The Effect of Fracture-Controlled Cementation on Fluid Flow in Carbonate Reservoirs
Giulio Casini, Fabio Lapponi, Sima Jonoud, Ole Petter Wennberg, Omid Karoussi, and Alex Larsen
Statoil ASA, Bergen, Norway
Characterization of fluid flow in fractured carbonate reservoirs is generally idealized using the traditional “floating sugar cube” concept of Warren and Root (1963). Carbonate rocks are in general very reactive, however, and diagenetic processes, where the reactive fluids are controlled by fractures¸ can greatly alter static and dynamic properties of both fractures and matrix. Reservoir properties can be enhanced by leaching or destroyed by cementation. Furthermore, field and core observations suggest that the fracture-controlled diagenesis increases the heterogeneity of carbonate reservoirs. This heterogeneity occurs at a wide range of scales, from large (e.g. fault-related dolomitization) to small (e.g. dissolution/cementation along micro-fractures).
Fracture-controlled cementation can affect fracture properties, matrix properties and the exchange of fluid between fracture and matrix. The former has received relatively large attention in the last decades, whereas the two latter, which are the focus of this study, have not been widely examined. Petrographic and porosity analyses have been performed on selected samples using standard transmitted optical microscopy, scanning electron microscope (SEM) in backscatter electrone mode (BSE) and micro-CT scan. BSE image analysis capture micro and macro porosity at a resolution of 0.7µm. SEE images on fresh sample surfaces were used to analyse cement distribution and pore connectivity at different distances from the fracture wall. Porosity profiles were generated from the BSE images using an in-house developed MatLab code.
AAPG Search and Discovery Article #120034©2012 AAPG Hedberg Conference Fundamental Controls on Flow in Carbonates, Saint-Cyr Sur Mer, Provence, France, July 8-13, 2012