within apparatus 10 in order to maintain the inflation pressure in the packer at the preselected value e g 1 25 times the injection pressure an increase in steam injection pressure will therefore cause the piston 136 to rise upward increasing the inflation pressure proportionately when the increased temperature of the inflation fluid raises the inflation pressure to a value exceeding 1 25 times the injection pressure the compensator piston 136 will have moved downward until the piston 136 bottoms out with surface 140 and engagement with stop surface 148 at this stage the increase in inflation pressure due to continued steam injection overcomes the compensation ratio and the increased downhole pressure and the inflation pressure is equal to or more than 1 25 times the downhole pressure continued steam injection and the resultant increase in injection fluid temperature will thereafter raise the inflation pressure until it is equal to the preselected pressure in the accumulator pressure 34 an additional volume increase of the inflation fluid will therefore be absorbed by the accumulator piston 50 and the increase in pressure of the accumulator gas to prevent overpressuring and rupturing of the inflatable packer element fig1 a depicts the piston 50 39 in a typical position with the nitrogen in the chamber 34 further compressed by upward movement of the piston 50 39 since the minimum volume of the inflation pressure chamber is fixed an ever increasing inflation pressure will be required to cause additional upward movement of piston 50 as explained subsequently the components of the present invention are sized so that the piston 50 will likely not top out against stop surface 58 when steam injection has stopped and the well is shut in for the soak operation the formation.