THE BENEFICIATION OF OIL SHALE BY THE. Gale Peters Gale Peters and Associates Broadway (DRC) School Sodium Lease located on the

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1 THE BENEFICIATION OF OIL SHALE BY THE SOLUTION MINING OF NAHCOLITE By Gale Peters Gale Peters and Associates 2036 Broadway Grand Junction, CO ABSTRACT Several successful projects have INTRODUCTION Denison Resources (USA) Corporation demonstrated the feasibility of solution (DRC) is the operator of the Rock mining nahcolite (the mineral form of School Sodium Lease located on the sodium bicarbonate, NaHC03> and trona western side of T1S R98W, Rio Blanco (the mineral form of sodium sesquicarbonate, Na2C03-NaHC03-2H20. Mining techniques have been proven by both County, Colorado. The lease area is 1,320 acres and is estimated to contain approximately six hundred pilot projects and commercial ventures. million tons of nahcolite. The resource Information and data published exists in a number of continuous, by the Shell Oil Company, Kerr McGee predictable beds. The beds are located Chemical Company, Industrial Resources in the Saline Zone and are 630 meters Inc., FMC Corp., Denison Resources Ltd. to about 820 meters below the surface. of Queensland, Australia and several others have been studied and analyzed. These data indicate that a single well, The beds are classified in three resource intervals named from the deepest, TI Bed, Greeno Bed and Lcve solution mining technique to extract Bed. up to 80% of the nahcolite from a DRC was formed specifically cylinder 40 meters in diameter and to develop the Rock School Lease. approximately 170 meters in height Its former owner, Denison Resources is physically, chemically and economic Ltd. of Brisbane, Queensland, Australia, ally practical. The removal of the had explored the Denison Trough in nahcolite would beneficiate the oil eastern Queensland seeking nahcolite shale within the cylinder and render and/or trona deposits. Failure it available for in-situ retorting and removal. The world-wide market situations for sodium alkali chemicals and the forecasted future demand for sodium to discover a significant resource resulted in Denison transferring its experience to the Piceance Creek Basin where the nahcolite reserves had been quantified. bicarbonate as a flue gas desulfuriza DRC is midway in a two year tion sorbent indicate excellent profit ability for an operation producing sodium bicarbonate and related chemicals, The profitability of a multi-product operation (chemicals and shale oil) program to : 1. Prepare the permits and licenses needed to solution mine nahcolite and produce high quality sodium bicarbonate (99.5% NaHC03 remains to be determined. minimum assay). The permiting 142

2 activity includes the preparation of an Environmental Impact Statement, an Underground Injection Control Permit, continuous intervals are much more difficult to dissolve and extract. Nahcolite has a known, predictable BLM Exploration permits, Colorado State solubility chemistry. It exists Water Discharge permits, and several county and state operating licenses. 2. Develop and test solution in uniform, continuous mineral seams in the center area of the Piceance Creek Basin. Several companies have mining techniques to dissolve and studied the solution mining of nahcolite extract sodium bicarbonate in a con trollable manner, forming predictable cavities of leached oil shale. and two have successfully demonstrated it. The Superior Oil Company, Church 3. Design a surface operation and Dwight Company and the Multi and production plant to initially Minerals Company spent tens of millions produce 50,000 tons per year of food of dollars studying the characteristics grade sodium bicarbonate. And make of nahcolite. Superior and Multi provision to expand the plant to a 500,000 ton per year operation to supply sodium bicarbonate to the emerging flue gas desulfurization industry. Minerals were most interested in separating nahcolite from oil shale to produce a sellable sodium bicarbonate and to beneficiate the oil shale 4. Identify sources of electric for retoring. power, natural gas and water to operate the plant, and During the 1960s and early 1970s T.N. Beard and