Subsea Advantages and Challenges

Based ExxonMobil Subsea Developments

Subsea Advantages

Produce from satellite wells.

Decentralized resource will not support using surface platforms.

Extend field life of older platforms.

Faster development time

Scaleable developments

Economic viability

o Water depth

o Resource density

Subsea Challenges

Operability and Integrity

Operability and integrity impact opex and downtime

Flow assurance challenges

Integrity of subsea and pipeline systems

Subsea valve integrity

Controls and distribution integrity

Aging equipment

As seen above control systems accounted for the majority of subsea equipment

failures.

There are many reasons for failure. The list below is indicative rather than all encompassing:

Direct Failures: Corrosion, joint failure, splice failure, sensor failure, solenoid valve

failure, water creep, SEM failure (power supply, modem, solenoid driver,

microprocessor, etc), hydraulic coupling leak, hose failure, weld failure,

dynamic umbilical fatigue, electrical connection failure.

Indirect Failures: Dropped object, umbilical dragged by anchor chain or trawl board, wax or

hydrate blocking sensor port,

Subsea equipment reliability

Control systems: Reliability can be improved by proper burn-in of electronics, and testing,

such as shock and vibration. Minor details such as hydraulic coupling seal compatibility

should not be overlooked. Electronic components sourced by manufacturers can vary from

full 'military' specification, through ‘industrial’ high or low grade to 'commercial' (household

quality) with little visibility or control by the purchaser.

Electric and hydraulic connections: As electro-hydraulic control systems are widely used in

deepwater applications and require a high level of umbilical reliability and tube cleanliness,

the test requirements from the reception of core components in the manufacturing facility to

the umbilical installation in the field are presented in chapter 4.

Flow assurance: As discussed in chapter 3

QA/QC: During manufacture, components should be dimensionally controlled to verify

conformance with design drawings. Acceptable deviations will occur and should be recorded

Subsea Processing Technologies

Near-term technology applications

Multi-phase or liquid boosting

Gas-liquid or oil-water separation

Emerging Technologies

Three-phase separation

Compact separators and coalescers

Gas dehydration and compression

Water treating

Higher power pumps and motors

Longer-distance power transmission and distribution

Instruments and control

Complexity is an under-appreciated challenge

Reliability / operability / upset recovery

Performance prediction and testing

Solids management

Instrumentation and controls