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Abstract: Stochastic Modeling of Lower Delta and Coastal Plain Reservoir in the Eocene-Misoa Formation, Ceuta Field, Venezuela

Izaskun Azpiritxaga, Edwin Hernandez, Marcos Vivas, Tito Lozada, Zulay Jimenez, Adnan Saman

Stochastic modeling technique minimizes uncertainties in the values used for reservoir parameters and this reduces the risk in reservoir management practices. This technique was successfully employed in modeling south Ceuta field in Venezuela which will be subjected to secondary recovery due to significant pressure decline.

The Lower Misoa reservoir is divided into five sedimentological units; the upper three units are characterized by distributary channels, mouth bars and crevasse plains, whereas the lower units are deposited in coastal plain bars and tidal channels. The resulting sedimentary bodies are composed of five lithofacies, whose petrophysical properties have been quantified.

The deterministic data was used to build a stochastic model with HERESIM simulator which employs a Gaussian Truncated Technique. Eight stochastic realizations were generated and the geometry and the quality of each sedimentary unit was defined for every realization. A quantitative flow unit model was developed in a grid of 125 × 60 × 280 uniform blocks, the dimensions of each block being 180 m square and .3048 m in height.

The two uppermost units exhibit better quality rocks. Eighty percent of this interval contains facies with good lateral continuity, ranging from 1-3 km within the coastal bar deposits, and from 1-2 km within the tidal channels. Also the best developed sedimentary bodies are located in the central part of south Ceuta in a northeast-southwest alignment, where the coastal bar deposits are concentrated. The quality of the deposits degrades towards southwest and west. Permeability ranges from 100 to 480 md in the best units and from 31 to 250 md in the lower units. Reservoir porosity varies from 10-14%. These properties were assigned directly to the facies model for developing the fluid flow model and was compressed into a 29 × 42 × 11 grid.

An interface between HERESIM and the ECLIPSE reservoir simulator was developed to establish a dynamic fluid flow simulation. Four out of the eight realizations produced excellent match for the pressure-production history without any need for data manipulation. The technique therefore, could save approximately 60% of history match time.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France