Injectivity Characteristics of EOR Polymers
- 27 October 2009
- journal article
- Published by Society of Petroleum Engineers (SPE) in SPE Reservoir Evaluation & Engineering
- Vol. 12 (05), 783-792
- https://doi.org/10.2118/115142-pa
Abstract
Summary: For applications in which enhanced-oil-recovery (EOR) polymer solutions are injected, we estimate injectivity losses (relative to water injectivity) if fractures are not open. We also consider the degree of fracture extension that may occur if fractures are open. Three principal EOR polymer properties are examined that affect injectivity: (1) debris in the polymer, (2) polymer rheology in porous media, and (3) polymer mechanical degradation. An improved test was developed to measure the tendency of EOR polymers to plug porous media. The new test demonstrated that plugging tendencies varied considerably among both partially hydrolyzed polyacrylamide (HPAM) and xanthan polymers. Rheology and mechanical degradation in porous media were quantified for a xanthan and an HPAM polymer. Consistent with previous work, we confirmed that xanthan solutions show pseudoplastic behavior in porous rock that closely parallels that in a viscometer. Xanthan was remarkably resistant to mechanical degradation, with a 0.1% xanthan solution (in seawater) experiencing only a 19% viscosity loss after flow through 102-md Berea sandstone at a pressure gradient of 24,600 psi/ft. For 0.1% HPAM in both 0.3% NaCl brine and seawater in 573-md Berea sandstone, Newtonian behavior was observed at low to moderate fluid fluxes, while pseudodilatant behavior was seen at moderate to high fluxes. No evidence of pseudoplastic behavior was seen in the porous rock, even though one solution exhibited a power-law index of 0.64 in a viscometer. For this HPAM in both brines, the onset of mechanical degradation occurred at a flux of 14 ft/d in 573-md Berea. Considering the polymer solutions investigated, satisfactory injection of more than 0.1 pore volume (PV) in field applications could only be expected for the cleanest polymers (i.e., that do not plug before 1,000 cm3/cm2 throughput), without inducing fractures (or formation parts for unconsolidated sands). Even in the absence of face plugging, the viscous nature of the solutions investigated requires that injectivity must be less than one-fifth that of water if formation parting is to be avoided (unless the injectant reduces the residual oil saturation and substantially increases the relative permeability to water). Since injectivity reductions of this magnitude are often economically unacceptable, fractures or fracture-like features are expected to open and extend significantly during the course of most polymer floods. Thus, an understanding of the orientation and growth of fractures may be crucial for EOR projects in which polymer solutions are injected.Keywords
This publication has 27 references indexed in Scilit:
- Injectivity Decline in Water-Injection Wells: An Offshore Gulf of Mexico Case StudySPE Production & Facilities, 2000
- A Model for Predicting Injectivity Decline in Water-Injection WellsSPE Formation Evaluation, 1997
- Influence of Microgels in Polysaccharide Solutions on Their Flow Behavior Through Porous MediaSociety of Petroleum Engineers Journal, 1984
- The Effects of Mechanical Degradation and Viscoelastic Behavior on Injectivity of Polyacrylamide SolutionsSociety of Petroleum Engineers Journal, 1983
- Rodlike Polymer Solution Flow through Fine Pores: Influence of Pore Size on Rheological BehaviorJournal of Rheology, 1982
- Mechanical Degradation of Partially Hydrolyzed Polyacrylamide Solutions in Unconsolidated Porous MediaSociety of Petroleum Engineers Journal, 1976
- Shear Degradation of Partially Hydrolyzed Polyacrylamide SolutionsSociety of Petroleum Engineers Journal, 1975
- Analysis of Factors Influencing Mobility and Adsorption in the Flow of Polymer Solution Through Porous MediaSociety of Petroleum Engineers Journal, 1974
- Factors Influencing Mobility Control By Polymer SolutionsJournal of Petroleum Technology, 1971
- Estimated Effect of Vertical Fractures on Secondary RecoveryJournal of Petroleum Technology, 1954