As used in Sections 3227 and 3227.5, the following terms have the following meaning:

1. (a) “Field” means the same general surface area which is underlain, or reasonably appears to be underlain, by one or more pools.
2. (b) “Pool” means an underground reservoir containing, or appearing at the time of determination to contain, a common accumulation of crude petroleum oil or natural gas or both. Each zone of a general structure which is separated from any other zone in the structure is a separate pool.