A. Ireson of the Shell 5. Start detailed civil and struc Oil Company (Shell Research Inc.) tural engineering struction during to begin plant con the summer of developed and patented a process to inject hot water into nahcolitic Presently DRC is on schedule or near schedule in all phases of its project except the preparation of the oil shale to dissolve and remove the sodium bicarbonate. The removal of the nahcolite would create a porous Environmental Impact Study. Federal cavity of purified oil shale. Next budget restrictions have caused slight super heated steam was injected to delays and resulted in DRC having to fund a portion of the EIS work. retort the shale oil. pumped from the cavity. The oil was then The nahcolite extraction phase of the project was SOLUTION MINING TECHNOLOGIES Solution extraction of salts and certain minerals is a proven, low capital successfully demonstrated, and the results have been published. About twelve years later ( ) and low cost method of mining. Two Industrial Resource Inc. demonstrated key factors relative to the feasibility of solution extraction are the salts a technique by which it solution mined the upper most nahcolite bed physical and chemical characteristics in the Basin, the Boise Bed. I.R.I. and its desposition underground. Salts drilled two wells to the Boise Bed such as NaCl, KC1 and Na2S04 are success and connected the wells by horizontal fully extracted because they usually are found in a pure form and exist in thick, drilling along the bottom of the nahcolite seam. The wells were cased uniform beds. Other salts or minerals and cemented to the top of the Bed. that have complex solubility chemistry or that do not exist in concentrated, A hot sodium bicarbonate solution was injected down one well and a saturated 143

3 solution extracted from the second well. I.R.I.'s pilot project was successful and a commercial operation has been announced using this mining technique. Besides the work done on nahcolite deposits there is a wealth of data and information on the chemistry and solution mining of trona. Trona is the mineral form of sodium sesquicarbonate. It is found in very large quantities in southwestern Wyoming California. mineral world wide. and Southern It is a relatively common The single largest deposit and the largest commercial developments of it are in Green River, Wyoming where about 9,200,000 tons per year of sodium carbonate are manufactured. Trona solution mining and process to the well field lay out, design and placement of the monitoring wells, hydrofracturing and operating tech niques, the well design and solution temperature profiles of the production wells. A complete analysis of all publish ed information and known data on the solution of sodium alkali mining salts and minerals has lead DRC to the conclusion that nahcolite can be profitably extracted with minor risk or disturbance to the oil shale reserves. DRC also evaluated problems or failures encountered during these other programs and can explain every one. Looking back at problems, the general conclusion can be drawn is chemistry are of interest to DRC for that the oil and mineral based companies several reasons. 1. Trona is a mixed salt of NaHC03 and Na2C03. Sodium bicarbonate tends to decompose into Na2C03, CO2 and H2O and form a mixed salt similar to a trona based solution. were successful in well design, geologi cal analysis and the mechanical aspects of such a process. Whereas, the chemical based companies have demon strated their abilities to handle and process the solution extracted, 2. Many of the impurities and con but have fallen short relative to taminates found in Colorado nahcolite are also found in the Wyoming and the geology techniques. and mineral extraction California resources. An understanding All of the information described of the complete chemical system is in this section have been considered valuable in designing the operating or incorporated in the DRC solution parameters of a process and selecting the appropriate materials of construction. mining plan. DRC plans to utilize the success of others and avoid their 3. Kerr McGee Chemical Company failures in its process design. And operates a trona solution mining process at Searles Lake, California. The brine pumped from the Lake is carbonated during its initial operation, DRC will improve and fine tune its tech nology. to form sodium bicarbonate which is a separation process. The solution THE DRC SOLUTION MINING PLAN handling and pre-carbonation process steps, and the bicarb crystal habit can be correlated to the DRC process methodology. 