Formation Mechanism and Prediction way of the Quaternary Biogenic Methane Gas

Zhao, Fan ¹; Zh, HongJun ¹; Cao, ZhenLin ¹
(1) Research Institute of Petroleum Exploration & Development Northwest, Beijing, China.

Biogenic methane is methane bacteria under anaerobic conditions the substrate consumption of simple nutrition Organic matter generated metabolites, general, because of its shallow layer easily released into the atmosphere, become important components of the greenhouse effect; However, if a suitable accumulation conditions and reasonable use of biogenic methane can be gathered into a clean, efficient energy, the sanhu region Qaidam Basin of methane biogas There are two main ways to generate: Acetic acid fermentation and carbon dioxide reduction, Regardless of which way the major with a special sedimentary environment of the region concerned, in the shallow, multi-carbonaceous shale indicates that the layers appear soluble organic matter is high and the area is part of the sedimentary environment of high salinity inhibited the degradation rate of organic matter, organic matter degradation led to the current performance of the fermentation process is still mainly produced a large number of acetic acid to form acetic acid fermentation bio methane gas, carbon dioxide reduction gas is also a prototype bio-organic matter buried at an early stage in the biochemical effects produced by microorganisms to methane as the main ingredient of natural gas, in the anaerobic environment, microbial populations in a variety of synergies, the variety of complex polymers and macromolecules organic matter gradually being broken down into alcohol, propionic acid, butyric acid and other products; The intermediate alcohols and acids under the action of production hydrogen bacteria are broken down into acetic acid, formic acid, carbon dioxide and hydrogen and other small molecules, finally, under the action of methane bacteria use small molecules of carbon dioxide and hydrogen to produce bio-methane.

Tertiary Pliocene, Altun strong rises in the east basin center moved to the three lake areas, Late Tertiary lake deposition rate is accelerating , Quaternary Pleistocene basin with high rates of deposition of thick dark lake with muddy sediments, lakes, muddy sand with the rapid accumulation of not only provide a thick gas source rocks, but also in the rapid accumulation of organic matter to avoid the shallow surface oxidation, Freshwater, brackish water and brackish water biology, alternating salt water organisms, Bio-gas source rocks of the organic matter percentage, cold climate and high salinity water is an important condition for the formation of biogas.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.