Laramie Energy Technology Center Research Articles

CSAMT Mapping of a Utah Tar Sand Steamflood

The mapping of thermal fronts associated with EOR techniques from the surface has important application to improved reservoir stimulation. Real-time knowledge of how a thermal EOR front is developing would help and operator to optimize production well placement as well as to take corrective steps to maximize production. The surface mapping technique that we are evaluating is the controlled-source audio frequency magnetotelluric (CSAMT) electromagnetic (EM) induction geophysical prospecting technique. The analysis of the field data, using results from laboratory studies, is described. Normalized maps show the location of the steam front that is in agreement with production data, temperature data from monitoring wells, and posttest coring data. The location of a major bypass of steam into an underlying formation was also mapped. The results indicate that the CSAMT technique shows promise for monitoring steam-front locations.

Multi‐Stage Air Flotation of Tar Sand Wastewater

In 1980, the Department of Energy’s Laramie Energy Technology Center conducted a steam-driven tar sand recovery experiment near Vernal, Utah. This experiment yielded 1,150 barrels of bitumen and 6,250 barrels of process water, which was highly contaminated with emulsified oils and dissolved organics. The process waters were successfully treated by bench-scale, continuous-flow air flotation (AF), but significant amounts of very dilute sludge were generated. The present study investigated the effects of adding a second flotation stage to the AF system to thicken stage I sludge, produce a clean effluent suitable for recycling, and thereby increase the hydraulic efficiency of the system. Key stage II operating variables were polymer dose, air flowrate, and liquid residence time. These were optimized to minimize sludge volume and maximize effluent quality and volume. Total organic carbon and total suspended solids removals in the stage II system were 96 and 99%, respectively. Overall sludge production equalled about 2% of the total influent flow.

MODELING VENTURI SCRUBBER PERFORMANCE FOR H2S REMOVAL FROM OIL-SHALE RETORT GASES

A mathematical model has been developed for predicting the removal of hydrogen sulfide from oil shale retort gas streams in a venturi scrubber, using dilute ammonium hydroxide solutions in water. The model has been compared to experimental data obtained by the Laramie Energy Technology Center in a 150-ton oil shale retort system. The effects of liquid pH and of the liquid-to-gas ratio on H2S removal, as predicted by the model, generally agree with the observed behavior. The new model is different from previous ones in that the details of diffusion and the shifting of chemical equilibria due to pH gradients in the liquid phase are accounted for.

Development and Testing of Spent Shale Grouts for Backfilling Abandoned In-Situ Oil Shale Retorts

