Polymer flooding is a commercial enhanced oil recovery (EOR) method used to increase the sweep efficiency of water floods. Hydrolyzed polyacrylamide (HPAM), a synthetic commercial polymer, is widely used in commercial polymer floods and it is also used for mobility control of chemical floods using surfactants such as surfactant-polymer flooding and alkaline-surfactant-polymer flooding. The increase in the degree of hydrolysis of HPAM at elevated temperature or pH with time affects the polymer solution viscosity and its adsorption on rock surfaces. A polymer hydrolysis model based on published laboratory data was implemented in UTCHEM, a chemical EOR simulator, in order to assess the effect of hydrolysis on reservoir performance. Both 1D and 3D simulations were performed to validate the implementation of the model. The simulation results are consistent with the laboratory observations that show an increase in polymer solution viscosity as hydrolysis progresses. The numerical results indicate that hydrolysis occurs very rapidly and impacts the near wellbore region polymer injectivity. / text

Polymer hydrolysis is the first (and rate limiting) step for biomethanation of heterogeneous biomass feedstock’s. Satisfactory hydrolysis has been difficult to achieve, understand and predict adequately, to run anaerobic bioreactors with such feedstock’s efficiently. The fraction of hot water soluble extracts (crude proteins and extractables, Fcpe), the nature and material of intercellular binding and the extent and complexity of lignin present have been considered as key parameters for hydrolysis and has been analyzed for a variety of biomass degradation data available at the Centre for Sustainable Technologies, Indian Institute of Science. Feedstocks were grouped into those bound with high levels of pectic/protein materials or lignin-bound types. The data on the initial (10-15d) as well as the overall rates of hydrolysis (0-50d) has been analyzed. The extent of hydrolysis achieved for pectin bound substrates were high (≥65%) and that of lignin bound substrate was low (≤30% VS, Acacia). The initial hydrolysis rates were strongly correlated to the content of extractables (=0.117Fcpe). Subsequently, the hydrolysis rates rise to reach maxima and then begin to fall. Most fresh feedstock had somewhat similar rates of the increase in hydrolysis rates but the time to reach maximum and its value varied among feed stocks. Many lignin bound feed stocks did not have such a pattern. With regards to the overall hydrolysis rate constant, it was found that these clustered into two groups that represented pectin bound (0.154/d) and lignin bound (0.045/d) types. Therefore from this study it was concluded that anaerobic decomposition of heterogeneous biomass could be predicted using two rate parameters and one intrinsic property of the biomass feedstock, namely, a. the initial rate of hydrolysis (based on the extent of extractables =0.117 Fcpe) b.the maximum rate achieved and the time when it is reached (an intrinsic property based on feed stock and but not determined in this study) c. the overall hydrolysis rate (choosing between 0.154 /d or 0.045 /d depending upon the nature of inter-cellular binding material, pectin or lignin, respectively). This research provides new insights into the prediction of hydrolysis rate a key limiting step for heterogeneous biomass biomethanation (hydrolysis) based on the level of extractables, the type of cellular cementing material and the maxima that can be achieved.