Special core analysis includes static and dynamic tests designed to acquire data for both reservoir description and reservoir management. It is highly recommended that sample selection, either by Winland, Hydraulic Units, Petrographic or Hybrid methods include all rock types. These tests generally include:
Capillary pressure defines the magnitude and distribution of fluids in the reservoir. It is one of the most important measurements that can be made because it relates reservoir rock and reservoir fluid properties. Capillary pressure can be determined by centrifuge, porous plate and mercury injection methods. Gas-Oil, Oil-Water and Gas-Water capillary pressure can be determined by porous plate and centrifuge methods. The mercury injection method allows for characterization of a wide range of rock quality because data can be acquired up to a pressure of 60,000 psi
Reservoir rock wettability determines the location, distribution and flow characteristics of a porous medium. Wettability is defined as “the tendency of one fluid to spread or adhere to a solid surface in the presence of other immiscible fluids” therefore, wettability is an indication of the reservoir rock wetting preference. This preference controls fluids distribution and affects capillary pressure, resistivity index, and relative permeability data. Wettability can be characterized by Contact Angle, Amott, Amott-Harvey, USBM and Amott-USBM methods. OilNet has the capability for all methods.
Relative permeability data is used to gain mechanistic insight of multi-phase flow behavior and to determine recovery performance of different drive mechanisms. Laboratory tests are designed for application to reservoir processes such as; Water-Oil, Oil-Water, Gas-Oil, Oil-Gas, Gas-Water, and Water-Gas. These measurements can be performed by steady state, unsteady state, single-speed and multi-speed centrifuge methods.
Laboratory-derived properties; cementation exponent (m), saturation exponent (n) and cementation constant (a) are used to calibrate logs for determination of water saturation. OilNet has the capability to determine these properties by equilibrium and non-equilibrium methods. The equilibrium method includes capillary pressure using porous plate. The non-equilibrium method, commonly known as the continuous injection method that can be completed in about 14 days does not include capillary pressure. Data required to correct for the effects of clay (m* and n*) can be determined by:
· Multi-Salinity (Co-Cw)
· Cation Exchange capacity (CEC)
