Identifying And Modeling Research On Structural Fractures Of Chang6 Formation In Jiyuan Area,Ordos Basin

The Chang6 Formation,as one of the main oil-gas exploration reservoirs in Jiyuan Area,is affected by hydrocarbon-generating overpressure,diagenesis and multiphase tectonic superimposition and transformation.The structural fractures of it are well-developed and complex.Structural fractures not only control the seepage system,reservoir properties,oil-gas migration and accumulation,transformation and destruction of oil and gas reservoirs,but also have an influence on reservoir development scheme deployment and its development effect in research area.In this paper,the identification 'research on structural fracture is carried out with comprehensive utilization of outcrop,core and imaging logging data.And combined with the latest discrete fracture network(DFN)stochastic modeling technology,three-dimensional geological model of fractures for exploring the implementation of the quantitative description and characterization of the fracture system and its parameters in the well-well unknown area and even the area can be established.It is of great significance for predicting structural fracture system and the effective distribution of fracture zone,understanding and grasping the law of exploration and development in reservoir area objectively,improving the reservoir development effect,enhancing oil recovery and for other destinations.The structural fracture identification and modeling of the study area show that:(1)The structural fractures of research area are extremely developed and the horizontal and vertical density distributions are different.The transverse length of the fractures is about 2-20m.The longitudinal depth is about 0.5-2m.The peak of the fracture aperture and porosity is respectively between 20-70 ?m and 0.005-0.03,which indicates that the fractures have little contribution to the reservoir space,and are mainly to improve the reservoir seepage capacity.(2)The NEE-NNW and NE-NW direction conjugate shear fractures are mainly developed in the Chang 6 reservoir,especially NEE-near EW direction fractures.(3)Structural fractures are characterized by high angle fractures(inclination>70°)followed by oblique fractures.Then there are less low angle and horizontal fractures.(4)The structural fractures are mostly open,and the closed fractures and filling fractures are less.Fracture fillings are mainly calcite,and include a small amount of carbon and asphaltene.(5)The structural fractures are controlled by stratum,which are mainly developed in stratum,mostly terminated at the interface of the rock form and convergently distributed in the longitudinal direction.(6)Lithology,layer thickness,tectonic movement and others are the main factors influencing the development and distribution of structural fractures in research area.(7)DFN model can visually reflect the three-dimensional spatial distribution of structural fractures,and quantitatively characterize the parameters such as porosity,permeability,and the effective zone of fractures.And it can effectively reveal the improvement and contribution of structural fractures to the reservoir performance.