To me it means that they have installed a back pre

To me it means that they have installed a back pressure valve in the tubing(wireline retrievable) and it is holding back 1200psi. A back pressure valve in the tubing will hold the pressure back(Back Pressure Valve) to keep the reservoir pressurized. You can pump oil through this valve all the while saving the pressure of the sand that hold the hydrocarbons. As long as we have pressure in the reservoir the oil will the flow into the tubing and our pumpjack will pump it out and the differential pressure, between the reservoir and the tubing, created by pumping that oil out will allow the oil to flow into the tubing and we keep pumping it out. We don't use these method offshore but is a common practice on land. We gas lift the fluid out but buying gas is expensive unless you make your own in a field. We use back pressure valves in a different way. We set one when we are moving a rig on or off location. If something was to hit the wellhead and break it the back pressure valve would seal off the well.