--> ABSTRACT: Oil- and Gas-in-Place Assessment Under Geological Uncertainty, Jobal-Zuron Area, Guarico Subbasin, Central Venezuela, by Guillermo Martinez; #91022 (1989)

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Oil- and Gas-in-Place Assessment Under Geological Uncertainty, Jobal-Zuron Area, Guarico Subbasin, Central Venezuela

Guillermo Martinez

Oil- and gas-in-place assessment has been a major problem in the evaluation of the Jobal-Zuron area of the Guarico subbasin of the Eastern Venezuela basin. The area is now undergoing an integrated appraisal in order to determine its economic viability for supplying the Venezuelan domestic gas market. The area has been known as a gas producer from the Miocene Chaguaramas Formation. Currently stated reserves are estimated at 21.7 million bbl of condensate and 313.8 billion ft3 of gas; daily production is 23 million ft3 of gas from nine wells. Recent tests and appraisals would increase reserves to 60 million bbl of condensate and 888.6 billion ft3 of gas and daily production up to 4.2 million ft3 of gas per well.

Although the Venezuelan domestic gas market is increasing, the Jobal-Zuron area is still lacking deep geological and reserve definition. The area is, geologically speaking, one of the most complex in Venezuela from both the stratigraphic and structural points of view. The Guarico subbasin was tectonically very active during the upper Miocene-Pliocene; compaction and diagenesis are the main factors affecting porosity.

As stated above, geological definition is still a main concern. Corpoven, S.A., has decided to adopt an oil- and gas-in-place assessment methodology that takes into consideration the risks that this incomplete geological definition carries. The oil- and gas-in-place assessment presented in this paper has been achieved using the TOTAL-C.F.P. methodology, which is based on decision theory, subjective probabilities, log-normal, law of probabilistic distribution, and worldwide statistics of reservoir behavior.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.