Experimental and Theoretical Study of Polymer Flow in Porous Media
- K.S. Sorbie (Atomic Energy Establishment Winfrith, U.K.) | A. Parker (Atomic Energy Establishment Winfrith, U.K.) | P.J. Clifford (Atomic Energy Establishment Winfrith, U.K.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- August 1987
- Document Type
- Journal Paper
- 281 - 304
- 1987. Society of Petroleum Engineers
- 4.1.5 Processing Equipment, 1.6.9 Coring, Fishing, 5.2.2 Fluid Modeling, Equations of State, 5.3.2 Multiphase Flow, 4.1.2 Separation and Treating, 5.4.1 Waterflooding, 5.3.1 Flow in Porous Media, 5.2.1 Phase Behavior and PVT Measurements, 5.1 Reservoir Characterisation, 5.7.2 Recovery Factors, 4.3.4 Scale, 5.5 Reservoir Simulation, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 1.8 Formation Damage, 5.4.10 Microbial Methods, 5.6.5 Tracers, 5.3.4 Reduction of Residual Oil Saturation
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Summary. In this paper, an extensive study is presented on the single-phase flow of xanthan/tracer slugs in a consolidated sandstone. The phenomena studied include polymer/tracer dispersion, excluded/inaccessible volume effects, polymer adsorption, and viscous fingering. In some floods, there is also evidence of nonequilibrium effects. Macroscopic flow equation are derived that include terms to model all the behaviors listed above. A microscopic approach is also developed that describes certain features of polymer flow in porous media semiquantitatively.
Polymer flooding has been applied in many oil reservoirs Polymer flooding has been applied in many oil reservoirs to improve the vertical and areal sweep efficiency of waterfloods. Many supporting laboratory studies have been published that have contributed to our understanding of polymer flow in porous media. Most of these studies present data on a specific aspect of polymer behavior (e.g., adsorption), but there is usually no attempt to model mathematically the experimental polymer floods presented. presented. We present an extensive study of the single-phase flow of xanthan biopolymer in well-characterized outcrop sandstone cores at 100% brine and at residual oil saturations. In our experiments, beta-labeled brine (36Cl) and xanthan (14C) are used extensively to obtain accurate effluent profiles. All the observed physical phenomena in the transport of xanthan are studied, including polymer/tracer dispersion, excluded/inaccessible-volume polymer/tracer dispersion, excluded/inaccessible-volume phenoniena, adsorption, viscous fingering, and phenoniena, adsorption, viscous fingering, and nonequilibrium effects. Dispersion coefficients are calculated by use of an accurate analytic fitting procedure. With this procedure, we have found some new results on the relative procedure, we have found some new results on the relative magnitudes of polymer and tracer dispersion.
There are two main approaches to the modeling of polymer flow in porous media. The macroscopic approach polymer flow in porous media. The macroscopic approach uses a continuum formulation to model the various effects observed in a polymer flow experiment; e.g.. dispersion, excluded volume, and viscous fingering. The microscopic approach attempts to set up a simplified model of the porous medium and, in some cases, a description of the porous medium and, in some cases, a description of the polymer at the molecular scale. These models can then polymer at the molecular scale. These models can then be used qualitatively or semiquantitatively as a basis for explaining why certain phenomena are observed; e.g., excluded volume effects for various molecular sizes and rheological effects.
Both macroscopic and microscopic modeling have been used to match and to interpret our results. Macroscopic flow equations have been developed that describe all the observed behavior. These are based on generalized convection/dispersion equations that, in the most general case, must be solved numerically. Analytic methods are used, however, to obtain most of the flow parameters for a given flood. Matches to experimental floods with these macroscopic flow equations are very good. Microscopic modeling is used semiquantitatively to interpret the excluded/ inaccessible-volume behavior. Models based on a combination of depleted layer theory and capillary tube and bundle arrays have been used for this purpose. An approach to interpreting dispersion is also outlined.
Experimental Details of 36Cl/Xanthan Floods
Materials. The sandstone cores used in this work were cut along the bedding plane of a block of sandstone obtained from the Clashach quarry in Scotland. This material is more than 99.5 % quartzitic and has a very low clay concentration. 4 Cores were fitted with stainless steel end caps (dead volume 2 cm3) and five equidistant pressure tappings, and then were resin-coated and baked at 170deg.C [338deg.F]. Details of the cores used in this work are given in Table 1.
The solvent used throughout the experiments was a solution of 32 g/L artificial seawater with 400 mg/L sodium azide as a bactericide. The composition of the British Drug House (BDH) artificial seawater is given in Table
2. All solvent was filtered through a 0.45-um Millipore filter.
Beta-radio-labeled chemicals, 36Cl as NaCl and 14C as glycerol and glucose, were obtained, together with a scintillation mixture "phase combining system." Two Xanthans were used: Pfizer Flocon 48000TM and a 14C labeled product. The latter polymer was produced by a Xanthomonas Strain C and was 35% pyruvylated. 14C glucose was added to the fermentation broth as the sole carbon source late in the growth cycle, ensuring that most of the 14C was incorporated as xanthan. It was provided as a clear, cell-free solution with a specific activity provided as a clear, cell-free solution with a specific activity of 1.8 MBq/cm 3 [48.6 x 10 -6 Ci/cm 3 ] and a xanthan concentration of 3200 mg/L. The intrinsic viscosity of the Flocon was 7500 cm 3/g, and that of the labeled xanthan was approximately 2000 cm 3/g. Some properties of these two xanthans are summarized in Table 3.
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