Origin of Deep Marine Gas and Oil Cracking Gas Potential of Paleozoic Source Rocks in Tarim Basin

Key words: 
• origin of deep marine gas /
• successive gas generation machanism of organic matter /
• change of gas source kitchen /
• oil cracking gas potential

Abstract: The marine strata in China is of old age and in high evolution period, and the potential of gas generated from highovermature source rocks is limited, but the gas exploration of this marine strata in Tarim, Sichuan and Ordos basin has greatly effective with large oil and gas fields constantly discovered. This paper brings up the successive gas generation machanism for the origin of deep marine gas, including three meanings of transformation of gas generation matter, replacement of gas generation time,and change of gas source kitchen. The gas source kitchen of dispersive liquid hydrocarbon inside of source rocks inherits the characteristics of original gas source kitchen, but the gas source kitchen of dispersive & concentrated liquid hydrocarbon outside of source rocks has occurred the spacial change comparing with original gas source kitchen. The above three liquid hydrocarbon can be cracked into gas at highover mature stage, but the latter is embeded flatter and its time of cracking and gas generation is later than the former, which makes for the late gas accumulations. 
This paper creates expulsion oil rate plates of different organic matter abundance through simulation experiments of hydrocarbon generation and expulsion of different organic matter abundance and different lithology source rocks, providing the basis for the reasearch of allocation proportion and quantity of dispersive liquid hydrocarbon inside & outside of source rocks. This paper demonstrates the quantity, distribution and cracking degree of dispersive soluble organic materials of Palaeozoic strata in Tarim basin from the evaluating indicator S1 of hydrocarbon generating potential, heatorigin asphalt and the fluorescence characteristic of reserviors, and makes sure of the reality of successive gas generation of organic matter of Palaeozoic marine source rocks in Tarim basin, and also calculates the cracking gas quantity of dispersive soluble organic matter in middle and lower Cambrian of Tarim basin.The application of successive gas generation mechanism of organic matter can greatly increase the gas exploration potential and hopeness of palaeozoic strata in Tarim basin.