Study On The Fracture Characteristics And Formation Mechanism Of Yong 3 Fault Block In Dongxin Oilfield

Located in the northeast of Dongying sag,Yong 3 fault block is a complicated reservoir with multi-layers,medium and high permeability,transected by many interior multilevel faults.The main oil-bearing layer is Shahejie Formation.There are many problems in the block including the unsystematic research of fracture development characteristics and evolution process,uncertainty of structural mechanism and indetermination of hydrocarbon enrichment under the control of fracture,which seriously affect the subsequent development in the region.Based on geological information,3d seismic data,well logging,and measured data,the fracture morphology and assemble pattern,fault activity,tectonic evolution analysis are analyzed in detail to clarify and verify the Genetic mechanism of the fracture in the study area,meanwhile reveal the influence of fracture on target layer of oil and gas distribution.The following are the achievements:(1)Analyze major faults characteristics and flat profile assemble pattern.Fracture system of Yong 3 is divided into nearly EW,NW and SN three sets;Tectonic styles that combine senior sequence faults with low-level sequence faults mainly show “y”,trapezium,graben-horst type etc.;Meanwhile styles show on the flat surface are echelon,parallel,radial and angular type,In short,the static characteristics of fracture reflect the superposition of stretching stress and strike-slip shear stress;(2)Make the activity characteristics of major faults and tectonic evolution history clear.With features of segmentation and staging,Dip angle is generally more than 60°,which embodies the strike-slip properties,and with the development of the evolution,trend and dip angle are changeable.(3)Illustrate the fracture formation mechanism in the study area.Affected by the regional tectonic stress in Dongying sag,the right-lateral strike-slip of Tanlu fault zone and upper-bend action of salt-shale plastic structure,the multi-phase structural evolution in two phases could be considered to be two directions stretch,stretch-strike-slip and diapirism and be divided into Ek-Es4,Es3-Es2,Es2-Es1,Ed-Nm four tectonic evolution stages.(4)Combine structural physical simulation with tectonic stress inverse modeling to simulate the evolution process of faults development in paleogene,and prove multiphase evolution of NNE direction stretch in the Paleocene-Middle Eocene,NW and NNE two-direction stretch,dextral shear,and diapirism in the late Eocene-late Oligocene is true.(5)Summarize the fracture control action for hydrocarbon distribution.Grades,activity,and assemle pattern control the distribution of the reservoir.With strong fault sealing ability,senior sequence can completely block the oil and gas from migration and diffusion,meanwhile low-level and senior sequence faults form pinnate faults combination style to make oil and gas accumulate with narrow band shape along the top of senior sequence distribution.