DFN Model Optimization Based On Focal Mechanism Solution

Naturally fractured reservoirs play a major role in the whole world's hydrocarbon resources.Only by establishing the fracture model to strengthen the understanding of the spatial distribution of cracks can we better achieve the production and development of hydrocarbon resources.Therefore,this paper chooses to study Discrete Fracture Network(DFN)model.The DFN model is an advanced technology for describing cracks in the world at present.It can construct a subterranean fracture model in a three-dimensional space and reflect the non-uniformity and discontinuity of fractured reservoirs.The methods for establishing DFN models in different disciplines are different.Microseismic is the main method of monitoring in the hydraulic fracturing process,and it is also an important method for establishing DFN model.However,it is difficult to obtain an effective and reliable fracture model based on microseismic positioning data alone.Therefore,the introduction of the focal mechanism solution in the process of establishing the DFN model and increasing the fault plane information is a development direction for further optimizing the DFN model.This paper develops a method to optimize the modeling process from the aspects of cluster analysis,objective function constraints,distance-azimuth transformation,and perturbation process.In the process of DFN modeling,we assumed that the microseismic event occurred on the surface of the fracture,and the events on the same fracture had similar information on the fault plane inclination and dip angle.For the sake of convenience,we use elliptical surfaces to characterize actual cracks.The DFN model obtained from the theoretical data test can be used to restore and reconstruct the actual crack model in the fracture morphology and location.It is demonstrated that the method has strong stability and reliability.We used the true three-axis acoustic emission fracturing experiments in the laboratory to perform the practical application of the method.The feasibility of the method was proved by comparing the established DFN model with the CT scanning section.The finally obtained DFN model basically realizes the description and characterization of the laboratory acoustic emission crack network.The DFN modeling method based on the focal mechanism solution optimization has great guiding significance for the fracture modeling in the actual production process.