Determining the capillary pressure behavior of rocks at reservoir temperature and pressure is vital in understanding the displacement mechanism in the reservoir. An understanding of the displacement mechanism is essential to evaluate its effect on fluid saturations and oil recovery. The evaluation of saturations and thus oil reserves from resistivity logs requires laboratory determination of both the cementation factor (m) and the saturation exponent (n) under conditions as representative as possible of reservoir ones. Special laboratory equipment using air and actual formation brine at reservoir temperature and under effective overburden pressure was developed. The porous plate method was used to determine capillary pressure curves and saturation exponent at ambient conditions and at full reservoir conditions, (reservoir pressure and temperature) on sandstone core plugs from a Libyan reservoir.
The main objective of this study was to determine whether any difference exists between the capillary and electrical properties obtained at ambient conditions and those obtained at reservoir conditions for rock samples. Prior to the test, the effect of overburden pressure on porosity and formation factor can be studied.