4. FMC Corporation has been operating a semi-commercial, solution mining process at Green River, Wyoming. The FMC project is of special interest relative Figure 1 illustrates the general DRC scheme. DRC will use a single well for both injection and production. Of all the techniques used this is most similar to the Shell Oil process. The intent of the single well arrange ment is to create a cavity with a cylinder shape having a diameter 144

4 TOP VIEW OF CAVERN AND PILLAR SPACING OOO oooooo FIGURE I. GENERAL SOLUTION MINING SCHEME AND - CAVITY PILLAR ARRANGEMENT. 145

5 solution" of about 40 meters and a height of about 170 meters. Depth Meters rl) The cylinder shape offers several benefits to DRC. ttz 1. The cylinder allows DRC to extract nahcolite across the richest intervals in the Saline Zone. All three 85 Casing cemented through the dis Injection Tube resource beds, TI, Greeno and Love can be mined. zone to top of l.ove Bed. Product Inn 2. Rock mechanical studies indicate that such a cylinder would maintain structural integrity and support the 600 meters of overburden Tubeannular between Inner and outer pipe 3. The diameter and shape of the -255 cylinder should be controllable. 4. The capital cost and operating expenses of a one well system would be less than two well designs that involve horizontal-directional drilling Pressurized Casing 5. The creation of a cylinder can be controlled by movement of the injection and production tubes up and down the cylinder thereby maximizing total recovery 41 5 Dissolution Surface of the resource. 6. A leached cylinder allows for in-situ oil shale retorting and oil 510 recovery. Figure 2 illustrates the well arrangement. Two tubes will be used within the casing. The hot injection 595 liquor would be pumped down the inner tube to the bottom of the cavity. hot and dilute its direction would be Being LOVE BED upward and outward. The solution would -680 dissolve sodium bicarbonate, and due GREENO BED to the endothermic heat of solution and underground heat losses, the solution would cool. The flow rate, injection -765 TI BED temperature, down hole pressure and retention period would be controlled Blue Marker to produce a nearly-saturated solution. The production liquor would exit the u850 cavity through the annular space between the outer and inner tubes flowing under pressure to the surface. The casing will be pressurized with nitrogen gas to maintain the liquor level in the Figure 2. Production Well Arrange ment. 146

6 cavity and force outward solution mining flow. The cavity should maintain an even temperature range within the volume of liquor injection and extraction. Because the solution is hot and saturated it functions as a cavity sealant. Any liquor that seeps outside of the cavity would cool and solidify, thereby tightly sealing cracks or fractures in the formation. This has been FMC's exper PROCESSING FACILITY From a unit operations point the processing plant or surface facility appears relatively simple. There would be five major operations. 1. Production liquor filtration, cooling and reheating, 2. Bicarb crystallization, 3. Bicarb filtration, 4. Bicarb drying and sizing, and 5. Steam boiler operation. ience with hot, saturated sodium carbonate As in the case with many things that solutions. The major disadvantages of most appear simple, the recovery of a high assay product (99.5% NaHC03) would sodium alkali solution mining processes require extremely good process control, is the well development period. That is, the long period needed to have one well in a well system become fully productive. This is true for bedded minerals as well as disseminated deposits. DRC estimates that four to six months would be required before a well is fully operational on a capacity basis. To overcome this problem DRC plans to start its operation with three wells