Simulation Experimental Study On The Formation Mechanism Of Diapir Structure In Bohai Bay Basin

There are diapirs in many tectonic belts of Cenozoic basins in Bohai Bay,which have important influence on hydrocarbon accumulation.Because the deformation evolution of the basin is the result of the superposition of many tectonic processes,the research on the deformation characteristics and control mechanism of the diapir structure is weak.On the basis of previous studies,the geometric deformation characteristics of diapirs in different tectonic units of Bohai Bay Basin were analyzed in detail,and the deformation controlling factors were summarized.The development process of diapirs under the control of different factors was discussed by using structural physical simulation and other experimental methods.The differences of controlling effects of different factors on the development of diapir structures are compared in detail.The results show that :(1)there are two types of diapirs in bohai bay basin: salt diapirs and mud diapirs.Salt diapirs are mainly distributed in Dongpu sag,Dongying sag and Laizhouwan sag.They are salt arch tensioning anticline,salt roll,salt-mud arch tensioning structure,penetrating salt nose structure and integrated salt pillow structure.The mud diapir is mainly concentrated in liaodong Bay depression,and it is mainly characterized by punctured arch tension structure.(2)It is revealed that the important controlling factors affecting the formation and evolution of the diapir structure in the basin are extension,plastic layer thickness,plastic layer properties,synsedimentation and preexisting faults.The controlling effects of various factors on diapir structure are as follows: Stretch tectonic stress is the fundamental forces of the development of basin diapirs basement faults developed position is often late diapir priority,the stronger the salt layer thickness,the sole monarch role,with the sedimentation deformation effectively inhibit the growth of the diapirs,plastic layer properties(rock mechanics properties)change also has obvious influence on structural deformation.(3)Model 1 shows a good reduction of the diapir form based on the salt structure developed in the fourth member of the Inner Shahejie formation in Wenliu Structure,Dongpu Depression.Similar salt structures such as salt uplift,salt welding,salt layer integration and salt pinching have appeared.The formation deformation morphology also corresponds to it.(4)The most easily formed oil and gas traps in Bohai Bay Basin are usually developed in subsalt fault block trap,extensional fold trap,rolling anticline trap,salt detachment fault footwall trap and reverse traction fault trap.It has important guiding significance to oil and gas exploration.