On the Nature of Organic Matter from the Deposits of the Tyumen Formation in the Peredovaya Area of Tomsk Oblast
Abstract Generated abstract
This paper examines coal-like organic matter recovered from the Tyumen Formation in well 190 of the Peredovaya area, Tomsk Region, in relation to the area’s oil and gas prospects. The authors describe macroscopic properties and use proximate and elemental analyses, calorific value, stable carbon isotope composition, and petrographic examination of thin and polished sections to determine the material’s nature. The data indicate a high heat of combustion, carbon and hydrogen contents consistent with sapropelic and humic-sapropelic caustobioliths, and an isotopic composition intermediate between hard coal and kennel coal. Petrographic observations lead the authors to classify the material as humito-sapropelite, a type of organic matter regarded as a possible precursor for oil or gas formation.
Full Text
Izvestiya of the Tomsk Polytechnic Institute named after S. M. Kirov
Vol. 253, 1976
On the Nature of Organic Matter from Deposits of the Tyumen Formation in the Peredovaya Area of Tomsk Region
V. L. Kokunov, N. K. Grigoriev
(Presented by Professor A. V. Aksarin)
During the drilling of well 190 in the Peredovaya area in the Vasyugan district of Tomsk Region, a core was recovered from deposits of the Tyumen Formation in the depth interval 2540–2560 m; it was represented by solid, black, coal-like formations with a total thickness of about 4 m.
Since the Peredovaya area is located in a highly promising region of Tomsk Region, analysis of the nature of this organic matter is of interest for evaluating the oil-and-gas prospects of the area, all the more so because no inflow of oil was obtained in well 190.
The pieces of core taken for analysis consisted of small fragments, 1.0 × 1.0 cm and smaller, of black coal-like material with a resinous luster and conchoidal fracture. The material is rather brittle, since its pieces crumble when pressed with the fingers. A characteristic feature of the material is its ability to ignite from a match flame with a sooty flame. This property, in macroscopic examination, does not allow the studied formation to be assigned to humic coals, especially since one of the larger pieces behaves in a match flame like a resin-like formation, i.e., it begins to melt and run downward in drops. The odor produced during combustion strongly resembles the smell of rubber.
Thus, the results of macroscopic study make it possible to conclude that the material under study may belong to sapropelic formations.
For more precise diagnosis, proximate and incomplete ultimate analyses were carried out, and the isotopic composition of carbon was also studied by a mass-spectrometric precision method.
The proximate and ultimate analyses were performed in the laboratory of the Faculty of Thermal Power Engineering by Cand. Tech. Sci. N. V. Grikashny. The results of the analyses are summarized in Tables 1 and 2.
Table 1
Proximate analysis
| $W_a$ avg., % | $A$ avg., % | Heating value, kcal/kg | Heating value, kcal/kg | Heating value, kcal/kg | Heating value, kcal/kg |
|---|---|---|---|---|---|
| $Q_b$ | $Q_{v}^{a}$ | $Q_{v}^{g}$ | $Q_{n}^{g}$ | ||
| 1.3 | 1.86 | 8110 | 8100 | 8300 | 7980 |
Elemental analysis
Table 2
| Name of element | C^a | C^r | H^a | H^r |
|---|---|---|---|---|
| Percentage composition | 79.25 | 81.0 | 5.84 | 5.98 |
Judging from the obtained value of the calorific capacity, the substance under study has a considerable heat of combustion and, according to our data [3], may be assigned to humito-sapropelites.
The results of the elemental analysis with respect to the carbon and hydrogen content, judging from the data of K. V. Mironov [4], A. F. Dobryanskii [2], and U. L. Russell [5], make it possible to assign the substance under study either to sapropelite-humites or to humito-sapropelites, since for representatives of both classes of caustobioliths the hydrogen content varies within the limits indicated in [4].
The content of the heavy stable isotope C^13/%, determined in the mass-spectrometric laboratory by N. K. Grigor’ev in the sample under study, was \(\delta C^{13} = -2.48\%\) relative to the RDB standard. If the obtained value is compared with the tabulated data of E. M. Galimov [1], given in Table 3, it turns out that the material under study falls in the series
Table 3
Isotopic composition of carbon in caustobioliths
| Name of caustobiolith type | Isotopic composition in C^13%, RDB |
|---|---|
| Bituminous coal | −2.35 |
| Brown coal | −2.36 |
| Hard coal | −2.38 |
| Substance under study | −2.48 |
| Kennel coal | −2.61 |
| Oil | −3.10 |
between hard coals and kennel coals, i.e., it should also be assigned either to humito-sapropelites or to sapropelite-humites.
To refine the characteristics of the substance under study, G. K. Borodin prepared a transparent thin section and a polished section, which was examined on a POOS-1 apparatus in consultation with P. A. Trushkov. The determined reflectance makes it possible to assign the substance under study to organic matter at the yearly stage of metamorphism: (stage 11 according to the classification of IGIRGI, 1967), \(R^{v}_{\mathrm{av}} = 7.9\%\).
The study of the polished section made it possible to refine the final diagnosis of the organic matter studied according to the color characteristic of the structureless mass. Since the color of the structureless mass is yellow, this substance should be assigned to the class of humito-sapropelites.
Thus, the substance studied should be classified as a humito-sapropelite, which, according to the views of most petroleum geologists, may be considered the initial material for the formation of oil or gas.
LITERATURE
- E. M. Galimov. Geochemistry of Stable Carbon Isotopes. Nedra Publishing House, 1968.
- A. F. Dobryanskii. Combustible Shales of the USSR. Lengostoptekhizdat, 1947.
- V. L. Kokunov. Dependence of the qualitative and technological characteristics of coals of the Irsha-Borodino deposit of the Kansk-Achinsk Basin on their petrographic composition. Izvestiya TPI, 1966.
- K. V. Mironov. Prospecting and Exploration of Coal Deposits. Nedra Publishing House, 1966.
- U. L. Russell. Fundamentals of the Geology of Oil and Gas. Gostoptekhizdat, 1958.