Definition - What does Damaged Zone mean?
A Damaged Zone is an area inside a reservoir that surrounds the wellbore. This area creates certain resistance to the smooth flow of hydrocarbons into the wellbore thereby affecting the productivity of the well. A zone becomes damaged as a result of inefficient drilling practices that cause accumulation of mud and cement filtrate near the opening where the hydrocarbons enter the wellbore.
Petropedia explains Damaged Zone
During the drilling process of an oil well, it is almost certain that some damage is caused to the reservoir formation adjacent the wellbore. Minimizing the reservoir zone damage is a key objective during the drilling and cementing operations of a well.
A lightly damaged zone near the wellbore is always be present in the reservoir, however, this can be bypassed with the help of perforation tunnels which consist of perforating guns that make multiple perforations (small holes or multiple connected conduits) in the cemented wellbore to the undamaged reservoir formation. Since this zone is undamaged, there will be a constant smooth flow of hydrocarbons inside the wellbore through the perforated conduits.
If the zone is severely damaged across the perforated conduits it requires special and advanced treatment techniques which include:
- Matrix acidizing treatment that helps in bringing back the natural permeability of the reservoir rock.
- Drilling a secondary high conductivity flow path using hydraulic fracturing technique.