Chemistry and mineralogy of natural bitumens and heavy oils and their reservoir rocks from the United States, Canada, Tr

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By JOHN W. HOSTERMAN, RICHARD F. MEYER, CURTIS A. PALMER, MICHAEL W. DOUGHTEN, and DONALD E. ANDERS

U.S. GEOLOGICAL SURVEY CIRCULAR 1047 DEPARTMENT OF THE INTERIOR MANUEL LUJAN, Jr., Secretary

Federal Center, Box 25425 Denver, CO 80225

Abstract 1 Introduction 1 Acknowledgments 2 Analytical Techniques 2 Dividing Reservoir Rock Samples into Available Hydrocarbon and Sediment Residue 2 Determining the Composition of the Available Hydrocarbon Determining the Mineral Content of the Sediment Residue 2 Determining the Trace-Element Distribution Bitumen and Heavy Oil Deposits 3 California 3 Kentucky 3 New Mexico 3 Oklahoma 4 Texas 4 Utah 4 Wyoming 4 Canada 5 Trinidad and Tobago 5 Venezuela 5 Discussion 5 References Cited 5 Appendix, Description of Sample Localities 17

1. Mineral content of the reservoir rock samples as determined semiquantitatively by X-ray diffraction 8
2. Composition of natural bitumen, heavy oil, and gilsonite 9

3-8. Trace-element content of reservoir rock, sediment residue, bitumen, heavy oil, and gilsonite samples from:

3. California 10
4. Kentucky and New Mexico 11
5. Oklahoma 12
6. Texas and Wyoming 13
7. Utah 14
8. Canada, Trinidad and Tobago, and Venezuela 15
9. Maximum and minimum trace-element contents of reservoir rock, sediment residue, and bitumen or heavy oil samples from all deposits 16

INTRODUCTION

Supplies of conventional crude oil are diminishing; therefore, it is important to understand the reservoir characteristics of unconventional oil deposits to enhance the recovery of the contained resource. Unconventional deposits contain oils heavier than 20 o API gravity and less viscous than 10,000 centipoises (cP) or natural bitumens (in tar sands and oil sands), which are more viscous than 10,000 cP. The resources of these hydrocarbons are very large, particularly for the heavy oil of the Orinoco oil belt of Venezuela as well as the natural bitumen of the 'Nestern Canada Sedimentary Basin of Alberta. In addition, many deposits of heavy oil and bitumen occur in the United States. Although the total resources of unconventional oil deposits are extensive, many environmental, economic, and technological factors inhibit their productivity. To facilitate their exploitation, we need to know the mineralogy of the host rock, the amount and type of clay minerals pres ~nt, the physical and chemical composition of the hydroc"'rbons, and the trace-element distribution.

The U.S. Geological Survey (USGS) is undertaking a program to analyze the reservoir rock mineralo~y and hydrocarbon chemistry of samples from natural l'~tumen and heavy oil deposits of the world. Results from the first phase are reported in this Circular. The samples a'lalyzed are from Canada, Trinidad and Tobago, the United States, and Venezuela. Sample localities are provided in the appendix.

Twenty-one samples from natural bitumen an1 heavy oil deposits in seven States of the United States and six samples from outside the United States form the basis of this initial study. The hydrocarbons were extracted from each sample, leaving the ground rock as a sediment residue. X-ray diffraction analysis of the residue and its clay fraction identified the minerals present in the reservoir rock (table 1). The components of the available hydrocarbo:'ls were determined (table 2). Trace-element contents were determined in the reservoir rock sample, in the sediment residue remaining after the hydrocarbons were removed, ard in the extracted hydrocarbons (tables 3-9).

The authors divided the work as follows. The program was conceived by Meyer, and he obtained the samples and prepared the appendix. Extraction of the bitumen and X-ray diffraction to determine sample mineralogy were done by Hosterman. The distribution of 29 trace elements in reservoir rock and sediment residue was determined by Palmer by instrumental neutron activation analysis (INAA). INAA determinations of the distribution of the same 29 trace elements in bitumen and heavy oil were made by the Nuclear Radiation Center, Washington State University, Pullman, Wash., under a contract from the USGS. Contents of nine other trace elements in all samples were determined by Doughten by atomic absorption spectrometry, atomic emission spectroscopy, and thermal combustion infrared spectroscopy. Hydrocarbon components were determined by Anders by chromatography.

Acknowledgments

We are grateful to the following individuals for providing samples of bitumen and heavy oil for this study: Cynthia Brandt and M.D. Laine, Utah Geological and Mineralogical Survey; Antonius J. Budding, New Mexico Institute of Mining and Technology; Margaret R. Burchfield, Oklahoma Geological Survey; James W. Earley, consultant, Santa Maria, Calif.; Deborah Henry, Alberta Research Council; Caroline M. Issacs, USGS; Jeffrey D. Meyers, Conoco, Inc.; Martin C. Noger, Kentucky Geological Survey; and H. Rambarran, Trinidad and Tobago Oil Company, Ltd.

