Hydrocarbon production can be divided into several phases, depending on the methods used. Some of these methods and technologies fall under Class II UIC regulations.
Primary Oil Recovery
In most conventional hydrocarbon reservoirs, either the expansion of natural gas at the top of the reservoir or the formation pressure forces hydrocarbons into the well and up to the surface. Valves at the surface control the flow as the fluids are prepared for storage and sale. Pump jacks or other forms of equipment used to create artificial lift are considered primary oil recovery.
Secondary Oil Recovery
As production continues, formation pressure falls under the level required to force hydrocarbons to the surface. Operators can add fluids to the reservoir to increase the formation pressure and thereby extract more hydrocarbons. The most common secondary recovery techniques are gas injection and waterflooding. The secondary recovery stage reaches its limit when the injected fluid (water or gas) is produced in considerable amounts from the production wells and the production is no longer economical. The successive use of primary recovery and secondary recovery in an oil reservoir produces about 15% to 40% of the original oil in place.
THUMS Islands Case Study
California’s headline-making 1921 oil discovery at Signal Hill launched a drilling boom. So many derricks sprouted it became known as “Porcupine Hill.” By the early 1930s, the massive Wilmington oilfield extended through the surrounding city of Long Beach.1American Oil & Gas Historical Society. (2021, June 22). Signal Hill boom by B.A. Wells and K.L. Wells. Retrieved 12/30/2022 from https://www.aoghs.org/petroleum-pioneers/signal-hill-oil.
Although Californians had experience dealing with groundwater induced subsidence and the building damage it caused, by 1951 Long Beach was sinking at the alarming rate of about two feet each year.2American Oil & Gas Historical Society. (2022, February 18). THUMS-California hidden oil islands by B.A. Wells and K.L. Wells. Retrieved 12/30/2022 from https://www.aoghs.org/technology/thums-california-hidden-oil-islands.
During the 1950’s, experts showed that water injection would repressure the oil-bearing units, stop underground compaction as well as surface subsidence, and increase oil recovery.
By the time the THUMS Islands were built in 1965 to tap into the East Wilmington Oil Field, the community of Long Beach had sunk 30 ft.3American Oil & Gas Historical Society. (2022, February 18). THUMS-California hidden oil islands by B.A. Wells and K.L. Wells. Retrieved 12/30/2022 from https://www.aoghs.org/technology/thums-california-hidden-oil-islands. The islands were operated by THUMS, a consortium named after the parent companies involved: Texaco, Humble, Union Oil, Mobil and Shell.
The rim of the islands were made of boulders from Catalina Island, and the islands were then filled with dredged material from the bay. In 1967 the islands were named Grissom, White, Chaffee and Freemen in honor of lost NASA astronauts.4THUMS Islands. (n.d.). In Wikipedia. Retrieved 11/10/2020 from https://en.wikipedia.org/wiki/THUMS_Islands.
A peak of 148,495 BOPD were produced in 1969. By 1992, the pumping volume was 44,444 BOPD through the water injection method of oil recovery, producing low-grade crude oil. The one-billionth barrel of oil was produced in 2011. As with many water flood projects, water production overtook oil production: water cut was 20% in 1965, and by 1994 it was 92%.5THUMS Islands. (n.d.). In Wikipedia. Retrieved 11/10/2020 from https://en.wikipedia.org/wiki/THUMS_Islands. To counter subsidence, water injection pumps were established to offset extracted petroleum, sustain reservoir pressures and extend oil recovery.6American Oil & Gas Historical Society. (2022, February 18). THUMS-California hidden oil islands by B.A. Wells and K.L. Wells. Retrieved 12/30/2022 from https://www.aoghs.org/technology/thums-california-hidden-oil-islands.
Images: “Oil pumps” by huyangshu via Shutterstock; “Pumpjack pumping crude oil” by Anan Kaewkhammul via Shutterstock