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Geology
The Tranquilo Block is located in the
foreland of the Magellan's Basin where Cretaceous and Tertiary basin
are the main components of the oil system with a Lower Cretaceous source
rock.
The Petroleum System is proven in the
gas field Tranquilo and in Esperanza 3 and 4 wells containing gas and
condensate shows. In Manzano 5 through 9 there are shallow objectives
with gas.
In the western half of the block, there
are deltaic system of Upper Cretaceous (mainly fracture plays) as well
as conventional tertiary plays. Traps are created by faults propagation
folding and inversion of the external thrust belt. In the Eastern half
of the block, Tertiary stratigraphic traps, CBM Tertiary play and leads
and prospects in deltaic phases of Oligocene-Miocene platform.
Estimated Reserves: Unknown estimated
resources volume but using Tanquilo gas field as analogue may go from
0 to 2000 millions m3S
(Tranquilo had GOIS of 1200 million m3S,
9 wells)
Cretaceous (Skyring area)
- The Titonian - Aptian Erezcano/Zapata
fm. mainly hemipelagic black shales, siltstones and laminated sands
deposited in a platform and slope facies, 300 to 500 m. thick, organic
rich, across the block.
- Canal Bertrand fm., Aptian-Early
Coniacian, lower fan tubidites with submarine volcanics (La Pera Fm)
and La Torre fm., Coniacian-Santonian Sand rich turbidite complex, both
outcrping to the West of the block.
- Escarpada fm., Santonian-Campanian,
deep water, submarine channel conglomerates and levee/overbank sandstones
within the western most part of the block.
- Fuentes fm. Campanian Early
Maastrichtian hemipelagic muds grading upwards into slope and shallow
water platform facies to the Norh grade into Tres Pasos Fms. sandstones.
- Rocallosa fm., Maastrichtian-Danian,
mid to coarse, lower shoreface/stuarine deltaic sanstone that to the
North grade into Dorotea Fm.
Tertiary
- Chorrillo Chico Fm.: Early
Paleocene-Eocene, marine mudstones in part calcareous and glauconitic.
- Agua Fresca Fm.: Late Eocene
(470-776 m) mainly glauconitic clay stone some thin limestone beds with
fine to very fine glauconitic sandstones interbeds; deposited in a lower
neritic at the base, to shallower toward the top of the unit.
- Tres Brazos Fm.: Mid to Late
Eocene (450-700 m) deltaic clay stones and fine to very fine glauconitic
sandstones with thin limestone layers.
- Leņa Dura Fm.: Eocene (130-250
m) clay stones with minor fine to very fine glauconitic sandstones.
- Loreto Fm.: Oligo-Miocene
(630-945 m) deltaic facies with several litologies depending on the
environment of deposition marine through continental. Marine sandstones
partially conglomeratic and clays tones, with coal interbeds.
- El Salto Fm.: Late Miocene-Early
Pliocene (25-1080 m) interbeded sandstones and clay stones. The sandstones
are fine up to coarse conglomeratic. The fine fraction is mainly clay
stones and siltstones and tuff.
- Palomares fm. Mio-Pliocene
(75 m) volcanic breccias, tuff, conglomerates, sandstones and clay stones.
Structure:
The folded belt in the Skyring-Otway
and Peninsula Brunswick area is a basement involved deformation with
displacement transfer toward the sedimentary cover. It is subdivided
into three domains from west to east: Internal, Central and External,
that evolve by stages Coniacian, Maastrichtian-Eocene and Oligocene ,
respectively
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