Features of the distribution of hydrocarbon accumulations in lithologically different-type deposits at the ancient continental margins of the North American and South American platforms

Abstract

Lithologically diverse sedimentary complexes were formed within the North and South American platforms. The most general groups of the sediments are distinguished as follows: continental (alluvial, limnic), deltaic, shallow-marine, and deepwater—for the terrigeneous formations, reef limestones and limestones of other origins (oolitic, algaes, etc.), and dolomites—for carbonate varieties. In addition to this, tuffs, tuff-sandstones, and crystalline schists (quartzites) were studied separately. The lasts were marked only in the Permian Basin. The comparative analysis of the sedimentary basins located in the peripheral parts of the North American and South American platforms showed the following: the most important stage in the evolution of the North American platform is the first stage of existence of the ancient Paleozoic continental margins, which developed under passive tectonic conditions and determined its future potential of oil and gas bearing. At this stage, the main resources of oil and gas hydrocarbons are concentrated in carbonate rocks. As for the sedimentary basins located on the margins of the South American platform, the second stage is the most important stage in their evolution when the foredeeps were formed and developed laying on the earlier structures. This period is related to the oil and gas bearing potential of the basins on the margins of the South American platform. For both platforms, a common circumstance is that, at the second stage of development of all the sedimentary basins, all the resources of hydrocarbons are focused in the terrigeneous sediments.The stratigraphic range of oil and gas occurrence in the basins of the ancient continental margins is determined by the following regularity: the fold structures is younger confining these margins, the age range of the oil and gas reservoirs is broader.