Well Head Mounted
Well head Mounted Hydraulic Pumping Units
The sucker rod beam type pumping units are surface equipment connected to a steel rod, typically between 25 and 30 feet (7 to 9 meters) in length, used to operate a down hole pump and increase oil production. The maximum stroke length is in the range o of 15ft (5m) for the bigger size of beam type pumping unit.
The old technology of sucker rod (pumpjack) used to transfer the energy from the rotary motion of the primemover to the sucker rod string by means of walking beam; a gear reducer is also used to reduce the speed to suitable pumping stroke.
The new technology of pumping units instead uses a vertical hydraulic piston directly connected to the sucker rod string where a max pumping stroke 336" (8.5m) may be directly achieved by regulating also the hydraulic piston speed.
How It Works
The well head long stroke surface hydraulic pumping is comprised of two basic components:
- Cylinder (directly mounted to the wellhead)
- Power Unit
The Cylinder includes two internal high pressure seal units; one seal unit (‘fixed type’) located on the bottom section of the cylinder is sealing against the polished rod and so acting as the stuffing box of the system; a second seal unit (‘mobile type’) installed on top of the polished rod and acting as piston for the movement of the same when the power oil is pumped between it and the fixed seal unit.
Cylinders are mounted directly to the wellhead requiring no changes, eliminating the stuffing box and so any possibility of ‘oil spillage’ and needing no special tools and only minimal ancillary equipment.
The advantage of this system is that no electronic parts at the well head; all the electronic are installed in the power unit that can be located as far as 500 feet from the wellhead.
There are two different types of hydraulic cylinders available:Subsurface and Above ground
The subsurface style is designed to fit inside the well bore (below the wellhead).
Both types of cylinders eliminate the need for standard stuffing boxes, as the cylinders include integrated polished rods and polished rod seals; they also have the same lifting capabilities and are compatible for harsh produced fluids.
Subsurface cylinders are designed to fit inside the well casing, eliminating overhead clearance requirements. These cylinders install inside the tubing string and remain submerged in the production fluids while operating.
The Power Unit provides fluid power to a hydraulic oil cylinder, which is connected to the sucker rod string and is mounted directly to the wellhead.
The hydraulic power is applied to a piston (in the cylinder), which in turn lifts the rod string. On the return or down stroke, the hydraulic oil pressure is released at a controlled rate and the cylinder extends, lowering the rod string and bottom hole pump plunger. A PLC controls the operation and timing of the power unit.
The system maintains the frequency and duration of the strokes, and also monitors the hydraulic power unit system pressures, temperatures, and general functions for safety and trend analysis.
The PLC communicates with the operator via indicator lights on the PLC panel, an operator interface panel, or via web interface.
A single power unit can operate up to two cylinders positioned within a distance of 500 feet reducing the energy consumption by approximately of 25%.
The following performances of the system either in single or dual cylinder mode is controlled by PLC also in remote mode (advanced monitoring):
- Stroke per minute
- Stroke length
- Power oil pressure and temperature
- Upstroke and down stroke speed
- Bottom pump efficiency
- Gas lock or rods sticking effects
The hydraulic rod pumps' exclusive software guides the operator through the system. The intuitive user interface keeps current on operating conditions and allows to access and control the system via remote telemetry from anywhere in the world.
Rugged programmable logic controllers manage complicated tasks with an emphasis towards safety, efficiency and longevity of equipment.
All well head mounted power units are PLC Controlled, to afford excellent reliability, flexibility, and automation. PLC automation is used to manage stroke time (length and position) and stroke frequencies (SPM).the PLC automatically calculates SPM timing and stroke ratios.
Operator Interface Terminal (OIT)
The optional OIT (Operator Interface Terminal) allows field personnel to monitor and/or adjust hydraulic system settings at the power unit, for cursory maintenance.
Password levels are used to protect unauthorized users from changing system settings.
Remote controlled operations
Well head mounted equipment provides advanced computer control, monitoring, and diagnostics. The most notable control feature of the system is the ability to remotely adjust the well's Strokes Per Minute (SPM). This allows for a more optimized pump rate given changing conditions. Live dyno graphs are streamed as they are collected, stored both locally and on a central web based analysis server.
The well head mounted pump long & ultra-long stroke cylinder system is available up to 53,576 pounds of PPRL (Peak Polished Rod Load) capacity and with polished rod stroke lengths up to 336”.
Standard size models offer peak polished rod load capacities from 12,364 to 42,390 pounds, with stroke lengths up to 336 inches. These cylinders are mounted inside the wellhead, which eliminates the stuffing box.
The Long/ultra-long stroke pumping system have the following advantages versus the conventional sucker road (pumpjack) pumps:
- Higher volumetric pump: Due to the rod stretch ratio between min and max polisher rod load at each stroke
- Reducing bottom hole equipment wear: The travelling and standing valves are cycled less times
- Reducing rod string fatigue: Linear travelling speeds drastically reduce the dynamic wave-form load conditions by accelerating to a slower fixed rate and holding a constant rate for the majority of the stroke. This reduces the magnitude of the momentum-reversal-generated energy and allows it to dissipate quickly, drastically reducing rod compression and acceleration-generated higher stresses
- Minimizing rod and tubing wear: Lower speed and distributing wear patterns over larger areas or longer distances
- Reduced gas locking problems: Longer strokes and larger pump diameters increase the pump compression ratios and help to reduce the gas-locking problems
- Ease of installation: Installation typically requires no changes to the wellhead
- Lower power consumption: compared to the pumpjack pumping unit
Additionally the Subsurface Cylinder type has the following advantages versus the above the ground type:
- No environment impact
- Easy to install
- Very low profile
- Compatible with any type of fluid