(1) A method of searching for petroleum and gas deposits based on the identification of gaseous hydrocarbons that migrate from the oil and gas beds through the overlying rock to the earth’s surface. The quantities of these hydrocarbons reaching the surface deposits, though not very great, are nevertheless direct indications of the presence of oil and gas beds beneath the surface. A gas survey consists of sampling the gas (subsoil air) or rock with subsequent extraction from the rock of gas from depths of 2-3 m or more (10-50 m and deeper). The sampling points are laid out according to profiles in the area to be surveyed at distances of several hundred m from each other. The gas probes obtained are analyzed in instruments that indicate the presence of methane, ethane, propane, and other hydrocarbons with a sensitivity of 10-5 to 10-6 percent. The results of the analyses yield “gas anomalies,” that is, increased and regularly located concentrations of hydrocarbons. A gas anomaly in the surveyed area indicates the possible presence of an oil or gas deposit within the rock series. The gas survey method was developed in the USSR by V. A. Sokolov (1932).
REFERENCESSokolov, V. A., and G. G. Grigor’ev. Metodika i rezul’taty gazovykh geokhimicheskikh neftegazopoiskovykh robot. Moscow, 1962.
Sokolov, V. A. Geokhimiia gazov zemnoikory i atmosfery. Moscow, 1966.
Sokolov, V. A. Geokhimiia prirodnykh gazov. Moscow, 1971.
(2) A method of determining the intensity of the release of methane in mine shafts. A gas survey is conducted by sampling and analyzing the air to establish the methane concentration and measuring the quantity of air passing through the mine area. Gas surveys may be longitudinal or cross-sectional. In the longitudinal gas survey the change in the concentration and output of gas is ascertained along the length of the mine, and in the cross-sectional gas survey the gas concentration is determined for a cross section of the mine. Repeated gas surveys permit the measurement of the intensity of gas generation over time.