EMPLOYMENT OF GAS LOGGING IN PROSPECTING OPERATIONS

Gas logging may be used for the geochemical study of exploratory and other wells in prospecting for oil and gas pools in deep deposits. The analysis of gas logging data in known oil and gas deposits makes it possible to observe definite regularities in hydrocarbon-gas distribution that are associated with the process of the migration of these gases. The most important elements in the hydrocarbon characteristics of gas logging are: the depth of the first appearance of hydrocarbons in the well, the magnitude of the concentration gradient, and the shape of the hydrocarbon curve. Quantitative changes can be noted between the gas logging data of areas with the more permeable rocks of Tertiary and Cretaceous age and areas composed of more dense and less permeable strata of Paleozoic age. In the Stavropol province, Stalingrad region, and in western and eastern Siberia, studies of gas-logging data show the following: In structures containing significant accumulation of oil and gas, the hydrocarbon gases produce maxima in the crests of uplifts and minima on the flanks. These maxima have been traced in different stratigraphic horizons, and their intensity diminishes towards the earth's surface. In structures with insignificant accumulations of oil and gas, the hydrocarbon maxima are either poorly developed or absent entirely.

Also observed is a zonal distribution of nitrogen and carbon dioxide depending on the structural elements of the uplift. It is necessary to improve the apparatus used in core sampling and gas analysis. Apparatus used in gas analysis should be capable of fractional determinations of heavy hydrocarbons to within hundredths and thousandths of a percent. It is also necessary to be able to determine methane and nitrogen over a wider range of concentrations. — Auth. English Summ.