Characteristics Of Gas Source Kitchen And Gas Generation Potential Assessment Of Dispersed Liquid Hydrocarbon Outside The Source Rock Of Cambrian In Sichuan Basin

Dispersed liquid hydrocarbons outside source rock have attracted extensive attention from scholars at home and abroad as an important source of natural gas in the high-overmaturation marine system.Previous studies have shown that the dispersed soluble organic matter cracking into gas outside the source has a certain contribution to gas pool formation.The contribution of the source of dispersed liquid hydrocarbon cracked gas from outside sources cannot be ignored.Taking the Cambrian in the Sichuan Basin as the target layer,taking into account the large amount of water in the outsourced dispersed area,and the paleo-reservoir area with no water or low water content,thermal simulation experiments with different crude oil and different water contents were carried out with different water addition rates.Represents the source of dispersed liquid hydrocarbons and paleo-oil reservoirs of liquid hydrocarbons.(1)Fourier infrared spectroscopy analysis of pyrobitumen obtained by the thermal simulation experiments determines three characteristic absorption peaks and two infrared parameter indexes for different types of pyrobitumen.Combining with the results of the gas yield in the gold-tube pyrolysis experiments,it can be known that water participates in the cracking of liquid hydrocarbons(or oils)into gas.It not only provides hydrogen and oxygen sources for gas production,but also provides more fatty chains and oxygen-containing groups for crude oil cracking intermediates(residual solids).And the presence of water inhibits the progress of the secondary cracking of the crude oil.(2)According to the characteristics of fat parameters and oxygen parameters of pyrobitumen produced by thermal simulation,it can be seen that the content of fat-containing hydrogen and oxygen in the pyrobitumen produced by thermal cracking of dispersed liquid hydrocarbons are higher than that of paleo-oil reservoirs.Based on this,combined with the TOC values of reservoir rock samples,an identification chart based on TOC value to identify pyrobitumen derived from the source-derived dispersed liquid hydrocarbons and paleo-oil reservoirs is established.With TOC=0.6% as the limit,TOC<0.6% is regarded as source-derived dispersed liquid hydrocarbons,and TOC?0.6% as paleo-oil reservoir.(3)Using the improved ?logR method to predict the TOC content of the target horizon,and combining the experimental data(including hydrocarbon gas yield,dead carbon yield,and hydrocarbon conversion rate,etc.)of the obtained oil sample in the working zone to calibrate the kinetic parameters of oil gas formation,and finally using the dead carbon inversion evaluation method to determine the thermal cracking gas content of the source-extracted liquid hydrocarbons in the target layer.In the Cambrian in the Sichuan Basin,the total amount of out-of-source dispersed liquid hydrocarbons in the target area is 0.98 trillion square meters,and the total gas generation in paleo-oil reservoirs is 0.47 trillion square meters.