Research On Preparation Of Preformed Particle Gel With Low Elasticity And High Viscosity And Its Compatibility With Oil Reservoir

The central north part of Dagang oil field is typical of unconsolidated sandstone structure.Severe heterogeneity of oil-bearing formations cause poor plugging effect of ordinary profile control agent.Preformed particle gel can modify reservoir heterogeneity and enhance oil recovery effectively.But the strength of existing particles is typically high,which leads to poor deformability.Therefore,this paper presents a new kind of preformed particle gel with low elasticity and easy deformation,and basic properties and compatibility with oil reservoir were investigated.A type of preformed particle gel with low elasticity and high viscosity(D-PPG)was prepared using solution polymerization method.According to the viscoelastic strain,the synthesis conditions of preformed gel were optimized.The preformed particle gel(D-PPG)was characterized by FTIR spectra.The thermal stability of D-PPG was studied by DSC and TG.The three dimensional network structure of swollen preformed particle gel was observed by ESEM.Swelling kinetics of D-PPG were simulated and analyzed,and the influence of different environmental factors on D-PPG swelling behaviors was obtained.The initial swelling stages were thought to be controlled by the non-Fickian diffusion.The whole swelling process was well fitted into the Schott second-order kinetic equation.The initial swelling rates,the equilibrium swelling ratio and swelling time of D-PPG increased with the temperature increasing.The swelling ratio of D-PPG decreased with metal ion concentration increasing,divalent ions having greater shielding effect than monovalent ion.The swelling ratio of D-PPG increased with pH value increasing.D-PPG/HPAM disperse system exists the critical shear rate.When the shear rate is lower than the critical value,the system showed shear thinning properties,and it shows shear-thickening behavior when shear rate higher than this value.particles make great influence on the viscosity of the system.The phenomenon of shear-thickening is much more obvious with increasing D-PPG concentration in high shear rate.The matching relationship between preformed particle gel and pore throat and the profile control property were studied by using sand packed tube model.Then,the filtration and the damage extent of preformed particle gel were evaluated by using high temperature static loss test.Pore throat of cores and swollen D-PPG sizes had better compatibility when the diameter ratio was approximately 0.05.Preformed particle gel has selective profile control ability to oil and water as well as high permeable layer.D-PPG/HPAM disperse system shows significant ability of fluid diversion when permeability contrast increased.The water plugging rate of preformed particle gel is higher than its oil plugging rate.The filtration of D-PPG may cause damage on low permeability layer,but when the filter formed by filtration is removed,the effect of profile control will be improved.HPAM and D-PPG can make influence cooperatively on plugging dominant channel,changing direction of fluid flow and expanding sweep efficiency.D-PPG/HPAM disperse system can significantly decrease formation heterogeneity.Results of parallel heterogeneity model experiments show that D-PPG/HPAM disperse system can improve recovery factor 17.56% after polymer flooding when the permeability contrast is 10.