The Combination Characteristics of the Biomarkers of Microbial Degradation of Organic Matter in LowEvolution SourceRock

Key words: 
• low evolution /
• source rock /
• combination of biomarkers /
• bacteriummicroorganism degradation /
• the activation energy of hydrocarbon generation

Abstract: Researched the distributing characteristics of biomarkers of lowevolution source rocks in TurpanHami basin, the organic matter has been transformed by microorganism. The result shows: The bacterium  microorganism acting on deposit organic matter relative strength, there is a “quasistepwise” sequence to describe the general order of susceptibility of various biomarker compound classes to biodegradation, that is nalkanes > acyclic isoprenoids> hopanes >steranes> aromatic hydrocarbon, C29ββ/(ββ+αα) and 9MP/ΣMP are sensitive parameters to the reforming of bacteriummicroorganism effect on organic matter. The biomarkerparameters of the same source rock appear: OEP2>OEP1(perhaps OEP1＜1,show even carbon number predominance), hopane C31αβ22S/22(S+R)＞steraneC29αα20S/20(S+R), sterane C29αββ/(αββ+ααα)＞C29αα20S/20(S+R) etc. abnormal combination characteristics of the biomarkers, suggests the source rock had experienced stronger bacterium–microorganism degradation process, and these ratios can be used to scale the extent of biodegradation,
as well as be further served as meaningful basis to judge whether the biogenic hydrocarbon (gas and oil) generated from the source rocks in the area. The characteristic of source rock organic matter would be changed by the reforming of bacterium microorganism in the study area, these changes will enable decreasing the activation energy of hydrocarbon generated, and they are favorable for lowmature gas(oil) generation.