Organic Petrology of Mesozoic Source Rocks in the Northern Piedmont Zone of the Kuqa Depression

doi:10.19657/j.geoscience.1000-8527.2018.06.03

Abstract

Abstract:

Using whole-rock organic petrological analysis, the macerals, major hydrogen-rich components, organic matter types and thermal evolution of organic matter in the Triassic-Jurassic source rocks from the northern piedmont zone of the Kuqa depression are revealed. The results show that the total maceral content of the Jurassic Kezilenuer Formation source rocks is the highest in the northern piedmont zone, and that in the Qiakemake Formation source rocks is the lowest. The Mesozoic source rocks lack sapropelite, but are rich in vitrinite and relatively rich in exinite and inertinite. The maceral contents of these source rocks vary according to their respective formations.The vitrinite contents of the Kezilenuer and Qiakemake formations are relatively high, and exinite in the Qiakemake Formation is relatively well developed.It is suggested that sporinite, liptodetrinite, cutinite and alginate are the main hydrocarbon-forming macerals, and the hydrocarbon-forming maceral content in the Qiakemake Formation is the highest.Organic matter in the source rocks are mainly of Type Ⅲ and Ⅱ₂, which are beneficial for gas formation. Thermal evolution level in these source rocks are in the mature and high-mature stage,with the vitrinite reflectance (R_o) of 0.56% to 1.87%. The results show that the hydrocarbon-forming center locates in the thrusting front of the Kelasu thrust belt, with the highest total maceral content and thermal evolution. High oil-forming potential of hydrocarbon source rock is related to high proportion of liptinite macerals and low content of terrigenous organic matter.

Key words: Mesozoic source rock, maceral, organic matter type, thermal evolution, the Kuqa depression, organic petrology

CLC Number:

TE122.1

LIANG Wanle, LI Xianqing, WEI Qiang, LI Jin, SUN Kexin, ZHANG Min. Organic Petrology of Mesozoic Source Rocks in the Northern Piedmont Zone of the Kuqa Depression[J]. Geoscience, 2018, 32(06): 1137-1149.

Figures/Tables 13

Fig.1 Sketch map showing tectonic units (a), sample locations (b), and schematic Mesozic stratigraphic column (c) in the northern piedmont zone of the Kuqa depression

Table 1 Distribution of Mesozoic source rock samples in the northern piedmont zone of the Kuqa depression

样品号	井名或剖面	深度/m	层位	岩性	样品号	井名或剖面	深度/m	层位	岩性
KZ1-1	克孜1井	1 659	J₂q	灰色泥岩	YN2-3	依南2井	4 405	J₁y	暗色泥岩
KCH1	库车河	/	J₂q	灰色泥岩	YN2-4	依南2井	4 408	J₁y	暗色泥岩
KPL1	卡普沙良河	/	J₂q	深灰色泥岩	YN4-1	依南4井	4 126	J₁y	碳质泥岩
KPL2	卡普沙良河	/	J₂q	深灰色泥岩	YX1-3	依西1井	1 927	J₁y	灰色泥岩
KPL3	卡普沙良河	/	J₂q	钙质泥页岩	KZ1-2	克孜1井	3 507	J₁y	碳质泥岩
KPL4	卡普沙良河	/	J₂q	暗色泥岩	KZ1-3	克孜1井	3 303	J₁y	灰色泥岩
KPL5	卡普沙良河	/	J₂q	暗色泥岩	KCH7	库车河	/	J₁y	暗色泥岩
KPL6	卡普沙良河	/	J₂q	暗色泥岩	KCH8	库车河	/	J₁y	暗色泥岩
KPL7	卡普沙良河	/	J₂q	暗色泥岩	KCH9	库车河	/	J₁y	碳质泥岩
KPL8	卡普沙良河	/	J₂q	碳质泥岩	KCH10	库车河	/	J₁y	暗色泥岩
YN2-1	依南2井	3 880	J₂kz	灰色泥岩	YN2-5	依南2井	5 048	T₃t	灰色泥岩
YN2-2	依南2井	4 314	J₂kz	碳质泥岩	KCH11	库车河	/	T₃t	灰色泥岩
YS4-1	依深4井	945.5	J₂kz	碳质泥岩	KCH12	库车河	/	T₃t	灰色泥岩
YX1-1	依西1井	2 906	J₂kz	暗色泥岩	KCH13	库车河	/	T₃t	灰色泥岩
YX1-2	依西1井	2 975	J₂kz	碳质泥岩	KCH14	库车河	/	T₃t	粉砂质泥岩
KCH2	库车河	/	J₂kz	碳质泥岩	YN2-6	依南2井	5 310	T₃h	灰色泥岩
KCH3	库车河	/	J₂kz	碳质泥岩	KCH15	库车河	/	T₃h	含粉砂泥岩
KCH4	库车河	/	J₂kz	灰色泥岩	KPL9	卡普沙良河	/	T₃h	深灰色泥岩
KCH5	库车河	/	J₂kz	暗色泥岩	KPL10	卡普沙良河	/	T₃h	深灰色泥岩
KCH6	库车河	/	J₂kz	碳质泥岩	KPL11	卡普沙良河	/	T₃h	深灰色泥岩

