Fractal-based Multi-stage Hydraulically Fracture Network Characterization And Flow Modeling

The potential of new type of unconventional resources,“unconventional reservoir” has attracted a great deal of public interest,compare to conventional reservoirs,Compared to conventional reservoirs,fluid flow in unconventional reservoirs is driven by ultra-lowpermeability and discontinuous fractures and involves many coexisting processes due to the presence of multi-scale fracture networks.The purpose of multi-staged fracture networks is intent to provide flow pathway in ultra-tight formation,which has already become most useful technics in unconventional oil & gas stimulation.But quantifying complex fracture network in unconventional reservoirs remains a significant challenge,the existing flow mechanism and theoretical models are limited from fully representing the geometry of complex fracture networks and simulation approach.To account for the structure of complex fracture and stimulated reservoir volume,we proposed composite dual-porosity linear flow model.our model is based on four linear flow regions including the hydraulic fracture,the stimulated reservoir,the unstimulated reservoir,and the outer reservoir region,which accurately depict the coupling of multiple flow region,we perform the sensitivity studies to present the degree to which the vary as size and other properties of SRV change.Secondly,multi-scale feature is proposed to consider the ultra-tight porous media and discontinued fracture medium,fractal permeability and porosity relationship is introduced to develop fractal anomalous diffusion mathematical model.The study revealed that matrix/fracture fractal dimension、anomalous diffusion parameter have an important impact on flow mechanism in fractured horizontal well,we also stated that the presence of lower limit of stimulated reservoir threshold permeability,which is strongly influence by fracture fractal dimension.Thirdly,we develop dual-porosity based multiple fractured horizontal well model,which complex fractures and hydraulic fracture are modeled explicitly as one or more 1D,finite element method is employed to carry out a discrete solution for a macro fractures and solve for wellbore pressure.The model could precisely describe the flow behavior inside the stimulated reservoir volume or belong the hydraulic fracture,which clarify the flow characteristic with respect to the typical reservoir stimulated volume.The result show that with higher stimulated reservoir volume and fairway length,the higher well performance will have.Then,we propose new numerical method to characterize the structure of fractal bifurcate complex fracture network.Fractal theory and discrete fracture method is employed to set up the mathematical model,we also perform sensitivity studies to present the degree to which the rate transient behavior very as bifurcate fracture density,bifurcate fracture network mode and conductivity.By increasing bifurcate density,higher reservoir contact area will have,but also the well production could be decreased with bifurcate fracture network interference.Finally,we develop random fractal based fracture network geometry and inversion approach.By using L-system algorithm,we generate random fractal fracture network geometry,meanwhile,apply the integer programming algorithm and the micro-seismic data to do the fitting complex geometry of fracture network.Adsorption and desorption,transient flow behavior are considered in shale gas reservoir simulation model,then GA algorithm is applied to solve the history matching problem and invert the fracture properties.In this paper,we study the complex fracture characterization method systematically,and provide a new methodology and technology for flow simulation in multiple-fractured horizontal well.