Observations on Tailoring Chemical Slugs and Simulating Reservoir Cores for an Oil-Wet Reservoir

Abstract

Members SPE-AIME "Retired. Formerly with U.S. DOE. This paper was presented at the SPE/DOE Fourth Symfmsium on Enhanced Oil Recovery held in Tulsa, OK, April 15-18, 1S64. The material is subject to correction by the author. Permission to copy is restricted to an abstract of not more than 3DD words. Write SPE, 6200 North Central Expressway, Draww 64706, Dallas, Texas 75206 USA. Telex 730969 SPEDAL. kBS'TMCT of three petroleum sulfonates, with a built-in cosurfactant that was primarily amyl and ethoxylated hexylResults are presented from three areaa of the alcohola. Its phase behavior with Delaware-Childers laboratory studies in connection with the surfactant-crude was classical Winsor (~)with an optimal salinity polymer pilot field teat conducted by the U. S. Depart-of 1.3% NaC1. The surfactant slug was injected at the nent of Bnergy: 1. Sulfonate produced, both in the suboptimal ealinity 0.8% NaC1. The polymer was Nalco Eield and laboratory tests, was chiefly in the oil Chemical Co. Nal-flo B, a polyacrylamide 30% anionic phase, indicating a marked departure from the optimal and said to have an average molecular weight 8-10 :ondition of equal distribution. This cannot be attri-inillion. The mobility buffer slug hae a salinity of buted to increased salinity, as the salinity of the 2.29% NaCl, and was graded in eight logarithmic stepe produced brine waa not very different from that of the ranging from 20cp (SaPa.s)to 0.8 cp (mPa.s) (water at Lnjectedsurfactant slug. Suggeeted causes are dilu-reeervoir temperature). The laboratory parametric tion and changing waterfoil ratio that resulted in study presented here and previously Q) was carried out Fractional repartitioning of the complex alcohol and on an outdated polymer sample having about 80% of its sulfonate.original viscoeity. Therefore the values reported 2.The use of dilute brine instead of fresh water for should be considered on a relative basic only. the polymer slug avoided large variations in viscosity that would have resulted from eeaeonal variations in EXPERIMENTAL PROCEDURES the supply water. In this connection, it was found that the non-Newtonian character of the polymer wae Flood tests iifferent for two solutions at the same viscosity but Cores were vacuum-saturated with synthetic proiifferent polynter/saltcomposition. duced brine, mounted in a Hassler holder with confining 3.Berea cores, when fired, behaved like the oil-wet preseure of 180-400 psi (1.2-2.8 MPa), oil flooded to reservoir coree in respect to oil recovery, relative irreducible water, and then flooded at 1-6 ftfda (0.3-2 permeability, and flow-resistance history. A supple-n/da) with 0.88% NaCl, to residual oil. Chemical nentary eilicone treatment to give the same nettability flooding, at 1-2 ft/da (0.3-0.6 m/da) consisted of IS the oilfield cores had no beneficial effect. sequentially injecting 0.