Six major types of petroleum reservoir are distinguished according to the principal trapping mechanism involved. They are structural, lithologic, stratigraphic, structural-lithologic, structural-stratigraphic and lithologic-stratigraphic. Each is described in terms of its characteristic features and setting in different geotectonic environments, particularly in ancient and younger platforms, foredeeps and intermontane areas. Lithologic and stratigraphic traps are of great importance, but exploring for them is much more complex than for structural traps. It involves a scientific study of the factors controlling the distribution and development of reservoir and cap rocks, palaeogeography, palaeomorphology and palaeotectonics being particularly important. Success depends upon a wise choice of techniques and priorities. Two main stages are recognised, exploration and development. The former involves in turn (1) regional, geological and geophysical investigation, including a careful evaluation of lithological and unconformity pinch-Outs, (2) selection of areas for wildcat drilling, and (3) search for specific traps. Each step of the programme by A. G. ALEKSIN, Institute of Geology and Exploitation OJ Combustible Fuels, I. KH. ABRIKOSOV, Ministry of Petroleum Industry, V. A. GROSSHEIM, All- Union Research Institute of Petroleum Exploration, I. P. ZHABREV, Ministry of Petroleum Industry, V. I. KORNEYEV, Krasnodar Trust of Petroleum Exploratory Geophysics, All- Union Research Institute of Petroleum Exploration, G. P. OVANESOV, Ministry of Petroleum Industry, M. K. POLSHKOV, All- Union Research Institute of Exploration Geophysics, S. G. SARKISYAN, Institute of Geology and Combustible Fuels Minerals, R. O. KHACHATRYAN and G. T. UDIN, Institute of Geology and Exploitation of Combustible Fuels, 50 Fersman Street, Moscow V-312, U.S.S.R.
K. S. MASLOV, V. S. MELIK-PASHAEV, of subsurface geological mapping and the principal methods of geophysical surveying are outlined.
Emphasis is put on geophysical, notably seismic, techniques and suggestions made for increasing their effectiveness. Priorities in wildcattjng for lithologic and stratigraphic traps are discussed for various geological situations. The prospects of finding such traps in different regions of the U.S.S.R. are summarised.
Six types majeures de gîtes petroliers sont distingués selon la méthode principale de leur empiègement. Ce sont les types suivants: structural, lithologique, stratigraphique, structural-lithologique, structuralstratigraphique et lithologique-stratigraphique. Les particularités de chacun et les conditions géotectonique de sa présentation, notamment dans les plateformes anciennes et jeunes, dans les avantsfosses et les dépressions intermontagneuses, sont
