An Echoing In-Situ Combustion Oil Recovery Project in a Utah Tar Sand
Authors: Johnson L.A. , Fahy L.J. , Romanowski L.J. , Barbour R.V. , Thomas K.P. 
Published: December 2007

Johnson Jr., L.A., SPE-AIME, U.S. DOE, Laramie Energy Technology Center Fahy, L.J., U.S. DOE, Laramie Energy Technology Center Romanowski, L.J., U.S. DOE, Laramie Energy Technology Center Barbour, R.V., U.S. DOE, Laramie Energy Technology Center Thomas, K.P., U.S. DOE, Laramie Energy Technology Center
This paper presents the description and analysis of a combination reverse and forward combustion experiment for the production of oil from a Utah tar sand. The experiment produced 25% of the OOIP from a 13-ft thick tar sand zone containing at 14 deg. API, million-plus cp oil. The results were encouraging for future tar sand production.

Introduction
U.S. tar sand resources contain an estimated 30 billion bbl (4.7 Gm) of oil in place in about 550 occurrences in 22 states. Over 90% of the known resources are in six large deposits in Utah, each containing from 1 to 16 billion bbl (0.15 to 2.5 Gm) of oil. Four major tar sand deposits in Alberta, Canada, contain some 900 billion bbl (143 Gm) of oil, and deposits in Venezuela and Colombia contain an estimated 1 to 1.8 trillion bbl (0.15 to 0.28 Tm t).
The first U.S. DOE tar sand field experiment (LERC TS-1C) was conducted in Utah's Northwest Asphalt Ridge deposit in late 1975. LERC TS-1C accomplished its two primary goals:to demonstrate the feasibility of applying a reverse combustion process to a heterogeneous tar sand reservoir with a process to a heterogeneous tar sand reservoir with a high average oil saturation andto provide the Laramie Energy Technology Center (LETC) research personnel with valuable experience in application of personnel with valuable experience in application of the combustion process and operation of its related equipment.
Results of LERC TS-1C and supporting research are reported in several publications. LERC TS-1C provided encouragement for a second field experiment (LERC TS-2C) designed to use reverse combustion as a preparatory phase for forward combustion. LERC TS-2C tested the technical feasibility of the application of a combination thermal recovery process - reverse and forward combustion - for the process - reverse and forward combustion - for the in-situ extraction of oil from tar sands. The reverse combustion (preparatory) phase improved the natural reservoir conditions for application of the forward combustion (production) phase. However, the fire front moved through the pattern in a series of reverse and forward combustion phases (echoing combustion) during the experiment. The experiment was ignited in late Aug. 1977 and completed in Feb. 1978. More than 25% of the oil in place was produced in 183 days from a 13-ft (4-m) thick test produced in 183 days from a 13-ft (4-m) thick test zone at a depth of 350 ft (107 m) within a 40 × 120 ft (12 × 36 m) nine-well line drive pattern.

Experimental Plan
The design of LERC TS-2C was based on laboratory combustion experiments and LERC TS-1C. Laboratory studies provided the parameters of optimum air flux, combustion front velocities, flame front temperatures, and theoretical oil recovery. Three main observations from LERC TS-1C were (1) the test zone had a preferential direction of permeability along the strike line, (2) the reverse permeability along the strike line, (2) the reverse combustion front tended to travel through the most permeable portion of the test zone with little vertical permeable portion of the test zone with little vertical spreading, and (3) the produced fluids contained a large portion of heavy viscous oil and solids, which caused conventional oil production equipment to fail.
JPT
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