Abstracts

In petroliferous provinces in the Soviet Union numerous oil pools are found in deltaic Sediments. The palaeogeographic, palaeogeomorphologic and palaeotectonic peculiarities of delta formation in the geological history of sedimentary basins are presented.

These peculiarities are different for old and young platforms, interior depressions and exogenic belts.

The influence of polyfacial deltaic rocks on trap formation, non-homogeneous structure of reservoirs, the accumulation and preservation of organic matter, its alteration into hydrocarbons and the latter's migration and entrapment are elaborated. In view of the specific structure of deltaic Sediments, appropriate methods of petroleum prospecting, combining geophysics and deep drilling, are suggested.

Résumé

Dans les provinces pétrolières de l'URSS de nombreux gisements se trouvent dans des dépôts deltaïques. On décrit les particularités paléogéographiques, paléogéomorphologiques et paléotectoniques des dépôts deltaïques des différents stades de l'histoire géologique des bassins sédimentaires. Ces particularités diffèrent pour les plateformes anciennes et récentes, pour les dépressions internes et pour les ceintures exogènes. On explique dans cette communication l'influence des complexes deltaïques à faciès multiples sur l'hétérogénéité des réservoirs, l'accumulation et la transformation de matières organiques, la migration, l'accumulation et le piégeage des hydrocarbures. Des systèmes différents de recherche géophysique et de forage profond, adaptés aux caractéristiques particulières des dépôts deltaïques, sont proposés pour l'exploration de ces régions.

1. INTRODUCTION

In fluvial environments and particularly in palaeodeltaic Sediments, both structural and stratigraphic traps are found. The first type of trap has been studied in detail and suitable methods of exploration have been developed. The second type represents a very complex natural phenomenon which requires further investigation. While petroleum exploration in structural traps nears its completion, the quest for stratigraphic traps will be of great importance. Stratigraphic traps developed in deltaic Sediments by G. P. OVANESOV, I. KH. ABRIKOSOV, are of especial value. Recognition of diagnostic Ministry of Petroleum Industry, U.S.S.R., features of palaeodeltaic deposits favourable for A. G. ALEXIN, S. G. SARKISYAH, petroleum accumulation and the development of mapping procedure is a complex problem because of the specific features of deltaic Sediments, their depth and mode of burial and the imperfection of our geological and geophysical exploratory methods.

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