operating an excellent knowledge of bicarb physical chemistry and an understanding of oil shale chemistry. The liquor flow loop is a closed system and therefore the stream would require both particulate filtration and organic contamination removal with activated granular carbon. The build up of soluable salts, especially sodium salts, must be limited because in series. Once the surface area of sodium salts can reduce NaHC03 solubil exposed nahcolite has increased suffi ciently per well and higher production rates are obtainable, wells can be separated and operated individually. Once the single well concept has been proven there is a proposal to operate a three well set in a triangular pattern. If the rock mechanical data supports the concept, the pillars between the wells would be solution mined by injecting into one well and extracting from the other two wells. This proposal would require extensive testing and analysis before it could be implemented. Present plans are to discontinue operation by leaving a cavity full ity and contaminate the final product. Tight monitoring and control of the flow rate into and out of the cavity is important. Loss of injection liquor would be an operating problem and it could be a source of contamina tion to the aquafere that supplies drinking water. into the cavity Likewise, water flow would dilute and contaminate the production liquor and could overload the plant's liquor handling system. The cavity operating temperature, pressure and liquor flow rate must all be controlled so as not to cause side chemical reactions or competing of solution and plugging the well casing. reactions. Also, the objective of the process is to maximize the removal of nahcolite so as not to interfer with or retort the oil shale. An 147

7 overloading of the liquor system with organic contamination would cause severe problems. It is beyond the scope of this paper to discuss the complete process design. A key point is that very tight "down-hole" and process parameter controls are absolutely essential to an efficient operation. due to the limited supply of electro lytic caustic soda. A second market demand factor acting on sodium carbonate and bicarbon ate will be the requirements of the 1990 Clean Air Act. A stated goal of the act is to reduce sulfur dioxide emission by 10,000,000 tons per year. MARKET OPPORTUNITIES Ten million tons of SO2 equates to fifteen million tons of sulfuric acid Oil men see the Saline Zone of that would be removed from our environ the Piceance Creek Basin as a rich ment. Sodium bicarbonate is a proven, deposit of oil shale contaminated with nahcolite. Chemical people see the Saline Zone of the Piceance Creek Basin effective chemical in dry sorbent desulfurization. Sodium carbonate would be used in several spray dryer as a rich deposit of nahcolite contaminated and scrubber applications. The amount with oil shale. Until recently market situations and prices were such that neither resource could be profitably mined and processed. Major structural changes in the sodium alkali market and the 1990 Clean Air Act have changed the outlook for of sodium bicarbonate and carbonate needed for these uses is estimated to be millions of tons per year. Sodium bicarbonate can be produced from Piceance Creek Basin nahcolite less expensively than from any other process or from any other type of nahcolite. Three chemicals provide resource in the world. the world with sodium alkali; they are caustic soda (NaOH), sodium carbonate BENEFICIATION OF OIL SHALE and sodium bicarbonate. On an alkalinity basis, caustic soda is the major contributor of alkalinity or Na20. Caustic soda is made by the electrolysis of brine (NaCl). extremely Saline Zone oil shale is an rich resource. Its value is diminished because much of it is mixed with nahcolite and it lies a significant The co-product of this process is chlorine distance below the surface. The gas (CI2) During the past four years, nahcolite is both a physical contaminate the demand for chlorine and chlorinated and a "thermal contaminate". Most oil chemicals has been decreasing. The demand for caustic soda has been increas ing steadily. Caustic prices are very strong and predicted to remain high. Because