QUANTITATIVE CALCULATION OF HYDROCARBON EXPULSIVE COEFFICIENT OF COAL FORMATION——TAKE WELL KANGGU-4 IN THE EAST OF LINQING DEPRESSION AS AN EXAMPLE

Coal formation is not only an important source rock but also a kind of important reservoir of coal-formed gas.In a definite thermoevolutional degree,the generated gas quantity and methane quantity are also definite.The adsorption quantity and the expulsion quantity are convertible and in a dynamic equilibrium state.The method of calculating compulsive coefficient can be obtained according to this understanding.In this article,a method to calculate the gas-generated quantity was put forward based on the thermal-pressure simulating tests,by which the gas-generated quantities of different microlithotypes in different coal formations in different areas can be determined.At the same time,a way to determine the coal formation absorption quantity is introduced briefly.The curve showing the relations of coal formation methane content and it's metamorphic grade and burial depth developed by Kim was fitted using computer.A series of curves showing the relationship between burial depth and absorption quantity during different evolutional periods are gotten.These can be used to predict gas-generated quantities.All the methods have been used to calculate the gas-generated quantity of Permo-Carboniferous coal formation and absorption coefficient in well Kanggu-4 area in the east of Linqing Depression.The calculated methane quantity matches the simulated methane quantity with the error less than 5%.The calculated hydrocarbon expulsive coefficients are increased with increased maturities,from 77% in the low evolutional period to 99% in the high evolutional period.