REPORT OF INVESTIGATION NO. 37 UTAH GEOLOGICAL AND MINERALOGICAL SURVEY

Transcription

1 REPORT OF INVESTIGATION NO. 37 UTAH GEOLOGICAL AND MINERALOGICAL SURVEY DETERMINATION OF OIL.SHALE POTENTIAL GREEN RIVER FORMATION, UINTA BASIN NORTHEAST UTAH Prepared by Howard R..Ritzma Petroleum Geologist Utah Geological & Mineralogical Survey Based on strati graphic study by de Benneville K. Seeley,.Jr. Consulting Geologist Salt Lake City, Utah November 3, 1967

2 TABLE OF CONTENTS Page OBJECTIVES 1 METHODS OF INVESTIGATION 2 STANDARD NOMENCLATURE 2 EXHIBITS 3 DEPOSITIONAL HISTORY AND PATTERNS 3 DETERMINATION OF DEPOSITIONAL ENVIRONMENT AND OIL SHALE 5 CONCLUSIONS 5 RECOMMENDATIONS 7

3 UNIVERSITY OF UTAH SALT LAKE CITY. UTAH COLLEGE OF MIXES AXD MINERAL INDUSTRIES Office of the Utah Geological and Mineralogical Survey 103 Utah Geological Survey Building Library of Samples for Geologic Research November 3, 1967 MEMORANDUM TO: FROM: William P. Hewitt, Director, Utah Geological Survey Howard R. Ritzma, Petroleum Geologist SUBJECT: Determination of oil shale potential, Green River Formation, Uinta Basin, Northeast Utah OBTECTIVES This investigation was undertaken in July, 1967 with the following objectives: 1. To correlate known and recognized members "or intervals" of the oil shale-rich Green River Formation from the eastern Uinta Basin into the western part of the basin where they are less known or unrecognized (Maps 2 thru 7). 2. To determine the thickness of these units "or intervals" and total thickness of the Green River Formation (Maps 2 thru 7). 3. To relate the depositional patterns of the Green River Formation to those of the underlying Wasatch Formation and the overlying Uinta Formation so that the long-term structural and depositional history of the site of the Uinta Basin could be understood, particularly the environment in which oil shale is deposited.. 4. To determine what part of the total Green River Formation was deposited in a lacustrine environment and whether these lake deposits are organic oil shale. 5. To determine where the greatest volume of rich oil shale is located in the Uinta Basin (Map 1).

4 -2- METHODS OF INVESTIGATION The Utah Geological Survey retained Mr. de Benneville K. Seeley, Jr., Consulting Geologist,. Salt Lake City, for the study, Mr. Seeley, in consultation with Mr, Howard Ritzma, Petroleum Geologist, Utah Geological and Mineralogical Survey, and with geologists of the petroleum industry on specific aspects of stratigraphic problems, compiled the attached maps. Basic nomenclature and correlations were adopted from Roberts, P.'JC., "Stratigraphy of the Green River Formation" unpublished Ph.D. thesis, University of Utah, 1963, Roberts' correlations in the eastern part of the basin were used without major change. However, in the western two-thirds of the basin information from new wells scattered across previously undrilled areas made necessary an almost complete restudy of old wells and a revision of correlations for this important area. Electrical and other mechanical logs were the main bases for picking formation and member "tops", supplemented wherever possible by lithologic logs, "Tops" picked by companies operating wells and published in petroleum industry data summaries generally were inconsistent from well to well and inaccurate in many cases, Sources of logs used were: Utah Geological Survey Library of Samples, Utah Division of Oil and Gas Conservation and petroleum industry files (anonymous loans and contributions). Extensive study of existing literature was undertaken. References cited are listed at the close of this report. STANDARD NOMENCLATURE Stratigraphic nomenclature adopted as standard for the basin for this study is (in descending order): Uinta Formation Green River Formation Evacuation Creek Member Parachute Creek Member Containing Mahogany Bed and other principal oil shale beds of eastern third of Uinta Basin Douglas Creek Member Willow Creek Member Wasatch Formation With exception of the Willow Creek, all members of the Green River Formation correspond in name and general lithology with those in the adjacent Piceance Basin of northwestern Colorado, The Willow Creek Member does not exist in the Piceance Basin.

