鄂尔多斯盆地延长组石油充注动力的包裹体热动力学模拟

Petroleum Inclusion Thermodynamic Simulation on Oil Charging Pressure of Yanchang Formation in Ordos Basin

基于包裹体热动力学与油气成分模型的PIT软件可利用包裹体均一温度与气液比模拟计算出捕获压力,由于不需要测定单个包裹体的成分而使得模拟过程简单且模拟结果具有一定的可靠性。利用该软件对鄂尔多斯盆地延长组烃源岩层系内裂缝脉体和砂岩储层中油包裹体的捕获压力进行了模拟计算。结果表明,延长组烃源岩与储层中包裹体的捕获压力多为异常高压,其剩余古压力一般大于3 MPa,压力系数多在1.2以上。异常高压不但是延长组长7段烃源岩排烃与石油垂向充注的主要动力,而且可能是驱动低渗透储层中石油侧向运移的重要动力。

PIT is modeling software for the trapping pressure of inclusions from homogenization temperature and vapor liquid ratio,which is based on petroleum inclusion thermodynamic and hydrocarbon compositional model.Its simulation processes are simple and simulation results are reliable to a certain extent.The trapping pressures of oil inclusions existing in fracture veins of source rocks and sandstone reservoirs of Yanchang Formation in Ordos Basin were calculated by means of PIT.The results show that the trapping pressures of oil inclusions are all abnormally high.The excess paleo-pressures are generally greater than 3MPa and the pressure coefficients are more than 1.2.The abnormally high pressure is probably not only the main driving force for hydrocarbon expulsion and vertical oil charge of Chang 7 member source rocks but also the significant driving force for lateral migration of oil in low permeability reservoirs.