ADSORPTION AND DEGRADATION BEHAVIOR OF METHANOL IN PRODUCED WATER IN THE SOILS OF NORTHERN SHAANXI GAS FIELD, CHINA

Injection of methanol as a thermodynamic inhibitor is a common approach in the petroleum industry.Due to the volatility and recovery process of methanol, it could be found in natural waters, sediments, soil, and so on.This study focused on adsorption and degradation behavior of methanol in produced water (PW) at northern Shaanxi oil and gas fields soil, China.Through dynamic tests, the results showed that the pH, gas condensate, salinity of PW and temperature have weak influences on methanol adsorption on the soil.Through the simulated degradation experiments, the chemical oxidation, photo and thermal degradation were found not to be the main mechanism of methanol degradation (MD) in nature.The methanol in some soil could not de degraded completely by Nitrate-reducing bacteria (NRB) in the soil within 60 days unless methanol content was less than 600 mg/L with NRB medium.The Griess detection verified that there were NRB in five soils.Even without the NRB medium, there are great differences in MD of the soils.If the concentration of methanol was more than 1000 mg/L, the MD efficiencies were obviously slowing down, nearly 0. The longer the gas development time of the study region, the stronger the MD ability of the region's soil.