A formation tester consists of an upper assembly, an impeller unit, a straddle packer unit, and an inverted reservoir description tool string. The upper assembly seals off the wireline cable at the rig and connects the wireline cable to the formation tester. The impeller unit includes an upper turbine which converts hydraulic power from circulation of drilling mud into mechanical power. The mechanical power is used to drive a lower impeller which is capable of pumping formation fluids at high flow rates. The straddle packer unit isolates a portion of the formation tester which is open to the borehole to allow entry and exit of formation fluids through the formation tester. The inverted reservoir description tool string contains a combination of formation description modules which are inverted from traditional reservoir description tool modules to allow fluid flow paths to bypass electrical components.