fluids from the fluid supply vessel 8 from flowing around bypassing the rock samples the first pressure vessel 9 is further enclosed in a first heating device 11 which will emit heat to the first pressure vessel 9 so as to increase the temperature in containment vessel 1 the amount of heat emitted to the first pressure vessel 9 may be controlled by means of a temperature sensor 19 positioned in the first pressure vessel 9 the heating device 11 and pressure vessel 9 are used to simulate elevated temperatures and pressures as fluids flow through a rock sample in containment vessel 1 a first differential pressure device 20 is used to measure the pressure drop across the first rock sample as internal fluids flow through the first rock sample located in containment vessel 1 the size and configuration of the first containment vessel 1 and the flow rate of the internal fluids into the first containment vessel 1 are selected so that the internal fluids will remain in containment vessel 1 for that period of time sufficient to simulate a geological environment the internal fluids in containment vessel 1 are subsequently passed from the internal fluids outlet 4 of containment vessel 1 by means of line 13 to the internal fluids inlet 14 of containment vessel 2 containment vessel 2 may contain the same type or a different type rock sample as found in containment vessel 1 the containment vessel 2 is located in a second pressure.