考虑断层发育史并适用于欠压实的地史模型

在盆地模拟系统中,地史模型的功能是重建油气盆地的沉积史和构造史.其模拟方法分为正演和反演两种类型.正演是指从古到今恢复地史,如超压技术,适用于欠压实带;反演是指由今溯古恢复地史,如回剥技术,适用于正常压实带.回剥技术的优点是精度高,缺点是因未考虑超压而不适用于欠压实带.相反,超压技术的优点是适用于欠压实带,缺点是精度低.作者首先提出的回剥与超压相结合的技术,既考虑超压又确保精度,其主要思路是:从已知的盆地现状出发,先采用回剥技术,由今溯古重建各地层的地史;然后对各地层进行超压计算,从古到今修正回剥技术所得的地史.为确保重建精度,地史模型应考虑尽可能多的地质现象,如沉积间断、沉积压实、欠压实(超压)、单层剥蚀、多层连续剥蚀、断层及古水深等,其中断层发育史的模拟最难实现.提出了考虑断层发育史的回剥技术

A GEOHISTORY MODEL CONSIDERING FAULT DEVELOPMENT HISTORY AND APPLICABLE TO UNDERCOMPACTION

In the basin modeling system,the function of geohistry model is to rebuild the depositional and structural histories of a petroliferous basin.There are two kinds of method of forward deduction and backward deduction in this model."Forward"refers to the restoration of geohistory from past to present,e.g.,the technique of overpressure,which is applicable to normal compacted formations;"Backward"refers to the restoration of geohistory from present to past,e.g.,the technique of backstripping,which is applicable to under compacted formations.The advantage of backstripping is highly accurate while its disadvantage is not applicable to under compacted formations because overpressure is not taken into account.On the contrary,the advantage of overpressure is applicable to under compacted formations but low accurate.The combination of backstripping and overpressure,which is first proposed by the author,can consider the overpressure and ensure the accuracy.Its main idea is that from presently known basin conditions to deduce backward in time the geohistory of every individual formation with backstripping first,to deduce forward in time the overpressure of the formations,and finally to modify the backstripping results.For more accurate reconstruction,geohistory model should consider as many significant geological phenomena as possible,such as depositional hiatus,sedimentary compaction,undercompaction (overpressure),single formation erosion,multi formation continuous erosion,fault and paleo bathymetry etc.Among them,the simulation of fault development history is the most difficult.The author is the first one to present the backstripping considering the fault development history.