利用生烃量减去残烃量的方法研究了煤系源岩排烃门限。数值模拟计算结果表明 ,煤和煤系泥岩的排烃门限随有机质生烃潜力的增强而变早 ,随有机质丰度的升高而变浅 ,但丰度升高到一定程度之后 ,对排烃门限的影响已不明显。随地温梯度的升高 ,排烃门限深度也变浅 ,但成熟度门限升高。煤及煤系泥岩的排气门限一般早于排油门限 ,排气量大于排油量。进入生烃门限的源岩不一定进入排烃门限 ,而进入排烃门限的源岩也不一定进入传统意义上的生烃门限。因而 ,由排烃门限来评价源岩可能比由生烃门限来评价源岩更为客观 The hydrocarbon expulsion threshold of coal-bearing source rocks was studied by using the method of hydrocarbon generation minus hydrocarbon residuals. The numerical simulation results show that the hydrocarbon expulsion threshold of coal and coal series mudstone becomes earlier with the increase of hydrocarbon generating potential of organic matter and becomes shallower with the increase of organic matter abundance. However, after the abundance increases to a certain degree, The impact of the threshold is not obvious. With the geothermal gradient increases, the depth of hydrocarbon expulsion threshold also shallow, but the threshold of maturity increases. Exhaust gas threshold of coal and coal series mudstone generally earlier than the oil discharge threshold, the displacement is greater than the oil displacement. The source rock entering the hydrocarbon generation threshold does not necessarily enter the hydrocarbon expulsion threshold, and the source rock entering the hydrocarbon expulsion threshold does not necessarily enter the traditional hydrocarbon generation threshold. Therefore, it may be more objective to assess the source rocks by the hydrocarbon expulsion threshold than to evaluate the source rocks by the hydrocarbon generation threshold