Geology Reference
In-Depth Information
Bolivar zone with unique reserves of 4.3 billion tons, the Mene Grande
Motatan zone (the Bolivar Falcon oil and gas area), the Mene de Mauroa-
Las Palmas zone, the Mara- San Jose zone and the southern zone of uplifts
(the Western oil and gas area).
The Oligocene-Miocene and Eocene accumulations in the Bolivar zone
are mostly fault- and facies change-trapped. At the top of the Eocene are
also found stratigraphic accumulations associated with the unconform-
ably overlying Oligocene deposits. The Upper Miocene-Pliocene accu-
mulations are discovered in the sand members, pinching-out updip the
monocline and sealed in a number of cases with asphalt and “kir” (weath-
ered asphalt). The dominant type of the Eocene hydrocarbon accumula-
tions near the south portion of the basin's east flank and in the central part
of Lake Maracaibo is sheet-type anticlinal. There are some fault-trapped
accumulations in the Cretaceous limestones and facies-change trapped
accumulations in the Miocene sandstones. The western flank is dominated
by the fault-trapped, stratigraphic and sheet-type anticlinal accumulations.
The region contains mostly oil accumulations, caused by intense faulting of
the local structures.
The discovery in recent years of a number of gas and condensate accu-
mulations at depths exceeding 4,500 m may suggest that lower gas-con-
densate is present in the basin. The largest fields are Bolivar, Lama, La Paz,
Mara, Lamar, Boscán, Urdaneta, La Concepcion and Mene Grande.
1.2 Foredeeps
1.2.1 heCarpathianForedeep
The foredeep is positioned between the Volyn-Podolsk edge of the Russian
Platform and the Carpathian folded mountains. It is bounded in the north-
northwest by a large regional Rava-Russian Fault, in the southeast by a
band of faults extending along the north slope of the Bukovina cross-uplift
and in the south-southeast by the Beregovoy overthrust of the Eastern
Carpathians (Figure 1.9).
Based on the sum of tectonic features, stratigraphy, lithofacies and the
geologic history, two tectonic zones are identified within the foredeep, the
Internal and the External ones. The Internal zone is the geosynclinal folded
flank and the External zone is the platform flank. The zones are separated
by the Stebnik overthrust on which the folded flank is thrust over the plat-
form flank by up to 20 km.
