Abstract: How Clean Should Our Water
Be? Reservoir Engineering Perspective on
Water
Quality
in the Long Beach Unit, Wilmington Field
HARRIS, RANDALL, THUMS Long Beach Co., Long Beach, CA
Facilities Managers in the Long Beach Unit are actively working to determine the
optimum treating processes for produced water
. With numerous
water
quality
improvements
already in effect, including increased data gathering and monitoring, and more planned,
the
water
is cleaner. The question is - how clean does this
water
need to be to maintain
injectivity, reduce stimulation expenditures, and reduce injector equipment failures? A
study was made to reevaluate
water
quality
specifications, aligning them with reservoir
pool requirements.
Relating water
quality
parameters to reservoir variables is often labeled
"impossible" in the technical literature. This is primarily due to the numerous
formation damage processes taking place during injection, including solids plugging, scale
deposition, plugging from corrosion byproducts, rock wettability changes, microbiological
problems, facilities upsets, etc. The large number of reservoir variables, and the
inaccuracies often found in the data, also cause difficulty. Only a few models are
available, only for solids plugging, and almost all require reservoir-specific testing.
A solids plugging model was found in the paper "Water
Quality
for
Water
Injection
Wells", by Rochon, Creusot, Rivet, Roque, & Renard (SPE #31122, 1996). This model
did not require special laboratory tests. The model cannot account for all the formation
damage processes occurring in Long Beach Unit injectors, but solids plugging is believed
to be the most important factor.
Injection well case histories were also evaluated. Combining the results from the case
histories and the model allowed us to establish the cost of maintaining specified levels
of suspended solids. Facilities operations estimated plant costs to maintain water
quality
at different solids levels. Combining this information allowed us to determine what was
the most economically efficient way to run the
water
facilities.
AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California