5 -3- EXHIBITS The following maps accompany this report; 1, Generalized geologic map of Green River Formation (File 800-D) 2. Thickness Map - Willow Creek Member (File 801-D) 3. Thickness Map - Douglas Creek.Member (File 802-D) 4. Thickness Map - Parachute Creek Member (File 803-D) 5 0 Thickness Map - Evacuation Creek Member (File 804-D) 6. Thickness Map - Parachute Creek - Evacuation Creek Interval (File 805-D) 7 Thickness Map - Total Green River Formation (File 806-D) A northwest to southeast cross-section depicting depositional environments of the Green River Formation accompanies each map, Map 1 is a combination of the studies of Messrs, Seeley and Ritzma Maps 2 through 7 result from Mr. Seeley's work, It was necessary to prepare a combined Parachute Creek and Evacuation Creek map (Map 6) because the boundary between these two intervals became indistinct across the western half of the basin Separate maps of the Parachute Creek and Evacuation Creek intervals (Maps 4 & 5) could be prepared only for the eastern Uinta Basin, The base of the Parachute Creek and top of Evacuation Creek were well defined across the basin, thus bracketing the combined thickness of the two intervals, DEPOSITIONAL HISTORY AND PATTERNS The study reveals that lacustrine deposition commenced in the western Uinta Basin in pre-green River time,, during deposition of the Wasatch Formation. The lake persisted throughout Green River time in the western basin and continued into post-green River time into the time of deposition of the Uinta Formation. Separation of the Uinta Basin into western and eastern depositional areas was affected by a mass of fluviatile and deltaic clastic sediments apparently built outward to the north and northeast from the rising Sen Rafael Swell to the southwest In the cross-section accompanying Maps 1 through 7, this delta can be seen to develop from the Carter No, 1 Smith well (Well No. 5) on the west to the Delhi-Taylor No, 1-15 Govt, well (Well No, 8) on the east. In contrast with the western part of the basin, lacustrine deposition took place in the eastern part of the basin, principally during the upper Douglas Creek, Parachute Creek and lower Evacuation Creek intervals Green River Formation lacustrine deposits are at least twice as thick in the western basin as the eastern; and if Wasatch and the Uinta Formation beds are considered, this ratio rises to 3.5 to 4,0 to 1 (Cross-Section, Maps 1 through 7).

6 The western part of the basin, adjacent to more active structural units, the Wasatch, Uinta and San Rafael uplifts, was apparently warped downward more rapidly and received a greater load of sediments. -4- The area of greatest thickness of Green River Formation sediments (depocenter) is definitely in the west part of the basin (Maps 1 and 7). Considering separate intervals, the depocenter migrates and spreads north and east from Willow Creek time (Map 2) through Douglas Creek and Parachute Creek - Evacuation Creek time (Maps 3 & 6) with the depositional axis of the basin changing from a southwest to northeast-oriented localized area to a west to east elongate, extensive area. The depocenter also is crowded north against the south flank of the Uinta Mountains. This crowding to the north and change in the depositional axis was in response to three factors, the first mainly depositional and the others structural in origin: 1 Northward push of deltaic and fluviatile sediments from the rising San Rafael Swell. 2, Downwarp and "underthrust" of the Uinta Basin adjacent to uplift and overthrust of the Uinta Mountains (see below). s ROTATIONAL MOVEMENT AT MOUNTAIN-BASIN BOUNDARY 3. Activity of the north-south aligned Wasatch Uplift in Willow Creek time, which became less intense but was replaced by growing activity of the west-east, cross-folded Uinta Uplift thereafter.

