Migration Rule Of Gel System Under Reservoir Dynamic Condition And Its Field Application

The gel injection system in high water-cut reservoirs is an important means to improve the inefficient and ineffective circulation and expand the swept volume.At present,the migration law,shear viscosity reduction and gelation law of gel system under dynamic conditions in porous media are still unclear.In order to provide the basis and theoretical support for the optimal design of the injection scheme of the gel system,the optimization of the field construction parameters,and the optimization of the numerical simulation parameters,it is necessary to clarify the adsorption and retention laws,the characterization parameters of the gel formation,and the formation laws under the dynamic conditions of the gel system.In view of the above problems,this research mainly uses the combination of indoor experiments,theoretical analysis and numerical simulation to carry out research work in four aspects.(1)A long sand-packed tube model with 7 sampling test points equidistantly distributed is designed to test the viscosity,concentration,and microscopic morphology of the non-gelling gel system flowing through the porous medium at different distances.On this basis,the adsorption and retention,shear viscosity reduction and retention morphology of each component in the dynamic migration process of the gel system in porous media are given.The calculation model of dynamic adsorption retention/adsorption rate of polymer and crosslinking agent was established,and the prediction of dynamic adsorption retention/adsorption rate during the injection process of gel system was realized.(2)Characteristic parameters capable of characterizing the dynamic gelation of gel systems in porous media are presented for the first time in this article.In this paper,a 10 m long sand-packing pipe(17 pressure measuring points)was used to test the pressure of each pressure measuring point in different injection stages during the injection process.The experiment proves that the non-gelling equivalent viscosity of the gel system can evaluate whether the profile control agent can be successfully injected into the reservoir,the dimensionless gelling thickness can evaluate the gelling thickness under dynamic conditions,and the breakthrough pressure gradient can evaluate the gelling strength under dynamic conditions and the plugging rate can evaluate the effect of gel-forming plugging under dynamic conditions.Based on the above results,a comprehensive evaluation method for injection capacity and plugging capacity under dynamic conditions of gel system was formed in this paper.(3)In this paper,an experiment was carried out to determine the static gelation parameters of the gel system with different component concentrations.The experimental results showed that gel strength increases exponentially with polymer concentration and logarithmically with crosslinker concentration,with little effect from retarder;the initial gel formation time decreases with the power function of the polymer concentration,which is hardly affected by the concentration of the cross-linking agent,and increases linearly with the concentration of the retarder;the stable gelation time decreases with the power function of the polymer concentration,decreases linearly with the crosslinker concentration,and basically increases linearly with the retarder concentration.The model was established to predict the non-gelling equivalent viscosity(average error 6.42%),the gelling breakthrough pressure gradient(average error 7.33%),the dimensionless gelling thickness(average error 4.32%),and the gelling blocking rate(average error 0.05%)under the dynamic conditions of the profile control agent.And the prediction of gelation characteristic parameters under dynamic conditions of profile control agent in reservoir is realized.(4)This paper establishes a facies-controlled fine 3D geological model of the field test block,completes the fitting of layered geological reserves and the history fitting of production indicators,accurately quantifies the distribution characteristics of remaining oil in space,and determines the identification boundaries of dominant water flow channels and injection Identification of dominant seepage channels between mining units.Based on the numerical simulation of the experimental results,the injection scheme of the gel system and the prediction of the development indicators are studied.The calculation results show that the injection rate of the gel system in the test area is 0.075PV/a,the front slug is 0.03 PV,the main slug is 0.075 PV,and the auxiliary slug is 0.075 PV,the secondary slugis 0.045 PV.It is expected that the test block will enhance the recovery factor by 3.7%.In this study,an experimental research method for the migration law of gel systems under dynamic conditions in porous media was systematically designed.The adsorption and retention laws,shear viscosity reduction laws,and gel formation laws of each component of the gel system under dynamic conditions in porous media were determined.The prediction model of adsorption retention and gelation characteristic parameters under dynamic conditions of gel system was established.Based on the experimental research results,the optimization of the injection scheme of the on-site gel system and the prediction of the development indicators were realized by numerical simulation.The research results have important guiding significance for improving the development effect of high water-cut stage of high-permeability oil reservoirs in heterogeneous sandstone.