Extraction of Dissolved Methane in Brines by CO_2 Injection: Implication for CO_2 Sequestration

摘要

The solubility of carbon dioxide (CO_2) in underground saline formations is considered to offer significant long-term storage capability to effectively sequester large amounts of anthropogenic CO_2. Unlike enhanced oil recovery (EOR), geosequestration relies on longer time scales and involves significantly greater volumes of CO_2. Many geosequestration studies assume that the initial brine state is one containing no dissolved hydrocarbons and, therefore, apply simplistic two-component solubility models starting from a zero dissolved-gas state. Many brine formations near hydrocarbons, however, tend to be close to saturation by methane (CH_4). The introduction of excess CO_2 in such systems results in an extraction of the CH_4 into the CO_2-rich phase, which, in turn, has implications for monitoring of any sequestration project and offers the possibly additional CH_4 mobilization and recovery.