A Mechanistic Interpretation of the Torchlight Micellar/Polymer Pilot
- Kevin T. Raterman (Amoco Production Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- November 1990
- Document Type
- Journal Paper
- 459 - 466
- 1990. Society of Petroleum Engineers
- 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 6.5.2 Water use, produced water discharge and disposal, 2.7.1 Completion Fluids, 5.4 Enhanced Recovery, 4.1.9 Tanks and storage systems, 4.1.2 Separation and Treating, 5.3.2 Multiphase Flow, 5.3.4 Reduction of Residual Oil Saturation, 4.1.5 Processing Equipment, 1.8 Formation Damage, 3 Production and Well Operations, 5.2.1 Phase Behavior and PVT Measurements, 5.6.5 Tracers, 5.4.1 Waterflooding, 2.5.2 Fracturing Materials (Fluids, Proppant), 1.8.5 Phase Trapping, 1.6.9 Coring, Fishing
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This paper describes laboratory studies to interpret the production- and observation-well data obtained from the Torch-light production- and observation-well data obtained from the Torch-light micellar/polymer pilot. The underlying causes for poor pilot performance were identified through correlation of laboratory field core tests and phase-behavior studies to pilot data.
The Torchlight micellar/polymer pilot was conducted in a normal isolated five-spot pattern in the Tensleep formation of the Torch-light field in Big Horn County, WY. The pattern area included 6.4 acres [2.59 ha] and contained a PV of about 218,000 bbl [34 660 M] bounded by the injectors (Fig. 1). Average pay thickness was 31 ft [9.45 m], and porosity-thickness, [phi h], was 4.4 ft [1.34 m]. Injection of the high-salinity preflush/waterflood began in Jan. 1977 and continued through July 1981. The preflush consisted of low-salinity Torchlight Tensleep injection (TTI) water (7.88 10- N total salinity, 5.19 mN hardness) supplemented with 18,000 ppm (0.308 N) NaCl. The high-salinity preflush was intended to provide a salinity gradient for the ensuing micellar fluid bank. The water injection rate during the waterflood averaged 210 B/D [33.4 m/d] per well and the WOR rose from 20 to 75. At waterflood completion, about 36,500 STB [5800 stock-tank M] of oil had been recovered, corresponding to a remaining average oil saturation of 34 % in the pilot area. Residual oil saturation, Sor, to waterflooding for fresh-state Torchlight field cores is 20%.
Micellar fluid injection began Aug. 9, 1981, and continued until a total of 39,400 STB [6260 stock-tank M] (18.1 % PV) had been injected. The injection/withdrawal ratio of the five pilot wells was maintained between 0.95 and 1. The additional fluid withdrawal was intended to maintain the average pressure in the pilot area at a constant level. Injectivity was pressure-constrained. The micellar fluid consisted of 3.4 wt% active Amoco 151 (polybutene sulfonate) 0.8 wt% Shell Neodolo 25-3S, 5 wt% n-butanol, 1,200 ppm Cyanatrol 950-S, and 0.3 wt% formalin in TTI. Of the bulk ppm Cyanatrol 950-S, and 0.3 wt% formalin in TTI. Of the bulk sulfonate (51 % active), 19.4 wt% consisted of inorganic salts, primarily Na2SO4. Fluid formulation and design were based on primarily Na2SO4. Fluid formulation and design were based on fluid stability criteria in the makeup brine. Small slug displacements in Berea typically showed tertiary oil recoveries (TOR's) >95 %.
The micellar bank was followed by 34,700 STB [5520 stock-tank M] (16.5 % PV) of phase-control fluid. This fluid consisted of 1,200 ppm Cyanatrol 950-S, 2.5 wt% n-butanol, and 0.6 wt% active Neodol 25-3S in 5,000-ppm-NaCl-supplemented TTI. The phase-control bank was intended to eliminate any adverse phase-control bank was intended to eliminate any adverse interactions between the micellar and mobility-control fluids.
About 175,300 STB [27 870 stock-tank M] of 1,200 ppm Cyanatrot 950-S in TTI water were initially intended to follow the phase-control fluid. Severe injectivity problems, however, precluded phase-control fluid. Severe injectivity problems, however, precluded injection of this bank despite several remedial workovers of the pilot injectors. As of May 1986, about 133,700 STB [21 260 pilot injectors. As of May 1986, about 133,700 STB [21 260 stock-tank M] of phase-control fluid and mobility polymer had been injected into the pilot wells. Total fluid injection at this point was 314,600 STB [50 020 stock-tank M].
In July 1986, pilot operations were suspended. Before termination, sulfonate and tracer production in produced fluids peaked and were declining. At suspension, cumulative oil production totaled 11,635 STB [1850 stock-tank-M]. On the basis of a 5% final oil saturation, Sof, to a micellar displacement, predicted recovery was estimated at nearly 40,000 STB [6360 stock-tank M]. Hence, pilot performance fell well short of expectations. pilot performance fell well short of expectations. Concurrent to normal pilot operations, two observation wells (Wells 57 and 58) were monitored throughout the pilot lifetime (Fig. 1). These wells were located on a straight line between Injector 56 and Producer 54. As such, they were intended to provide valuable information on micellar performance in a presumably linear streamtube within the pilot area.
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