Experimental data on water soluble polymers thermal and hydrolytic stability, reactivity ratios of monomers and Frr calculation for thermally stable preformed particle gels therefrom

Experimental data on water soluble polymer thermal and hydrolytic stability in acidic, neutral and basic pH conditions in aqueous solution is presented. Thermal and hydrolytic stability of polymer aqueous solutions were monitored in variable pH medium by aging at 130 °C temperature for different aging time. Polymer viscosity measurements were performed periodically for 3 months. Furthermore, this data can serve as a basis of monomer selection for thermally stable hydrogels for applications like oil recovery, hydrogel coatings for steam sterilized medical devices and other applications. Reactivity ratios were determined for monomers associated to the most stable polymers using 1H NMR analysis. Monomer reactivity ratios for DMA (M1) and NaSS (M2) depicted to be r1 = 0.031 and r2 = 5.379 using Fineman-Ross method and r1 = 0.028 and r2 = 5.495 using Kelen-Tudos method. The performance of preformed particle gels developed based on these monomers, in plugging the open fractures is explained using residual resistance factor (Frr) calculation.

Thermal stability of polymers Hydrolytic stability of polymers Viscosity measurements Thermogravimetric analysis (TGA) Reactivity ratio Residual resistance factor (Frr) a b s t r a c t Experimental data on water soluble polymer thermal and hydrolytic stability in acidic, neutral and basic pH conditions in aqueous solution is presented. Thermal and hydrolytic stability of polymer aqueous solutions were monitored in variable pH medium by aging at 130 °C temperature for different aging time. Polymer viscosity measurements were performed periodically for 3 months. Furthermore, this data can serve as a basis of monomer selection for thermally stable hydrogels for applications like oil recovery, hydrogel coatings for steam sterilized medical devices and other applications. Reactivity ratios were determined for monomers associated to the most stable polymers using 1 H NMR analysis. Monomer reactivity ratios for DMA (M 1 ) and NaSS (M 2 ) depicted to be r 1 = 0.031 and r 2 = 5.379 using Fineman-Ross method and r 1 = 0.028 and r 2 = 5.495 using Kelen-Tudos method. The performance of preformed particle gels developed based on these monomers, in plugging the open fractures is explained using residual resistance factor (Frr) calculation. For hydrolytic thermal stability of polymer aqueous solutions, viscosity at 23 °C was determined for samples that were exposed to 130 °C temperature for variable time in acidic, basic and neutral pH. The change in viscosity was correlated to polymer molecular weight change and determine polymer backbone stability. For reactivity ratios, polymerization was conducted at different co-monomers feed, and by collecting the copolymer at early stage of polymerization (preferably less than 10% conversion) and analysed using 1

Value of the Data
• The dataset represents viscosity measurements data to determine thermal and hydrolytic stability when polymer aqueous solutions were prepared in acidic, neutral and basic medium. • The data on reactivity ratios of p-Sodium styrene sulfonate and N, N'-Dimethylacrylamide was reported and can be beneficial for researchers who are interested in synthesizing copolymer compositions based on these monomers for variety of applications. This is the first report of reactivity ratio data for this monomer combination.

Data Description
Data for thermal and hydrolytic stability of a polymer aqueous solutions is represented in Fig. 1 . The dataset represents the viscosity values of polymer aqueous solutions recorded as a function of time (# of days exposed at 130 °C) when prepared in medium of pH 2 (acidic), pH 7 (neutral) and pH 13 (basic). The obtained viscosity values for polyacrylamide and polyacrylic acid depicts that these polymers are hydrolytically and thermally unstable at 130 °C in all pH media. For Polyvinylpyrrolidone polymer, viscosity increase as a function of time in all pH media was noted, which can be attributed to partial hydrolysis of polymers. Polydimethylacrylamide showed increase in viscosity as a function of time under acidic condition, on the other hand, under neutral and basic condition, less significant changes to the initial reported viscosity values were observed. Poly (sodium styrenesulfonate) polymer solutions showed almost similar viscosity values over the period of exposure under all pH conditions, depicting the thermal and hydrolytic stability of this polymer. Actual values for all polymer solutions are reported in attached excel file. This dataset can be useful in screening of polymers for applications involving variable moisture, pH and temperature conditions. Fig. 2 shows the reactivity ratio plots for monomers dimethylacrylamide and p-(sodium styrenesulfonate) using Fineman-ross method ( Fig. 2 a) and Kelen-Tudos method ( Fig. 2 b). The monomer reactivity ratios estimated to be r 1 = 0.031 and r 2 = 5.379 using Fineman-Ross method and r 1 = 0.028 and r 2 = 5.495 using Kelen-Tudos method where M 1 and M 2 monomers are for DMA and NaSS, respectively. These parameters indicate that NaSS has very high reactivity than that of DMA.
The Residual resistance factor (F rr ) is an important parameter to confirm plugging efficiency performance data obtained in core-flooding test. F rr was calculated in order to determine the extent of the permeability reduction to water of the fractured core after the gel placement. Residual resistance factor (Frr) and fracture permeability ( K after) at variable brine injection rates is shown in Fig. 3 . The Frr values decreased with the increase in brine injection flow rates, likely indicating that the chase water created a path through or around the packed gel since no gel washout was observed with the increase in brine injection rates (explanation can be found in our CEJ paper).

Sample preparation for thermal and hydrolytic stability
Polymer aqueous solutions were prepared in different pH medium as acidic, neutral and basic in deionized water. Acidic solution of pH = 2 was prepared using 0.1 M HCl and basic solution of pH = 12 was prepared using 0.1 M NaOH along with neutral pH = 7 solution. Polymer aqueous solutions prepared in these solutions, at a concentration, just enough to get measurable value on Brookfield viscometer. Glass pressure tubes were used for testing, where sample was transferred through canula transfer and sealed under argon atmosphere. These glass tubes were then kept in oven maintained at 130 °C and periodic measurements viscosity measurements were performed.  . 1a), neutral pH = 7 (Fig. 1b) and basic pH = 13 (Fig. 1c) as a function of aging time (days).

Monomer reactivity ratio determination
The polymerization of NaSS and DMA were conducted at different monomer feed ratio using VA-044 initiator in D 2 O. The polymerization reaction was conducted under argon inert atmosphere at 40 °C. After specific time, 1 H NMR spectrum was collected on 400 MHz NMR sys-tem, where monomer conversions were determined by monitoring the change in the intensity of peaks associated with vinylic protons of the monomers.

Residual resistance factor (Frr) calculation for coreflooding experiments
The Frr is defined as the ratio of the mobility of water before the gel placement to the mobility of water after the gel placement [1] .
Where K b represents the initial permeability of the fractured core including both the matrix and the fracture parts, and Ka is the permeability of the fractured core to brine after the HT-PPG placement. μ w is the viscosity of the injected brine.
By applying Darcy's law Where q is the volumetric injection flow rate (cc/sec), A is the cross sectional area of the fractured core (cm 2 ), P is the pressure drop along the fractured core (atm), μ is the viscosity of the brine and L is the length of the fractured core. The Frr can be expressed in terms of pressure gradient along the fractured core once the steady state condition is achieved as a function of the injection flow rate. The data file for pressure gradient values obtained during a core-flood experiment is attached. These pressure gradient values were used for further calculations. The initial permeability of the fractured core K b = 11313 Darcy. The pressure drop across the fractured core during the first water flooding was calculated using the following equation of the flow through the parallel plate model