulator that includes water, brine, CO2, tracer, and CH4 in nonisothermal conditions has been developed. Simulations based on the Rio Vista Gas Field in the Central Valley of California are used to test the feasibility of CSEGR using CO2 separated from flue gas generated by the 680 MW Antioch gas-fired power plant. Model results show that CO2 injection allows additional CH4 to be produced during and after CO2 injection.