What Does Surface-Treating Pressure (STP) Mean?
Surface-treating pressure (STP) (otherwise known as surface pressure or tubing-head pressure) is the pressure measured at or near the surface of a well. It is performed by inserting a pressure gauge into the production string below the shut-in valve.
Recent developments in digital gauges have proved to be helpful in transient testing of surface pressure.
Trenchlesspedia Explains Surface-Treating Pressure (STP)
When a drilling rig or workover rig is in operation on a well, the surface pressure is maintained at zero. If surface pressure unexpectedly occurs during the operation, the blowout preventer (BOP) installed on the casing is used. It is also important in calculating the bottomhole pressure (BHP), which is the sum of the surface pressure and hydrostatic pressure.
There are different types of surface pressures that can be understood:
- The Surface Pressure when it is at its maximum value is known as the Maximum Anticipated Surface Pressure (MASP). This is the maximum pressure that can occur during the well construction.
- Expected Surface Pressure – This is the highest predicted pressure that is to be exerted upon the surface of a well. The reservoir pressure is also considered during the calculation of expected surface pressure.