Polyacrylamide Chemistry Degradation

Polyacrylamide (PAM) is a kind of important water-soluble high polymer,and has widespread applications in the domains such as petroleum extraction, water treatment , spinning and weaving ,papermaking,dressing,medicine,agriculture and so on. Which is also called"hundred industry assistants". At present,the polyacrylamide displacement technology has been promoted comprehensively in the Daqing Oilfield. However,the produced fluid contains polyacrylamide with a certain density and bigger relative molecular mass,which increases the viscosity of the solution,and the detention of polyacrylamide in crude oil will certainly affect the refinery products in quality. How to degrade the polyacrylamide in the produced fluid effectively has become a problem to be solved urgently at the well site. Through reading literature,we knew that the polyacrylamide oxidative degradation is an effective measure to obviously reduce the molecular weight of part of hydrolyzed polyacrylamide. Therefore, through designating several kinds of degeneration medicinal preparations,inspecting such factors influencing the degradation to polyacrylamide as density,solution PH value,reaction temperature,reaction time and so on,then gradually carry on analysis, optimization to these influencing factor, and try to find out the optimum reaction condition and screen the ideal degeneration medicinal preparation. By duplicated matching technology to choose more ideal polyacrylamide degeneration medicinal preparation again,we can make greater contribution to oilfield development.1 ExperimentingUsing HPAM with molecular weight 10,160,000 made in America to compound HPAM peroxide solution.Excepting particular accounting,for the HPAM peroxide solution used in experiments,the density is all 1500ppm,the Alpha value is 6.0. The experimental condition requires 45℃reaction temperature,27r/min rotor speed and 145.8s-1shear rate. The HPAM chemistry degradability displays on viscosity losing,determining viscosity with RV-2 rotational viscosimeter , because of linear relationship between the meter reading Alpha value and the solution viscosity,and for convenience,Alpha value is used to directly represent the viscosity change situation instead of converting it into viscosity value in the experiments.2 Experimenting Result Analysis and DiscussionS₂O₈^2-+Fe²⁺ is an oxidation– deoxidation initiation system. The merits of this system are: activation energy of reaction is low,so degradation can be initiated at comparatively low temperature,and the degeneration speed is comparatively fast.S₂O₈^2-+Fe²⁺initiation system is water-soluble,the activation energy of S2O82- is 140KJ/mol when it is independently thermal decomposed , the activation energy reduces to 50 KJ/mol after it composes with Fe²⁺ and forms oxidation– deoxidation initiation system,under degeneration can be initiated at 5℃. The action mechanism of S₂O₈^2- and Fe²⁺ is as follow:S₂O₈^2-+Fe²⁺ SO₄^2-+SO₄^2-·+Fe³⁺ The experimental result indicated: The degeneration system of S₂O₈^2-+Fe²⁺ is more ideal degeneration medicinal preparation than S₂O₈^2- or Fe²⁺ . Its function effect is much better than S₂O₈^2- or Fe²⁺ existing along. As HPAM ideal degeneration medicinal preparation,S₂O₈^2-+Fe²⁺ degeneration system has the following merit:First, The degeneration speed is fast, most degradation reaction occurs in a short time at the beginning of the reaction.Second,The HPAM degeneration degree is high.Third,The limitations to degradation reaction condition (for example the solution PH value, reaction temperature) are small.2.1 Fixing the density, reaction temperature and reaction time of Fe²⁺,inspect the degeneration function of S₂O₈^2- with different densities to HPAM under two kinds of PH value. CFe²⁺=10ppm t=45℃τ=1 day * note: This value is obtained under the reaction condition of PH 8.1,room temperatures (17℃) . The goal is to inspect if the reaction is influenced by reaction temperature . 