OBMI HIGH PRESSURE OVERBURDEN MERCURY INJECTION CAPILLARY PRESSURE SYSTEM, system designed to re-create the down-hole pore configuration for high pressure mercury injection experiments. A unique design tri-axial core holder allows confining pressures of up to 20,000 psig to be applied to sample and mercury to be injected at pressures up to 15,000 psig. By allowing samples to be confined at reservoir pressure the pore structure more closely resembles its original reservoir state allowing more representative capillary pressure determinations to be made.