of the caustic-chlorine unbal retorting processes prescribe the removal of the nahcolite before the oil shale is retorted. By separating the two materials the nahcolite can be recovered and the oil shale can ance many alkali users have substituted be processed less expensively and sodium carbonate. Thus, the demand in a purer form. If the nahcolite is and price of it has increased. The not removed, the retoring process will demand and price of sodium bicarbonate has remained strong. Most forecasters see a long-term tight market for both sodium carbonate and sodium bicarbonate require additional heat to decompose the nahcolite, and the resulting sodium carbonate will contaminate the shale oil and reduce the yield 148

8 due to competing Leaching only beneficiates and side reactions. of the nahcolite not concentrates the oil shale, but it creates a slightly rubblized, porous cavity that lends itself to in-situ, oil shale retorting. This was the Shell Oil concept of the 1960's. Unfortunately the sodium alkali market could not absorb the quantity of chemicals that would have been produced. Thus, the chemicals were not viable co-products but presented a waste stream. This decade presents totally dif ferent economies and an encouraging market situation. The chemical project can stand on its own. And, the success ful implementation of the DRC process will create an oil resource suitable for in-situ retorting. Thus, the nahcolite in Saline Zone oil shale can be viewed as a "pre-product" of oil recovery rather than as a co-product, by-product or waste stream. The DRC cavities will be an oil resource waiting for the financial situation to develop that will make them valuable. REFERENCES Beard, T.N., Tait, D.B., and Smith, J.W., 1974, Nahcolite and dawsonite resources in the Green River Formation, Piceance Creek Basin, Colorado: Rocky Mtn. Assoc, of Geologists Guidebook (1974). Coffin, D.L., Welder, F.A., and Glanzman, R.K., 1971, Geohydrology of the Piceance Creek structural Basin between the White and Colorado Rivers, northwestern Colorado. U.S. Geological Survey Hydrology Inv. Atlas HA Cole, R.D., 1975, Sedimentology and sulfur isotope geochemistry of Green River Formation (Eocene), Uinta Basin, Utah, Piceance Creek Basin, Colorado (Ph.D. Dissertation) : Salt Lake City, Univer sity of Utah. Cole, R.D., and Picard, M.D., 1978, Comparative mineralogy of nearshore and offshore lacustrine lithofacies, Parachute Creek Member of the Green River Formation, Piceance Creek Basin, Colorado, and eastern Uinta Basin, Utah: Geol. Soc. American Bull., v. 89. Cole, R.D., Daub, G.J., and Weichman, B.E., 1982, Geology of the Horse Draw nahcolite and oil shale mine, Piceance Creek Basin, Colorado: Colo. Sch. Mines 15th Oil Shale Symposium Pro ceedings. Cole, R.D., and Daub, G.J., 1983, Microcrystalline nahcolite on the 1840 level, Horse Draw Mine, Piceance Creek Basin, Colorado: Colo. Sch. Mines 16th Oil Shale Symposium Proceedings. Colorado Department of Natural Resources, Division of Mines, 1983, A summary of mineral industry activities in Colo rado Denver, Colorado. Dale, R.H., and Weeks, J.B., 1978, Hydrologic analysis of the U.S. Bureau of Mines ' underground oil shale re search facility site, Piceance Creek Basin, Rio Blanco County, Colorado: U.S. Geological Survey Water-Resources Investigation Daub, G. J., Weston, L.K., and Rosar, E.C., 1985, Detailed lithologic, rock quality and hydrologic data from four drill holes in the central Piceance Creek Basin, Rio Blanco County, Colo rado: Colo. Sch. Mines 18th Oil Shale Symposium Proceedings. Desborough, G.A., 1978, A biogenicchemical stratified lake model for the origin of oil shale of the Green River Formation: An alternative to the playalake model: Geol. Soc. American Bull., v. 89. Donnell, J.R., 1961, Tertiary geology and oil- shale resources of the Piceance Creek Basin between the Colorado and 149

