--> ABSTRACT: Geological Study of Guafita Field Reservoirs, Apure Basin, Southwestern Venezuela, by Eduardo Moya, Juan Abud, and Jose Hernandez; #91022 (1989)

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Geological Study of Guafita Field Reservoirs, Apure Basin, Southwestern Venezuela

Eduardo Moya, Juan Abud, Jose Hernandez

The medium-grade oil reservoirs of the Guafita field, Apure basin, southwestern Venezuela, represent the northeastern extension of the La Yuca-Cano Limon fields of Colombia. A detailed integrated reservoir study is being carried out in Guafita in order to define the geological model and to improve its development plan.

The stratigraphic sequence of interest in the southern block of the Guafita field contains approximately 600 ft of sediments of Cretaceous and Oligocene-Miocene ages (Quevedo Member of the Navay and Guafita Formations, respectively). Fifteen prospective intervals, with approximately 150 ft of net oil sand, have been defined within this sequence by detailed correlation in the Colombian fields and four have been defined in the Quevedo Member. Lower delta-plain and delta-front depositional environments have been recognized from core studies in the Tertiary sediments.

The structural pattern of the area is related to a major northwest-southeast regional stress direction which produced two events of deformation: (1) folding and associated reverse faulting oriented in a northeast-southwest direction (La Yuca fault) and (2) transtensional right-lateral strike-slip faulting in a northeast-southwest direction (Guafita-Cano Limon fault) with associated normal riddle faults of an almost east-west orientation (Arauca fault).

A combination of both structural and stratigraphic traps controls the hydrocarbon accumulations in the Guafita field, and at least two sealing shale regional markers have been defined.

As a preliminary result of the approach of defining reservoir geometry and mapping each major sand body separately, the proven reserves of the Guafita field will decrease by approximately 12%. The possibility of fluid communication with the Colombian fields through the small-displacement riddle faults was established by means of juxtaposition of sand bodies.

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