The Study On Three-dimensional Model Of Fractures In The Tight Reservoir Of The Yanchang Formation In Wellblock 92 Of Honghe Oilfield

Chang 8₁² single layer of the Yanchang Formation is tight sandstone reservoir in wellblock 92 of Honghe oilfield.In the development of this tight sandstone reservoir,there are many problems such as fast decline rate,low accumulative production and low recovery,so it is necessary to conduct the exploitation of water injection to complement energy.Due to the influence of tectonism,natural fractures develop in the tight sandstone reservoir of Chang 8₁².Although fractures have greatly improved the permeability of the reservoir,they have a greater impact on water-flooding development.This paper comprehensively applies core,well logging and seismic data to identify and describe fractures in Chang 8₁² single layer in the research area,and clarifies the development characteristics of fractures.In addition,three-dimensional geological models of tight sandstone reservoir matrix and fractures are established,which provide the geological basis for the arrangement of water-flooding development pattern and reservoir numerical simulation.Through core observation and description,the parameters of fractures such as occurrence,size and density are obtained quantitatively.The conventional logs are calibrated by using cores,and summarize the response characteristics of fractures in conventional logs.Then the conventional logs sensitive to fractures are selected to identify fractured zones of each well.Five seismic attributes sensitive to fractures are selected,including ant cube,variance cube,structural dip attribute,envelope attribute and RMS amplitude.According to these seismic attributes,the fractures mainly develop in the northern part of wellblock 92 of Honghe oilfield with four NEE trending fracture development zones,while in the southern part,the fracture development degree is relatively low.A method of establishing three-dimensional geological models of tight sandstone reservoir matrix by multi-facies control is proposed.That is,the matrix reservoir parameters models are established by multiple constraints of plane distribution of ratio of sandstone thickness to formation thickness,three-dimensional sedimentary microfacies model and three-dimensional lithofacies model,which have higher precision than those built by the single sedimentary facies controlled method.The idea of hierarchical modeling of fractures is proposed.Deterministic modeling and an object-based marked point processes simulation are used to build the discrete network models of large scale fractures,mesoscale fractures and small scale fractures..And then,a comprehensive discrete fracture network model is built by integrating the discrete network models of various scale fractures,and fracture equivalent physical parameters models are established by upscaling.In the small scale fracture discrete modeling,the modeling idea of combination of well data and seismic data and multistage fusion is formed.This paper innovatively proposes a seismic attribute fusion method based on correlation analysis and a method of establishing a three-dimensional brittleness index model by multi-facies control.For the first time,the PR?Permanence of Ratio?multivariate probability combination model is introduced into the fracture modeling.The fracture probability model is constructed by using PR model to combine the seismic attribute fusion body,the brittleness index and the distance to the fault,and then is used as the constraint to build fracture models,which improves the reliability of fracture models.It has been proved that the established fracture models are in good agreement with the geological knowledge and production data,which can be used for the reservoir numerical simulation.