Greenhouse Gases (GHG) Emissions from Gas Field Water in Southern Gas Field, Sichuan Basin, China

In order to assess correctly the gases emissions from oil/gas field water and its contributions to the source of greenhouse gases (GHG) at the atmospheric temperature and pressure, a simulation experiment was first developed to study the natural emissions of GHG into the atmosphere in the southern gas field, Sichuan Basin, China. The result showed that methane (CH4) and carbon dioxide (CO2) were the two gases that released from the gas field water. Time and temperature played important roles in GHG emissions, and the higher temperature was found to enhance carbon emissions. Under the lower/intermediate temperature conditions (5 and 15 °C), majority of gases were released from the gas field water during the first 2 h, whereas under the higher temperature conditions (30 °C), the majority of gas released from the gas field water continued for 12 h. By dividing the whole emission duration into six time durations (one time duration was 12 h), we calculated the fluxes of CH4 and CO2. The substantial variation in the gas fluxes reflected that the cumulation of time also played a crucial role in the process of GHG emissions. In the first emission duration (0–12 h) at 30 °C, the maximum fluxes of CH4 and CO2 were 1.47 and 1.87 g/m3·h, respectively. The values were obviously higher than those in other durations, so were the fluxes shift in different durations at 5 and 15 °C. Additionally, we found that the emissions released from the gas field water which came from overpressure formation formed higher carbon emissions.