A high-energy surface expression is the flow of crude oil, water, and/or steam to the Earth’s surface during the extraction of oil. Recall that sometimes to increase flow of oil to the surface through the wellbore, other fluids are injected into the subsurface as part of operations. In some cases, injection of steam is the solution to better flow, especially when the oil is very viscous (resistant to flow). Many oil fields in the San Joaquin Valley of California inject steam at depth as part of their production program. Operators must carefully design these injection programs and monitor operations as subsurface integrity can be a challenge in many areas where production is only several hundred feet below the ground surface (rather than thousands of feet). In such cases, the overburden is not thick and its properties must be well understood as it is an important barrier between steam injected at depth in a well and the ground surface. A surface expression can occur in these types of wells when steam that is injected under pressure to produce oil breaks through natural geologic barriers and comes to the surface.
A sign in a California oil field in the San Joaquin Valley warns of potential surface expressions or events and how to recognize the warning signs.
A cleaned up oil/water surface expression in an oil field in California in 2016. A berm and netting remain in place as a precaution. The berm is to contain any further oil. The netting is to keep birds and animals out.
A CalGEM inspector checks on a surface expression in a California oil field to ensure there are no new outbreaks of steam or liquid.
Image Credits
- surface expression sign olson: Hilary Olson
- surface expression olson: Hilary Olson
- CalGEM Inspector: CalGEM