The Genoil Diamond, a three phase well testing separator efficiently separates three immiscible phases with different densities, such as associated natural gas, crude oil, water and sand.The system is designed to operate as a self-contained and compact unit that can be used to test oil well production in remote areas. It can be mounted in a permanent location or on a flat-bed trailer and moved from well to well. When the well test separator is towed to an oil well and connected to the wellhead it can connect to a well production line from atop the trailer. Amazingly separated oil is returned to the production line while sand and other sediments, gas and water are discharged separately. The Genoil Diamond well testing system has several advantages over conventional well testing technologies that cannot be utilized as mobile units. Unlike conventional well test separators, the Diamond achieves separation of the three phases with virtually no heat consumption and no chemical requirements. Competing well testing technologies achieve separation by gravity with the fluid heated to elevated temperatures.