Abstract: The present invention is a method and apparatus for injecting compressible fluids into multiple zones of a hydrocarbon bearing formation, in particular injecting compressible fluid at a predetermined, constant rate into multiple zones through a single tubing string. Producing zones are packed off and limited entry outlets are installed on the injection tubing string at each producing zone. Injection pressure is maintained and limited entry outlets are designed and sized such that the compressible fluid reaches sonic flow through the outlets so that the flow rate no longer responds to changes in downstream pressures.