An apparatus and method for simulating production conditions in hydrocarbon-bearing reservoirs, as an example, by flooding of core samples from such reservoirs, are described. Full recirculation flow measurements permit several fluids (for example, crude oil, brine, and gas) to be simultaneously injected into core samples having varying dimensions. Accurate and stable back pressures are maintained at total flow rates of as high as 200 cc/min., for a large range of fluid viscosities. Accurate and stable net overburden pressures relative to pore pressure are also maintained, thereby simulating the formations at depth. Core samples from formations may also be investigated using the apparatus and method hereof, for carbon dioxide sequestration potential, as another example.