Abstract: A high-speed downhole motor-driven artificial-lift gas compressor assembly comprising an aerodynamic, gas-bearing supported, multi-stage centrifugal compressor is deployed downhole to work with other components such as electric submersible pumps and separators disposed in a multizone reservoir. Water may be injected into an injection water zone and hydrocarbons allowed to escape from a hydrocarbon producing zone to the surface. Compressed gas may be introduced into an annulus between a casing and tubing and directed into an injection gas zone. In addition, gas being produced in the hydrocarbon producing zone may flow back through the annulus between the casing and tubing or through one or more water separators and/or gas separators into the high-speed downhole motor-driven artificial-lift gas compressor assembly and, once compressed, exit the high-speed downhole motor-driven artificial-lift gas compressor assembly and routed back to the injection gas zone.