Geofluids

Research Article

Deep-Buried Triassic Oil-Source Correlation in the Central Junggar Basin, NW China

Table 4

Key geochemical differences between Triassic mudstone source rocks and other three identified end-member source rocks (i.e., Jurassic and Permian) in the central Junggar Basin.


End-member source rocks		T	J	P₂	P₁

δ¹³C

Paraffins	Main peak (maximum concentration) of n-alkanes	C₂₀, C₂₁	Mostly C₂₃ or C₂₅	C₁₉, C₂₀	C₁₇
	Pr/Ph	1.0–2.0	>3.0	1.0–2.0	<1.0
	Pr/n-C₁₇ Ph/n-C₁₈	0.3–0.6	Pr/n-C₁₇ > 1.0, Ph/n-C₁₈ < 0.5	0.3–0.6	>0.5

β-Carotane	β-Carotane/maximum n-alkane	0.2–0.4	Very less/no	<0.2	>0.4

Terpanes	C₁₉/C₂₁TT	<0.2	>1.0	<0.2	<0.2
	C₁₉/C₂₃TT	<0.2	>1.0	<0.3	<0.2
	Distribution pattern of C₂₀, C₂₁ or C₂₃TT	No defined distribution pattern	C₂₀ > C₂₁ > C₂₃, C₂₀ > C₂₁ < C₂₃	C₂₀ < C₂₁ > C₂₃	C₂₀ < C₂₁ < C₂₃
	Main peak of TT/main peak of hopanes	<0.5	<0.1	0.2–1.0	0.2–1.0
	C₂₄TeT/C₂₆TT	>0.5	>3.0	0.2–0.5	<0.3
	Gammacerane/C₃₀ hopane		Very less/no	<0.2	>0.3
	Ts/Tm	<1.0	<0.1	<0.5	<0.5

Steranes	C₂₇, C₂₈, C₂₉ regular steranes	Predominance of C₂₉ = 40–60%, C₂₇ > C₂₈	Predominance of C₂₉ > 70%, C₂₇ < C₂₈	Predominance of C₂₉ = 40–50%, generally C₂₇ < C₂₈	Predominance of C₂₉ = 40–60%, generally C₂₇ < C₂₈
Steranes	Diasteranes/regular steranes	0.1–0.2	>0.4	<0.4	<0.4