The Study On Geological Modeling Of The Typical Underground River Type Fracture-cave Karst Reservoirs In The 6^th And 7^th Block,Tahe Oilfield

The storage space of fracture-cave karst carbonate reservoirs is dominated by karst caves,crust and fractures,and has irregular geometrical shape and stochastic spatial distribution.Therefore,it is of great significance for the efficient development of the reservoir to establish 3D geological model of reservoir and clarify the structural relationship of reservoirs.Based on the typical underground river type fracture-cave karst reservoirs in the 6th and 7th block of Tahe Oilfield as the research object,this paper comprehensively applies outcrops,well logging and seismic data to classify and characterize the type of karst reservoirs in the research area,and integrate the geological model information and the seismic information to form multiple restraints.Ultimately all types of karst resevoir models are established through the different modeling methods and are reasonably integrated,which provide geological basis for the further development.The main karst storage space in the research area are underground river reservoir,fault-controlled karst reservoir,weathering crust reservoir and multi-scale fractures.Based on the “classifying,categorizing” modeling idea,this paper used different modeling methods to characterize various reservoirs.The underground river reservoir model and fault-controlled karst reservoir model are both built by multi-point geostatistical simulation.The weathering crust reservoir model is built by collaborative sequential indicating simulation,while multi-scale fractures models are built by deterministic modeling and an object-based marked point processes simulation.Underground river reservoir and fault-controlled karst reservoir are identified as in single wells by logging information.The outcrop,logging and seismic information are used to characterize the underground river reservoir in three-dimensional space.After geological model correction and upscaling into the grid,the underground river reservoir training image is built,while the fault-controlled karst reservoir training image is built by object based simulation with different zones.The development characteristics of underground river reservoir,fault-controlled karst reservoir and weathering crust reservoir are analyzed.With making full use of geological pattern and seismic information,the development probability models controlled by genesis pattern and that based on seismic data are built.Then they are combined by ? model which is based on data independence and the fusion development probability model of reservoir is constructed.It realizes the multivariate constraint of geological pattern and seismic information in stochastic modeling and improves the prediction accuracy of inter-well reservoir.Based on the mentioned modeling methods,the optimum modeling parameters are selected by multiple realizations to reduce the uncertainty of model with multivariate restraints.Then the combining principle of discrete reservoir models is proposed.According to the fusion principle for different types of reservoirs,the fractured-cave karst reservoir model is formed and the corresponding attribute model is established on this basis.By verifying the model from geological information,model reserves and production history,it shows that the model has high reliability and can be used in reservoir numerical simulation.