|Publisher||Society of Petroleum Engineers||Language||English|
|Content Type||Conference Paper|
|Title||Modified In-Situ Retorting Results of Two Field Retorts|
|Authors||Berry, Kay L., Hutson, Roy L., Sterrett, John S., Knepper, Jay C., Rio Blanco Oil Shale Co.|
SPE Annual Technical Conference and Exhibition, 26-29 September 1982, New Orleans, Louisiana
|Copyright||1982. Society of Petroleum Engineers|
Rio Blanco Oil Shale Company (RBOSC) has designed, constructed and processed two Modified In Situ (MIS) retorts at Tract C-a using newly processed two Modified In Situ (MIS) retorts at Tract C-a using newly developed techniques for rubbling, ignition and operation through surface drill holes. Retort Zero was ignited in October 1980, nominal dimensions 30' x 30' 165' (9 x 9 x 50 meters), oil yield was 1,876 barrels (298,300 liters). Retort One was ignited June 1981, nominal dimensions 60' x 60' x 400' (18 x 18 x 122 meters), oil yield was 24,444 barrels (3,886,000 liters). RBOSC's MIS method was proved very successful; ignition was achieved in less than 36 hours, average front advance rates were 2.7 and 3.0 ft/day (.8 and .9 meter/day) and oil yields were 68 percent of Fischer Assay, close to model predictions for both retorts. This paper will describe conceptually the MIS method developed by RBOSC and give the process results. Details of how the results were achieved are proprietary. process results. Details of how the results were achieved are proprietary
Rio Blanco Oil Shale Company (RBOSC) is a 50/50 general partnership of Gulf Oil Corporation and Standard Oil Company (Indiana). It was formed after submitting the winning bid in January 1974 for Federal Oil Shale Lease C-a. Rio Blanco began site preparation in late 1977 to demonstrate modified in-situ (MIS) retorting on Tract C-a. The MIS program cost $132,000,000 and required four-and-one half years concluding with the successful demonstration of two retorts.
The specific objective of the program was to develop Rio Blanco's mining and rubbling methods for MIS retorts and to burn, study and evaluate retorting operations of the Rio Blanco process. Surface equipment was designed, installed and tested and safe operating procedures established for carrying out the underground combustion. The feasibility and safety of mining and simultaneously processing on a semi-commercial scale was demonstrated; the yields of oil and gas were determined; and environmental and process data were collected which would be needed to evaluate and improve the process.
Figure 1 summarizes the timing of the operating phase of the MIS program during the past two years. During the summer of 1980, a number of program during the past two years. During the summer of 1980, a number of preburn tests were run on Retort Zero. These tests included gas tracer preburn tests were run on Retort Zero. These tests included gas tracer experiments, pressure tests and testing of the retort ignition control systems. Retort Zero was ignited on October 13, 1980, and the retorting operation was completed on December 23, 1980. Meanwhile, Retort One rubbling proceeded in parallel with Retort Zero burn, and was completed in January of 1981. Retort One preburn testing was carried out during the spring of 1981, and the retort was ignited on June 21, 1981; retort operation was completed on December 14, 1981. An item of particular significance, as shown on Figure 1, is the overlap between Retort Zero burn and Retort One rubbling. This increases confidence that systems can be designed to safely conduct mining and retorting operations in close proximity. proximity. MINE DESIGN AND DEVELOPMENT
Figure 2 is an isometric layout of the mine and the two experimental retorts. Key features of the mine include the production shaft which was constructed first -- using conventional shaft sinking equipment -- followed by the exhaust shaft which was raise bored to the surface in order to establish a conventional exhaust ventilation system for the mine, and the service/escape shaft which was also raise bored to the surface. A separate circuit, for supplying air and steam to the retorts through the surface drilled blast holes and piping the off gases back to the surface through the off gas shaft, was sealed from the working areas of the mine.
The main production level of the mine is the G-level, 850 feet (260 meters) below the surface. G-level consists of a network of drifts which provides access to the bottom of the retorts before bulkheads were provides access to the bottom of the retorts before bulkheads were installed to seal off the mine from the retorts.
The upper portion of Retort One extends through the Upper Aquifer of the Piceance Basin.
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