What is the difference between cased hole and open hole drilling in the oil industry ?

All oil well drilling starts out uncased. Typically there is a short distance that is drilled and then a ';surface'; casing is installed. This will protect any near surface aquifers and to keep the softer surface formations from caving in.





Depending on the depth of the well and the type of rock formations being drilled, a second or even third casing may be set at different depths. Again these can keep any softer formations from sluffing of into the well bore. These casing can also seal of any high pressure zones that the driller encounters. These casing can also seal off any zones (called lost circulation zones) where the drilling mud might attempt to flow out into the formation and not return to the surface.





Finally after reaching total depth and a log is run to determine if that is sufficient ';pay'; to make a well and also to determine the exact depth of the ';pay'; the production casing will be run.





All of these casings are cemented in place.What is the difference between cased hole and open hole drilling in the oil industry ?
A hole with a casing to prevent collapsing of hole walls is called a cased hole. A hole without any casing is called an open hole.What is the difference between cased hole and open hole drilling in the oil industry ?
A cased hole would be sleeved so the earth wouldn't fall in the hole.