In this chapter,
(1) “commission” means the Regulatory Commission of Alaska;
(2) “field” means a general area which is underlain or appears to be underlain by at least one pool, and includes the underground reservoir containing oil or gas; and the words “pool” and “field” mean the same thing when only one underground reservoir is involved, but “field” unlike “pool” may relate to two or more pools;
(3) “oil” includes crude petroleum oil and other hydrocarbons regardless of gravity which are produced at the wellhead in liquid form and the liquid hydrocarbons known as distillate or condensate recovered or extracted from gas, other than gas produced in association with oil and commonly known as casinghead gas;
(4) “pool” means an underground reservoir containing oil; each zone of a general structure which is completely separated from any other zone in the structure is covered by the term “pool”;
(5) “purchaser” means a person who purchases oil in the state.