  This work presents a procedure that can quickly identify and isolate methane
emission sources leading to expedient remediation. Minimizing the time required
to identify a leak and the subsequent time to dispatch repair crews can
significantly reduce the amount of methane released into the atmosphere. The
procedure developed utilizes permanently installed low-cost methane sensors at
an oilfield facility to continuously monitor leaked gas concentration above
background levels. The methods developed for optimal sensor placement and leak
inversion in consideration of predefined subspaces and restricted zones are
presented. In particular, subspaces represent regions comprising one or more
equipment items that may leak, and restricted zones define regions in which a
sensor may not be placed due to site restrictions by design. Thus, subspaces
constrain the inversion problem to specified locales, while restricted zones
constrain sensor placement to feasible zones. The development of synthetic wind
models, and those based on historical data, are also presented as a means to
accommodate optimal sensor placement under wind uncertainty. The wind models
serve as realizations for planning purposes, with the aim of maximizing the
mean coverage measure for a given number of sensors. Once the optimal design is
established, continuous real-time monitoring permits localization and
quantification of a methane leak source. The necessary methods, mathematical
formulation and demonstrative test results are presented.
