利用盆地模拟方法分析莫里青断陷地层压力演化

Modelling of Pressure Evolution in the Moliqing Rift,Yitong Basin

基于现今压力场特征分析,应用PetroMod盆地模拟软件中1D及2D古超压计算方法,对伊通盆地莫里青断陷地层压力演化进行了模拟恢复,现今莫里青断陷纵向上大致以2 700m为储层超压顶面,超压大于双阳组二段及其以下地层。莫里青断陷双阳组及奢岭组地层压力演化都经历了始新世早-中期（57.8～39Ma）、中始新世-晚渐新世（39～23.7Ma）、晚渐新世-现今（23.7～0 Ma）3个压力积累-释放旋回,不同之处在于奢岭组超压形成较晚且不同压力旋回内最大剩余压力及超压释放幅度都小于双阳组超压。超压演化的旋回性与构造运动的旋回性具有明显的一致性,抬升剥蚀是导致泄压的主要因素且构造抬升活动强度与剩余压力释放具有正相关性。第一次超压积累主要为始新统双阳组及奢岭组地层欠压实增压所致,第二次、三次增压则以双阳组及奢岭组源岩的生烃作用为主导,现存超压形成于中新世初期以来,属晚期超压。应用盆地模拟方法研究沉积盆地古压力是一种行之有效的方法,不仅能够为压力演化的研究提供可靠的依据,而且可以预测现今压力分布。

Based on the analysis of present pressure field,we applied the 1Dand 2DPetroMod system on restoring the formation pressure evolution of the Moliqing rift in Yitong Basin.The following results are obtained.1The reservoir overpressure vertically starts from 2 700 mand is mainly distributed below the middle Shuangyang Formation.2The formation pressure evolution of the Eocene Shuangyang and Sheling Formations have obviously undegone three cycles of accumulation and expulsion,which occurred from the Early Eocene to the Middle Eocene（57.8-39Ma）,the Middle Eocene to Late Oligocene（39-23.7 Ma）,and the Late Oligocene to the present（23.7-0Ma）,respectively.In addition,compared with that of the Shuangyang Formation,the overpressure in Sheling Formation formed later and showed smaller expulsion rate and max-exessive pressure in the three cycles.3The cycles of pressure are controlled by tectonic movements.The erosions could have led to pressure expulsion and proved that the tectonic uplift intensity showed positive correlation with the pressure expulsion rate.In terms of the overpressure mechanism,the disequilibrium compaction could be the main factor for the first pressure accumulation and the hydrocarbon generation could be the main factor for the later two pressure accumulations.The present overpressure in the Eocene formed after the Early Miocene and should belong to late overpressure.4It is feasible to analyze the formation pressure evolution in sedimentary basin by using the method of basin modeling,and it is reliable for the basin modeling method to give some evidence for the research of formation pressure evolution and prediction of the present overpressure distibution.