Cementacion Con Tapones Balanceados O Equilibrados

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Cuenca de Tarija

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Sistemas Petroleros de las Cuencas Andinas
Carlos E. Cruz - Jorge F. Rodríguez - Jorge J. Hechem - Héctor J. Villar, eds.

LOS SISTEMAS PETROLEROS DEVÓNICOS DEL SUBANDINO SUR
Y PIE DE MONTE DE LA CUENCA DE TARIJA. BOLIVIA
Carlos E. Cruz1, Jaime Oller Veramendi2, Matías Di Benedetto3, MartínPereira4 y Héctor J. Villar5
Pluspetrol S.A., Buenos Aires, Argentina, ccruz@pluspetrol.net
Petrobras Bolivia, Santa Cruz de la Sierra, Bolivia, joller@petrobras.com.bo
3
Repsol YPF, Buenos Aires, Argentina, mdibenedettor@repsolypf.com
4
Pluspetrol S.A., Buenos Aires, Argentina, mpereira@pluspetrol.net
5
GeoLab Sur S.A., Buenos Aires, Argentina, lqvillar@fibertel.com.ar
1
2

Abstract. TheDevonian petroleum systems of the South Subandean and Foothill of the Tarija
Basin. Bolivia.
The charge system of the Tarija Basin involves Devonian sources that have poor to
moderate –occasionally good- quality for hydrocarbon generation. Thermal maturity of the
source intervals show wide thermal maturity variations from the initial stages of the oil
window to very advanced phases of gasgeneration, depending on the stratigraphic position
and geologic setting. Effective expulsion of hydrocarbons is believed to have begun at
relatively high levels of thermal maturity (VRE>0.9-1.0%), with prevalence of gassy
hydrocarbons. Modeling of hydrocarbon generation of the Devonian source rocks
demonstrates that the main episodes of expulsion and charge occurred coupled to the
Andeantectonics. A generally low thermal heat flow linked to the Tertiary foreland deposits
constrained the maturation process. Main generation areas are related to the synclines in the
South Subandean Thrust Belt and two main depocenters in the Santa Cruz and Pilcomayo
areas. Preferred migration pathways are interpreted to be the main thrusts and faults. GAE
estimations points to low efficiency petroleumsystems. The main trapping mechanism is
structural, both in the South Subandean and in the Foothills.
The predominance of condensate accumulations precludes assessing definite oilsource correlation patterns. Nevertheless, genetic relations were proved for the Eifelian
sources. Isotope data, arranged by reservoir and geographic location, is consistent with
significant variations in thermalmaturity, allowing for distinct kitchens of a same source rock
and/or co-sourcing.
Three petroleum zones are recognized in the Tarija Basin: Santa Cruz, Pilcomayo
(extending up to northern Argentina) and the South Subandean Thrust Belt. In addition to the
classical Los Monos-Huamampampa (!), a second petroleum system is proposed with the
name Sección Lochkoviano-Carbónico(.). 2P EUR reserveswere allocated to these
Devonian systems; yet to find resources were estimated in the range 17.5-56.0 x 1012 cfg.
Contributions of a Silurian petroleum system have a hypothetical significance for deep gas
in the Subandean Thrust Belt.

INTRODUCCIÓN
La región del Subandino Sur y Pie de Monte de la Cuenca de Tarija, en Bolivia, es una provincia
gasífera que abarca un área cercana a los 100,000km2. Sus reservas recuperables finales probadas
más probables (EUR P1 + P2) de petróleo y gas al año 2005, según Yacimientos Petrolíferos Fiscales
Bolivianos, ascienden a 956 x 106 bo y 52 x 1012 cfg (CBH, 2008). El sector analizado comprende, desde
el punto de vista geológico, la Faja Corrida Externa y el Pie de Monte ubicado entre el Codo de Santa
Cruz al Norte y la región del límite políticoBolivia – Argentina hacia el Sur (Figura 1). Se excluye de este
análisis la zona de la cuenca denominada Boomerang, situada al Norte del Codo de Santa Cruz.
Este trabajo pretende caracterizar el hábitat de hidrocarburos del área y su entrampamiento,
diferenciando regiones con patrones determinados de generación y tipo de hidrocarburos. Sobre esta
base, se definen zonas donde las evidencias...