The Structural Evolution And Dynamic Mechanism Of Paleogene Transfer Structure In Huimin Sag

The Huimin sag is located in the southwest of Jiyang depression and primarily distributed NEE-or almost EW-striking.Large amount of faults developed in Huimin sag.The faults with multi-propriety,multi-direction and multi-periodic activities led to the widely development of transfer structures in Huimin sag,which control the migration,accumulation and distribution of oil and gas in the study area.Based on three dimensional seismic data,well-logging data and regional geological background,this paper identified transfer structures of Paleogene in Huimin sag.According to geometric characteristics,the classification of the transfer structures was set up,which present the characteristics and distribution of different types of transfer structures.According to fault activation analysis of primary faults and transfer faults,this paper reconstructed the evolution processes of typical Paleogene transfer structures in Huimin sag and established evolution patterns of typical transfer structures.Based on the regional tectonic setting and structural characteristics of Huimin sag,physical simulation experiments was used to discuss the dynamic mechanism of different kinds of transfer structures.The Paleogene transfer structures in Huimin sag can be divided into 1^st,2^nd,3^rd even lower-level transfer structures.The geometric characteristics of transfer structures are various.According to the tendency of main faults and their spatial distribution,they can also be divided into five types:convergent conjugate approach,convergent conjugate overlap,divergent conjugate overlap,synthetic approach and synthetic overlap.Different types of transfer structures have different characteristics and space-time distribution.Different types of transfer structures experienced different evolution process.The activity time of main faults determine activity time of transfer faults,and the activity intensity of main faults control the formation of the transfer faults.The strike-slip shearing of Linshang faults is stronger than the extensional stress of that,showing the tension-shearing stress field.The tension-shearing transfer structures at the end of each faults and between the faults in Linshang faults mainly experienced five periods:main fault development period,initial deformation period,2^nd derivation transfer faults formation period,3^rd transfer fault formation period and extinction period.The extensional stress in the Xiakou faults is stronger than that in the strike-slip stress,thus this area shows the shearing-tension stress field.The Xinglongsi and Qianxie 19 well shearing-tension transfer structures mainly experienced four periods:pre-existing faults development period,faults on both sides activity period,pre-existing faults reactivation periods and extinction period.The southern slope of Huimin sag is dominated by extensional stress and developed with extensional transfer structures.The extension transfer structures mainly experienced four periods:main faults activity period,initial deformation period,complex rupture period and extinction period.The regional transtensional tectonic setting,relationship between extension and strike-slip shearing stress and the development of pre-existing faults jointly control and affect the development location and characteristics of transfer structures in the Huimin sag.The change of the regional stress field determines the development of two north-western 1^st transfer structures,which divided the Huimin sag.The differences and changes of the local stress field under the uniform regional stress background influence the development of the transfer structures.The different relationship between extension and strike-slip shearing stress controls the developmental characteristics of transfer structures.The development of pre-existing basement faults affects the plane distribution of transfer structures.