Phuel 145-2884-HV0, Руководство пользователя, Страница: 7 / 24

User Manual
Greasehead
145-2884-HV0
OPS-2884 Rev E 3
3 Technical
3.1 Description
The grease injection control head (greasehead) provides a pressure seal
around stationary or moving wireline that is run into or out of wells to prevent
the escape of well fluids to the environment. The assembly consists of a
hydraulic pack off and a series of flow tube assemblies.
The flow tube assembly consists of a number of close fitting steel tubes
through which the wire line passes. Each flow tube is approximately 14” long
and these are slipped onto the wire and connected together with the fast collar
connection to build up the required length. Viscous grease is injected between
the bore of the flow tube and the outside of the wire and travels along the
length of the flow tube stack creating a pressure drop. Grease injection
pressure can then be increased to about 25% more than the well pressure to
create a liquid seal that allows the wire to move but prevents the escape of
well fluids. The inside diameter of the flow tubes needs to be from 0.003” to
0.008” larger than the actual wire diameter for the seal to be effective so the
flow tubes must be selected based on the wire being used.
Figure 3: Pressure gradient inside the flow tube assembly
The length of flow tube required depends on the well pressure, the wire size,
the flow tube size, the grease viscosity and pump rate and the effectiveness of
the seal will depend on the pull out speed of the wire. The relationship for the
pressure drop can be expressed mathematically by Couettes flow equation.
This shows that the clearance between the wire and the flow tube has a great