Annual Report 2015

Annual Report 2015

Multiphase booster models

Project manager and main

PhD supervisor, Prof.

Sigbjørn Sangesland

Subsea multiphase boosting offers several advan-

tages in field development for both greenfield and

brownfield projects. Furthermore, it seems to be

a key enabler for development of remote fields.

Currently several subsea boosting technologies

are commercially available and have been suc-

cessfully installed and tested in fields around the

world. However, for the early phases in the as-

sessment of a subsea field, models are required

for an appropriate selection of available technol-

ogies, including preliminary calculations of flow

and discharge pressure capabilities and power

requirements. At this stage, uncertainty level is

very high and therefore accurate models are not

required. Simplified models coupled with process

simulators and other commercial tools will be

sufficient. Simplified models will also enable an

integrated modelling of the field and production

optimisation in the conceptual design phase. Nev-

ertheless, detailed performance prediction mod-

els of multiphase boosters is also required under

changing conditions in the field lifetime (e.g. flow

rates, fluid properties, gas void fraction)

(Figure 6)

This calls for an increased understanding of ther-

modynamics and fluid dynamics phenomena in

multiphase boosters. Therefore, the main goal in

this project is the development of numerical mod-

els for prediction of multiphase booster perfor-

mance. In the first phase of the project, the main

goal is the development of a simplified and robust

model for currently available technologies for sub-

sea multiphase boosting. Subsequently, the focus

will be a detailed study of thermodynamic and flu-

id dynamics phenomena in multiphase boosters.

Finally, the comprehensive study of multiphase

behaviour of pumps and compressors will aid the

development of more accurate proxy-models for

performance prediction. After discussion with the

industrial partners, it has been decided to focus on

one specific type of booster (Semi-axial impeller).

PhD Candidate,

Gilberto Nunez

Co-Supervisor, Postdoc

Jesus De Andrade

Co-Supervisor, Prof.

emeritus Michael Golan

Subsea gate box

Different we ls i a subsea

field have differ nt production capacities, diffe

production constraints and different production targets dictated by rese

management. Therefore, they are subject to individual management and con

However, th luster nature of the field,

commingling the production streams of the

individual

wells,

creates

strong

inter ependence of the flow rates and

production pressures of the individual wells.

Thus, as the wells are producing in a network, a

change in operating conditions of one well,

affects all other wells in the cluster and

consequently the total network outcome. The

results of this interdependency is that the

production rate of the integrated system is,

most often, considerably sub-optimal.

This project explores new facilities and system

configurations, as well as novel strategies to

achieve efficient and optimal management of the integrated system. This include

optimization over the entire life of the field, accounting for the considerable cha

in production conditions associated with the reservoir recovery process.

In short, the challenge in the project is to optimise the recovery and revenue fro

asset by managing the interdependencies between the wells.

The project will identify and evaluate the feasibility and the implication of variou

subsea systems architecture alternatives. A central element of the project is the

development of a modular and multi-functional assembly to allow easy re-routin

well streams and a quick and easy deployment of separation and compression

capabilities to a single well, to a group of wells or to the entire cluster. The assem

named Subsea gate box will be configured to account for all the default demands

modern subsea process equipment, including; compactness, robustness, ease of

deployment and integration in the entire system and ease of operation.

The Subsea gate box is configurable as a template that can accommodate individ

well modules and compartments, containing process equipment (

Figure 3

). The

process equipment may include separators, pumps, compressors, control valves

or flow meters, according to the characteristics of the well stream. A task in the e

phase of the project (

Figure 4

) will be to identify the leading technology in the

market that suits best to a compact and modular solution. The project deliverabl

will include a description of the state-of-the-art subsea process technology,

Figure 3. Subsea Gate Box concept sk

Co-supervisor,

Professor Emeritus

Michael Golan

Co-supervisor,

Assoc. Professor

Milan Stanko

Postdoc,

Mariana Diaz

Project manager

and main

supervisor,

Prof. Sigbjørn

Sangesland

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0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Dimensionless differential pressure,

∆

ref

[-]

Dimensionless flow, Q/Q

ref

[-]

Single Phase

10% GVF

20% GVF

30% GVF

40% GVF

Figure.

Example of changing multiphase pump performance due to different gas void fraction (GVF)

Figure 6. Example of changing multiphase pump performance due to different gas void fraction (GVF)