| The polyacrylamide (PAM) and its copolymers as a linear water soluble polymer are highly versatile group used in a multitude of application. Partially Hydrolyzed Polyacrylamide (HPAM) is widely used in Daqing Oil Compancy, plays a very important role in oil recovery. Polymer Oil flooding becomes one of the important methods in later period of oilfield. Generally speaking, HPAM can adjust the injected water's rheology properties and improve the viscosity of driven solution, make better the efficiency of spread etc. However, the complex conditions in stratum and the rich ion makeup in underground water require the HPAM's molecular conformation and molecular weight in a proper status. So how to evaluate and determine the HPAM's molecular conformation and chain structure in different micro circumstance is very important in both theory and practice to explain the theory of polymer oil driven and make better the current resource. The effects of added salts (NaCl, Na2SO4 and CaCl2) on the conformational properties of partially hydrolyzed polyacrylamide (Mw =4.5×106) with different concentrations were investigated by using static laser light scattering. The data points with evidence to the strong dependence of the chain structure on the charge density and on the kinds and concentration of added salts. Our results show that the added salts makes the molecule size Rz and second virial coefficient A2 decrease. When the concentration of added salts increases to some amount, the effects of salts tended towards maximum. Some special interaction between CaCl2 and hydrolyzed polyacrylamide was investigated also. 1, The molecule size and A2 of HPAM change greatly in a narrow range of salt concentration until shielding effect reaches to maximum. This indicates that HPAM network gels would fall into phase transitions (It would fall into a swollen state at low salt concentration and a collapsed sate at high salt concentration) by varying the concentration of added monovalent cation. 2, Monovalent ion can effectively shield the repulsive interaction of polyelectrolyte and result in shrinking of the molecule. The shielding effect tends towards maximum as the salt concentration rises and the Rz loses about 30%. The shielding effect is also independent on the kind of anion.3, The coil conformation of HPAM is much more extending than that of it inθsolution and that of PAM without carboxylic groups even when shielding action tends towards maximum.4, The charge shielding effects and cross-linking action between Ca2+ and HPAM happen at the same time. The Rz still decreases as the Mw increases at certain salt concentration range, which indicates the influence of cross-linking action on coil size is dominant over that of shielding action.The long-distance structure parameters of partial hydrolyzed polyacrylamide (HPAM) used for oil-recovery with different time were obtained by using the Gel Permeation Chromatography/Laser Light Scattering (GPC-MALLS) techniques for the first time. We consider that the degradation of HPAM after oil-extraction mostly ascribes to the mechanical degradation. A multifunctional physical simulation instrument was utilized to simulate the high rate process in which polymer was pushed into shot hole and bore core from pipeline. The structure parameters of polymer sheared by the man-made rock core were also determined by GPC-MALLS. Other experiments concerning the degradation of HPAM were also done to discuss the mechanism of degradation. All of our work testified that the degradation of HPAM happened at the moment when HPAM was pushing into shot hole and rock core by the shearing action and pulling action. The mechanism of degradation was also discussed.In conclusion, our experiments testify that mechanical degradation of HPAM is the main loss in oil recovery. No matter how long the polymer solution underwent in stratum, the reduction of molecular weight is similar. Furthermore, our experiments testify most degradation of polymer in oil recovery happened at the entry point of strat...
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