The SEPP apparatus consists of a total of 6 externally heated oil pressure chambers, whose internal set-up allows combined measurements of permeability, P and S wave velocity, and complex electrical conductivity (leakage current-free 4-pole measurements) on rock cylinders (d = 25/30 mm, lmax = 60 mm) in long-term perfusion experiments. If a hydrophilic porous membrane is additionally used between the sample and the lower measuring head, the device can also be used to determine capillary pressure curves (drainage / imbibition). In this case, P- and S-wave velocities as well as electrical properties can be investigated in dependence of sample saturation. In addition, a hydraulic pressure booster piston is integrated into the lower plug of the pressure vessel, with which the sample can be put under bi-axial stress condition, if necessary. The pressure vessels are designed for a maximum confining pressure of 600 bar at a working temperature of 150 °C and thus allow experiments under simulated conditions of underground storage in 1000 - 3000 m depth. The maximum working temperature is 230 °C at a correspondingly lower confining pressure. For temperature control, the pressure vessels are equipped with oil-filled heating jackets. The pore fluid system for long-term flow tests is dimensioned for a maximum pore pressure of 400 bar and allows a parallel fluid supply of up to 6 samples/ pressure vessels via a switching valve. To perform capillary pressure experiments, the injection system can be replaced by a displacement spindle pump (pmax = 300 bar, Tmax = 150 °C).