There are multiple types of oil and gas title opinions. Each opinion has in common the purpose of presenting the state of ownership for the land in question.
Drilling Title Opinion
A drilling title opinion is also known as a base title opinion, original title opinion, or preliminary title opinion. It presents the ownership of the leasehold working interest and any defects in the title prior to drilling. A driller will use this to know how much of the production he will get and the costs of drilling he will bear.
Division Order Title Opinion
A division order title opinion (DOTO) concentrates on the ownership of production. It is created once a well is drilled, completed, and proven to be productive. This opinion can be based on previous DOTOs written while some prefer DOTOs without any prior baseline. This opinion brings to light any defects in ownership of the working interest and leasehold interests.
Supplemental Title Opinion
The purpose of a supplemental title opinion is to update the existing title based on the current state of record. A single well might have multiple supplemental title opinions. It can be used for but not limited to updating an old drilling opinion to reflect curative work, update a division order opinion to reflect ownership changes, and as a financial opinion on closing a loan.