Fig.2 Microscopic photos of Mesozoic source rock samples in the northern piedmont zone of the Kuqa depression

Table 2 Maceral contents and composition in the Mesozoic source rocks in the northern piedmont zone of the Kuqa depression

烃源岩层位	样品数 /个	TMC /%	(E+S) 含量/%	显微组分相对组成/%				S₃含量 /%
烃源岩层位	样品数 /个	TMC /%	(E+S) 含量/%	V	I	E	S	S₃含量 /%
J₂q	10	3.92	1.97	37.23	12.57	42.81	7.39	10.09
J₂kz	10	16.85	2.24	64.56	22.17	10.32	2.96	12.29
J₁y	10	7.47	2.01	62.69	10.37	19.22	7.72	16.96
T₃t	5	5.74	0.9	66.73	17.59	8.89	6.78	15.9
T₃h	5	6.78	1.98	50.81	19.97	18.55	10.68	14.11

Fig.3 Distribution of maceral contents of Mesozoic source rocks in the northern piedmont zone of the Kuqa depression

Fig.4 Triangular diagram of maceral composition of Mesozoic source rocks in the northern piedmont zone of the Kuqa depression

Fig.5 Distribution of maceral relative composition of Mesozoic source rocks in the northern piedmont zone of the Kuqa depression

Fig.6 Triangular diagram of hydrogen-rich maceral composition of Mesozoic source rocks in the northern piedmont zone of the Kuqa depression

Table 3 Pyrolysis parameters and the classification of organic matter types of Mesozoic source rock samples in the northern piedmont zone of the Kuqa depression

烃源岩层位	岩石热解参数				有机质类型
烃源岩层位	T_max/℃	(S₁+S₂)/(mg/g)	HI/(mg/g)	D/%	有机质类型
J₂q	$443 ~ 464 452.6 (10)$	$0.08 ~ 3.5 1.75 (10)$	$24.3 ~ 144.9 79.3 (10)$	$6.21 ~ 18.95 10.3 (10)$	Ⅱ₁—Ⅱ₂
J₂kz	$425 ~ 463 447.3 (10)$	$0.13 ~ 43.42 15.9 (10)$	$20.8 ~ 642 211.7 (10)$	$1.04 ~ 23.44 8.34 (10)$	Ⅱ₂—Ⅲ
J₁y	$443 ~ 489 460.4 (10)$	$0.23 ~ 22.44 4.16 (10)$	$18.7 ~ 258.4 61.5 (10)$	$2.27 ~ 22.38 6.2 (10)$	Ⅱ₂—Ⅲ
T₃t	$456 ~ 470 461.6 (5)$	$0.2 ~ 2.98 1.376 (5)$	$20.6 ~ 87.2 54.08 (5)$	$4.2 ~ 8.36 5.82 (5)$	Ⅱ₂—Ⅲ
T₃h	$429 ~ 481 457.2 (5)$	$0.28 ~ 9.66 2.67 (5)$	$30.5 ~ 200.7 74.8 (5)$	$2.94 ~ 17.94 12.2 (5)$	Ⅱ₂—Ⅲ

Table 3 Pyrolysis parameters and the classification of organic matter types of Mesozoic source rock samples in the northern piedmont zone of the Kuqa depression

烃源岩层位	岩石热解参数				有机质类型
烃源岩层位	T_max/℃	(S₁+S₂)/(mg/g)	HI/(mg/g)	D/%	有机质类型
J₂q	$443 ~ 464 452.6 (10)$	$0.08 ~ 3.5 1.75 (10)$	$24.3 ~ 144.9 79.3 (10)$	$6.21 ~ 18.95 10.3 (10)$	Ⅱ₁—Ⅱ₂
J₂kz	$425 ~ 463 447.3 (10)$	$0.13 ~ 43.42 15.9 (10)$	$20.8 ~ 642 211.7 (10)$	$1.04 ~ 23.44 8.34 (10)$	Ⅱ₂—Ⅲ
J₁y	$443 ~ 489 460.4 (10)$	$0.23 ~ 22.44 4.16 (10)$	$18.7 ~ 258.4 61.5 (10)$	$2.27 ~ 22.38 6.2 (10)$	Ⅱ₂—Ⅲ
T₃t	$456 ~ 470 461.6 (5)$	$0.2 ~ 2.98 1.376 (5)$	$20.6 ~ 87.2 54.08 (5)$	$4.2 ~ 8.36 5.82 (5)$	Ⅱ₂—Ⅲ
T₃h	$429 ~ 481 457.2 (5)$	$0.28 ~ 9.66 2.67 (5)$	$30.5 ~ 200.7 74.8 (5)$	$2.94 ~ 17.94 12.2 (5)$	Ⅱ₂—Ⅲ

Fig.7 HI—Tmax and D—Tmax of Mesozoic source rocks in the northern piedmont zone of the Kuqa depression

Fig.8 Tmax—Ro of Mesozoic source rocks in the northern piedmont zone of the Kuqa depression(modified from[28])

Fig.9 Ro contour maps of Mesozoic source rocks in the northern piedmont zone of the Kuqa depression

Fig.10 Relations between TMC—TOC, exinite—HI and Terrig.OM—HI of the Mesozoic source rocks in the northern piedmont zone of the Kuqa depression

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