Question

Prepare 5 pages (max. ) brief description about Multiphase flow pumps that work at high gas volume fraction or percentage ( high GVF).

The report should address the following important points:

-Differences between multiphase flow pump (for gas and liquid mixture) and single phase flow pump (for liquid).

-Difference between multiphase (gas-liquid) flow pump at high gas percentage (say 80% and above gas) and a compressor.

-Differences in pump head, pump speed, design and stages should be addressed.

-How can we modify a single phase flow pump (liquid only) to handle gas-liquid flow

-How can we modify a gas-liquid flow pump to handle gas percentage rather than low percentage of gas

Answer 1

Multiphase Flow Pumps:

Multiphase flow pumps are a type of pumps which can handle the oil / gas / water mixture from producing wells, without separating the gas from the liquids. They are successfully deployed onshore, offshore and subsea, in a variety of environments and climates.

Using multiphase pumps allows development of remote locations or previously uneconomical fields. Additionally, since the surface equipment, including separators, heater-treaters, dehydrators and pipes, is reduced, the impact on the environment is also reduced.

Multiphase pumps can handle high gas volumes as well as the slugging and different flow regimes associated with multiphase production.

Types of Multiphase pumps include twin-screw pumps, piston pumps and helicoaxial pumps.

Gas volume fraction is the ratio of the gas volumetric flow rate to the totalvolumetric flow rate.

Multiphase Flow Pumps for High GVF:

These are pumps which has the capability to pump the fluid with high concentration of gaseous phase and less concentration of liquid phase.

Single phase flow Pumps:

The single phase flow pumps for liquids are those which has the ability to pump the liquid only, if air or vapor is present in these pumps will cause cavitation and other serious effects which affects the performance and life of the pump.

Difference between operation of Multiphase Pump at High GVF and a compressor:

A twin-screw type of multiphase pump has some unique features. It is a constant positive displacement machine with each pumping chamber having a constant volume, which means any combination of gas and liquids can be pumped. It is possible to go from 0 to 100 percent gas in a fraction of a second passing a solid slug of liquid, and thereafter, go back to extended running on 100 percent gas. A compressor sucks the air and compresses the air, it increases the pressure of the air based on the rating of the motor..

Design and Operation

Multiphase Pumps of rotary positive displacement pumps based on Twin Screw Pump Technology. Due to the double volute design no axial forces are generated and the pumps are hydraulically balanced. Screw packages with opposed threads are installed in a replaceable liner. Both screws, which are manufactured from single piece bar stock for max. stiffness, are not in contact with each other. Special Screw Profiles guarantee minimum vibration over the entire operating envelope of the pumps. The drive torque is transmitted from the drive screw to the idler screw via oil lubricated timing gears. This makes Twin Screw Multiphase Pumps particularly suitable for the handling of non-lubricating products with high gas fractions, contaminations and crude oils with low API gravity. The pump shafts are sealed with either single or double acting mechanical seals which are exposed to suction pressure only. Twin Screw Multiphase Pumps are designed to handle untreated well flow with gas fractions (GVF) between 0 and 100 %. In order to maintain a dynamic seal between the screw packages and the pump casing at high GVF rates a small liquid flow must be provided at all times. An external liquid management system for continuous liquid injection guarantees uninterrupted operation with high GVF content and gas slugs and ensures dissipation of the compression heat. The size of the external liquid management system can be adapted to the actual operating conditions.