Peter H. Hennings1, Milt B. Enderlin2, Tom Thrasher2, Tom P. Gamwell2
(1) Phillips Petroleum Company, Bartlesville, OK
(2) Phillips Petroleum Company
ABSTRACT: Predicting Field-Wide Well Performance in Fractured Carbonates by Calibrating Structural Attributes with Wellbore and Production Data, Ambrosio Field, Western Venezuela
By integrating the structural attributes of the tight Cogollo carbonate reservoir in Ambrosio Field with quantitative wellbore characterizations of fault and fracture occurrence, we have developed a model for the intensity distribution of features that control well productivity.
Ambrosio has a complex structural history that produced a porosity system consisting of fault damage zones, regions of intense fracturing associated with folding, background joints, and networks of hairline fractures. The effectiveness of the (structural) porosity system is controlled by the intensity of faults and folding, and is substantially modified by the current stress state. Integration of the structural model with drilling, FMI, wellbore breakout, strength tests, and completions data, indicates that the field is undergoing oblique shortening with large horizontal stress differences. This drives the system to failure, especially in regions of complex fault interaction. The stress state acts with the structural fabric to produce a pronounced drainage anisotropy. Fault-zones are the primary productive elements. Within fault halos there are large fluid-conductive damage zones that are laterally-spaced 30 m on average. Large background fractures are spaced 5 m on average.
For mapping, we combined two structural attributes: one describing the fault-related deformation and one describing the fold-related deformation. These attributes were optimized by calibrating them to the productivity of eighteen wells. Moderate productivity occurs in regions of strong folding; high productivity occurs only in regions of elevated fault deformation. The resulting map has been used to distribute structurally porosity (and permeability) and thus directly impacts estimates of reserves and development planning.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado