| A key input for log evaluation is the measurement and interpretation of the Archie parameters for formation resisitivity, 'm' and 'n'. The relationships between the resistance of the rock and porosity or brine saturations can be determined in our laboratory. |
 Measured at hydrostatic confining pressures of up to 10,000 psi, using a two or four terminal electrode configuration within a broad frequency range. Platinum end stems are used to minimise polarisation effects. Pore volume reduction with increasing confining pressure is simultaneously measured with FRF. |
| Often performed in conjuction with Capillary Pressure measurements. It involves desaturating the sample and monitoring the change in resistance over time. The relationship between the measured sample resistance and the sample saturation is used to calculate FRI and 'n'. Samples can be desatured using gas or oil (depending on the reservoir system) at ambient conditions or at confining pressure up to 10,000 psi. |
 The presence of clays, particularly smectites, contributes to the electrical conductivity and might cause sandstones to exhibit lower resistivity values. Calculating water saturation from 'shaly' formations requires determination of the CEC and Qv. F*, m* and n* can be calculated by incorporating the Qv into Archie's equation. The Cation Exchange Capacity can be determined from core sample cut-offs using the wet chemistry technique or by using the multiple brine salinity method (Co-Cw) on core samples, at confining pressure up to 10,000 psi. |