Dividing Reservoir Rock Samples into Available Hydrocarbon and Sediment Residue

The weight of the available hydrocarbon (bitumen), or extractable organic matter (EOM), was derived by two methods. Both methods were used on all samples. In one method, a weighed sample of reservoir rock was crushed and elutriated with benzene. Subtracting the weight of the sediment residue from the weight of the original sample gave the weight of the EOM. The hydrocarbons extracted by this method were used to determine the trace-element content. In the other method, the EOM was separated from the crushed reservoir rock sample with chloroform in a Soxhlet apparatus. The extract was then used to determine the composition of the available hydrocarbon.

Determining the Composition of the Available Hydrocarbon

The EOM, heavy oil, or gilsonite was combined with iso-octane at room temperature; the precipitate was asphaltene. The remaining solution was decanted and evaporated in a nitrogen atmosphere until a constant weight was obtained. A sample of 4-5 mg was elutriated on an alumina-silica gel column to separate the major hydrocarbon components. The aromatic hydrocarbo'ls, resins, and heterocompounds (nitrogen-sulfur-oxygen) were adsorbed on the alumina gel, and the saturated hydrocarbons, on the silica gel. For chromatographic analysis, tl ~ column was elutriated progressively with more polar sC'lvents-cyclohexane or heptane for the saturated hydroca~bons, benzene for the aromatic hydrocarbons, and 50/50 berzene/methanol for the resins and in part for the aromatics. The saturated hydrocarbons are the paraffin series, that is, the alkanes; the aromatic hydrocarbons are the aromatic (benzene ring) series; and the resins are included with the: N-S-0 compounds as polar compounds.

Determining the Trace-Element Distril'ution

The trace-element distribution in all samples was determined by INAA, atomic absorption spectrometric (AAS) methods, and atomic emission spectroscopy (AES) methods. Twenty-nine elements were determined by INAA, four by AAS, and four by AES. Sulfur was determined by thermal combustion infrared spectroscopic analysis (Rait and Aruscavage, 1989).

The INAA method used for reservoir rock and sediment residue samples was similar to that used for determining trace-element distributions in coal (Palmer and Baedecker, 1989). It consisted of measuring the photon spectra (X-rays and f-rays) emitted from a neutronactivated sample; multielement coal, fly-ash, and gelatin standards were used as laboratory monitors. After irradiation of the sample, X-rays and r -rays were counted by a germanium detector. The peak areas were used to determine the amount of each element present according to an updated version of programs reported by Baedecker (1976).

Hg content was determined by cold-vapor AAS, where Hg was evolved from the sample solution by the addition of SnC12 • The Hg was amalgamated onto gold beads centered in the coil of an induction furnace. When the furnace was activated, the Hg was driven into a quartz cell, where its atomic absorption signal was measured (Wilson and others, 1987; Aruscavage and Moore, 1989).

The AES method, described briefly by Lichte and others (1987), is inductively coupled plasma-atomic emission spectroscopy (ICP-AES). It consists of using a highenergy heat source (a plasma) to excite the atoms into a higher energy state. As atoms relax back to their ground state, they emit light at a characteristic wavelength. This light emission is detected by a photomultiplier tube array. The intensity is used to determine the amount of each element present. Li, Mo, Nb, and Y concentrations were determined by ICP-AES.

BITUMEN AND HEAVY OIL DEPOSITS

The deposits sampled are described below. They are in California, Kentucky, New Mexico, Oklahoma, Texas, Utah, Wyoming, Canada, Trinidad and Tobago, and Venezuela. Sample localities are listed in the appendix. The samples are from well-known deposits that have been sources of natural asphalt, that are presently sources of petroleum or synthetic oil, or that are potential sources of petroleum.

California

Three of the four samples used for this study were also from the Monterey Shale. The three samples were from Santa Barbara County-two (CA-2 and CA-3) from Gaviota Beach approximately 45 km west-northwest of Santa Barbara and one (CA-l) from near Santa Maria. A fourth sample (CA-4) was medium-brown siltstone frcm the Pismo Formation in San Luis Obispo County, near Edna. The two samples of diatomaceous shale (CA-l and CA-2) contained cristobalite and were light to medium brown. One sample (CA-3) was a carbonaceous marl containing the zeolite heulandite. All samples except the marl contained abundant quartz, some feldspar, and a little clay. The available hydrocarbon in these four samples rangei from 2.80 to 14.37 weight percent. Data for these four s~mples are in tables 1-3.

Kentucky

Two samples from Kentucky were analyzed. Sample KY-1, from the Homer quarry in Logan Count~·, was fine-grained sandstone from the Big Clifty Sandston~ Member of the Mississippian Golconda Formation. Ths unit ranges in thickness from 0 to 23 m (Williams and others, 1982). The sample consisted of quartz, feldspar, and kaolinite. A trace of illite was present in the clay f~action, but no smectite was detected.

