Definition - What does Underground Blowout mean?
An Underground Blowout is a situation that occurs in a wellbore when uncontrolled fluids flow from high pressure zones to lower pressure zones. In the Underground Blowout scenario, the fluids keep flowing with the wellbore and the direction is usually from deep set high pressure zones to low pressure formations. Since the fluid does not flow up to the wellhead, it cannot escape. Ideally, the reservoir fluid can also flow from one wellbore to another wellbore. This situation can thus lead to a blowout and an oil well fire.
Petropedia explains Underground Blowout
An Underground Blowout is a situation that occurs in a drilled oil wellbore when the reservoir fluids from the wellbore flow nonstop within the wellbore or to another reservoir. When high pressure is detected, the well starts to flow and the drilling crew reacts by closing the blowout preventers. Then the pressure develops in the annulus resulting in the fracture of the weak-zone. The flowing-formation continues to flow in the fractured zone, depending on the pressure upon which fracturing occurred. Most Underground Blowouts remain unreported or unrecognized and there are no statistics available on them. The blowouts can also occur in the drilling phase due to unavailability of ample kick tolerance.
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