The Wilmington oil field (California, USA) is located under the City of Long Beach and adjoining harbor. When this field was developed in the late 1960s from artificial offshore islands, more than 20 water injection wells were drilled and completed in the aquifer. The objective was to create a peripheral waterflood using an injected water volume exceeding 100,000 barrels per day. This water was not expected to move downdip because of an interpreted sealing fault in the syncline between the Wilmington Field and the adjacent Seal Beach Field.
However, the fault turned out to be non-sealing, and the water moved through the syncline, creating a waterflood at Seal Beach Field. This led to an increase in the oil production rate and overpressuring of the reservoir (see the Figure below). Wells were flowing with a surface pressure of 200 to 350 psi adjacent to an area where houses had been built above abandoned wells.
In response, the Seal Beach operator contacted the Wilmington Field operator who proceeded to shut-in all the aquifer waterflood injectors for about six months. This allowed the pressure to decline in the aquifer before resuming injection at a reduced rate of 30,000 barrels per day. Additionally, the Seal Beach operator installed pressure gauges in idle wells to monitor the reservoir pressure and help ensure that no future well blowouts would occur. This case study is a good example of how injected fluids can cross barriers that were previously considered sealing.