9 , 1981, White Rivers, northwestern Colorado: U.S. Geol. Survey Bull L. Donnell, J.R., and Blair, R.W., Jr., 1970, Resource appraisal of three rich oil shale zones in the Green River Forma tion, Piceance Creek Basin, Colorado: Quart. Colo. Sch. Mines, v. 65. Duncan, D.C, 1976a, Preliminary geologic map of Wolf Ridge Quandrangle, Rio Blanco County, Colorado: U.S. Geol. Survey Misc. Fields Studies Map MF-753. Duncan, D.C, Hail, W.J., Jr., O'Sullivan, R.B., and Pipiringos, G.N., 1974, Four BASF Technical Dept., Ludwighoffen, W. Germany. Ochs, A.M., and Cole, R.D., 1981, Com parative petrology of Tertiary sand stones of southern Piceance Creek Basin, Colorado: New Mexico Geol. Soc. Guidebook (1981). O'Sullivan, R.B., 1975, Coughs Creek tongue-a new tongue of the Eocene Green River Formation, Piceance Creek Basin, Colorado: U.S. Geol. Survey Bull G. Pitman, J.K., 1982, Regional strati newly named tongues of Eocene Green graphic and depositional analysis of River Formation, northern Piceance Creek Basin, Colorado: U.S. Geol. Survey Bull F. Dyni, J.R., 1974, Stratigraphy and nahco lite resources of the saline facies of the Green River Formation in northwest Colorado: Rocky Mtn. Assoc. Geologists Guidebook (1974). rock units in the upper Garden Gulch and Parachute Creek Members of the Green River Formation, Piceance Creek Basin, Colorado: Colo. Sch. Mines 15th Oil Shale Symposium Proceedings. Robson, S.G., and Saulnier, G.J., Jr., 1981, Hydrogeochemistry and simulated solute transport, Piceance Basin, 1979, Lithologic description northwestern Colorado. U.S. Geologi of drill core from Sinclair Oil Company cal Survey Professional Paper Skyline Core Hole 1, Piceance Creek Basin, Rio Blanco County, Colorado: U.S. Geol. Survey Open-File Rept Roehler, H.W., 1974, Depositional environments of rocks in the Piceance Creek Basin, Colorado: Rocky Mtn. Geology of the nahco Assoc. Geologists Guidebook (1974). lite deposits and associated oil shales of the Green River Formation in the Piceance Creek Basin, Colorado (Ph.D. Dissertation): Boulder, Univ. of Colo Saulnier, G.J., Jr., 1978, Genesis of the saline waters of the Green River Formation, Piceance Basin, northwest ern Colorado: Ph.D. Dissertation, rado. Hou, T.P., 1942, Manufacturing of soda, University of Nevada, Reno, Nevada. Simon, R.B., 1972, Seismicity- -Rocky Reinhold Pub. Co., New York, New York. Latimer, D.A., and Ireson, R.G., 1980, Workbook for estimating visibility impairment. EPA Publication: EPA Mountian Assoc, of Geologists, Geologic cities of the Rocky Mountain region. Tiedeman, J. A., and Terwilliger, C, 450/ Research Triangle Park, Jr., 1978, Phyto-edaphic classifica North Carolina. tion of the Piceance Basin: Colorado Murray, D.K., and Haun, J.D., 1974, Intro State University, Range Science duction to the geology of the Piceance Department, Science Series no. 31, Creek Basin and vicinity, northwestern Fort Collins, Colorado. Colorado: Rocky Mtn. Assoc. Geologists Trudell, L.G., Beard, T.N., and Smith, Guidebook (1974). Nagel, M., Ph.D., 1977, Precipitation of sodium bicarbonate from sodium carbonate, J.W., 1974, Stratigraphic framework of Green River Formation oil shales in the Piceance Creek Basin, Colorado: 150

10 Rocky Mtn. Assoc. Geologists Guidebook (1974). U.S. Department of the Interior, BLM, 1979, Draft environmental statement proposed by Superior Oil Company Land Exchange and Oil Shale Resource Develop ment: U.S. Government Printing Office. U.S. Department of the Interior, 1985, Draft environmental impact statement for the federal prototype oil shale tract C-a offtract lease: BLM, White River Resource Area, Meeker, Colorado. U.S. Department of the Interior, BLM, 1986, Draft environmental impact statement, Wolf Ridge Corporation mine plan for a nahcolite solution mine: U.S. Government Printing Office. U.S. Department of the Interior, BLM, 1987, Final environmental impact statement, Wolf Ridge Corporation mine plan for a nahcolite solution mine: U.S. Government Printing Office. VTN, 1980, Working document for the U.S. Department of Interior Bureau of Land Management, Horse Draw oil shale research tract, Rio Blanco County, Colorado (Aug. 1, 1980). Weeks, J.B., Leavesley, G.H., Welder, F.A., and Saulnier, G.J., Jr., 1974, Simulated effects of oil shale development on the hydrology of Piceance Basin, Colorado: U.S. Geol. Survey Prof. Paper 908. Welder, F.A., and Saulnier, G.J., Jr., 1978, Geohydrologic data from twentyfour test holes drilled in the Piceance Basin, Rio Blanco County, Colorado, : U.S. Geol. Survey Open-File Rept