The Study on Simulation Experiments of Hydrocarbon Generation and Expulsion of Mud Limestone

Key words: 
• hydrocarbon generation and expulsion /
• simulation experiments /
• pyrolysis oil /
• light hydrocarbon

Abstract: Based on the hydrous pyrolysis simulation experiments of low-mature mud limestone,the characteristics of gas. liquid and solid products, especially the liquid products(including expelled oil. bitumen A and bitumen C) are discussed systematically in this paper.During thermal evolution, the vitrinite reflectance value of kerogen changes from 0.64 % (original sample)to 1. 76 % (360℃ /72 ) and the evolution route of kerogen elements on Van Krevelen's model is in line with the evolution path of type- I kerogen. These reflect that the process of the artificial simulation evolution is similar to that of natural evolution.The characteristics of gas products are that the yield of methane and hydrogen increases,while that of heavy hydrocarbon series(C₂- C₅) and alkene gases Increases at first, then decreases later, The value of δ¹³C of methane becomes lighter at the early stage and heavier at the late stage.The light oil (C₂- C₁₄) plays an important role in the expelled oil. The relative contentsof light oils are from the large to samll then to large in the process of thermal evolution, reflecting the process of hydrocarbon generation and expulsion. The accurate measurement of light oils provides an important parameter for evaluating the quantity of oil generation.The characteristics of geochemistry of bitumen C are different from those of bitumen A of the host rock, the former contains more aromatic hydrocarbons and the most of ratio values of saturated hydrocarbons and aromatic hydrocarbons are smaller than 1, but that of the latter are larger than 1. The results of component analyses and GC analyses on expelled oil, bitumen A and bitumen C as well as the correlation of their characteristics show that the different existing forms of organic matter have their special hydrocarbon expulsion ways and make different contribution to hydrocarbon generation during each evolution stage; the thermal degradation of a large amount of kerogen is in the leading role during mature stage, but in high mature stage,the hydrocarbon generation and expulsion(or release) of inclusion organic matter play an important role because the inclusion organic matter begins to be overally pyrolysed.