1 Surfactant/Polymer Flood of Midland Farms Dolomite Core D6Gary Pope David Levitt Adam Jackson Jon Holder The University of Texas at Austin

2 Outline Objective Phase behavior formulation Core flood design ResultsConclusions

3 Objectives Achieve initial oil saturation and residual oil saturation to water similar to MF reservoir values and at similar pressure gradients Recover 90% of waterflood residual oil with surfactant and polymer Achieve low surfactant retention

4 Phase Behavior and Surfactant FormulationCriteria: Low viscosity Low interfacial tension High solubilization ratio Short equilibration time [Photo] 0.75% N67-7PO, 0.25% IOS C1518, 2% SBA (WOR 1:1) with MF3 at 38C after 6 days Scan from 2 - 6% Equilibration time ~ 12 (days) Solubilization, s* = 12 (cc/cc)

5 Solubilization and Optimal SalinitySolubilization (cc/cc)

6 HPAM Polymer Hydrolyzed Polyacrylamide (HPAM)Flopaam 3330S from SNF Floeger

7 HPAM Polymer

8 HPAM Polymer

9 Midland Farms Dolomite Core Design and Configuration = 0.18 kbrine= 166 md kro = 0.40 krw = 0.03 Swi= 0.26 Sorw= 0.39 Formation Brine: 6.1% TDS (8:1 NaCl:CaCl2)

10 Injected Fluids Pore Volumes Mixture 0.80.75% N67[7PO], 0.25% IOS C1518, 2% SBA 0.02% Na2CO3, 4.45% NaCl 1500 ppm Flopaam 3330S 0.2 2% SBA 3.05% NaCl 1.5 1.93% NaCl 1200 ppm Flopaam 3330S

11 Oil Flood Pressures

12 Water Flood Pressures

13 Sulfate Detected in Produced Formation BrineEffluent Sample Sulfate Concentration (ppm) 1 1268 2 1686 3 2094 4 2615 Samples taken from tubes preceding oil breakthrough

14 Oil Recovery Results Free Oil = 90% Oil from Emulsion = 5%

15 Surfactant Recovery ResultsSurfactant Retention: mg/g

16 Surfactant/Polymer Pressure Results

17 Post-flood Polymer AssessmentPolymer Resistance Factor (Rf): Rf = (DPp/DPw)q, Sw = 23/0.3 = 87 Polymer Permeability Reduction Factor (Rk): Rk = Rf / (mp/mw) = 87/(5.5/0.911) = 14.5 Previous core flood indicated: Rk = 2 (Prior HPAM used 2000 ppm Alcomer 60RD)

18 Conclusions Cumulative oil recovery of 95% Sorc = 0.01High oil recovery in a dolomite without sodium carbonate 50% of the surfactant was recovered No plugging occurred Anhydrite is present in core Sodium carbonate can not be used Polymer concentration may be reduced