Estimation of efficiency lithogeochemical surveys for petroleum and gas prospecting

Abstract

The paper describes application of litho geochemical surveys for petroleum and gas prospecting within direct detection of hydrocarbons escaping from subsurface accumulations and source beds ? most common technique. The geochemical data came from shallow probes soil samples and shallow probes of soil gas. The adsorbed soil gases were analyzed for methane, ethane, ethylene, propane, propylene, iso-butane and normal butane by gas chromatography using a Flame Ionization detector. Samples of soil were analyzed for number of elements using spectral analysis. Direct relationships between distribution of hydrocarbons and certain elements in the vicinity of oil and gas accumulations were discovered. Those elements form halos marking structures perspective for oil and gas (Ni, Co, Cr, Sc, Mo, Li, B). Presence of positive correlation between hydrocarbon halos and active elements anomalies lends to the deduction that hydrocarbons migrating from oil and gas reservoirs affect on distribution elements in overlapping layers. These elements can be used for detecting chemical changes in the soils and rocks associated with the oil and gas deposits. Important result of these studies litho geochemical sur- vey pretty accurate showed board of Orenburg Gas Con- densate Oilfield, which has very complicated geological structure. Main advantage of using the complex litho and athmo geochemical methods is make geochemical surveys cheaper. Litho geochemical studies could be used to find out main regularities of the surveyed area. To approve anomalies discovered by litho geochemical surveys athmo geochemical and over methods should be used.