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Fig. 3 - Reliability, Availability
and Maintainability, where
(-) indicates constant, (↑)
indicates an increase and
(↓) indicates a decrease.
now this solution as very attractive as it is cheaper Selection of an efficient liquefaction process is
and quicker to build compared to a large scale decisive for an optimum ROI. Several liquefaction
FLNG. With a schedule of less than 3 years between technologies have been developed recently and all
concept and operation, the second small scale designers invest a lot of effort to produce system
FLNG ordered end 2014 by Exmar to the Wison with a high level of efficiency. However, Stine
Shipyard will clearly allow an early monetization of Faugstad and Inge L. Nilsen [6] demonstrate that
the gas reverses in a cost effective manner. efficiency hardly affects a project’s overall economy.
Thus, from their analysis, it has been concluded
FLNG: high Capex and that it is more important for the project economy to
high Opex issue strive for high availability than high efficiency.
This last decade, costs related to operation and Value of RAM modeling
maintenance but also Capex got increasingly high
and most of the operating companies are now Thus, it seems that one of the most important
struggling to develop cost reduction strategies. parameter to quantify, when an operator wants
A glaring example is the metric cost that is defined to optimize the ROI of an asset, is the production
as the ratio of cost of the plant in millions of US$ availability. Once the production rate and the
to the capacity in million tonnes per annum. Thus, production availability target are set by the project,
metric cost increased from $300/tpa in the 2000’s a proper assessment needs to be carrying out in
to $1200/tpa in the 2010’s (Songhurst B, 2014 order to ensure that the process is designed to
[5]). In some cases, such as Prelude, metric cost reach, as a minimum, this availability target. That
is reaching $3000/tpa. With such explosion of the is why, for most of the operating companies, RAM
costs of production, it is often complicated for an Analysis is often considered as one of the most
operator to invest judiciously and see where they powerful assessment tool to valid the project
can get the greatest reward all along the operating economics.
life of the unit. Carrying out a RAM analysis to better understand
the production availability and the constraints
Both giant and mini FLNGs projects can on maintainability during the different phases
be economically viable as ROI will not of the project is then a powerful approach that
depend only on the production capacity will provide with important inputs to the decision
but also on the type of reservoir the making process. The RAM analysis will allow
unit will have to deal with as well as the understanding of the reliability based interactions
size of the field. Production capacity within the facilities and will provide the different
design teams with a tool for quantifying system
will then not be the most efficient performance, identifying the critical aspects
parameter to play with of the design and allow the impact of varying
design, operations and maintenance criteria to be
As FLNG is a production unit, it seems obvious that understood. It will ensure the process design is
more the unit will produce during its life, greater will reliable and that production availability will not be
be the Return On Investment (ROI) for the operating impacted by specific bottleneck.
company. But what is quantifying businesswise The ideal timing for a RAM analysis is immediately
this notion of “producing more”? As it has been following conceptual design. Operators often
presented in the previous section, both giant and considered RAM as important as the Capex
mini FLNGs projects can be economically viable definition.
as ROI will not depend only on the production RAM modeling can then be updated at each phase
capacity but also on the type of reservoir the unit of the project to ensure the recommendation of
will have to deal with as well as the size of the the study have been implemented and that other
field. Production capacity will then not be the most modifications performed during detailed phases
efficient parameter to play with. will not impact negatively the project. General ideas
to achieve an increase in availability are presented
in figure 3.
Some of the benefits of the RAM analysis are:
• quantification of production availability on a
time varying basis to predict performance over
Impiantistica Italiana - Maggio-Giugno 2015 91
