Research progress of methane microseepage in petroliferous basins and its significance for oil-gas exploration

Great progress has been made in the formation mechanisms of surface characteristics of gas microseepagesince the start of the 21st century, which is significant for oil-gas exploration. The microseepage in petroliferous basins is dominated by methane, which migrates nearly vertically from source rocks or reservoirs toward ground surface. The chemical, physical, and biological variation characteristics produced on the ground surface approximately reflect the oil reservoirs underground. Therefore, the methane microseepage is an objective and important part of the petroleum seepage system and has replaced microseepage as the most effective window for the tracing of underground reservoirs on the ground surface at present. Methane microseepage can be directly monitored on ground surface and in water and atmosphere, and the component concentrations and isotopic composition of methane-bearing hydrocarbon gases serve as the first-hand important data for the assessment of underground oil and gas. The data indirectly monitored mainly source from microorganisms, vegetation, minerals, radioactivity, and magnetism on the ground surface. Similar to the geochemical exploration data directly obtained, these abnormal data canbe distinguished from the background values of the ground surface far away from the oil reservoirs, and the distribution areas of the anomalies will become important targets of favorable exploration areas. It will play an increasingly important role in the future integrated oil and gas explorationto gain in-depth understanding of methane microseepage mechanisms, avoid single monitoring method and one-sided understanding, transform ideas to adoptsurface integrated monitoring methods, and establish new mathematical analysis systems.