Research On Weak Gel Displacement System Formula After Polymer Flooding In H1 Block

Aiming at high temperature,high permeability and characteristics of large pore path of H1 blocks and water channeling occurs after polymer flooding,invalid water cycle. Experimenting on weak gel system formula, through gel forming characterization,stability, viscoelastic,rheological property and other parameters,selecting the best formula from these experiments.And measuring the factors of influencing gel formula, mainly contains the dissolved oxygen content of water,bacteria content,insoluble suspended solids content and metal ions content.At 70 ℃,gelation forming after ten hours,gel breaking after nine hundred hours,the gel reached maximum viscosity of 32000 mPa.s after twenty-one hours,the intensity of gel system nearly stabilization,with viscosity range from 11000 to 13000 mPa.s. Both elastic modulus and viscous modulus are moderate. energy storage well during solution deformation.As the dissolved oxygen content reached 1.5mg/L,with the worse gelling effect of weak gel solution,lower intensity, shorter gel breaking time,when the oxygen content reached 7mg/L the weak gel flooding achieving the best effect. The bacteria implementing intensify degradation on weak gel system. When the bacteria content reached one thousand per milliliter,the solution viscosity decreased 15% comparing with sterile samples. Insoluble substance reached 60mg/L implementing the strongest effect,the gel system solution were broken after six days.Fe3+ exerting no influence on the weak gel system. Fe2+influencing the weak gel severely,when the concentration of Fe2+ reaching 5mg/L, the viscosity loss rate of weak gel solution reached 5 percent,weak gel viscosity decreased deeping with the increasing concentration of Fe2+.Finally,exerting these formulas on core experiments,measuring plugging ability,pressure gradient,diversion rate and the best slug injection on different permeability of cores. The third formula exerting preferably on EOR,with the pressure gradient of 24 MPa/m,the EOR increasing 19.06% when the injection volume was 0.2PV,the strengthening effect of EOR was poor beyond 0.2PV.