Sample KY-2, from the Indian Creek qu~ in Edmonson County, was taken from part of the Kyrock Sandstone Member of McGrain (1976) of the Lower Pennsylvanian Caseyville Formation. The brown asphalfr. sandstone part of the Kyrock ranges in thickness from 3 to 27 m (McGrain, 1976). The sample contained quartz, feldspar, and kaolinite. A trace of illite, but no smectite, was indicated by X-ray diffraction. The available hydrocarbon averaged 7.6 weight percent in these samples. Data for the two samples from Kentucky are in tables 1, 2, an~ 4.

New Mexico

One sample (NM-1) of tar sand was obtain~d from the Triassic Santa Rosa Sandstone in Guadalupe County, N. Mex. The sandstone is asphaltic in an area of about 3,600 ha north of Santa Rosa (Foster, 1965); its S"'turated zones range in thickness from 3 to 18 m. The brown sandstone was composed of quartz, kaolinite, and traces of feldspar, dolomite, and illite. This one sample contained

Utah

content of the sample was 15.35 weight percent. Data for this sample are in tables 1, 2, and 6.

Sample AB-8 was from the Lower Cretaceous McMurray Formation from Alberta, Canada. The sample was a medium-brown, fine-grained sandstone containing quartz, feldspar, pyrite, kaolinite, and illite. Smectite was not indicated by the XRD trace. The available hydrocarbon content for the sample was 14.73 weight percent (table 2). The hydrocarbon components have not been determined. The mineralogy of the reservoir rock and trace-element contents are in tables 1 and 8.

Trinidad and Tobago

One sample (TT-l) of Trinidad's reservoir rock containing heavy oil was analyzed for comparison with the samples from the United States. This sample was taken from an outcrop in the lower part of the Tertiary Morne L'Enfer Formation in the Parrylands area, St. Patrick County. The gray, fine-grained sandstone was composed of quartz, feldspar, and clay minerals. The clay minerals were kaolinite, illite, chlorite, and mixed-layer clay. The available hydrocarbon content was 11.96 weight percent. Data for this sample are in tables 1, 2, and 8.

Venezuela

One sample (VE-4) of Venezuela's reservoir rock containing heavy oil was also analyzed for comparison. This sample was taken from the Oficina Formation in the Orinoco oil belt. The gray, medium-grained sandstone contained quartz and trace amounts of feldspar and clay minerals (kaolinite, illite, and smectite). Kaolinite was the dominant clay mineral. The available hydrocarbon content was 17.29 weight percent. In addition to the one sample of reservoir rock, three samples of heavy oil (VE-l, 2, and 3) were analyzed for their hydrocarbon and trace-element contents. These data and the reservoir rock mineralogy are in tables 1, 2, and 8.

DISCUSSION

The reservoir rock and sediment residue samples richest in trace elements were the four samples from California (table 9). The trace-element distribution in the reservoir rock samples shows that 35 of the 38 trace elements detected were most abundant in the four California samples. In the sediment residue samples, 33 trace elements were most abundant in the four California samples. This concentration of trace elements was probably due to the low quartz content of the California samples and to the presence of heulandite, cristobalite, siderite, and pyrite.

In the reservoir rock and sediment residue sa"nples, trace elements were scarcest in the five Oklahoma sa"nples. In the reservoir rock samples, 27 of 38 trace elements were least abundant in the five Oklahoma samples. In the sediment residue samples, 25 trace elements were least abundant in the five Oklahoma samples. This scarcity of trace elements was probably due to the high quartz content of four of the Oklahoma samples and to the high calcite content of the fifth sample.

The trace-element distribution in the available hydrocarbon differs from that in the reservoir rock and sediment residue. The maximum and minimum contents cf trace elements in bitumen or heavy oil listed in table 9 do not include the values for the heavy oil and gilsonite fro"TI Utah or the heavy oil samples VE-l, 2, and 3 from Ve"'ezuela because we lack the chemical and mineralogical dat(l for the reservoir rock of these hydrocarbons. The bitumer in the four Utah samples for which we have reservoir rock and sediment residue data contains the highest concentra+ions of trace elements among all hydrocarbon samples compared. Nineteen of the 38 trace elements detected were most abundant in the available hydrocarbon of these fo·u Utah samples. No pattern in trace-element scarcity is obvious for the hydrocarbon samples.

REFERENCES CITED

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APPENDIX, DESCRIPTION OF SAMPLE LOCALITIES

The standard codes for localities in the United States are from the U.S. National Bureau of Standards Federal Information Processing Standards Publication 6-3 (1979). Each U.S. code begins with US, has a two-digit code for the State, has a three-digit code for the county, and ends with a dash and a unique number to distinguish the samples from the same county. The codes for localities in other countries are from the U.S. Defense Intelligence Agency Manual 65-18 (1972). Each code for a locality in another country begins with a two-letter designation for the country, has a two-digit code for the State, Province, or county, and ends with a dash and a unique number to distinguish the samples from the same political subdivision.

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