Open hole completion or bare foot completion is one type of completion where the production casing is set on top of the reservoir, but the open hole section is left without cemented casing. Typically, drilling into a pay zone is drilled with non-damage drilling mud or drilling mud weighted with calcium carbonate, which can be dissolved with acid later if needed.
The pros and cons of this completion are as follows;
Advantages of Open Hole Completion
- Full exposure of reservoir zone
- No cementing or perforating expense
- Minimize formation damage
- Minimize flow path restriction due to cementing and perforating
- Minimize wellbore skin
- Improve wellbore performance due to a large inflow area
Disadvantages of Open Hole Completion
- Unable to control excessive water or gas production
- Unable to isolate hydrocarbon zones
- Difficult to do reservoir management
- Has large potential to produce sand
- Inability to produce at different zones
Nowadays, this completion is not very popular due to several limitations as stated earlier. However, some horizontal wells which have competent rock are completed with bare foot completion because the wells can produce at considerable rates compared to cemented casing completion.
Jonathan Bellarby, 2009. Well Completion Design, Volume 56 (Developments in Petroleum Science). 1 Edition. Elsevier Science.
Wan Renpu, 2011. Advanced Well Completion Engineering, Third Edition. 3 Edition. Gulf Professional Publishing.
Ted G. Byrom, 2014. Casing and Liners for Drilling and Completion, Second Edition: Design and Application (Gulf Drilling Guides). 2 Edition. Gulf Professional Publishing.