Environmental Risk Arising from Well Construction Failure
The quality of construction and maintenance of oil and gas wells has
been called into question by media sources with reports of high rates of
leakage and fears of pollution. This presentation looks at studies
covering over 650,000 wells, primarily in but not limited to North
America. Concepts of well construction are explained with emphasis on
performance of properly constructed barriers within the well design in
preventing leaks.
When examined in detail, most claims of leaks are found to be a
single barrier failure within a multi-barrier system where a leak path
is not formed. True well integrity failure rates (where a leak path is
created) are two to three orders of magnitude lower than single barrier
failure rates. Well integrity performance is shown to be related to
several factors including best practice construction, era of well
construction, type of well, changes in well operation, age of well and
application of consistent, high quality maintenance.
Failure frequency numbers are estimated for wells in several specific
sets of environmental conditions (location, geologic strata, produced
fluid composition, soils, etc.). Accuracy of these numbers depends on a
sufficient database of wells with documented failures, divided into: 1)
barrier failures in a multiple barrier system that do not create
pollution, and 2) well integrity failures that create a leak path,
whether or not pollution is created. Estimated failure frequency is only
valid for a specific set of wells operating under the same conditions
with similar design and construction quality. Well integrity failures
have generally decreased where learnings from an earlier era have been
incorporated into new well designs. There is absolutely no
one-size-fits-all well failure frequency.
Local: Evento Web
Data: 5 de novembro de 2013
Mais informações em: http://eo2.commpartners.com/users/spe/session.php?id=11601
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