Summary Grouts based on Lurgi spent shale were developed for backfilling in-situ oil shale retorts. Lignosulfonate fluidizer (0.25%) was used to achieve adequate fluidity. Addition of 10% fly ash increased the strength of the grouts. Permeabilities of the grouts decreased at higher confining pressures and were low enough to reduce leaching by groundwater. Introduction Water-quality problems of oil shale retorting are mainly related to the ultimate disposal of spent shale. In in-situ retorting, spent shale remains underground, where it can be leached by reinvading groundwater. To minimize leaching, it has been proposed to backfill abandoned retorts with a grout, reducing their permeability. Mallon discusses a possible grout injection procedure. The large volume of voids to be filled requires that the grout be based on spent shale. A hydraulic cement has been produced by calcining a mixture of spent shale and limestone, but the requirements for importing limestone to the site make this uneconomical. Therefore grouts were developed that contained only spent shale from a demonstrated retorting process and small amounts of additives. Materials. Low permeability of a noncementitious grout results not from chemical properties but from fine particle size. The finest spent shale is the fraction of spent particle size. The finest spent shale is the fraction of spent shale from the Lurgi process that is collected by electrostatic precipitation. This material was 57.7% finer than 0.00394 mm [0.00016 in.]. Analysis by X-ray diffraction showed that the major minerals present were quartz, calcite, dolomite, and feldspar (same as in raw shale). Free lime and silicates were not detected. A pozzolanic Class F fly ash and a pozzolanic, pozzolanic Class F fly ash and a pozzolanic, cementitious Class C fly ash with 5% added CaSO4 were tested as strength-increasing additives. Two lignosulfonate fluidizers (refined sodium salts of lignosulfonic acid, a waste product from the sulfite pulping process) were tested: Crown-Zellerbach product 512 pulping process) were tested: Crown-Zellerbach product 512 is desugared; Crown-Zellerbach product 503 has not been desugared (sugars are removed because they retard the setting of portl and cement). Grout Fluidity and Bleeding. Formulating grouts for injection into rubble is limited by two opposing constraints. Bleeding (separation of a clear supernatant) must be as low as possible, but the grout must still be fluid enough to penetrate through the voids of an abandoned in-situ retort. Particulate grouts are non-Newtonian fluids with nonzero yield stress, which limits penetration of grout through small pores. Bleeding penetration of grout through small pores. Bleeding increases and yield stress decreases with increasing water/solids ratio (WSR). Thus the objective is to formulate a grout that has a low enough yield stress without unacceptable bleeding. Yield stress was not used directly as a criterion. Rather, grouts were formulated to have flow cone times between 18 and 22 seconds. Experience with intrusion grouting of preplaced aggregate concrete has shown this to be a realistic requirement. Experiment. Grout ingredients (Table 1) were dry blended and water was added in increments to reduce the flow cone time to the target range. Grouts were mixed at 1,300 rev/min for 3 minutes initially and after each incremental addition of water. Bleeding was less than 2 % for all the grouts. Samples were cast in 2-in. ×4-in. [5. 1-cm× 10.2-cm] waxed cardboard cylinders for both permeability and strength testing. Permeability samples contained no aggregate because the permeability of a grouted retort would be controlled by the grout (the continuous phase) rather than the in-situ spent shale (the discontinuous phase). Simulated grouted cores for strength phase). Simulated grouted cores for strength measurement were prepared with grout and aggregate (simulated in-situ spent shale from Laramie Energy Technology Center retort run 5–55, crushed and sieved to - % + 1 in. [0.64 to 0.95 cm]). All samples were cured in 100% relative humidity for 5 months at 73 deg. F [23 deg. C]. Permeability was measured at a range of confining Permeability was measured at a range of confining pressures (Fig. 1) and electrical conductivity of pressures (Fig. 1) and electrical conductivity of permeates produced during these tests was measured. permeates produced during these tests was measured. Experimental details are presented in Ref. 13. Discussion. The grout formulas, flow cone times, and the unconfined compressive strengths are shown in Table 1. The permeabilities are shown in Fig. 1. Points shown in Fig. 1 are measurements on duplicate specimens of each grout at three different confining pressures (data points for R-4 overlap). r = product-moment correlation points for R-4 overlap). r = product-moment correlation coefficient. The conductivity of leachates produced during permeability measurement decreased over time as shown in Fig. 2. JPT P. 1033

Bituminous Sandstone Resource Evaluation of PR Spring Deposit, Uintah and Grand Counties, Utah: ABSTRACT

The Laramie Energy Technology Center (LETC), Department of Energy, completed a seven-corehole drilling program in 1980 at the PR Spring tar sand deposit, southeastern Uinta Basin, Utah. The core data from these locations were integrated with data from 70 other locations to update the following deposit characteristics: vertical and aerial extent, stratigraphy, and rock properties. Oil-impregnated sandstones are found as surface outcrops and to depths of 475 ft (145 m). Three main tar sand zones in the Douglas Creek Member of the Eocene Green River Formation were correlated across the deposit. Up to 27 separate tar sand beds were identified across the deposit, ranging from 1-35 ft (0.5-11 m) thick. These saturated zones and beds are lenticular and discontinuous, both vertic lly and horizontally. Analytical results from 6 of the LETC cores and 32 other cores were interpreted to further evaluate the deposit. Computer-generated isopleth maps identified the following general trends: the thickest zones are found in the south-central portion of the deposit; extracted permeability and extracted porosity decrease downdip (northwest); oil saturation decreases to the west-southwest; and water saturation decreases to the east. End_of_Article - Last_Page 528------------

