Hyperbranched Polymer That Prepared With Produced Water And Its Displacement Characteristics For Polymer Flooding

The Original Oil in Place(OOIP)of Karamay Oilfield covers 0.356 billion ton for polymer flooding.On the other hand,the strategy that polymer directly prepared with oilfield produced water is indispensable due to the lack of fresh water of this oilfield.However,the high total dissolve substance(TDS)together with the complex salinity of the produced water hinders the comb-shaped polymer named KYPAM application.KYPAM has the limited thickening efficiency and poor long-term stability when it was prepared with the harsh produced water.Based on the notion mentioned above,this thesis firstly synthesized hyperbranched polymers abbreviated HBAPAM that directly prepared with Karamay Oilfield produced water for polymer flooding.Secondly,the comprehensive displacement,injectivity and propagation in porous media of polymer solution were deeply and systematically investigated.The relationship between the mass concentration of variable averaged molecular weight(Mw)of HBAPAM,and permeability of formation was constructed.Thirdly,the main factors and mechanisms that dominated the nonlinear flow for HBAPAM solution in cores were explained.Finally,the enhanced oil recovery efficiency and application potential of HBAPAM was investigated.The main works are summarized as follows:(1)PAMAM hybrid nano-SiO2 monomers with branched chains of 56,105,203,respectively,were prepared through controlled reaction of surface modification of nano-SiO2,Michael addition and amidation reactions.A novel type of core-shell hyperbranched polymers HBAPAM that contained nano-SiO2 as core,multi-branched polymeric chains with small proportion of N,N-twin tailed alkyl chains as shell,was prepared based on PAMAM hybrid nano-SiO2 monomers and hydrophobic monomer of N,N-twin tailed alkyl acrylamide.By varying the numbers of functionalized branch-cell units of PAMAM hybrid nano-SiO2 monomer,the Mw of HBAPAM could be tuned with Mw of 7.5×106g/mol for HBAPAM-1,9.3×106g/mol for HBAPAM-2 and 1.27×107g/mol for HBAPAM-2,respectively.(2)The multiple hydrophilic structure endowed HBAPAM with desirable solubility in the produced water and the total soluble time ranged 120?140min.By varying the critical associative concentration(CAC)to minimize to the error in the slope of a double-lg plot of plateau modulus(G0)versus(c-CAC),the CAC was 1180mg/L for HBAPAM-1,1050mg/L for HBAPAM-2,and 920mg/L for HBAPAM-3,respectively.HBAPAM had the more expected filtrability than that for ultrahigh Mw of KYPAM 2500.The core-shell structure,multi-branched morphology and supramolecular interaction provided HBAPAM specimens with more desirable viscosified efficiency,long-term stability and excellent viscoelastic modulus in harsh water in comparison to that for KYPAM 2500 with the equivalent mass concentration.The apparent viscosity of HBAPAM-3 at the concentration of 2000mg/L prepared with produced water was 149.6mPa·s,as much 2.6 times as that for KYPAM 2500 at the identical concentration;it was 85%?89%to the original viscosity even HBAPAM samples suffered from the seriously mechanical shear stress of 15000s-1;the retention of apparent viscosity was higher 90%to the original viscosity after HBAPAM samples were aged for 90d at the formation condition.(3)The static(dynamic)hydrodynamic size Hs(d)for HBAPAM solution was consistent with the Mw.Above the CAC,the supramolecular interaction between multi-branched associative polymeric chains upgraded the Hs(d)that were exponent equation to polymer concentration.HS was higher than Hd at the identical polymer concentration.(4)The internal factors of Mw and mass concentration of HBAPAM and external factor of permeability of cores dominated its injectivity and propagation in porous media.The charts of averaged hydrodynamic pore-throat size of conglomerate core(rp)to the Hs(d)was constructed based on the limited injectivity of polymer solution.The data indicated that face plugging or internal filter cake of HBAPAM polymer occurred if rp/Hd is lower to 5.2.HBAPAM-1 was the favorable chemical agent when the permeability of formation is lower 0.15?m2;both HBAPAM-2 and HBAPAM-3 were expected candidates when the permeability of formation ranges from 0.15?m2 to 0.5?m2;and HBAPAM-3 was the best option once the permeability of formation is higher 0.5?m2.(5)The internal factor of relaxation time and the external factor of shear rate of porous media dominated the nonlinear flow of HBAPAM in porous media.HBAPAM featured the rheology in multiscale and viscoelasticity in temporal-spatial scales consistently in deionized water and produced water.The viscoelastic flow for HBAPAM specimens would shift to the lower shear rate as the increase in polymer mass concentration or the higher Mw at the identical concentration.There was a monolayer adsorption of polymer coils onto the surface of cores,which was just controlled by polymer concentration and Mw.(6)According to the adaptability of HBAPAM to the permeability of reservoir,0.3PV of polymer solution was flooded following the initial water flooded to the water cut of 98%.The results revealed that more than 30%of OOIP was recovered at the strong heterogeneity cores.In the two parallel cores experiments,when the permeability range was higher than 8.5 with the permeability of secondary core lower 0.05?m2,HBAPAM preferentially propagated in the primary core,enhanced oil recovery more than 39%OOIP due to its viscoelastic displacement and profile modified characteristic;when the permeability range was mediate with the permeability of secondary core higher 0.5?m2,HBAPAM flooding enhanced the primary and secondary cores oil recovery more than 20%and 25%,respectively higher than 13%and 5%to that for KYPAM flooding with KYPAM concentration 500mg/L higher than that for HBAPAM.The results of this thesis indicated that HBAPAM had the robust application with the high cost performance in the harsh produced water condition of reservoirs.