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。

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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。

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Bakken crude is a sweet, light crude that typically has a gravity of 40 to 42 degrees, ideal for most U.S. refineries.

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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.

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