关键词: 超压体系, 压力系数, 地温梯度, 伸展盆地, 前陆盆地, 油气聚集

Abstract: With the deepening of petroleum exploration and drilling,the overpressures are revealed in China's hydrocarbon-bearing basins and so far 29 overpressure provinces are found.The provinces have close ties with the petroleum concept.The overpressure systems are generally source rocks and sometimes also caprocks acting as pressure confining bed for the underlying petroleum and gas accumulation.The overpressure,which is the motive power for hydrocarbon migration,compels the fluids pass through various fractured faults or transporting strata and migrates from high potential zone to low potential zone and then accumulate.The hard overpressure reservoir(pressure coefficient >2)is difficult to form,except the pressure coefficient in the adjoining mudstone(source rock)is bigger than that in the reservoir.Under some special conditions,the hard overpressure reservoir may also form.Therefore the first thing is to get a clear understanding about the origin and distribution of overpressures,especially the zones with abnormal pressure and temperature.Because both horizontally and vertically these abnormal zones are the main leak zones for subsurface fluid and favorable accumulation zones of hydrocarbon,as well as the target zones for drilling.

Key words: overpressure system, pressure coefficient, temperature gradient, extensional basin, foreland basin, hydrocarbon accumulation