Composition of oils produced during an echoing, in-situ combustion of a Utah tar sand

The Laramie Energy Technology Center (DOE) has completed its second in-situ combustion experiment (TS-2C), which was carried out in the Northwest Asphalt Ridge tar sand deposit near Vernal, Utah. During the experiment (183 days) 92 m 3 (580 barrels) of oil was produced, 25% of the original oil in place. The in-situ process utilized is best described as a series of reverse- and forward-combustion phases or echoes traversing the 405 m 2 (0.1 acre) pattern. Several of the chemical and physical properties of the oil produced are significantly altered with respect to the original bitumen. These include pour point, specific gravity, average molecular weight, wax and nickel content, and the percentage of residue boiling at >538 °C (1000 °F). These and other changes effected on the bitumen during this experiment result in a product oil that closely resembles a heavy fuel oil.

AN INVESTIGATION OF WAXES ISOLATED FROM HEAVY OILS PRODUCED FROM NORTHWEST ASPHALT RIDGE TAR SANDS

ABSTRACT During the late 1970's, the Laramie Energy Technology Center operated two in-situ combustion projects in the Northwest Asphalt Ridge tar sand deposit of Utah. Some of the heavy oils produced were observed to have high pour points, which resulted in handling problems in cold weather. These heavy oils contain waxes, which were found to be n-alkane homologues ranging past carbon number 60. These alkanes seem to have been derived from what are probably Ozokerite veins, which are found in the tar sand deposit. Samples from these veins and waxes derived from produced heavy oils were studied using 13C NMR, IR, and chemical ionization mass spectrometry.

An Evaluation of a Steamflood Experiment in a Utah Tar Sand Deposit

Johnson Jr., Lyle A., SPE, Laramie Energy Technology Center, U.S.DOE Fahy, L. John, SPE, Laramie Energy Technology Center, U.S.DOE Romanowski Jr., Leo J., SPE, Laramie Energy Technology Center, U.S.DOE Thomas, Kenneth P., Laramie Energy Technology Center, U.S.DOE Hutchinson, Harold L., SPE, U. of Wyoming Summary The first U.S. DOE Laramie Energy Technology Center (LETC) steamflood experiment in a Utah tar sand, LETC TS-1S was conducted in the Northwest Asphalt Ridge deposit near Vernal, UT. Steam was injected into the center well of two concentric inverted five-spot patterns. The zone chosen for the experiment was a sandstone 45 ft (14 m) thick in the Rimrock member of the Mesaverde formation. The pattern area was 0.25 acres (1012 M2) and contained a 13 degrees API (979 kg/m) bitumen with a viscosity greater than 10 Cp (10 Pa.s) at reservoir conditions. The average oil saturation was 78.9% PV. During 160 days of operation, 65,700 bbl (10.4 × 10 m) of water-equivalent steam were injected at 360 to 530 psig (2.5 to 3.7 MPa) and 180 to 650 B/D (29 to 103 m /d). Total production during the test amounted to 1,150 bbl (183 m) of oil and 6,250 bbl (994 M) of water. Introduction LETC has been working toward development of U.S. tar sands since 1973. To date LETC has conducted several laboratory studies and three field tests of the technical feasibility of in-situ thermal processing of Utah tar sand. The first two field tests, LERC TS-1C and LERC TS-2C, were conducted in 1975 and 1977-78 to test the technical feasibility of the reverse combustion process and a combination reverse/forward combustion process, respectively. Results of these laboratory and field tests have been reported in several publications. The third field test (LETC TS-1S conducted during 1980) tested the technical feasibility of steamflooding a tar sand formation; it is the basis for this paper. LETC TS-1S steamflood began April 23, 1980, and ended Sept 29, 1980. During 160 days of operation, 65,700 bbl (10.4 × 10 m) of water-equivalent steam were injected into the 45-ft (14-m) thick, 500-ft (152-m) deep tar sand zone. During the operational period, 1,150 bbl (183 m) of oil and 6,250 bbl (994 m) of water were produced. Experimental Plan The objectives of LETC's first steam in-situ recovery experiment were (1) to determine the technical and economic feasibility of using a steamflood as an in-situ recovery technique in a Utah tar sand deposit, (2) to evaluate an injection well completion scheme with a high-temperature packer, (3) to evaluate several types of downhole completion schemes for the production wells, and (4) to determine recycle and fuel use possibilities for produced water and oil. Design of LETC TS-1S was based on core analysis, data from a small two-well steam injection test, laboratory studies, a literature survey, and computer modeling. The pattern was two concentric inverted five-spot patterns (Fig. 1). The outer four producers (Wells 3P1 through 3P4) were on the perimeter of 0.25 acres (1012 m), while the inner four producers (Wells 3PS through 3P8) bounded 0.1 acres (405 m2). Monitor Wells 3M1 through 3M4 were spaced at approximately half the spacing of the 0.1-acre (405-m2) pattern. On the basis of preliminary computer modeling results, the 0.25-acre (1012-m2) and 0.1-acre (405-m2) areas represented the best estimates of the maximum and minimum areal sweeps expected during the desired 120-day test period. Test Zone Description The major source of tar sand on Northwest Asphalt Ridge is the Rimrock sandstone member of the Cretaceous Mesaverde formation. The Rimrock is a highly saturated, semiconsolidated, fine-grained sand- stone interrupted by many low-saturated siltstone or shale intervals that vary in thickness from less than 1 in. (2.54 cm) to more than 10 ft (3 m). JPT P. 1119^

