Page 36 - Handbook Of Multiphase Flow Assurance

30 1. Introduction

for systems where blockages are easily remediated and leaks easily addressed. However, for
remote systems in deep and ultra-deep water the amount and the level of detail of required
knowledge about the reservoir fluids and the environment is substantial.

Process safety

One of the more notable yet sad examples of the interaction of flow assurance and process
safety is the 1989 Piper Alpha disaster. The Lord Cullen investigation report named gas hy-
drates as one of the four potential causes for the condensate leak which was the root cause of
the explosion.
Loss of primary containment (also known as leaks) are known to have been caused by
hydrate or ice blockages formation because both expand upon freezing or by their sudden
dislodging and movement, mainly onshore or on topsides. Subsea water may act as a buffer
partially absorbing movement of the pipe with blockage moving inside it, thus subsea leaks
caused by flow assurance blockages are less known.
A field operation example and learning of process safety during depressurization of hy-
drate blockages has been described by Makogon (ICGH9, 2017).

System of measures for flow assurance

Three characteristics named above (safety, reliability and economics) are related to the so-
called iron triangle of flow assurance project management which measures are: quality, time
and cost. Safety includes both process safety and personal safety. Safety and reliability fall
under the quality category; a higher quality system will have fewer incidents and will be
safer to operate. Reliability is measured as time and economics is measured as cost; a lower
cost system may have more failures, and project economics will be affected. Reliability trans-
lates into the expected frequency of failures. Safety and economics also have the time metric;
non- productive downtime and the number of recordable incidents and reportable process ex-
cursions are reported per unit time. Thus every component of flow assurance project manage-
ment is related to time, the only measure not subject to inflation. A flow assurance engineer
engaged in a design of a new project has to keep all three metrics in mind, otherwise designs
will be too costly and not get sanctioned for implementation.
A proper design addresses all personal and process safety threats presented by produced
fluids, strikes a price-performance balance between complete prevention and partial control
of flow assurance threats for the duration of the life of field, and allows the operator to reli-
ably produce reservoir fluids.

Outlook for flow assurance

Easy flow assurance challenges in onshore and deepwater have been solved with multiple
technologies developed and deployed over the past two decades. As energy operators may
be moving to new ultra-deep basins or to more complex fluids, flow assurance will be faced
with new challenges and with their combinations, where one change in fluid composition