by Dachnial Dan Imansyah
Introduction
HPU (Hydraulic Pumping Unit) is one type of Sucker Rod Pump (SRP). Hydraulic Pump is used as an alternative to the artificial lift system. The use of this pump is carried out if there is not enough gas available in the field, so the gas lift system cannot be applied.
The reality in the field states that the existence of HPU is more of a substitute for the conventional beam-type pumping unit. When the water cut percentage starts to get high, HPU will be called to replace. However, the performance level of the HPU is quite good because of its advantages in being able to adjust the stroke length and strokes per minute. And also smooth up and down movements, which can be adjusted from the hydraulic controls. Usually, the operator will set a fast up motion and a slightly slow down motion.
Hydraulic Pumping Unit Design
There are several types of hydraulic pumping units (HPU), both in terms of tower structure (which is installed in the wellhead and connected to the polished sucker rod), or in terms of the type of hydraulic power.
Tower Structure
In terms of the tower structure, there are HPUs that have one or two hydraulic cylinders. Using the sprockets system or direct lifting by connecting the polished sucker rod with the hydraulic cylinder.
A tower structure with one hydraulic cylinder is usually connected to a sprocket mounted on the top of the hydraulic cylinder head. Some use a bar on the hydraulic cylinder head and connected (to synchronize) to two or four slings/rods and connected to a polished sucker rod. Another model uses a hollow-type hydraulic cylinder. The sucker rod is inside the hydraulic cylinder so that the up and down motion will follow the movement of the hydraulic cylinder itself.
Hydraulic Power Pack
The hydraulic power pack will usually adjust to the needs in the field. For example, adjusted to:
– PPRL (peak polished rod load) wells.
– Type of power source in the oil well area.
– Hydraulic system, i.e single or double-acting hydraulic system.
– The use of hydraulic pumps, whether using a standard pump (gear pump or vane pump) or using a variable displacement pump.
– Use of a nitrogen accumulator to increase power and reduce electrical power to a hydraulic system.
– Etc.
Other things that need to be prepared :
Looking for well technical data.
Determines the rod string factor of the HPU.
Fluid factors and rods without or with variables.
Determine the plunger effective stroke value (Sp).
Knowing the value of the parameters in determining the optimal weight that can be loaded on the rod or Peak Polished Rod.
DESIGN SAMPLE
This is an example of HPU requirements based on PPRL calculations from rods combination, plunger, and fluid load average per foot.
I have made a formula to facilitate calculation as follows:
We take an example and reference the use of two hydraulic cylinders – the direct lift model.
The diameter of the hydraulic cylinder used (assumed) is 65 mm OD. With an oil well depth of 5000 ft. The PPRL calculation result is 22,550 lbs.
By setting SPM 10 and SL 100 “, the required pressure is 2234 psi. The Q pump or hydraulic flow rate required is 169 lpm, with the need for an electric motor of 51 kW or 67 HP.
Of course, the need for electrical energy and the pump flow rate capacity is quite large. To overcome this problem, the use of a variable displacement pump and accumulator with nitrogen should be considered.
Tower Structure Design ever made by Author.
Below is the other model of tower structure when I worked for an oil service company around 1999 to 2003.
Hydraulic Cylinder Design
Using 65 mm OD hydraulic cylinder, as below drawing.
This HPU has been used in the field (Pertamina-Lirik Jambi area) in 1999.
Below is some manufacturing drawings as samples and designed.
