Study On The Method And Application Of Improving Oil Recovery By Combination Of Profile Control,water Plugging And Fracturing In Oil Layer After Polymer Flooding

After polymer flooding in the main oil layer of Daqing oilfield,there are still about 50% of the crude oil reserves remaining in the underground,and the potential of improving oil recovery is great.Based on the study of reservoir characteristics after polymer flooding in Sazhong development zone,the microfacies building structure of reservoir is described,the physical property change degree is evaluated,and the thief zone position and residual oil distribution are determined.The method of enhanced oil recovery by MGC flooding after polymer flooding was put forward,and evaluated the performance of MGC flooding,and understanding its microscopic oil displacement mechanism.Finally,the optimal slug combination mode was determined.Through numerical simulation,physical simulation and field test dynamic analysis,the technical policy limits of profile control,water washing,and water plugging,and fracturing are determined,and the compressibility and construction parameters of the residual oil covered by the side-product interlayer are determined.Finally,a set of comprehensive matching adjustment technology is formed.The application in two test areas has achieved good results,the results are as follows:Two phases,six subfacies and ten microfacies were identified in the study area.The target layer is dominated by river sediments,and the phenomenon of superposition is serious.Each unit has different degrees of abandoned river and point-bar sand body development,of which PI21 and PI22 units are particularly prominent.The whole process of polymer flooding was accompanied by a time-varying permeability.The calculations and coring results after polymer flooding showed that the permeability increased by approximately 14.78% and 18.81%.At the same time,the reservoir became more deformable after the polymer flooding,and the fracturing process was easier to implement.The development of thief zone after polymer flooding is even more serious.The remaining oils appear as four modes on a macroscopic level and are more fragmented,and the proportion of bound states on the microscopic level increases,showing the features that are more difficult to exploit.The MGC solution has a spatial network structure,and has a better viscosity-enhancing and intermolecular self-crosslinking ability than the polymer.At the same time,it also showed better shear resistance,salt resistance and adsorption retention than the polymer.It also has dynamic profile control,and its own activity can change the wettableility of the rock.The fluidity control effect of MGC-1 solution is significant,and the activity of MGC-2 solution is strong.The MGC solution achieves emulsion stripping,emulsification solubilization and carrying effects by reducing the interfacial tension at the oil-water interface.The best combination of slug mode was to use 0.3PV profile control type MGC-1(2000mg/L)+0.7PV water washing type MGC-2(1000mg/L).The best way to solve contradictions between layers is to implement mechanical layering as early as possible.The best solution to the contradiction in thick layers is to use the MGC-1 solution to exert dynamic profile control.Considering the best development effect and the starting pressure of the thin-poor oil layer,the timing for opening the thin-poor oil layer and starting to transfer the MGC-2 solution is about 0.3PV.The emulsification plugging mode exists in the injection process of MGC-2 and it needs timely fracturing and induction.A fluid-solid coupling mathematical model of reservoir fracturing was established by using the method of determining the coefficient of lateral interbedded crack penetration.The finite element software Abaqus was used to simulate the fracturing process,and the resulting construction parameter chart clearly defined the boundaries of the construction technology.In the process of fracturing of the lateral product interlayer,timely increase of the displacement can increase the pressure of the seam and allow it to penetrate the lateral lamination layer.A method for the implementation of comprehensive potential tapping and fracturing techniques has been developed for emulsified oil enrichment zone in thick layer top side layer and thin-poor oil layer.Through “Profile Control”,the pre-slug adopts the regulating-driving agent inside the thick oil layer,greatly increasing the viscosity control flow,and in case of high-washing rock adsorption,dynamic and intelligent profile control can be achieved.“Flooding”,transfer of MGC-2,which increase speed and decrease concentration,further expand the sweep volume and wash more residual oil.“Water Plugging”,through strong emulsification,further greatly increase the viscosity,blocking the thief zone.“Fracturing”,deep penetrating deep-thickness thick oil top side intercalation barrier remaining oil and thin layer emulsified residual oil to release of production capacity.The technology combination of releasing production capacity forms a comprehensive potential tapping technology for “Profile Control,Flooding,Water Plugging,and Fracturing” after polymer flooding.In the pilot test and field test of Sazhong Development Zone,the effect of increasing the recovery rate by more than 8% after polymer flooding.