Steam injection

Steam injection is an increasingly common method of extracting heavy crude oil. It is considered an enhanced oil recovery (EOR) method and is the main type of thermal stimulation of oil reservoirs. There are several different forms of the technology, with the two main ones being Cyclic Steam Stimulation and Steam Flooding. Both are most commonly applied to oil reservoirs, which are relatively shallow and which contain crude oils which are very viscous at the temperature of the native underground formation. Steam injection is widely used in the San Joaquin Valley and other parts of California (USA), the Lake Maracaibo area of Venezuela, and the oil sands of northern Alberta (Canada).

Cyclic Steam Stimulation
As defined by the US DOE: "To utilize this EOR method [Cyclic Steam Stimulation], a predetermined amount of steam is injected into wells that have been drilled or converted for injection purposes. These wells are then shut in to allow the steam to heat or "soak" the producing formation around the well. After a sufficient time has elapsed to allow adequate heating, the injection wells are back in production until the heat is dissipated with the produced fluids. This cycle of soak-and-produce, or "huff-and-puff," may be repeated until the response becomes marginal because of declining natural reservoir pressure and increased water production."

Risks
Some have compared the process of Cyclic Steam Stimulation (CSS) to a chemical-free version of fracking. Unlike the more common well stimulation practice called steam flooding, cyclic steaming injects steam at high pressure specifically to break up relatively shallow, diatomaceous soil. California state regulators began scrutinizing the practice in the aftermath of a Chevron manager's sinkhole death at the Midway-Sunset oil field in 2011. The theory behind the sinkhole is that high-pressure steam "migrated" from a nearby injection project and escaped through Chevron's problem well.

According to the Bakersfield Californian, CSS created ongoing problems at the oil fields: "Other oil fields in Kern County have repeatedly experienced seepage and even violent volcanoes in which oil, water, and rocks can shoot 50 to 60 yards through the air. In fact, about a month and a half after [Chevron manager] Taylor's death, one such eruption at the sinkhole site continued for three days. That event prompted DOGGR to shut down steam injection activity within 500 feet of Chevron's 'broken' well."

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