Usually
when the well reaches its economic limit the operator plugs and abandons it.
But the risks and hazards that can happen due to this are neglected. Gas leak
from one of the plugged wells of Elgin gas field shows that abandoned wells can
cause serious threats. With this incident which occurred recently shows that, accidents
can happen even if we have methods to completely seal or plug a well. No human
life was threatened by this accident, but oil and gas leaks from the abandoned
wells can cause serious environmental impacts. Reason for the gas leak in Elgin
field was due to the outdated plugging method used to seal the well by Total.
This gas leak in Elgin would be costing the operator, Total a great deal of
money which was estimated to be around GBP 94,0000 a day in lost production. All these unnecessary
expenditure and risk could have been avoided if Total had updated their method
of plugging and abandoning. From this it can be understood that the
things which are consider as of less priority can give a backlash.
In this energy demanding world the need for fossil fuel never declines. Depletion is an unavoidable part of hydrocarbon production and all the reservoirs around the globe faces this. Depletion due to hydrocarbon production can also pose threats that can even make a scar on the earth's face.
1) Land subscidence
2) Fault reactivation
3) Earthquakes
4) Casing damages
5) Formation damage
and further more...
Nowadays these issues are not only caused by depleting but the inappropriate use of depleted reservoirs for co2 sequestration, EOR etc.
The root cause for all these issues are the changes in the chemical and physical nature of a reservoir. The reduction in reservoir pressure plays an important role in this.
Ekofisk is field that is affected by land subsidence due to hydrocarbon production, similarly the wet land loss in Louisiana are examples. It can be noted that a large number of active fields are situated near fault zones, this poses a threat to the reactivation of these faults and possible sesmic activities. The proper knowledge regarding the reservoir is the important fact that can help to foresee these changes. Creating a possible reservoir managment criterion can also provide a barrier against these issues or threats.