7 -5- DETERMINATION OF DEPOSITIONAL ENVIRONMENT AND OIL SHALE Electrical induction logs or other mechanical logs and gamma ray-neutron logs were available for most wells in the western part of the basin. Some wells had a large number of different mechanical logs available, Lithologic logs of key wells were also incorporated into the study, An accurate estimate of lithology - sandstone, siltstone and shale was made from examination of the mechanical logs and definite confirmation was obtained by comparison with lithologic logs. It was possible from this to determine in general depositional environment, whether lacustrine (lake), lacustrine strand (nearshore lake) or fluviatile (river and flood plain). Oil shale is a product of lacustrine, quiet water environment, away; from shorelines. As determined from mechanical logs, no definite way was found to assess shale intervals for oil shale content. Descriptions accompanying lithologic logs, although suggestive of oil shale content ("brown shale," "organic shale," etc.), did not definitely prove oil shale had been penetrated by the drill. Possible oil content in gallons per ton most certainly could not be deduced. Evaluating oil shale from analysis of mechanical logs (Bardsley and Algermissen, 1963), although promising, is practicable only where several types of logs - mainly density logs (gamma-gamma or sonic) and electrical logs - are run under uniform conditions in closely spaced wells (Bardsley, 1967, personal communication). Control of this sort is not available in the areas in which this study is concentrated, However, rapid advances are being made in analytical methods. CONCLUSIONS 1. Since the richest, thickest oil shale in the Piceance Basin of northwest Colorado is found in the basin's depocenter, by analogy it might be easily concluded that the area of thickest Green River deposition in the Uinta Basin might also contain its richest oil shale. However this does not appear to be so, at least from the fragmentary information available for the western Uinta Basin. Deposition within the two basins differed considerably. The depocenter of Colorado's Piceance Basin was a broad oval-shaped area at considerable distance from the uplifts which surrounded the basin, Those uplifts were not as sharp and were apparently mildly active, particularly those closest to the depocenter, In contrast, the depocenter of the Uinta Basin was a rapidly subsiding trough repeatedly flooded with coarse sediments from the "Wasatch and Uinta Uplifts to the west and north and with fluviatile and deltaic sediments from the

8 San Rafael Swell to the southwest, The uplift of the San Rafael Swell was particularly active through deposition of the lower half of the Green River Formation; and lacustrine deposion in the Willow Creek, Douglas Creek and lower Parachute Creek members tended to be separated into eastern and western areas by a mass of fluviatile and deltaic sediment which constricted the lake through the central third of the basin, tending to push lake beds northward against the Uinta Uplift. 2. Conditions within the Eocene lake that occupied the Uinta Basin apparently varied considerably These variations are reflected in sharp variations in quality and quantity of oil shale across the basin. Many areas of exceptionally rich oil shale have been found in the Uinta Basin, but these appear to be more erratic in areal extent and more subject to vertical variation than the Colorado deposits. (Smith and Stanfield, 1964) 3. Conclusions 1 and 2 above are valid only to the extent of fragmentary and sparse data available in the western Uinta Basin, It is possible to project the trend of rich oil shale deposits in the eastern Uinta Basin westward through an area of very sparse information (Map 1) Many townships in this area have no wells that reach or penetrate the Green River Formation, Available data are frequently based on incomplete samples or cuttings from oil and gas test wells. Analyses of these cuttings frequently do not accurately reflect the oil shale content of the beds penetrated {Cashion, 1964, p. 211; Smith and Stanfield, 1964, p. 216). 4. Oil shale prospects of the eastern Uinta Basin have been more extensively investigated because of the more abundant "free" outcrop information, shallower depths to sub-surface deposits, presence of the Naval Oil Shale Reserve which has been core drilled extensively and the greater density of oil and gas test wells from which data are obtainable Various estimates of the oil shale reserves of the basin have been made: Total Oil Shale Reserve in Basin - 1,300 Billion Bbls. (Quigley and Price, 1963, p. 211) Total Oil Shale Reserve in Basin 15 Gals/Ton or more 31 Billion Bbls. (potential) (Cashion., 19 67, p. 30) 290 Billion Bbls. (inferred) Total Oil Shale Reserve in Basin 25 Gals/Ton or more 120 Billion Bbls. (Approx.) (Donnell, 1964, p. 162; Duncan, 1958) Other estimates and calculations for limited areas and zoned intervals and for single wells are also available, (Quigley and Price, 1963; Cashion, 1967; Stanfield, Rose, McCauley and Tesch, 1954; Stanfield, Smith and Trudell, 1964; and others),