Fingerprinting and characterization of carboxylic acids in in-situ oil shale retort and process waters by capillary column gas chromatography-mass spectrometry

Six important in-situ oil shale retort and process waters have been analysed for carboxylic acids by capillary column gas chromatography-mass spectrometry. A fingerprint or profile was obtained for Occidental boiler blowdown process water, retort water and heater-treater process water; Geokinetics retort water, and Laramie Energy Technology Center Omega-9 and 150 Ton retort waters. The results clearly show significant differences in that each retort or process water contains various mono-, di-, branched, keto-aliphatic and aromatic carboxylic acids. The Occidental retort and process waters contained straight-chain monocarboxylic acids from C 2–C 13 and C 2–C 14, whereas the Geokinetics retort water contained C 2–C 10, the 150 Ton retort water C 2–C 10, and Omega-9 retort water C 2–C 14 acids. Variations among the retort waters and process waters were more important for the normal dicarboxylic acids. The Occidental retort and process water contained no C 2–C 7 straight-chain dicarboxylic acids, but those from C 8–C 12 were present. The Omega-9 retort water contained all the straight-chain dicarboxylic acids, C 2–C 12, that were identified, whereas the 150 Ton sample contained only C 2 and C 4 dicarboxylic acids, and the Geokinetics sample C 2–C 4 and C 8–C 12 acids. The implications of the results in pyrolysis of oil shale kerogen are discussed.

Geologic Controls of In-Situ Processing of Tar Sands, N.W. Asphalt Ridge, Utah: ABSTRACT

End_Page 630------------------------------The Laramie Energy Technology Center completed three in-situ oil-recovery experiments from tar sands at N.W. Asphalt Ridge, Utah. The 10-acre (4 ha.) tract is part of the Sohio Shale Oil Co. D tract located west of Vernal, in Uintah County. Asphalt Ridge, lying on the northern boundary of the Uinta basin, is a northwest-southeast-trending ridge. The area on the northwest is structurally a monocline dipping southwest. The 3.28 to 14.75 m thick experimental tar-sand zones are in the Rim Rock Sandstone Member of the Mesaverde Formation of Cretaceous age. The beds dip 28°SW, and overburden thicknesses range from 89 to 164 m. Two known faults, with throws up to 66 m, bound the tract. Three experiments were performed at the tract on varying partial acreages from 1975 to 1980. Two combustion tests using reverse combustion and a combination reverse and forward combustion were completed in a tar-sand bed 3.28 to 3.93 m thick. Recovered oil and water for the experiments ranged from 65 to 580 bbl and 167 to 600 bbl, respectively. The third test used steam injection on a 14.75 m thick bed. Production was 1,150 bbl of oil and 6,250 bbl of water. Tar-sand analyses yielded the following range of data for the three tests: extracted porosity, 26.1 to 31.1%; absolute air permeability, 651 to 2,175 md; oil saturation, 62 to 75% pore volume; water saturation, 2.4 to 7.9% pore volume. Various geologic controls can determine the effectiveness of the extraction process. These inclu e the dip of the beds, reservoir thickness, water and oil saturation, porosity, permeability, vertical and horizontal continuity of section, confinement of zone, and potential fractures and faulting in area. End_of_Article - Last_Page 631------------

