| Quantifying
Risks of Well Intervention, Oil Deferment and Loss of Reserves
In Complex Smart Wells
SPE
Offshore Technology Conference; 5 - 8 May 2003, Houston, Texas,
U.S.A.
Authors
- John Hother, Proneta Ltd., Steve Braithwaite and
Hans van Dongen, Shell International Exploration and Production
BV.
Abstract
This
paper reports on the results of a Reversionary Mode Analysis
Level-1 (RMA-1) to assess the do-ability
of three novel, complex, smart well designs. These are
the Spider Well, Stacked Internal Gravel Packs (IGP) and Conventional
Smart Wells options studied for the Suzy-Q subsea field in
the Gulf of Mexico.
Whole
life-cycle plans are defined for each of the three options.
RMA-1 accumulates “Risk-Dollars”
from subsystem failure modes, both during installation and
production. Quantitative failure mode analysis incorporating
economic consequences are performed on all well construction
processes and production subsystems. The RMA software calculates
“Risk-Dollars” by multiplying the
probability of failure by the consequential costs of well
intervention, oil deferment and/or loss of reserves.
The
resulting risks are broken down into system and process elements,
and into the economic categories of intervention, deferred
production and lost reserves. The assessed risks, together
with various other factors, are input to the selection process
of the preferred development concept, which is outside the
scope of this paper. Key risk drivers are identified from
the analysis, allowing cost-effective targeting of reliability
improvement actions. The three designs studied, the analysis
method and the results are presented in the paper.
The
use of quantitative risk results, expressed in economic terms,
has wide application in making systematic comparisons between
complex systems, both inside and outside the energy industry.
Results for the smart well options analysed for Suzy-Q are
applicable to similar systems in other fields. The results
clarify the reliability risks present in conventional smart
well options, even before considering more advanced alternatives.
The results
show that failures are inevitable in all three options, but
the spider well carries the greatest overall risk, the highest
total number of failure modes and more high-cost failures. Reliability
improvements are however identified which would reduce the spider
well risk to the same level as the other options. Full-scale
testing of prototype equipment can be applied to mitigate risks.
Quality management and reliability engineering are recommended.
After risk mitigation, similar project risks result for all
three designs. Sand control failures present the largest remaining
risk. |
