TITLE
Recommendation to receive and file the report, "Elevation Changes in the City of Long Beach, November 2004 to May 2005." (Citywide)
DISCUSSION
The City of Long Beach (City) through the Department of Oil Properties (DOP),
supervises oil production and subsidence control operations in the Wilmington Oil Field.
DOP takes elevation surveys every six months to monitor elevation changes in the oil
field and surrounding City areas. This report focuses on elevation changes that have
occurred from November 2004 to May 2005. The DOP survey includes the following
areas: Civic Center, Central City, Alamitos Bay, Naples, Harbor District, and an offshore
area encompassing the four oil islands (Offshore).
The results of the six-month survey show elevations were stable in the Civic Center,
Central City, Alamitos Bay, Naples, and Offshore areas. Harbor District elevations were
stable except for a localized area of elevation loss along Henry Ford Avenue just north
of the Cerritos Channel. The DOP is watching this area and acquiring data to further
assess the elevation loss of approximately 0.08 feet (0.96 inches). This area is located
over an oil reservoir that had been previously steam flooded. The steam flood was shut
down in 1999 after high steam temperatures were found to cause compaction in the
reservoir resulting in elevation loss. A program of cold-water injection was initiated and
is cooling the reservoir to mitigate the elevation loss.
The DOP survey uses a series of benchmarks to determine elevation changes. Studies
by the department’s engineers and geologists show that the benchmarks may rise and
fall in such a manner as to make an entire survey either optimistic (slightly up in
elevation) or pessimistic (slightly down in elevation). These changes in elevations can
be seasonal or random and may be associated with tidal cycles, temperature changes,
and/or deep earth tectonic changes. Repressuring operations and the resulting
rebound alter or mask these pattern...
Click here for full text