Experimental Study On Polymer Flooding In Marine Fluvial Facies

Qinhuangdao 32-6 is a typical sedimentary reservoir of Marine fluvial facies,and the geological reserves of it reach up to 2.05×108m3.In the development process,the viscosity ratio of the oil and water is large;the moisture content increases quickly and the recovery ratio is only 13.4%.In the site development,a series of measures,such as the adjusting the well pattern or well spacing,can alleviate the problem that the moisture content increases quickly to a certain extent.But with the deepening of development,the water content will increase again.Thus,a new kind of method to improve recovery efficiency is in urgent need.Polymer flooding is a kind of mature means in the process of offshore development.Therefore,it is necessary to carry out the experiment research by means of polymer flooding in sea fluvial facies reservoir.Based on the characteristics of thin reservoir,single flow,high porosity,high permeability and severe lateral heterogeneity of 32-6 oil reservoir in Qinhuangdao,by choosing and manifesting main parameter of it,the research designs and produces three different types of physical models,including the lateral homogeneous core,lateral trisection core and lateral elliptical core.The research also proves the rationality and repeatability of lateral elliptical core as a physical model in Marine fluvial facies through hole infiltration parameters analysis and water drive mode analysis.The reliability and repeatability of the transverse elliptical core model is also characterized by comparing and analyzing the physical model of the transverse elliptic core with the physical model of the simulated deltaic sedimentary reservoir.Combining the reservoir condition of Qinhuangdao 32-6,the research chooses three typical polymers:the high molecular weight polyacrylamide HPAM,hydrophobic associating polymer AP-P4 and graft polymer LSRP,and evaluates the relationships between temperature and viscosity,shear rheological property and viscoelasticity of three kinds of polymer solutions.The research indicates that these three polymer solutions are non-Newtonian fluids and all of them satisfy power law relationship.Among them,the curve of temperature and viscosity of HPAM meets the linear relationship;AP-P4 and LSRP satisfies variation trend of index model.In the shear rheological test,three kinds of polymers have certain tackifying and shear resistance,and LSRP is the strongest.Under the condition of physical model in Marine fluvial facies,this paper carries out three types of experiments of polymer solution seepage characteristics of HPAM,AP-P4 and LSRP.It is found that these three kinds of polymers in the fluvial facies model have good injectivity and pressure propagation,and the main factor that affects polymer solution in establishing drag coefficient under this model is the residual resistance coefficient.In polymer flooding experiment in the physical model in Marine fluvial facies,after the water flooding moisture content reaches 95%,when 1.0 PV polymer solution with same concentration is injected,HPAM polymer flooding recovery efficiency increases 29%,AP-P4 polymer flooding recovery efficiency increases 33%,and LSRP polymer flooding recovery efficiency increases 45%.Through correlation analysis for the viscosity and the residual resistance of mathematical statistics software SPSS,the rsearch finds that viscosity of significance(two-tailed)is 0.107 and Pearson correlation is 0.986;the significance of residual resistance coefficient(two-tailed)is 0.038 and Pearson correlation is 0.998.According to the principle of mathematical statistics,between the two factors of the viscosity and the residual resistance coefficient,the latter makes greater contribution to the polymer flooding recovery.In the experiment of saturation monitoring ripple effect,the fluidity control capacity of LSRP polymer solution with the characteristic of residual resistance coefficient is greater than that of HPAM and AP-P4 polymer solution with that of viscosity.Polymer solution can not only possess a certain fluidity control ability in the central water channeling area,but also improve the swept volume of two fluvial wings to a certain extent,achieving the purpose of improving the recovery efficiency effectively,providing important guidance for the development of offshore river facies reservoir.