Abstract: A method for retarding the effect of water coning during the production of oil from a subterranean formation is described. The retarding occurs by injecting into the subterranean formation, at or below the oil/water interface, a polymer solution having a viscosity at least twice that of the connate water to form a zone of high viscosity about the wellbore during the oil production.

Abstract: A differential pressure sensing means and method includes an inlet receiving a fluid having a first pressure. Another inlet receives a fluid having a second pressure. A plurality of pressure sensing devices are connected to the first and second inlets. Each pressure sensing device senses a pressure differential within a different predetermined range of pressures and provides a pressure signal representative thereof. An output circuit connected to the plurality of pressure signals provides a pressure signal selected from one of the signals provided by the plurality of pressure sensing devices so as to provide a pressure signal representative of the pressure difference between the first and second pressures of the fluids.