Geochemical Characteristics of Source Rocks of M53 Well and Chang-8 Member Oil-source in Pingliangbei Exploration Area, Ordos Basin

doi:10.19657/j.geoscience.1000-8527.2020.04.15

Abstract

Abstract:

Based on organic petrology and geochemistry, the dark mudstones of the Chang-7 Member (M53 well, Triassic Yanchang Formation) at Pingliangbei on the southwestern Ordos Basin margin was analyzed. Molecular geochemical characteristics and fine oil source comparison of Chang-8 Member oil (M53 well) and its surrounding was studied. We newly reveal the geological and geochemical characteristics, hydrocarbon generation potential and oil source of the dark Chang-7 Member mudstone in the Pingliangbei area. The results show that the Chang-7 Member mudstone in Pingliangbei area has medium-high organic contents, of I-and II₁-type and mature, and was formed in freshwater-brackish water environment. The source rocks have relatively good hydrocarbon generation capacity, and share much geological/geochemical similarities with the high-quality source rocks inside the basin. The Chang-8 Member crude oil has similar characteristics to the Chang-7 Member source rocks, in terms of maternal properties, sedimentary environment and maturity, and both have good genetic relationship. The Chang-8 Member crude oil in the Pingliangbei area may have come from the Chang-7 Member source rocks at/around M53 well. Our results expand the range of source rocks and broaden the field and scope of Mesozoic oil and gas exploration at Pingliangbei in the southwestern margin of the Ordos Basin.

Key words: geochemical characteristics, oil-source correlation, source rock, M53 well, Pingliangbei, Ordos Basin

CLC Number:

ZHAO Yande, DENG Xiuqing, QI Yalin, SHAO Xiaozhou, YANG Bin, LU Xinchuan, LUO Anxian, XIE Xiankui. Geochemical Characteristics of Source Rocks of M53 Well and Chang-8 Member Oil-source in Pingliangbei Exploration Area, Ordos Basin[J]. Geoscience, 2020, 34(04): 800-811.

Figures/Tables 13

References 24

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井名	井段/m	层位	腐泥组/%	镜质组/%	惰质组/%	类型	类型指数
M53	2 339	长7段	92.00	7.30	0.70	Ⅰ	85.80
M53	2 340	长7段	90.30	8.70	1.00	Ⅰ	82.80
M53	2 342	长7段	88.30	11.00	0.70	Ⅱ₁	79.40
M53	2 343	长7段	90.00	9.30	0.70	Ⅰ	82.30
M53	2 371	长7段	88.30	10.70	1.00	Ⅱ₁	79.30
M53	2 389	长7段	92.00	7.30	0.70	Ⅰ	85.80
M53	2 392	长7段	89.70	9.70	0.70	Ⅰ	81.80
M53	2 393	长7段	88.30	10.70	1.00	Ⅱ₁	79.30
M53	2 397	长7段	88.30	11.00	0.70	Ⅱ₁	79.40
M53	2 410	长7段	86.70	11.70	1.70	Ⅱ₁	76.30

井名	井段/m	层位	腐泥组/%	镜质组/%	惰质组/%	类型	类型指数
M53	2 339	长7段	92.00	7.30	0.70	Ⅰ	85.80
M53	2 340	长7段	90.30	8.70	1.00	Ⅰ	82.80
M53	2 342	长7段	88.30	11.00	0.70	Ⅱ₁	79.40
M53	2 343	长7段	90.00	9.30	0.70	Ⅰ	82.30
M53	2 371	长7段	88.30	10.70	1.00	Ⅱ₁	79.30
M53	2 389	长7段	92.00	7.30	0.70	Ⅰ	85.80
M53	2 392	长7段	89.70	9.70	0.70	Ⅰ	81.80
M53	2 393	长7段	88.30	10.70	1.00	Ⅱ₁	79.30
M53	2 397	长7段	88.30	11.00	0.70	Ⅱ₁	79.40
M53	2 410	长7段	86.70	11.70	1.70	Ⅱ₁	76.30

