The RamPump is one part of an overall strategy to supply pumping capability to move fluids from the reservoir to the tank.

Weatherford Artificial Lift Systems' RamPump has increased production by more than 700 b/d on Nexen Petroleum's Eugene Island Block 257 D platform, resulting in a gas surplus from wells that previously had to borrow gas for artificial lift. The hydraulically operated, plunger style, multi-phase pump was installed in March 2001. It has been operating continuously in parallel with a gas-lift compressor to lower the back pressure of four wells producing to that platform.


The program is one part of an overall strategy to supply the pumping capability to move fluids from the reservoir to the tank. Being able to lower the wellhead pressure by multi-phase boosting at the surface can enhance the application of downhole artificial-lift systems.


Multi-phase booster pump
The duplex piston pump operates using a hydraulic power system and can be driven with a gas engine, diesel engine or electric motor. This hydraulic drive design allows the pump to handle a variety of produced fluids across a wide range of gas-liquid ratios (including 100% gas), across a broad pressure range, without prior separation. The applications of this type of system are primarily where producers wish to lower the wellhead operating pressures (WHP) of wells to maintain or improve production but do not have the space to install the necessary separators, flash tanks, compressors, liquid pumps and vapor recovery units. A multi-phase pump such as this one can be used to lower the WHP on a well by creating a low-pressure zone between the well and the high back-pressure source (such as a long flow line or downstream separator), minimizing equipment requirements.


The pump has no mechanical seals and employs an exclusive injectible packing system and removeable cartridge-style check valves. A modular design allows interchangeability of hydraulic systems across all pump sizes. Beyond the application mentioned above, the pump also can be applied to full wellstream pressure boosting, wet-gas compression, produced gas re-injection for gas lift, well kick-off and remote site process equipment optimization.


Nexen platform case study
Prior to installation of the pump at Eugene Island Block 257 Platform D, the wells produced into a platform separation system operating at 230 psi, the pressure needed to move the liquids approximately 1.5 miles (2.4 km) downstream to Platform C for final separation. An engineering evaluation indicated that increased production rates could be obtained by lowering the pressure to 50 psi. The company used conventional types of pumps in the past, but sand or gas locking had been a source of operational problems. Nexen also wanted to limit the emissions normally associated with having to degas the liquids, and the pump appeared to provide an opportunity to both reduce pressure and eliminate the need to degas the produced fluids.


In March 2001 the pump was moved offshore and installed. Pumping commenced without difficulty. The wellhead pressure was lowered to approximately 45-55 psi, and the pump began moving the produced liquids along with any entrained gas to Platform C. The free gas from the platform separator was then diverted to the compressor, where it was recycled for gas lifting the wells. Over a 1-year evaluation period the well's productivity has been sustained, and the mechanical reliability of the pump has been excellent. Nexen is now evaluating opportunities for applying this pump at other properties that might capitalize on this method.


This installation established the reliability and durability of the pump for handling the full wellstream, as well as the ability of rig mechanics to handle the pumping system on a daily basis. Additional installations are planned, with units of varying capacity - from 10,000 boe/d to 150,000 boe/d - and functionality at discharge pressures as high as 1250 psi. Special models can increase this discharge capability to more than 3,000 psi. The ability of the pump to manage the full wellstream across a broad pressure range has led to expanding the role of the pump to include well kickoff and well stimulation applications. The pump is suited for unlocking production potential from wells that have been shut in or have had difficulty responding to standard stimulation practices.

Comments