This paper shows how to evaluate well performance under conditions of
reservoir and completion uncertainty while also considering the impact of
completion decisions and operating constraints. This topic is important
because it can help to reconcile the often large gap between short-term
deliverability and reliable and sustainable performance.
Table 1 presents a list of operating constraints, and this paper includes
examples regarding the application of some of the constraints. This table
also includes consideration for the type of surveillance that is needed to
apply the constraints. Discussion within the paper shows that the most
relevant types of operating constraints are often not being used and also
addresses appropriate operating limits for completions with sand
Completion selection and design influence operating constraints.
Examples within the paper illustrate methods to determine appropriate operating
constraints. The examples also demonstrate the potential advantage of
frac-packed completions or long horizontal completions with regard to
preventing fines movement and increasing the longevity of both the
completion equipment and the productivity.
To aid with probabilistic performance forecasting, the paper includes a
tabulation of published skin values including some permeability data.
Financial-risk analysis and petroleum-reservoir performance under conditions
of uncertainty have been addressed previously by many authors beginning at
least 40 years ago (Hertz 1964; Walstrom et al. 1967) and more recently in
several analyses of the Production Forecasting with Uncertainty
Quantification-S3 (PUNQ-S3) case study (Barker et al. 2001). Other
studies have addressed application of flexible production rules or constraints
to simulation (Miertschin and Weiser 1989).
Many operating constraints are needed to maintain reliability and
availability throughout the life of a project. A partial list of
production constraints investigated in the literature includes erosional
velocity (Shirazi et al. 1999), velocity through sand screens (Hamid and Ali 1997), critical
drawdown pressure for completions without sand control (Behrmann et al. 2002),
chemical composition and critical fluid velocity for fines movement (Gabriel
and Inamdar 1983), and minimum wellbore pressure and the impacts on scaling
(Mackay et al. 2002), casing collapse (Abbassian and Parfitt 1998; Morita and
McLeod 1995), screen collapse (Hamid and Ali 1997), or retrograde condensation
(Ahmed et al. 1998). The cited studies are not necessarily the earliest, and
there have been many other studies of each of these constraints.
Both uncertainty and constraints should be considered to produce realistic
forecasts, and examples showing how to address both are shown in this
Transient conditions during startup and shutdown procedures are also very
important considerations for operating a field in a reliable manner; however,
they are not addressed in this paper.
© 2006. Society of Petroleum Engineers
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- Original manuscript received:
31 January 2005
- Revised manuscript received:
1 April 2006
- Manuscript approved:
14 April 2006
- Version of record:
20 September 2006