A Postflood Evaluation Test of the North Burbank Surfactant/Polymer Pilot
- P.B. Lorenz (Natl. Inst. of Petroleum and Energy Research) | J.C. Trantham (Phillips Petroleum Co.) | D.R. Zornes (Phillips Petroleum Co.) | C.G. Dodd (Connecticut Technology Consultants)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- July 1986
- Document Type
- Journal Paper
- 341 - 353
- 1986. Society of Petroleum Engineers
- 1.6.9 Coring, Fishing, 2.5.2 Fracturing Materials (Fluids, Proppant), 1.2.3 Rock properties, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.5 Reservoir Simulation, 5.1 Reservoir Characterisation, 1.6 Drilling Operations, 5.5.2 Core Analysis, 1.10 Drilling Equipment, 5.6.5 Tracers, 5.5.8 History Matching, 4.1.9 Tanks and storage systems, 4.1.5 Processing Equipment, 2.2.2 Perforating, 1.14 Casing and Cementing, 2.4.3 Sand/Solids Control, 5.2.1 Phase Behavior and PVT Measurements, 5.4.1 Waterflooding, 5.6.2 Core Analysis, 5.3.2 Multiphase Flow, 4.1.2 Separation and Treating, 3 Production and Well Operations
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In a follow-up evaluation to a surfactant/polymer pilot in the North Burbank field of Osage County, OK, a test program was designed to determine the relative importance of the various detrimental factors-heterogeneity, crossflow, ion exchange, and partitioning-that lead to nonconformance and degradation of surfactant and polymer slugs. A diagnostic well was drilled within the drainage area of one of the best producing wells for tertiary oil. The location was selected because (1) producing wells for tertiary oil. The location was selected because (1) there was good communication between the injector and producer in this quadrant, (2) it was close to an injector and probably would be swept by injected chemicals, and (3) simulation suggested that a well at this location could encounter several zones swept by surfactant, polymer, and fresh water. Rock, brine, and oil samples were taken and analyzed for sulfonate, polyacrylamide, alcohol, calcium, and residual oil. Comparisons were made with core analyses on adjacent wells at the start of the project and with fluids produced from them.
Chloride and residual oil were low, indicating that the region had been swept and oil displaced. Sulfonate and alcohol were surprisingly high. Surfactant and cosurfactant were segregated, and the slug was markedly displaced toward the Type II+ direction from optimality. No polyacrylamide was detected in the brine or on the rock, suggesting a polyacrylamide was detected in the brine or on the rock, suggesting a change in flow patterns that diverted polymer around the region so that sulfonate and alcohol were not fully displaced. These observations indicate that the performance of the pilot was influenced by both heterogeneity and degradation of the chemical slug.
This paper presents the results of analyses of cores and fluids from a diagnostic well drilled during the mature stage of a surfactant/polymer pilot. The program was designed to determine (1) whether heterogeneity or surfactant/polymer performance was the dominant factor in tertiary oil recovery from the pilot; (2) the relative contributions to the observed pilot performance of the surfactant/polymer combination as opposed to the polymer alone; (3) sulfonate retention levels in zones where the surfactant flowed; and (4) the extent to which crossflow adversely affected preflush effectiveness.
The site of the pilot 1 was Tract 97 of the North Burbank Unit, shown in Fig. 1. Average reservoir properties are given in Table 1. The reservoir is heterogeneous properties are given in Table 1. The reservoir is heterogeneous horizontally and vertically (Fig. 2). There appears to be a fracture system with a generally east/west trend. The Burbank sand contains frequent thin shale laminae and dispersed shales but no observed water-sensitive clays. A representative mineral analysis is given in Table 2, along with morphological observations. The clay-iron reflects the presence of chamosite clay (Fe 3 Al 2 Si 2 O 10 3H 2 O). Scanning electron micrographs indicate that this covers about 70 % of the quartz surface. This is responsible for the oil-wetness of the reservoir, which has an average relative displacement index of -0.45 in Tract 97. The tract was preflushed successfully with 0.3 PV of fresh water and 0.2 PV of salinity-adjustment brine. The surfactant slug was 6% Witco TRS TM 10-410 petroleum sulfonate and 3% isobutyl alcohol in 0.9% sodium petroleum sulfonate and 3% isobutyl alcohol in 0.9% sodium chloride brine. The mobility buffer was Betz Hi- Vis TM polyacrylamide, graded from 2,300 to 160 ppm active polyacrylamide, graded from 2,300 to 160 ppm active over a 16-month period. A freshwater drive was maintained until the diagnostic test was complete. Project performance up to 1984 is given in Fig. 3. At the time of performance up to 1984 is given in Fig. 3. At the time of the drilling of the diagnostic well (July 198 1), tertiary oil recovery 4 was 240,000 STB [38 000 stock-tank m 3], reducing average oil saturation in the pilot area I to about 0.25 from an initial 0.30. Expected ultimate tertiary recovery projected in 1979 was 300,000 STB [48 000 stock-tank m 3].
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