沾化凹陷渤南洼陷沙四段～孔店组的热史及超压演化

THE RMAL HISTHORY AND OVERPRESSURE EVOLUTION IN SHA 4 MEMBER AND KONGDIAN FORMATION IN BONAN SAG ZHANHUA DEPRESSION

利用EASR%Ro模型,计算了渤南洼陷沙四段～孔店组(Es4-Ek)的古地温和古地温梯度的演变值。古地温的演变与盆地的构造演化关系密切,抬升剥蚀期地层温度下降,沉降期地层温度升高,地史过程中地温梯度的变化呈逐渐降低的趋势。采用盆地模拟技术,恢复且再现了渤南洼陷Es4-Ek地史期的超压演化过程。此过程与该区构造演化和有机质生烃增压作用紧密相关,沉积和剥蚀速率及地层地史期的孔渗性决定了早期超压幅度的高低,而后期构造运动的改造及有机质的生烃作用,决定了现今压力系数的大小。压力在漫长的发展演化过程中,经历了超压积累～破裂泄压～超压再积累～再破裂泄压的反复过程,说明盆地的压力场是一个动态发展的过程,其间伴随着高压流体的幕式排放。

By Easy%Ro method, palaeogeothermal and paleogeothermal gradient of Es4-Ek in Bonan subsag are calculated and it shows that the evolution is related to the tectonic evolution of basin. Formation temperature fell during uplifting, while formation temperature raised during basin subsidence. The evolution of paleogeothermal gradient during geological processes presents a gradually down trending. By basin modeling technique, the overpressure evolution in Es4-Ek of Bonan sub sag is reconstructed, which is related to tectonic evolution and hydrocarbon generation in source rocks. Rate of sedimentation and denudation and the permeability in formation history control the range of early overpressure; Tectonic movement and hydrocarbon generation in source rocks control the range of present pressure coefficient. Overpressure evolution repeated the following process, overpressure build-up and overpressure decompression by fracturing. It shows that pressure field in basin was a dynamic developing process accompanied by episodic releasing of high pressure fluid.