Radial and Linear Polymer Flow - Influence on Injectivity

Abstract

Polymer injectivity is a critical parameter for implementation of polymer flood projects. An improved understanding of polymer injectivity is important in order to facilitate an increase in polymer EOR implementation. Typically, injectivity studies are performed using linear core floods. Here we demonstrate that polymer flow in radial and linear models may be significantly different and discuss the concept in theoretical and experimental terms. Linear core floods using partially hydrolyzed polyacrylamides (HPAM) were performed at various rates to determine in-situ viscosity and polymer injectivity. Radial polymer floods were performed on Bentheimer discs (30 cm diameter, 2-3 cm thickness) with pressure taps distributed between a central injector and the perimeter production well. The in-situ rheological data are also compared to bulk rheology. The experimental set up allowed a detailed analysis of pressure changes from well injection to production line in the radial models and using internal pressure taps in linear cores. Linear core floods show degradation of polymer at high flow rates and a severe degree of shear thickening leading to presumably high injection pressures. This is in agreement with current literature. However, the radial injectivity experiments show a significant reduction in differential pressure compared to the linear core floods. Onset of shear thickening occurs at significantly higher flow velocities than for linear core floods. These data confirm that polymer flow is significantly different in linear and radial flow. This is partly explained by the fact that linear floods are being performed at steady state conditions, while radial injections go through transient (unsteady state) and semi-transient pressure regimes. History matching of polymer injectivity was performed for radial injection experiments. Differences in polymer injectivity are discussed in the framework of theoretical and experimental considerations. The results may have impact on evaluation of polymer flood projects as polymer injectivity is a key risk factor for implementation.

Polymer Flow in Porous Media: Relevance to Enhanced Oil Recovery

“…Skauge et al [37] reported that in radial flow, the onset of extensional viscosity occurred at higher shear rates than at typical core flooding. Since radial flow is more representative of real field conditions, results obtained from radial disks should be more accurate as laboratory data for field implementation.…”

“…In earlier studies of radial flow experiments, Skauge et al [37] used local pressure taps as a function of radial distance from the injection well to derive in-situ rheology. These experiments demonstrated both shear thinning and strong apparent shear thickening behavior.…”

“…Until now, there has been no direct method to obtain it and, generally it has been measured by performing core floods. However, Skauge et al [37] observed significantly different in-situ rheology for HPAM in linear compared to radial geometry. This discrepancy might be due to differing pressure regimes and flux conditions experienced by polymer solutions flowing through these inherently different flow geometries.…”

Historical and recent observations in polymer floods: An update review

“…History matching approaches of primary and water injection can also impact the prediction of polymer injection. Input variables required to predict polymer flood performance are also part of the uncertainties that needs to be considered in simulation studies (Aldhuwaihi, King & Muggeridge, 2015;Alkhatib, 2015;AlSofi and Blunt, 2011;Chiotoroiu et al, 2016;Fabbri et al, 2015;Romero et al, 2013;Skauge and Salmo, 2015;Skauge et al, 2016;Zhou, Y., Muggeridge, A. H., Berg, C. F., & King, P. R., 2015). Additionally, commercial simulation tools still have some limitations to properly represent the potential formation of in-situ emulsions and its impact on well injectivity/productivity.…”

Polymer Injectivity: Investigation of Mechanical Degradation of Enhanced Oil Recovery Polymers Using In-Situ Rheology

“…Regardless of the nature and differences in the molecular structure of these two polymers, polymer viscosity is the main physical property in the context of polymer flooding. Polymer viscosity depends on polymer molecular structure, molecular weight [3], polymer concentration [4], salinity [5,6], temperature [7,8], degree of hydrolysis [9], pH [10], flow model and type of forces dominating the flow [11].…”