Acute toxicity of anin situ shale oil process wastewater and its major components toDaphnia magna

An assessment of the potential environmental hazard of an in situ shale oil process wastewater to aquatic organisms is presented. The study determined the acute toxicity (48 hours) of the wastewater to Daphnia magma, a microcrustacean commonly found in lakes in northern and western North American and a sensitive test organism for many toxicity studies. The effluent under study was obtained from the Laramie Energy Technology Center's experimental in situ shale oil site near Rock Springs, Wyoming. In addition, a synthetic effluent was prepared by mixing each of the major inorganic components identified in the waste water at the concentrations found. The acute toxicity of the synthetic mixture was compared with that of the waste water and it was found that the waste water was approximately 1.5 times as toxic as the synthetic mixture. Because of the differences in toxicity, it was determined that not all of the chemicals present in the original effluent at acutely toxic concentrations have been identified.

Characterization of oil shales by differential scanning calorimetry

Oil shale blocks were cored to suitable dimensions (nominally 2.5 cm diameter and 1 cm thick). Specific gravity measurements were then carried out on these cylindrical cores to determine the organic content. Selected samples were also assayed at Laramie Energy Technology Center, WY, by the pulsed NMR technique. Oil yields obtained by the two methods on identical cores were in agreement with the limits of experimental error (vide infra). The cored shale samples were crushed to particles which passed through 100-mesh sieves. Ten to fifteen milligram batches of these crushed shale particles were then subjected to enthalpy measurements in the differential scanning calorimetry assembly. A sample of kerogen concentrate was obtained from Laramie Energy Technology Center. DSC measurements were carried out on a DuPont 990 thermal analysis system fitted with the DSC accessory module. All measurements were carried out in a flowing atmosphere of prepurified N/sub 2/. A heating rate of 10/sup 0/C/min was employed for the enthalpy determinations. The fusion endotherm of zinc (mp 419.4/sup 0/C, ..delta..H/sub f/ = 27.05 cal/g) was used as the calibration standard. The linear correlation that was observed between the enthalpy of decomposition of the organic matter (..delta..H) and oil yields for Green rivermore » oil shales suggests that this technique might be useful as a rapid screening tool for resource evaluation of an oil shale deposit.« less

The utility of simultaneous parameter measurements in thermal analysis

In recent years, it has become increasingly apparent that the information gleaned from conventional thermal analysis techniques such as differential scanning calorimetry (DSC) and thermogravimetry (TG) can be considerably magnified in scope by combining them with mechanistic probes which are responsive to changes taking place in the sample on a molecular level. This is particularly true in the case of naturally occurring complex materials such as coals, oil shales and tar sands. The utility of simultaneous parameter measurements was illustrated for such materials by combining dielectric measurements with differential thermal analysis (DTA) [l-3]. On the basis of this approach, it was proposed that an ideal combination would be that coupling “primary” thermal analysis techniques such as DSC (or DTA) and TG with mechanistic probes such as thermoelectrometry and thermoacoustimetry [ 41. In this communication, we present yet another piece of experimental evidence in favor of the above concept. It is shown that a combined use of the two techniques of DSC and thermoacoustimetry results in a powerful analytical tool which is responsive to changes both in the thermal as well as in the mechanical properties of the test sample as a function of temperature. More significantly, the extreme sensitivity of the thermoacoustimetric probe and the loss of valuable mechanistic information-that would have resulted from a DSC examination alone are highlighted by the present results. The proof-of-concept measurements are illustrated on a sample of Utah tar sand bitumen, although, in principle, the conclusions apply equally well to all materials. Thermoacoustimetry was carried out according to the technique and procedures outlined in a previous paper [5]. Differential scanning calorimetry was performed on a DuPont 990 Thermal Analysis System *:* equipped with the DSC accessory module. Both sets of measurements were carried out under identical conditions of heating rate, sample preparation, ambient atmosphere, etc. to eliminate artifacts in the correlation of thermoacoustimetric and DSC data. The sample of Utah tar sand bitumen (P.R. Springs, Main Canyon) was obtained from the Laramie Energy Technology Center.

