Keeping Ground Stable
Producing oil from the Wilmington Field and keeping Long Beach’s ground stable are not two separate goals. They are managed as a single, continuous balancing act.
How Waterflooding Works
Waterflooding is the process of injecting water into oil-bearing rock formations to replace the volume of fluids removed by production. This voidage replacement, filling the space left by extracted oil and water, maintains reservoir pressure. Maintained pressure has two critical benefits: it prevents the compaction of rock that causes land to sink, and it pushes remaining oil toward the producing wells.
Waterflooding was first used at the Wilmington Field in 1953 to halt the subsidence crisis. At West Wilmington, where production had fallen significantly, the program reversed the decline and drove a substantial rebound. In the Long Beach Unit, waterflooding was built in from day one, and it is expected to nearly double the field’s ultimate oil recovery compared to production without it.
Voidage Management
The City carefully monitors the balance between injected and produced fluids through a process called voidage management. The target is to inject slightly more fluid than is produced, maintaining a careful overpressure that keeps the ground stable. This balance is reviewed continuously and adjusted as field conditions change.
The vast majority of water injected comes from water produced alongside the oil and separated at surface. The remainder comes from dedicated water source wells and recycled water from Long Beach Utilities.
Ground Elevation Surveys
The ground elevation survey program is the City’s direct measure of whether the subsidence program is working. Surveys are conducted on a regular schedule throughout Long Beach using satellite imagery, GPS, and traditional leveling methods.
The program has been in operation since the 1950s and has grown considerably in sophistication. What began as a small crew measuring benchmarks on foot has evolved into a satellite-based monitoring program that provides more frequent and more accurate data than ever before.
