New Methodology for Fracture Attributes Determination Based on Petrographic Analyses, and Its Application in Two Naturally Fractured Carbonate Reservoirs of Southern of Mexico

Characterization studies of naturally fractured reservoirs (NFR) generally omit the impact of diagenetic processes that affect fracture systems, giving as a result fracture models not fully calibrated with hard data. This work presents the results of the application of the SDPS (Structural-Diagenetic Petrographic Study) methodology, for calculation of fracture attributes. The main objective is to identify and to characterize fracture sets, where the hydrocarbons flow, based on the relationship between fracturing and diagenesis, and the rock properties alteration during the tectonic and sedimentary evolution of the area. To demonstrate the application of this methodology, two oil and gas carbonated reservoirs from the southeastern México were selected: the first in limestones with porosity (Φ) exclusively due to fractures (Φmatrix <2%) and the second in dolostones with dual porosity (Φmatrix = 4-5%). Thirty-eight oriented thin sections form cores and nine hundred and twenty cutting samples from ten wells were analyzed.

In both reservoirs were identified five fracture sets. In the first, four fracture sets are conductive, with high connectivity: Set1 (105°/83°), Set3 (55°/77°), Set4 (03°/79°), and Set5 (140°/80°). In the second reservoir, two sets are conductive: Set4 (48°/88°) and Set5 (86°/87°), with good connectivity between matrix-fractures. The first reservoir presents a better fracture attributes (density, porosity, connectivity and conductive quality) than the second one. These differences are reflected in the productivity in both reservoirs.

The application of the SDPS allowed differentiates conductive fracture systems in the reservoirs, main fluid flow directions were corroborated with reservoir dynamic information.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California