Salt Resistance Supramolecular Polymer:synthesis,salt Effect And Flow Characteristic Research

Polymer flooding is an important part of tertiary oil recovery technology,which can enhance oil recovery economically and effectively.At present,in order to expand oil and gas production,it is necessary to implement tertiary oil recovery technology for some reservoirs with harsh conditions.As a kind of harsh oil reservoirs,a reservoir with high salty,especially high calcium and magnesium ions,is difficult to implement the technology.Due to the limitation of molecular structure and thickening mechanism,the conventional polymer viscosity will be reduced for the curled structure in silane water.Therefore,the application of conventional polymer in high salty reservoir is restricted.Carboxylic is sensitive to salt,especially calcium and magnesium ions,resulting in a low salt resistance of convertional polymer.In China,the concentration of calcium and magnesium ions of high salty reservoirs is generally higher than 500 mg/L.The viscosity of conventional polymer will be reduced to minimium value in the condition.In order to improve salt resistance of polymers,the method of reducing the effect of salt on polymer by strong hydration groups is abandoned.The intermolecular forces between functional groups and metal cations are used to enhance the property of polymer in high salty solution with high concentration of calcium and magnesium ions.Based on the recognition and evaluation of the two polymers including comb partially hydrolyzed polyacrylamide(CHPAM)and comb hydrophobic association polymer(CHAP),the polymer structure is further improved,and then the comb microblock hydrophobic associative polymer(CBHAP)is synthesized.The salt effects of CBHAP are researched systematically,including salt thickening property,shear thickening property,the mechanism of salt resistance,the flow characteristic.The main work and achievements of this paper are divided into the following aspects:(1)The three functional monomers are synthesized,including a macromolecular water-soluble monomer(Acryloyl-MPEG-1000),a macromolecular hydrophobic monomer(Acryloyl-O-20)and a double tailed hydrophobic monomer(PETMAM).(2)Two comb polymers are synthesized by using the two macromolecular monomers.Compared with partially hydrolyzed polyacrylamide(HPAM),salt resistances of the two poly1ers are improved significantly.The viscosity of CHAP can maintain above 100 mPa s in Nael solution with 1×105 mg/L salinity.However,the Ca2+ resistance is not improved significantly.(3)In order to enhance the thickening property in divalent ions,CBHAP is synthesized.The viscosity can reach 716.3mPa·s in saline water with 1×105mg/L salinity and 5740 mg/L Ca2+/Mg2+,which is much higher than that in frash water(277.5 mPa·s),showing an obvious salt thickening property.The shear thickening phenomenon will be observed when the concentration of polymer reaches 1000 mg/L and the salinity reaches 2×104mg/L.(4)The fractal aggregation process is explained by using light scattering technique and fractal theory.The aggregation morphology is confirmed by scanning electron microscope(SEM).Then the mechanism of salt resistance is achieved by analyzing the interaction between polymer chains and metal cations.(5)The flow characteristic is researched in porous media.The salt thickening and shear thickening phenomena are observed in porous media,showing a pressure rising.(6)The oil displacement of CBHAP in high salinity and high concentration of calcium and magnesium ions is evaluated.The ehanced oil recovery of CBHAP at 1000mg/L can reach 27.1%in saline water contained 5500 mg/L divalent cations,which is much higher than that of HPAM(11.5%)at 2000mg/L and CHAP(18.8%)at 1350 mg/L.Therefore,the CBHAP system is an effective agent for polymer flooding in high salinity reservoir.The molecular design is confirmed that the innovative combination of comb and micro-block structure can modify the salt resistance effectively.Compared with conventional polymer,the polymer system shows different salt effect and flow characteristic,for which the polymer system can establish high resistance coefficient and obtain high oil recovery at low concentration.Therefore,the comb and micro-blocked supramolecular polymer can be used at high salinity reservoirs.