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Quito, Ecuador

Di Pasquo M.,CONICET | Noetinger S.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Isaacson P.,University of Idaho | Grader G.,University of Idaho | And 3 more authors.
Journal of South American Earth Sciences | Year: 2015

Implications of a new collection of lycophytes of the genera Haplostigma Seward and Paleostigma Kräusel and Dolianiti from southern Bolivia and northern Argentina are presented. Fragmented herbaceous stems of lycophytes preserved as compressions, impressions and casts come from the Middle and Late Devonian Pescado (Huamampampa), Los Monos and Iquiri formations at Mataral, Yesera, Angosto del Pescado and Balapuca. The interbedded shales and siltstones bearing the lycophytes were also examined for palynology. They yielded mostly terrestrial palynomorphs with Grandispora pseudoreticulata and other Eifelian to Givetian species and fewer microplanktonic species (i.e., acritarchs, prasinophytes, chitinozoans). At Yesera, diagnostic spores and elements of the microplankton suggest a Givetian-Frasnian up to early Famennian age for the Haplostigma beds. Moreover, presence of the same brachiopod taxon in the Haplostigma intervals at Yesera Dique (palynologically barren) and Yesera Centro supports their correlation. This new information supports terrestrial connections between these Bolivian and Argentine areas and other regions of South America in the Eifelian - Givetian Afrosouthamerican Subrealm, which extended up to the early Famennian. © 2015 Elsevier Ltd.

Bona P.,CONICET | Starck D.,Tecpetrol SA | Galli C.,National University of Salta | Gasparini Z.,CONICET | Reguero M.,CONICET
Ameghiniana | Year: 2014

The three recognized species of Caiman -C. latirostris, C. yacare and C. crocodilus- currently live in northern and central South America. Except for the fragmentary dentary of a putative Caiman from Oligocene rocks in Brazil, the genus has been reliably recorded in rocks of ages spanning the Neogene, when species of Caiman were a constant component of the South American crocodyliofauna. The major taxonomical diversification of Caiman occurred during the late Miocene, which is well documented in the area of Paraná (northeastern Argentina). Fossil crocodylians in Paraná are represented by one gavialid and caimanines, with at least five species of Caiman (including C. latirostris). This assemblage represents the southernmost record of Crocodylia living in "Amazonia" during the Miocene. In this work we confirm the record of Miocene caimans outside the Paraná and we prove the presence of Caiman cf. latirostris in present-day northwestern Argentina during the late Miocene. The taxonomic identification is based on a fragment of a left mandible with the same ornamentation, outline and dentition as Caiman, and with a symphyseal morphology similar to that of Caiman latirostris. The material comes from the upper part of the Palo Pintado Formation in the southern region of Valle Calchaquí (Salta Province). This unit was deposited in a sand-gravel fluvial system with associated ponds between 10.29 ± 0.11 Ma (K/Ar) and 5.27 ±0.28 Ma (206Pb/238U).

The Golfo San Jorge Basin records a hydrocarbon production history of more than 100 years. The Pozo D-129 Formation, which is the main source rock of the basin, is a lacustrine unit with high pyroclastic participation that spreads over a wide extension within the subsurface of the basin; its thickness increases toward the central area of the basin, reaching up to 1500 meters. In the San Bernardo Fold Belt of Santa Cruz province, more than 200 wells were analyzed and three main sections in the Pozo D-129 Formation were recognized, based on lithological and geochemical variations. In the uppermost section of the unit an stratigraphic interval characterized by black shales rich in organic matter is interpreted as the last and most extended lacustrine transgression of this unit, informally named “cuello pelítico”. The analysis and characterization of this interval becomes the main objective of the present study. 3D seismic visualization and seismic facies identification allowed the recognition of the main geomorphologic patterns associated with the last lacustrine transgressive event. A strong thickness variation could be recognized mainly related to the distribution within isolated depocentres. The depositional characterization of the “cuello pelítico” in the area improves the knowledge of the current paleoenvironmental model of the unit. © 2014, Asociacion Geologica Argentina. All rights reserved.

Yuan Z.,Texas A&M University | Schubert J.,Texas A&M University | Esteban U.C.,Tecpetrol SA | Chantose P.,Add Energy LLC | Teodoriu C.,Clausthal University of Technology
Society of Petroleum Engineers - International Petroleum Technology Conference 2013, IPTC 2013: Challenging Technology and Economic Limits to Meet the Global Energy Demand | Year: 2013

Casing failure probability is high in Ann Mag Field, South Texas due to the high pressure high temperature operational environment. The formation sands are over-pressured where the pore pressure ranges from 0.85 to 0.93 psi/ft. Casing damage has been experienced in over 11 wells from 18 that have been drilled in the area, near 61% of total wells were damaged during their production life. Casing failure may be caused by formation shear failure, formation compressive failure, casing tension failure, casing collapse or fault activation. Casing buckling is not considered in the study because cement bond logging shows that the cement sheath is good. Triaxial tests were carried out to measure formation mechanical properties that were used for reservoir compaction, fault activation and formation failure analysis. The Mohr-Coulomb failure criterion was applied to study the formation failure and the minimum pore pressure required to activate the fault. The finite element methods were used to analyze the casing tension failure caused by reservoir compaction. According to the formation shear failure analysis, the minimum allowable pore pressure around the casing is around 2,000 psi. In the study of fault activation, for shale formation, at the internal friction coefficient of 0.51, the probability that the normal fault can be activated is very high. The maximum drawdown and depletion were calculated based on potential casing failure types. In the plot of workability operational limits, shale formation has narrower safe zone than the sand formation. Recommendations for drilling and production were made to increase the well service life and improve the gas recovery. This paper presents the casing failure mechanism and characterization under HPHT conditions in south Texas that can be prevented in the future wells and provides workability operational limits for different formations. Copyright © (2013) by the Society of Petroleum Engineers.

Biedma D.F.,Tecpetrol SA | Vela I.,Petroamazonas EP
Oilfield Review | Year: 2014

In less than three years, a consortium led by Schlumberger has resuscitated the ailing giant Shushufindi oil field in Ecuador. The consortium's team assimilated what was known about the field and made recommendations to remedy problems and stimulate production. Soon after a contract was signed, the consortium was performing workovers, drilling new wells and continuously monitoring all field operations. As a result, oil production has increased by more than 60% over rates from three years ago. Copyright © 2014 Schlumberger.

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