High-Tech Wells Conference & Exhibition, 11-13 February 2003, Galveston, Texas.

Title - Quantifying Risks Of Well Intervention, Oil Deferment And Loss Of Reserves In Complex Smart Wells

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.