@wikipedia

By recoverable volume

Super-Giant	Giant	Big	Medium	Small
> 5 billion bbl	> 500 million bbl	> 50 million bbl	> 5 million bbl	< 5 million bbl

By uncertainty (SPE)

2P = Proven P90 + Possible P50
1P = Proven P90		Probable P50	Possible P10
Proven developed (PD)	Proven Undeveloped (PUD)

By complexity

Conventional				Unconventional
Gas	Condensate	Oil	Heavy Oil	Shale Gas	Shale Oil	Bitumen

By oil density

	Gas	Condensate	Light crude	Medium crude	Heavy crude	Extra heavy crude
kg/m³			< 870	870 – 920	920 – 1000	> 1000
API			> 31.1°	22.3° – 31.1°	10° – 22.3°	< 10°

By sulfur content

Sweet crude	Sour crude oil
Sulfur < 0.5%	Sulfur > 0.5%

By mobility

	Specific Gravity	API Gravity	High perm	Medium perm	Low perm	Tight (Shale)
	frac	API	> 100 md	10 md ÷ 100 md	0.1 md ÷ 10 md	< 0.1 md
Gas	< 0.7	> 70°
Condensate	0.7 ÷ 0.87	> 45°
Light Oil	< 0.87	> 31.1°
Medium Oil	0.87 ÷ 0.92	22.3° ÷ 31.1°
Heavy Oil	0.92 ÷ 1.0	10° ÷ 22.3°
Extra Heavy Oil (Bitumen)	> 1.0	4° ÷ 10°

where box colors mean:

Conventional Reserves

Unconventional Reserves

Unrecoverable Reserves

and the ranges of properties in the table are only tentatively define the category based on the industry statistics and conventions, which vary over history and locations.

By reservoir homogeneity

Matrix

Fissured

Fractured

Faulted

Compartmentalized

By trap structure