| OCR Text |
Show C-a oil shale tract in situ retort ignited J. Blaine Miller, President of the Rio Blanco Oil Shale Company, announced that the Company ignited the second demonstration underground modified in situ retort on June 21st at 4:15 p.m. on Federal Prototype Oil Shale Tract C-a C-a in Rio Blanco County, Colorado. The retort is about 60 feet square and 400 feet high. It is the last of the company's com-pany's two planned underground retorts in a $140 million program to test the commercial feasibility of Rio Blanco's modified in situ technology. The burn is expected to take about four months and produce a total of between 17,000 and 25,000 barrels of oil which will be used primarily for research purposes. Miller said the retort was ignited at the top. some 450 feet below the earth's surface. A downhole burner was lowered from the surface through a twelve-inch vertical casing to the retort. A mixture of natural gas and air was used for ignition. In Rio Blanco's modified in situ technology, some 30 to 40 percent of planned retort volume is removed by mining and brought to the surface. In a commercial program, that oil shale would be retorted in a surface retort. The remainder of the underground retort is rubbled with conventional explosives to create the necessary permeability for burning. After ignition, the combustion zone of the retort burns at between 1,400 and 1.800 degrees Fahrenheit. However, the shale oil leaves the rock at about 900 deg. F before the flame front arrives. When the flame front reaches the retorting zone, the carbon residue left on the rock after the shale oil has left serves as the fuel for the burn. The shale oil leaves the rock in the form of a vapor. Once away from the retorting zone, it condenses into liquid and travels down to the bottom of the retort. There it is separated from the w ater and pumped to the surface. Gas produced with shale oil is separated and cleaned in surface processing facilities. The nonpolluting waste gases are vented to the atmosphere. Rio Blanco's first modified in situ demonstration retort produced about 1.750 barrels during its two-month burn late in 1980. In addition to the modified in situ project, Miller said Rio Blanco is reviewing a surface retort demonstration demon-stration program. Construction of a Lurgi retort had been anticipated to start this summer, but has been relayed. The company is also engaged in preliminary engineering design and commercial planning for an open pit development plan. That plan would require surface retorting of all of the mined oil shale. Miller said the merits of the modified in situ and open pit technologies will be assessed in the next two or three years. The company then expects to make a commercial decision. Commercial production of 50,000 barrels of shale oil per day could be reached toward the end of the lW)'s. Rio Blanco currently has some 250 workers at the 5,100- ac re C-a tract. The workforce is not expected to significantly increase in the next two to three years. Rio Blanco Oil Shale Company is a general partnership of Gulf Oil Corporation Cor-poration and Standard Oil Company (Indiana). The tract was leased from the U.S. Department of the Interior in 1974. |
