Storage of carbon dioxide in geologic reservoirs to reduce greenhouse gas emissions: A life cycle assessment approach

A wide range of industries are investigating methods to reduce their emissions of greenhouse gases, such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Several options have been identified ranging from energy efficiency and reforestation, to capture and storage in oceans, aquifers or underground. Although greenhouse gases are not yet regulated, the power generation and petroleum industries are already considering greenhouse gas capture and storage methods to reduce their emissions to the atmosphere. Preferred options are the ones utilizing CO2 as a product and therefore providing an additional economic benefit to the oil and gas production process. Currently CO2 is widely used for enhanced oil recovery (EOR) projects to extract more oil out of aging reservoirs. Thus, storage of CO2 in active reservoirs does not require technology advances and offers the advantage of reducing greenhouse gas emissions to the atmosphere. Alternatively, depleted reservoirs can be used for the same purpose. Depleted reservoirs offer the advantage of not being tampered with, so once the CO2 is injected in the formation, the volume remaining is constant except if seepage occurs.; The present research conducted a life cycle assessment to determine the benefits derived from storing CO2 in active reservoirs while enhancing the extraction of oil, and the impacts on the environment over the process lifetime. Active reservoir storage was compared to storage of CO2 in depleted reservoirs. The potential for CO2 storage in a specific active oil reservoir in Texas was demonstrated, as well as the mass balance of greenhouse gas emissions generated from the energy intensive process. Our findings suggest storage capacity of the studied reservoir is huge compared to the available potential of a comparable depleted oil reservoir per unit of production. Process emissions are minimal in comparison to the amount of CO2 stored, and the net amount of CO2 stored through EOR activity is comparable to the quantity of CO2 emitted by cars from the additional oil extracted with. We also found with a simple model that it would take more than 60,000 years for the CO2 to escape assuming complete integrity of the seal.