油气在烃源岩（泥岩）中的渗流速度与压力梯度呈非线性关系，不服从达西定律，本文用压力因子加以较正。在文中笔者推导出了油、气、水三相流体混流时的分流方程，建立了油、气初次运移的数学模型。和原来相比，减少了压力梯度、泥岩绝对渗透率这两个地质上很难确定的参数，从而大大提高了计算的精度和速度。最后，以大庆油田的一口井为例，说明了这一模型的应用。 The seepage velocity and pressure gradient of oil and gas in source rock (mudstone) are non-linear and do not obey Darcy’s law. In this paper, the authors derive the shunt equations of mixed flow of oil, gas and water three-phase fluid, and establish the mathematical model of the first migration of oil and gas. Compared with the original, the pressure gradient and absolute permeability of mudstone are reduced, which are difficult to be determined. Thus, the accuracy and speed of calculation are greatly improved. Finally, taking a well in Daqing Oilfield as an example, the application of this model is illustrated.