Unsteady state and steady state techniques are available for water-oil, gas-oil and water-gas displacements. In-situ Saturation Monitoring by the Attenuation of X-rays (SMAX™) is available on plug sizes up to 30 cm long or on composite stacks. SMAX™ saturation monitoring is available under full reservoir conditions of pressure and temperature (10,000 psi and 150°C) using live fluids which may contain H2S.