井号	深度/m	Pr/Ph	Pr/nC₁₇	Ph/nC₁₈	∑nC_21-/∑nC₂₂₊	(nC₂₁+nC₂₂)/(nC₂₈+nC₂₉)	CPI	OEP
M53	2 339	1.19	1.63	1.27	0.86	1.45	1.26	1.27
M53	2 340	1.33	1.77	1.18	0.90	1.56	1.26	1.26
M53	2 341	1.34	1.97	1.28	0.77	1.40	1.25	1.27
M53	2 342	1.19	1.53	1.20	1.00	1.53	1.27	1.25
M53	2 370	0.94	0.85	0.88	1.01	1.39	1.28	1.26
M53	2 389	0.85	0.78	0.96	1.50	1.89	1.29	1.20
M53	2 392	0.77	0.84	1.14	1.13	1.50	1.33	1.17
M53	2 393	0.93	0.84	0.94	1.34	1.77	1.28	1.20
M53	2 397	1.13	0.89	0.80	1.17	1.58	1.19	1.35
M53	2 409	1.17	0.46	0.18	1.13	1.58	1.20	1.38

井号	深度/m	Pr/Ph	Pr/nC₁₇	Ph/nC₁₈	∑nC_21-/∑nC₂₂₊	(nC₂₁+nC₂₂)/(nC₂₈+nC₂₉)	CPI	OEP
M53	2 339	1.19	1.63	1.27	0.86	1.45	1.26	1.27
M53	2 340	1.33	1.77	1.18	0.90	1.56	1.26	1.26
M53	2 341	1.34	1.97	1.28	0.77	1.40	1.25	1.27
M53	2 342	1.19	1.53	1.20	1.00	1.53	1.27	1.25
M53	2 370	0.94	0.85	0.88	1.01	1.39	1.28	1.26
M53	2 389	0.85	0.78	0.96	1.50	1.89	1.29	1.20
M53	2 392	0.77	0.84	1.14	1.13	1.50	1.33	1.17
M53	2 393	0.93	0.84	0.94	1.34	1.77	1.28	1.20
M53	2 397	1.13	0.89	0.80	1.17	1.58	1.19	1.35
M53	2 409	1.17	0.46	0.18	1.13	1.58	1.20	1.38

井号	深度/m	1	2	3	4	5	6	7	8	9	10	11	12	13
M53	2 339	0.45	0.36	0.57	0.66	0.07	0.70	1.16	0.22	0.06	0.17	0.02	0.20	0.47
M53	2 340	0.45	0.35	0.58	0.67	0.08	0.70	0.93	0.26	0.07	0.19	0.02	0.20	0.49
M53	2 341	0.45	0.36	0.57	0.67	0.08	0.72	0.99	0.29	0.07	0.20	0.02	0.20	0.47
M53	2 342	0.44	0.35	0.58	0.68	0.06	0.63	1.07	0.21	0.06	0.16	0.02	0.18	0.47
M53	2 370	0.47	0.36	0.57	0.79	0.07	0.49	1.39	0.27	0.06	0.16	0.02	0.13	0.39
M53	2 389	0.49	0.35	0.58	0.68	0.05	0.62	0.68	0.27	0.06	0.11	0.01	0.12	0.44
M53	2 392	0.48	0.38	0.57	0.72	0.05	0.63	0.78	0.32	0.06	0.13	0.01	0.13	0.42
M53	2 393	0.49	0.37	0.58	0.74	0.05	0.60	0.84	0.40	0.06	0.13	0.02	0.12	0.41
M53	2 397	0.49	0.37	0.58	0.74	0.05	0.51	0.97	0.24	0.07	0.10	0.01	0.12	0.40
M53	2 409	0.52	0.46	0.57	0.75	0.06	0.31	1.13	0.50	0.08	0.15	0.03	0.11	0.44
Z58^*	2 422	0.40	0.58	0.55	0.80	0.09	1.02	1.85	1.21	0.02	0.60	0.07	0.24	0.36
Z37^*	2 240	0.40	0.56	0.55	0.65	0.06	1.00	1.46	2.35	0.02	0.89	0.13	0.18	0.50
M13^*	2 490	0.38	0.60	0.52	0.86	0.10	0.69	0.74	1.32	0.00	0.71	0.09	0.24	0.41
M14^*	2 122	0.39	0.53	0.52	0.74	0.11	0.73	1.19	2.87	0.00	1.34	0.32	0.44	0.47
Y67^*	2 342	0.44	0.58	0.58	0.77	0.14	0.59	2.42	0.97	0.00	0.25	0.07	0.13	0.37
Y65^*	2 334	0.46	0.44	0.58	0.63	0.07	0.93	1.50	0.59	0.04	0.20	0.03	0.18	0.44