2.2 Fixing the density, reaction temperature and reaction time of S₂O₈^2- ,inspect the degeneration function of +Fe²⁺ with different densities under two kinds of PH value. CS₂O₈^2-=70ppm t=45℃τ=1day Table 2.2 relationship between alpha value and Fe²⁺density Table2.1 and Table 2.2 indicate that,when S₂O₈^2- density is 70ppm and Fe²⁺ density is 10ppm,the degeneration effect to HPAM is the best. Therefore, we can determine that the best duplicate matching density for S₂O₈^2- and Fe²⁺ are 70ppm and 10ppm respectively. 2.3 Fixing the density, reaction temperature and reaction time of S₂O₈^2- Table2.3 indicates that ,when the solution PH value is lower than 7.1,along with reduction of PH value ,the viscosity breaking percentage of HPAM solution increases,and degeneration degree of HPAM increases;When the solution PH value is higher than 7.1,the viscosity breaking percentage of HPAM solution no longer changes along with PH value,which has"the alkali resistance",comparing with taking S₂O₈^2-or Fe²⁺ along as degradation preparation ,namely when alkalinity enhances,this degeneration preparation keeps the viscosity breaking percentage of HPAM solution maintaining at the high level of 87%.2.4 Fixing the density,PH value,reaction time of S₂O₈^2- and Fe²⁺ ,inspect the influence of reaction temperature. Table 2.4 indicates that,the higher reaction temperature is,the higher HPAM degeneration degree is. Under the conditions that density of S2O82- is 70ppm, density of Fe2+ is 10ppm,PH value is 5.1,reaction times is 2 hours,when reaction temperature is 95℃, HPAM solution viscosity breaking percentage is 96.7%, when it is 22℃, HPAM solution viscosity breaking percentage reaches 80.0%,but under similar response conditions,when reaction temperature is 22℃,when the degeneration medicinal preparation is made only with S2O82- ,HPAM solution viscosity breaking percentage is only 30.0%. This indicates:S2O82- and Fe2+ degeneration system has high-activity characteristic at low temperature.2.5 Fixing the densities,solution PH values,the reaction temperatures of S₂O₈^2- and Fe²⁺,inspect degeneration degree of HPAM variation along with time. Table2.5 indicates,with reaction time's increase,HPAM degeneration degree increases. Under the conditions that density of S2O82- is 70ppm,density of Fe²⁺ is 10ppm,PH value is 5.1,reaction temperature is 45℃, when reaction time reaches 3 days,HPAM solution viscosity breaking percentage reaches the maximum value,which is 95%. Table2. 5 also indicates,under the same reaction conditions,HPAM solution viscosity breaking percentage reaches 83.3% and 85.0% at 5 minutes and 0.5 hours after the beginning of the reaction, which are 87.7% and 89.5% of the total viscosity breaking percentage. This indicates that HPAM degradation reaction of S2O82-+Fe2+ degeneration system is completed in the short time after the reaction starts, and has quick action characteristic.2.6 Fixing the densities, solution PH values, the reaction temperatures The experimental result indicated that,to HPAM solution with different densities,under the conditions that density of S2O82- is 70ppm,density of Fe2+ is 10ppm,PH value is 5.1,reaction time is 1hour and reaction temperature is 45℃,this degradation system makes the HPAM solution viscosity breaking percentage more than 90% with obvious effectiveness. As shown in Table 2.6.3 Experiment conclusionThe experimental result indicated that,regarding the assigned degeneration medicinal preparation,HPAM the degeneration effect is affected by solution PH value,reaction temperature,and reaction time. As a whole,low solution PH value and high reaction temperature are advantageous to HPAM degradation reaction, a fixed-length reaction time may make HPAM degeneration degree to increase.The degeneration effect of S₂O₈^2-+Fe²⁺degeneration system to HPAM surpasses independent employment of S₂O₈^2- or Fe²⁺. This system has characteristics such as quick reaction rate,high degeneration degree,less limitation to function effect (for example solution PH value,reaction temperature). Under the conditions that density of S₂O₈^2- is 70ppm,density of Fe²⁺ is 10ppm,PH value is 5.1,reaction temperature is 45℃,HPAM solution viscosity breaking percentage reaches 83.3% and 85.0% at 5 minutes and 0.5 hours after the beginning of the reaction,and in three days , HPAM solution viscosity breaking percentage reaches the maximum value, which is 95%.