Reservoir Fracture Modeling And Application Based On Well-seismic Combination

The Tahe Oilfield is the carbonate oilfield with the largest oil reserves discovered in China.Its main oil reservoir is an Ordovician carbonate fracture-cave oil reservoir.Fractures are the main oil and gas migration channel and effective storage space in this reservoir,which are very important for the exploration and development.However,the distribution of fractures in the reservoir is complex,highly heterogeneous and has a certain level of scale.The development and distribution of small-scale fractures are often affected and controlled by large-scale fractures.Therefore,in order to accurately describe the distribution and development of fractures in the reservoir,we not only need to use a variety of means to identify and predict fractures,but also to establish a fracture model to simulate the real fracture system.Relying only on logging data to build a model,it is not possible to fully display the fracture development characteristics of the entire study area,such as morphology,distribution density,etc.;while modeling with seismic data,there is a lack of combination with logging data,thus missing a large number of small fracture.Based on this situation,based on the seismic ant attribute and using discrete fracture network(DFN)technology,this paper explores the fracture modeling method of well-seismic combination,and finally completes the model construction of a fracture-cavity unit in Tahe Oilfield.The main research contents include:1.Establish a geological model of the study area and a matrix attribute model.The regional geological model is the basis of the reservoir fracture model and its attribute models such as porosity and permeability.Its accurate establishment guarantees the reliability of subsequent research.Combined with the checkshot data of the well and the layer formation of the well,the regional velocity surface is generated,and then the time-depth conversion of the seismic data is completed.After this,the regional geological model is established according to the relevant fault structure and the two known levels.By coarsening the porosity and permeability data on the well and under the constraints of seismic wave impedance properties,a deterministic matrix porosity model and matrix permeability model are established.2.Explore the modeling method of well-seismic combination,and then establish the discrete fracture network model of the reservoir under the constraints of fracture parameters.DFN model is divided into deterministic fracture model and random fracture model.The ant tracking technology is used to generate the seismic ant attribute,and then the fracture is automatically extracted from the ant data through human-computer interaction.According to the fracture distribution information reflected by other seismic attributes,relatively accurate fractures are selected,and a deterministic modeling method is used to establish a large-scale discrete model for determining fractures.Resample the seismic ant attributes to the grid,and establish a linear relationship between the fracture linear density of each well in the study area and the ant attributes.The fracture density development data can be transformed from the ant attributes through this relationship.The statistical data of fracture trend,dip angle,opening and other parameters are obtained from the interpretation results of imaging logs and core data.Under the common constraints of fracture development density and parameters,a discrete model of small-scale random fractures is established through a stochastic modeling method based on a point-based process.3.Use Oda data statistical algorithm to establish and analyze attribute models such as fracture porosity and permeability.The fracture porosity can reflect the reservoir performance that fractures contribute to the reservoir,and the fracture permeability will affect the flow of reservoir fluid.The Oda algorithm coarsens all parameters such as fracture orientation,size,opening,and density into the grid,thereby calculating the porosity of the fracture system of the reservoir and the permeability distribution model in different directions.Analysis of these models shows that fractures have little effect on reservoir porosity,but play a leading role in reservoir permeability,and greatly improve the fluidity of reservoir fluids.Combined with the porosity and permeability properties of the fracture and matrix in the grid,the double-pore and double-permeability model of the study area can be obtained,which is also ready for data for numerical simulation.