Abstract: In a multiple well completion, spaced apart production packers isolate independent production zones from one another. In each isolated production zone, a side pocket mandrel with a full opening bore has lengthwise extending side by side elongated pockets (1) for receiving a static pressure measuring instrument or tool (static pressure pocket); (2) for providing a venturi flow passageway (flow passageway pocket); and (3) for receiving a differential pressure measuring tool (differential pressure pocket). The static pressure measuring tool and the differential pressure measuring tool or instrument are commonly connected by a data coupling means to a single electrical conductor line which is strapped to the string of tubing and extends to the earth's surface for transmission of control signals and data signals between the earth's surface and the various side pocket tools.