Modelling experiments of clay and clastic sediments of various particle si-zes have been made and some empirical fomulations are obtained.This kind of work has proved that the compactibility varies with the particle size;and the differentia of compactibility depend remarkably on the difference of particle size also

when the same condition of pressure have been undertaken.The stratigraphical thickness is surely getting thinner with the increasing of compaction in the process of sedimentation and lithification.A calculating method is thus suggested for restoring the fossil stratigraphical thickness

with the Saertu structure

Daqing Oilfield

taken as an example

the fossil strati-graphical thickness of three formations of which have been restored on the ba-sis of one of its cross sections.The results have demonstrated that the fossil tectonic pattern restored by means of fossil stratigraphical thickness fits more the reality

and is quite different from that restored by means of recent stra-tigraphical thickness.