Shale Gas Generation Mechanism And Model Of Shanxi Formation In Yan'an Area

In this paper,shale gas generation mechanism and model are studied and shale gas generation potential is evaluated by using gold tube sealing thermal simulation experiment.The organic carbon content of shanl is 0.1%~2.8%and Shan2 is 0.2%~14.5%;the macerals of kerogen include humic amorphous(crustaceous),normal vitrinite(vitrinite),inert and filar,no sapropelic,and the calculated type index is between-60.5 and-16.0,which is type III kerogen;the thermal evolution of organic matter is in a high over mature stage;the gas composition is Methane is the main gas,followed by nitrogen and carbon dioxide;the dry coefficient of hydrocarbon gas is high,which is typical dry gas and the type is mainly coal gas.The results of thermal simulation experiments show that with the increase of temperature(the degree of thermal evolution increases),the yield of total pyrolysis gas is increasing gradually;at low temperature,the hydrocarbon gas in the composition of total pyrolysis gas is less than the majority of non hydrocarbon gas,with the increase of pyrolysis temperature,the content of hydrocarbon gas gradually increases and reaches the maximum value,and then the proportion of hydrocarbon gas basically remains the same or not With the increase of temperature,the yield of CO2 is higher than that of H2.For hydrocarbon,with the increase of temperature,the yield of methane first increases and then reaches the peak value and then tends to be stable.With the increase of pyrolysis temperature,the total yield of liquid hydrocarbon of different components increases first and then decreases.At different heating rates,the maximum yield of liquid hydrocarbon is higher than that of H2 Under different degrees of temperature,the peak value of liquid hydrocarbon yield appears earlier than that of high temperature rise rate under low temperature rise rate;RO:0.5%?0.9%in mature stage,mainly producing liquid hydrocarbon and a small amount of wet gas;RO:0.9%?1.9%in high maturity stage,gradually reducing liquid hydrocarbon and generating a large amount of wet gas,which is an important stage for shale gas to start to form in large quantity;RO>1.9%in over mature stage,heavy hydrocarbon gas starts to reduce in large quantity,hydrocarbon After the rapid increase stage,the gas production rate gradually slows down(RO>3.0%)and tends to the maximum value of gas production rate,which is another important stage of shale gas formation.The distribution of activation energy in Shan 1 is 40-46 kcal.mol-1.The distribution of activation energy in the second member of Shanshan formation is from 44 to 54 kcal.mol-1.With the increase of maturity or organic matter abundance,the shale gas potential of Shanxi formation is higher than 2m3/T rock,which has the basic hydrocarbon generating conditions for shale gas enrichment.