The essential elements are source rock, reservoir rock, sealrock and overburden rock, and the processes include trap formation and the generation-migration-accumulation of petroleum.
基本要素包括一套烃源岩、储集层、盖层和上覆岩层，作用是圈闭的形成和油气的生成—运移—聚集。
2
The third parameter needed for an oil field to occur is the cap rock or seal.
形成油田所必须的第三个参数是盖层岩石或封闭层。
3
The palm-sized seal is made of red and white steatite, a type of mineral rock.