| Gel particles profile control is an effective new developed technique to improve filed development performance in recent years.The research for gel particle migration now focuses on experiments study.The mechanistic micro migration simulation method is absent now.The project design of gel particles are usually determined by using empirical equations based on dynamic data.It still lacks a set of decision making and quantitative simulation method.It is necessary to study the micro migration and macroscopic profile control simulation study for gel particles in porous media.It can not only explore the migration laws in porous media,but also guide parameters optimization for gel particle profile control/multiple profile control and displacement system,which supply theory guide and technique support for continental heterogeneous oilfield development performance improvement.The force on gel particle is firstly analyzed in porous media.The construction method for porous media skeleton model is studied and some artificial core skeleton models are generated.A natural core skeleton model is created by matching the measured mechanical parameters,which is used to build fluid particle pore network simulation based on discrete element method(DEM).The force on suspension particle is approximately described by drag force model.A Darcy flow case is used to validate the skeleton particle fluid coupling process.The invasion process of gel particle into porous media is simulated to analyze the effect of particle diameter ratio and initial porosity on formation plugging.The convective diffusion deep bed filtration model for gel particle is established by considering the diffusion effect.After selecting dimensionless variables,the analytical solutions to particle concentration and retention are solved for infinite formation,semi-infinite formation and finite formation.A new deep bed filtration model is built by dividing the particle retention into particle deposition and particle blocking.The analytical solution to particle concentration and blocking are achieved by adopting method of characteristic.The effective filtration coefficient for series cores are studied based on classical deep bed filtration and an upscaling method for filtration coefficient is presented.Considering the non-Newtonian fluid characteristic,a fractional flow equation for gel particles is developed.A semi-analytical solution is presented to analyzed fractional flow curves in different position.The gel profile control physicochemical equations(viscosity and diameter variation)are established based on experiment results.A deep bed filtration migration equation is developed by considering critical pressure gradient.Combined with permeability-porosity dynamic equation and reservoir seepage equations,a coupled model is built for gel particle profile control or water shutoff.The pressure and saturation is solved by IMPSAT method and the particle concentration and retention are numerically solved by adopting iterative method.Furthermore,a new wellbore-reservoir coupled model is proposed for gel particle water shut off simulation.The new model considers the variable mass pipe flow and non-Newtonian characteristic in horizontal wellbore and a new iterative solving technique is developed.The new coupled model is used to predict injection pressure and production performance during and after water shut off treatment.Based on gel particle profile control model and polymer flooding model,coupled gel particle profile control model is established by considering the interaction between gel particle and polymer.To improve the accuracy of solution,pressure linear equation is solved by employing preconditioned conjugate gradient method,and polymer convective diffusion equation is solved by adopting fourth-order Runge-Kutta method,and gel particle equation is solved by using an operator separation method.The coupled model is validated with a core flooding data and a well pattern pilot data.The coupled model is adopted to optimize the slug composition and agent volume for an actual well pattern gel particle profile control project.In addition,a fast performance prediction method is presented by referring to numerical simulation results and analytical equations.The surfactant model is established by considering the main surfactant mechanisms,including water viscosity variance,oil water IFT,surfactant adsorption,miscibility degree,relative permeability and capillary pressure.The interaction mechanisms between gel microsphere and polymer/surfactant are mathematically described according to experiments.The coupled model is numerically solved by an implicit-pressure,explicit-compositions method.The surfactant module is verified with a commercial simulator.The robustness of the gel particle surfactant coupled model is validated with a fractured core flooding case and an artificial core flooding case.Furthermore,the coupled model provides an efficient method for predicting gel microsphere-surfactant flooding performance,which helps to determine the technical feasibility of the project. |
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