Surfactant/Polymer Flood of Midland Farms Dolomite Core D6 Gary Pope David Levitt Adam Jackson Jon Holder The University of Texas at Austin

Outline Objective Phase behavior formulation Core flood design Results Conclusions

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

Phase Behavior and Surfactant Formulation Criteria: 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)

Solubilization and Optimal Salinity Solubilization (cc/cc)

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

HPAM Polymer

HPAM Polymer

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)

Injected Fluids Pore Volumes Mixture 0.8 0.75% 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

Oil Flood Pressures

Water Flood Pressures

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

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

Surfactant Recovery Results Surfactant Retention: 0.43 mg/g

Surfactant/Polymer Pressure Results

Post-flood Polymer Assessment Polymer 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)

Conclusions Cumulative oil recovery of 95% Sorc = 0.01 High 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