『Abstract
Weathering crusts of the sedimentary basin basement are collectors
in several regions of the world. hey enclose huge reserves of
oil and gas. The paper considers the geochemical, mineral, and
petrophysical heterogeneities of weathering crusts that should
be taken into consideration in the prospecting, exploration, and
development of hydrocarbon raw material therein. areal and linear-fissure
types of weathering crust are defined. They were formed before
the overlapping of basement by rocks of the sedimentary cover.
Areal crusts are pervasive at the basement roof, whereas linear-fissure
crusts are formed along fractures. A complete weathering crust
profile includes the following zones (from the bottom to top):
disintegration, leaching and hydration, hydrolysis, and final
hydrolysis. Rocks of the lower two zones represent the cavernous-fissure
collector, while rocks of the upper zones are impermeable. In
the arches of uplifted blocks of the basement, weathering crusts
are subjected to erosion during marine transgressions. In such
places, the roof is composed of rocks of the lower permeable zones
that often make up a single heterogeneous natural reservoir overlapped
by sandy collectors of sedimentary sequences.
Linear-fissure weathering crusts show zonal distribution with
good filtration-capacity properties. Several large oil and gas
pools have been discovered in them.』
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