It is shown that physical characteristics of crude oil depend not only on group compositions, but also on maturity, burial depth, preservation condition and compositional gravity differentiation.

原油物性不仅受原油族组成的影响，而且也受成熟度、埋藏深度、保存条件、组分重力分异作用等的影响。

youdao

Crude oil is commonly classified as light, medium or heavy, referring to its gravity as measured on the American Petroleum Institute (API) Scale.

原油通常分为轻型，中型或重型，所指的是对美国石油学会(API)严重程度的规模衡量。

youdao

Steam Assisted Gravity Drainage (SAGD) pumps steam into the ground to liquefy the bitumen and stiff crude oil, making it thin enough to be pulled out of the ground.

FORBES: Has The Gulf Spill Opened Pandora's Box For Obama?