Reverse Combustion Instabilities in Tar Sands and Coal

Abstract A linear stability analysis shows that reverse combustion in coal and tar sands is only conditionally stable for mobility ratios less than one. However, high air-flow rates and gas generation at the combustion front can be stabilizing influences. For unstable operation, an estimate of the size of the reverse combustion channel may be obtained from the curve for the most highly amplified wave length. This provides a method for calculating the air flux, combustion front velocity, and rate of progress of the burn front. Recently the U.S. DOE Laramie Energy Technology Center (LETC) and Sandia Laboratories obtained experimental data about reverse combustion from a field test of in-situ coal gasification at Hanna, WY. These data show that 9.7 days were required for the development of a reverse combustion path 68 to 70 ft in length. The stability theory developed in this work predicts a length of 64 ft for this same 9.7-day period. In addition to quantitative predictions, stability theory provides an explanation of certain puzzling qualitative observations concerning reverse combustion.

An Echoing In-Situ Combustion Oil Recovery Project in a Utah Tar Sand

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 P. 295

Shallow Oil Shale Deposits of Southern Uinta Basin, Utah: ABSTRACT

In the southern part of the Uinta basin of northeastern Utah, the Mahogany zone of the Green River Formation occurs at or near the ground surface. This shallow Mahogany zone represents a resource of oil shale at depths of up to 200 ft (61 m), developable by horizontal in-situ methods such as demonstrated by Geokinetics Inc., which is operating in the study area. The geologic sections potentially attractive for near-surface oil production are described. The Mahogany zone is divided into seven correlatable units. Three cross sections constructed from oil-yield histograms detail the correlations. Thickness, average oil yield, and oil resource in place are used to create contour maps defining the resource. Production of shale oil from near-surface horizontal retorts involves creating permeability by blasting. This method lifts the surface, providing subsurface void space. Horizontal in-situ production of shale oil uses this void space to permit passage of air and product gasses. To this date, successful experimental horizontal retorts have been created to depths of about 60 ft (18 m) and further experimentation is expected to increase that depth limit. To determine and define the resource characteristics of this potentially developable section of the Green River Formation, the Laramie Energy Technology Center has drilled 12 core holes in the southern Uinta basin during the past 3 years. Data for 10 of these core holes are included. Information from 12 other cores taken by private companies is incorporated and 18 other test holes provided some data used in construction of structural contour and overburden maps. End_of_Article - Last_Page 696------------

Toxicity of underground coal gasification condenser water and selected constituents to aquatic biota.

The acute and embryo-larval toxicity of the Laramie Energy Technology Center's Hanna-3 underground coal gasification (UCG) condenser water and its constituents were studied in continuous-flow bioassays. The 96-hr LC50 dilution values for untreated Hanna-3 UCG condenser water were 0.1% for rainbow trout, 0.11% for fathead minnows and the 48-hr LC50 dilution forDaphnia pulicaria was 0.18%. Separate 96-hr acute tests with phenol, ammonia, and ammonia plus phenol showed that these two constituents, acting synergistically, were the major constituents affecting the acute toxicity of this coal conversion effluent to fishDaphnia pulicaria, on the other hand, was relatively insensitive to phenol exposure; the primary constituent of Hanna-3 UCG condenser water affecting this species was ammonia.