Displacement of a Viscous Oil by the Combined Injection of Hot Water and Chemical Additive
- M. Karakas (Schlumberger Well Services) | S. Saneie (U. of Southern California) | Y.C. Yortsos (U. of Southern California)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- July 1986
- Document Type
- Journal Paper
- 391 - 402
- 1986. Society of Petroleum Engineers
- 5.2.1 Phase Behavior and PVT Measurements, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.4.1 Waterflooding, 5.7.2 Recovery Factors, 4.1.5 Processing Equipment, 4.1.2 Separation and Treating, 5.3.4 Reduction of Residual Oil Saturation, 5.4.6 Thermal Methods, 5.1.1 Exploration, Development, Structural Geology, 5.3.2 Multiphase Flow
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The modeling of an adiabatic hot waterflood assisted by the simultaneousinjection of a chemical additive is presented. The process considered isone-dimensional, two-phase flow, with process considered is one-dimensional,two-phase flow, with negligible effects of dispersion, heat conduction, andlateral heat losses. The model allows for the chemical to partition into theaqueous phase and to be adsorbed on the solid rock. The effects of temperatureon the viscosity ratio and the adsorption kinetics and of chemicalconcentration on the fractional flow curves are included.
The theory of generalized simple waves (coherence) is used to developsolutions for the temperature, concentration, and oil saturation profiles, aswell as the oil recovery curves. The results obtained show that in theadiabatic case the combined injection of chemical and hot water considerablyenhances the oil recovery. The sensitivity of the recovery performance to theprocess parameters is discussed. It is shown that, for Langmuir processparameters is discussed. It is shown that, for Langmuir adsorption kinetics,the chemical resides in the heated region of the reservoir if its injectionconcentration is below a critical value, and in the unheated region if itsconcentration exceeds this critical value. Typical results for a chemical sluginjection in a tertiary recovery process indicate that recovery performance ismaximized when the chemical resides entirely in the heated region of thereservoir.
The displacement of a viscous crude oil by conventional recovery schemesoperating at the reservoir temperature is not very effective due to the lowmobility of the oleic phase. Taking advantage of the favorable alteration inthe viscosity of the fluid phases achieved at high temperatures, variousthermal processes phases achieved at high temperatures, various thermalprocesses have been successfully implemented for the economic recovery of heavyoils. Steam injection, and, to a lesser degree, in-situ combustion have beenalready established as commercially viable enhanced recovery methods for suchreservoirs. In an effort to further improve the recovery performance attainedin thermal processes, it has been recently suggested' to aid the displacementmechanisms by the simultaneous injection of chemical additives.
The primary function of chemical additives in enhanced recovery is to alterthe mobility characteristics of the fluid phases by reducing the interfacialtension between aqueous and oleic phases, thus increasing the relativepermeability of oil to flow. This effect if acting in a synergestic way withthe increased mobility achieved at higher temperatures, is expected toconsiderably enhance the recovery efficiency of standard thermal recoveryprocesses. Although factors other than the above may play important roles athigher temperatures, it is the combined effect of changes in relativepermeabilities and viscosity ratios that principally accounts for anenhancement in recovery.
Clearly, the viability of such a combined injection scheme rests on thehypothesis that the injected chemical additive asks its synergestic effect onthe heated region of the reservoir, and particularly on the hot liquid regionthat precedes any advancing particularly on the hot liquid region that precedesany advancing condensation fronts (e.g., in steam injection) (Fig. 1a).Therefore, it is important to determine the region of residence of thechemical, with ultimate objective the design of optimal injection schemes thatmaximize recovery performance. In an attempt to address this complex subject,we elect to study the simpler case of an adiabatic hot waterflood assisted bysimultaneous injection of a chemical additive. Such a study, besides its ownimportance for a combined hot water and chemical injection process, will enableus to gain considerable insight on the rates of propagation of chemical andtemperature fronts in the liquid zone preceding steam fronts in a combinedsteam injection process. process. In view of the above, the process to beconsidered here involves the combined injection of hot water and a chemicaladditive in one-dimensional reservoir geometries (linear or radial) (Figure1a). For simplicity, the study is restricted to high injection rates such thateffects of dispersion, heat conduction, capillarity, and lateral heat lossesare negligible.
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