Subsea Separation presentation

Subsea Separation:

A New Frontier for the Chemical

Engineer

Sunday Kanshio AMIChemE

Oil and Gas Engineering Centre,

Cranfield University

15th April 2015

Acknowledgement

• Petroleum Technology Development Fund, Abuja, Nigeria

• Prof Hoi Yeung- Oil and Gas Engineering Centre, Cranfield University

• IChemE Milton Keynes Committee

Presentation Outline

• Demand for Oil and Gas

• Subsea Field Development

• Subsea Separation Systems

• Academic Research and Findings

• Conclusion

Demand for Oil and Gas

“Oil is expected to remain the No. 1 energy source and demand will

increase by nearly 30 percent, driven by expanding needs for

transportation and chemicals”

ExxonMobil’s Outlook for Energy- A view to 2040; December 9, 2014

“Deepwater expenditure is expected to increase by 69%, compared to

the preceding five-year period, totalling $210 billion from 2015 to

2019”

Douglas-Westwood, London- March 9, 2015

Subsea Production Systems

• Flow assurance

• Environment regulations

• Maximising oil recovery

• Low temperature

• Water depth-Hydrostatic pressure

• Long distance

• Remoteness

• Seabed topography

Chemical Engineering

Unit Operations

Subsea

Separation

Where to go?

Courtesy: www.total.com

Challenges

Features of subsea oil and gas field

Subsea Separation

Subsea

Separation

Gas-Liquid

Separation

Oil-Water

Separation

Sand

Removal

• Hydrate prevention

• Slug flow mitigation

• Water re-injection

• Topside debottlenecking • Erosion

• Corrosion

• Reduce backpressure on wells

What is subsea separation all about?

It’s more than phase

separation!

Subsea Separation Principles

-Gravity

HORIZONTAL SEPARATOR

• Preferred for Oil-water separation

• As Subsea Slug Catcher

.

Texaco developed Highlander using SubseaSlug Catcher

• Required for slug flow mitigation• Water depth: 128 m• 13 km from existing platform• Low energy reservoir and low GOR• 35 million bbl of recoverable oil• Marginal field tieback to Tartan platform

Subsea Separation- Techniques

-Gravity

HORIZONTAL SEPARATOR

Good for Oil-water separation in shallow water

Field application: Tordis field operated by

Statoil

Tordis Subsea Separation, Boosting and

Injection Project

• Water depth : 200 m• Mature field• 25 m tieback distance to Gullfaks C Platform• Water production: 70-80%• Sand production: 500 kg/day• Bulk water separation• Multiphase boosting• Water and sand injection into dedicated well

Subsea Separation- Techniques

-Gravity

VERTICAL SEPARATOR

• Preferred for gas-liquid separation

• Easy sand removal

• Provides adequate suction head

Pazflor, Angola Courtesy of Total/FMC

Example: Pazflor, Angola block 17 operated

by Total

• First tested at Cranfield University

• Installed in 600 m-1200 m water depth

• Heavy oil –Miocene reservoirs

• Low reservoir pressure

• Gas flow freely through 6-in flowline

• Liquid boosted by Hybrid pump (18% GVF)

Subsea Separation- Techniques

-Caisson separation system

Source: FMC

Caisson separator system was

used to develop Perdido and BC-

10 field. Shell as operator

Perdido

• Tieback to Spar

• Heavy oil

• Low reservoir pressure

• Water depth : 2499 m

• Gas flow free to host facility

• ESP as boosting system

BC-10

• Tieback to FPSO

• Heavy oil

• Low reservoir pressure

• Water depth : 1499- 2000 m

• Gas flow free to host facility

• ESP as boosting system

HeavyOutlet

Inlet

Compact Separation Systems

-Centrifugal force

Technology inspired by nature…

Cyclonic separator utilizes the inertia of the incoming

stream to generate high g-force to accomplish:

⁻ Coalescence

⁻ Phase separation

Light

Outlet

Source : CALTEC

Compact Separation Systems

-Integrated systems

HI-SEP

I-SEP

Source: FMC

Marlim field operated by Petrobras was

developed by integrated compact separation

concept.

• Marginal field in 900 m water depth

• Heavy oil

• Oil and gas comingled and flow to FPSO

• Water re-injected into reservoir

CALTEC integrated two

compact separators

Research by Cranfield

University and CALTEC shows

that this system can mitigate

severe slugging in a way that

does not reduce production rate

unlike topside choking.

Design and Operational Challenges

-Can the Chemical Engineer help?

Compact separation is the future of subsea separation but there are

so many uncertainties concerning design and operation

• Fundamental understanding of multiphase flow dynamics inside

compact separators- Flow regimes, liquid holdup, phase distribution…

• Narrow operating envelope of compact separators

• Effect of upstream flow dynamics on separator performance

• Knowing when the separator is performing poorly

• Oil-water emulsion separation…Oil-in water measurement

• Discharging produced water and sand at seabed

• Predicting the performance of the separators over the field life

• Design rules for compact subsea separators My PhD is to help with the above challenges!

Academic Work

-Approach to Problem

• Prototype Gas-Liquid Pipe Cyclonic (GLPC)

separator fabricated, installed and tested.

• Installed multiphase flow measurement sensors

Trial GLPC Rig Standard GLPC Rig Tangential inlet

Wire Mesh Sensor (WMS)

ERT sensor

Results

Phase distribution prior to

Liquid Carryover

Phase distribution during

Liquid Carryover

ERT ERT

WMS

WMS

Results and Findings

Prior to liquid

carryover

During liquid

carryover

Findings

• ERT, WMS and pressure

transducers gave good

information on what is

going on inside the

separator

• Air-core has influence on

phase separation

• Mist, churn and annular

flow regime can coexist in

the gas discharge section

of the separator under

certain operating condition

of the separator

• Subsea separators does more than phase separation ; they solves flow

assurance issues, extends the life of field, and enhances assets

integrity

• Phase separation using compact separators is the future of subsea

separation

• Chemical engineers should embrace subsea separation by bringing

their understanding of unit operations to enhance the design of compact

separators

Conclusion

Thanks for listeningk.sunday@cranfield.ac.uk

sunday_kanshio@yahoo.com

07442978727