Study of the Composition of Natural and Associated Gases from Fields in Tomsk Oblast
Abstract Generated abstract
This study examines the composition of natural and associated gases from exploratory wells and newly identified oil and gas fields in Tomsk Oblast, with attention to variation by stratigraphic depth. A total of 130 samples from 23 oil-bearing areas were analyzed by a two-stage gas chromatographic procedure to quantify hydrocarbon and non-hydrocarbon components, excluding rare gases. The results indicate that methane, nitrogen, and carbon dioxide are the principal components, while hydrogen and heavier hydrocarbons are generally absent or present in minor amounts, and that heavier hydrocarbon content tends to increase with depth, especially in Lower Cretaceous and Jurassic deposits. The study also identifies recurring associations among ethane, propane, and heavier hydrocarbons and describes depth-related changes in individual gas components.
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BULLETIN
OF THE ORDER OF THE OCTOBER REVOLUTION AND ORDER OF THE RED BANNER OF LABOR POLYTECHNIC INSTITUTE
named after S. M. KIROV
Vol. 268 1976
STUDY OF THE COMPOSITION OF NATURAL AND ASSOCIATED GASES FROM DEPOSITS OF THE TOMSK REGION
N. M. SMOLYANINOVA, S. I. KHOROSHKO, V. A. KUZNETSOVA, E. N. SMETANIN
(Presented by the scientific-methodological seminar of the organic departments)
Determining the composition of natural gases is of exceptionally great importance for geological prospecting work, geochemical constructions and the forecasting of new oil and gas deposits, and, finally, for identifying and calculating the resources of hydrocarbon raw material.
The aim of the present study was to examine the composition of gases obtained from exploratory wells of new oil-and-gas-bearing areas and discovered fields of the Tomsk Region.
The content of individual gas components was determined by gas chromatography. The work was carried out in two stages. First, the sample was analyzed on an KhL-4 chromatograph (gas-liquid version; analysis conditions: stationary phase—TEGNM ether on INZ-600, fraction 0.25–0.5 mm; column length—1.5 m; carrier gas—hydrogen, flow rate 30–40 ml/min; detector current—110 mA; temperature 20°C); in this case all hydrocarbons and carbon dioxide were recorded on the chromatogram. To determine the remaining non-hydrocarbon components, the gas sample was subjected to repeated analysis on a GAKh-21.2 chromatograph (gas-adsorption version; analysis conditions: adsorbent—CaA zeolite, fraction 0.25–0.5 mm; column length 1.5 m; carrier gas—helium; carrier-gas pressure 0.5 atm; detector current—110 mA; temperature 20°C). The chromatograms were calculated by the method of internal normalization using correction coefficients. The use of a two-stage analysis scheme made it possible to detect qualitatively and determine quantitatively all components (with the exception of rare gases) of natural gases. In all, 130 samples obtained from 23 oil-bearing areas of the Tomsk Region were studied.
The results of studying the gas composition showed that their principal components are methane, nitrogen, and carbon dioxide, the contents of which vary within fairly wide limits. Hydrogen and heavy hydrocarbon gases are absent in most wells or occur in insignificant amounts.
Of greatest interest was clarification of the composition of the gases and its changes with the depth of sample collection. For this purpose graphs were constructed showing the dependence of the content of individual gas components on stratigraphic depth (Fig. 1).
The data obtained on gas composition made it possible to identify certain regularities in the distribution of their components as a function of depth.
- The presence of ethane in gases in the overwhelming majority of cases is accompanied by the appearance of propane and heavier hydrocarbons.
Fig. 1. Dependence of the content of individual components in the gas on burial depth
The regularity found had previously been noted for gases of fields in the Soviet Union and most likely can be explained by the genetic relationship of the hydrocarbons in the gases.
2. The content of “heavy” hydrocarbons in the gases steadily increases with stratigraphic depth (Fig. 1), and rises especially rapidly in the Lower Cretaceous and Jurassic deposits.
The content of individual hydrocarbons in the gases changes unevenly with depth. The ethane content increases most rapidly. In the Vartovskaya and Tarskaya suites, the averaged content of butanes grows faster than that of propane. In the Kulomzinskaya suite and below, the amount of propane becomes greater than that of butanes. The content of pentanes and hexanes increases significantly more slowly.
3. The amount of ethane decreases with depth, while the concentration of nitrogen and carbon dioxide increases.