9 -7- It is easily seen that reserves are very large, 6, Much oil shale in the eastern third of the basin is exposed on the outcrop or is found at shallow depth These deposits are the largest suitable for strip mining in the United States Most of the rest of the reserves of the eastern Uinta Basin are at intermediate depths suitable for some types of mining and in situ recovery of oil, but generally too shallow for nuclear methods presently being considered. 7, Potential of the western two-thirds of the basin is so poorly known from the fragmentary data available, no assessment can be made (Donnell, 1964, p. 162). It is almost certain that reserves equally as rich as those known to exist geographically east of the Green River will be found to exist. Since the Uinta Basin has yielded extremely rich local beds of oil shale, assaying 90 gallons per ton (Donnell, 1964, p 162), the possibility exists that sizeable areas of concentrated, rich oil shale are still to be discovered in areas now completely untouched by drilling, The oil shale of the western two-thirds of the basin exists at depths at which only in situ methods of recovery will be practicable, Thick sedimentary cover, coupled with the thickness of the oil shale beds, may make these deposits pripie targets for exploitation by in situ methods,, If rich localized areas can be pin-pointed, oil recovery from a single operation could be extremely large and profitable. 8. The only definitive method of certain evaluation of oil shale is careful coring and analysis (Smith and Stanfield, 1964, p : 218), The Uinta Basin, especially the western two-thirds, is almost completely deficient in information from cores. 9. No estimate of oil shale potential can be made without core information, and no activity other than speculative leasing can be anticipated in the absence of reliable information on which to base estimates and decisions RECOMMENDATIONS In order to assess accurately the oil shale potential of the Uinta Basin, the : following is recommended: 1. That one or more core holes be drilled in the western part of the basin in areas meeting the following conditions: a. where thick lacustrine Green River Formation or lacustrine Uinta plus Green River is known to exist;

10 -8- b, where thick, rich oil shale is more likely - probably along a crescentic northwest to west projection of the known rich oil shale trend of the eastern basin (see Map 1); c, away from areas where present deep well information tends to rule out conditions in (a) and (b) above, 2 That no decision on site or sites be made without full cpnsultation with the U, S Bureau of Mines and consideration of all data in their files relating to oil shale content of samples from wells drilled recently (post-1962) in the western part of the basin, 3. That the core hole (or holes) be carefully sampled and thoroughly logged mechanically to provide correlation with existing logs and to provide calibration data for interpretation of logs run in future wells. It is possible that improving techniques in qualitative evaluation of oil shale from mechanical logs will enable most evaluation work to be accomplished at modest cost from logs with more expensive core data needed only occasionally for calibration and correlation purposes. Respectfully submitted HRR:nn Enc. Howard R. Ritzma Petroleum Geologist

11 REFERENCES CITED Cashion, W, B., 1963, Distribution and quality of oil shale in the Green River Formation of the Uinta Basin: Intermountain Assoc, of Petrol, Geols. Guidebook, 13th Ann. Field Conf., p, , 1967, Geology and fuel resources of the Green River Formation, Southeastern Uinta Basin, Utah and Colorado: U, S. Geol. Survey Prof. Paper 548 Donnell, John R., 1964, Geology and oil-shale resources of the Green River Formation: Colorado School of Mines Quarterly, v. 59, no. 3, p Duncan, D, C., 1958, Known reserves - oil shale deposits in the United States: Independent Petrol Assoc, America, v, 29, no. 4, p. 22, Quigley, M Darwin and Price, Jack R,, 1963, Green River oil shale potential in Utah, in_ Utah Geol, and Mineralog. Survey Bull. 54, p Roberts, P, K,, 1963, Stratigraphy of the Green River Formation, unpublished Ph.D, thesis, University of Utah Smith, John Ward and Stanfield, Kenneth E,, 1963, Oil yields and properties of Green River oil shales in Uinta Basin, Utah: Intermountain Assoc. of Petrol. Geols, Guidebook, 13th Ann. Field Conf., p Stanfield, K. E,, Rose, C, K,, McAuley, W. S,, and Tesch, W. J, Jr., 1954, Oil yields of sections of Green River oil shale in Colorado, Utah and Wyoming, : U. S Bur, Mines Rpt, Inv, 5081, Smith, J, W, and Trudell, L G., 1964, Oil yields of sections of Green River oil shale in Utah, : U, S. Bur. Mines Rpt. Inv. 6420