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ABSTRACT: Deterministic modeling of stratigraphic reservoirs in Carisito and Aguasay Fields, Eastern Venezuela

Boulter, Ronald1, Juan Cabrera2, Ilsis Marruffo2, Daisy Medori2, Ana Salazar2, and Andreas Suter3
(1) Schlumberger Holditch Reservoir Technologies, Houston, TX 
(2) PDVSA, Puerto La Cruz, Venezuela 
(3) Schlumberger Holditch Reservoir Technologies, Caracas, Venezuela

The accurate modeling of these stratigraphic reservoirs, deposited in nearshore marine to coastal plane environments, required innovative modeling because only 44 wells had suitable logs for petrophysical analysis. The other 123 wells had only an SP or gamma ray log and resistivity logs.

A modeling technique was designed that utilized logs from all 167 wells. The primary property extracted from all the wells was a gross sand thickness for each layer to be modeled. These calculated sand thicknesses were then interactively contoured to produce gross sand maps using facies maps to shape the gross sand distribution.

The gross sand maps were used in deterministic modeling software to shape and control the mapping of some reservoir properties. The software uses various algorithms, including linear and nonlinear neural network calibration, kriging, cokriging, and conditional simulation to define correlations with a high confidence level.

After average reservoir properties were calculated in the wells with petrophysics, it was found that net reservoir sand, net pay thickness and average reservoir porosity often had high correlation coefficients to gross sand thickness. In deeper layers, there was a secondary correlation between porosity and depth. These correlations were used to guide the distribution of reservoir properties.

Dynamic engineering data were then integrated into the reservoir property maps to refine the positions of the lateral flow unit boundaries and in some cases the downdip water contacts.

This innovative modeling technique demonstrates how accurate reservoir models can be constructed in fields with limited log data.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia