鄂尔多斯盆地姬塬地区上三叠统延长组长6油层组沉积环境: 来自地球化学的证据

王腾飞, 金振奎, 楚美娟, 李士祥, 于小霞, 王昕尧, 李硕. (2019)鄂尔多斯盆地姬塬地区上三叠统延长组长6油层组沉积环境: 来自地球化学的证据[J]. 古地理学报, 21(3): 505-516
Wang Teng-Fei, Jin Zhen-Kui, Chu Mei-Juan, Li Shi-Xiang, Yu Xiao-Xia, Wang Xin-Yao, Li Shuo. (2019)Sedimentary environment of the Chang 6 oil￣bearing interval of Upper Triassic Yanchang Formation in Jiyuan area,Ordos Basin: Evidences from geochemical data[J]. Journal Of Palaeogeography, 21(3): 505-516. 复制到剪切板

Doi: 10.7605/gdlxb.2019.03.032
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王腾飞¹, 金振奎¹, 楚美娟^2,³, 李士祥^2,³, 于小霞¹, 王昕尧¹, 李硕¹

1 中国石油大学(北京)地球科学学院,北京 102249

2 中国石油长庆油田公司勘探开发研究院,陕西西安 710018

3 低渗透油气田勘探开发国家工程实验室,陕西西安 710018

通讯作者简介金振奎,男,1963年生,教授,博士生导师,研究方向为沉积学、层序地层学及油气储层预测等。E-mail: jinzhenkui@188.com。

第一作者简介王腾飞,男,1988年生,中国石油大学(北京)博士后,目前从事沉积学研究。E-mail: wang.tf@foxmail.com。

收稿日期:2018-04-01

摘要

姬塬地区位于鄂尔多斯盆地中西部,主要含油层位为上三叠统延长组。延长组长 6油层组是重要的含油层系,其沉积期跨越 2个三级层序,从底至顶又再分为长 6₃、长 6₂、长 6₁共 3个小层。依据元素地球化学资料,对姬塬地区长 6油层组氧化还原环境、古盐度、古水深、古气候进行研究。结果表明,姬塬地区长 6油层组沉积时期处于温暖湿润的气候条件下,整体为低盐度的淡水湖泊沉积;氧化和还原环境共存,还原环境范围逐步减小并有所迁移;湖盆有逐渐缩小和变浅的趋势,后期趋于稳定。长 6₃沉积时期,湖泊范围较大,砂体主要为河口坝和远砂坝沉积,半深湖发育浊积砂体。随着湖平面的下降,长 6₂沉积时期湖盆范围明显缩小,半深湖砂体基本不发育,以河口坝砂体为主。长 6₁沉积时期,湖盆范围相比长 6₂略有缩小,砂体厚度明显增大,在湖盆范围内发育多期河道叠加及河道—河口坝叠加成因的砂体。该研究成果有助于明确该地区的沉积演化规律,对进一步勘探开发提供参考。

关键词: 鄂尔多斯盆地; 姬塬地区; 上三叠统; 延长组; 沉积演化

中图分类号:P595 文献标志码:A 文章编号:1671-1505(2019)03-0505-12

Sedimentary environment of the Chang 6 oil￣bearing interval of Upper Triassic Yanchang Formation in Jiyuan area,Ordos Basin: Evidences from geochemical data

Wang Teng-Fei¹, Jin Zhen-Kui¹, Chu Mei-Juan^2,³, Li Shi-Xiang^2,³, Yu Xiao-Xia¹, Wang Xin-Yao¹, Li Shuo¹

1 College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China

2 Exploration and Development Research Institute of PetroChina Changqing Oil Field Company Ltd., Xi'an 710018,China

3 National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields, Xi'an 710018,China

About the corresponding author: Jin Zhen-Kui,born in 1963,is a professor and Ph.D. supervisor. He is mainly engaged in sedimentology, sequence stratigraphy and reservoir prediction. E-mail: jinzhenkui@188.com.

About the first author: Wang Teng-Fei,born in 1988,is a post-doctoral research assistant at China University of Petroleum(Beijing). Now he is mainly engaged in sedimentology. E-mail: wang.tf@foxmail.com.

Abstract

The Upper Triassic Yangchang Formation is the main oil-bearing strata in Jiyuan area,middle-western Ordos Basin. The Chang 6 oil￣bearing interval is one of the most important oil-bearing horizons,which can be subdivided into 3 layers, i.e., 6₃,6₂,and 6₁ layers in ascending order. The Chang 6 oil-bearing interval spans two three-order sequences. The redox environment,salinity,water depth and paleoclimate are reconstructed based on element geochemical data. In the warm and humid climate,the lake was generally low in paleo salinity. In addition,both oxidizing and reducing conditions co-existed. The reducing environment gradually decreased and migrated. While the water depth tended to decrease and become stable in the latter. In Jiyuan area,the sedimentary characteristics of Chang 6₁,6₂ and 6₃ layers are different. At the beginning of Chang 6,it inherited the sedimentary characteristics of the lacustrine basin in the end of Chang 7 oil-bearing interval. The lake range of Chang 6₃ was large and its sand bodies were mainly composed of the mouth bars and distal bars. Turbidite sand bodies developed in semi-deep lake. Along with the declining lake level,the length of the shoreline of Chang 6₂ was obviously reducing,and the-semi deep lake did not develop. The lake shoreline length of the Chang 6₁ was slightly smaller than that of the Chang 6₂,and the sand body thickness increased dramatically. In the range of the lakeshore line,there were many sand bodies formed by superposition of river channels and mouth bars. The results can help to clarify the sedimentary evolution laws of the Jiyuan area and provide reference for further exploration and development.

Key words: Ordos Basin; Jiyuan area; Upper Triassic; Yangchang Formation; sedimentary evolution

文章图片

1 概述

鄂尔多斯盆地是中国第二大沉积盆地, 面积28× 10⁴km²(图1), 横跨陕、甘、宁、蒙、晋等5省区(郝蜀民, 2001)。上三叠统延长组是鄂尔多斯盆地重要的含油层位(梅志超等, 1988; 姚泾利等, 2013), 自上而下共划分出长1至长10等10个油层组(郑荣才和柳梅青, 1999), 每个油层组又可细分为若干小层。本次研究目的层位为长6油层组, 其从顶到底又可划分为长6₁、长6₂、长6₃共3个小层(图2)。长6油层组是盆地主力勘探目的层之一, 累计探明储量达14.5× 10⁸t, 主要分布在陕北地区和华庆地区。

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	图 2 鄂尔多斯盆地姬塬地区长6油层组层序地层划分(郭彦如等, 2008; 周桂芹, 2012)Fig.2 Sequence stratigraphy division of the Chang 6 oil-bearing interval in Jiyuan area, Ordos Basin (after Guo et al., 2008; Zhou, 2012)

姬塬地区位于鄂尔多斯盆地中西部(图 1), 面积约1.2× 10⁴km²。近年来勘探证实, 该地区长6油层组油藏富集, 勘探潜力巨大, 但其在横向和纵向上的富集程度差异均较大, 分布规律不够明确。前人研究认为, 姬塬地区长6油层组沉积时期存在北东、北西两大物源, 且主要为三角洲相和湖相沉积(郑荣才等, 2008; 公繁浩等, 2010; 王昌勇等, 2010)。然而, 相较于陕北和华庆地区, 姬塬地区长6油层组的研究程度较低, 油藏横向非均质性更强, 因此现有的研究成果远达不到油田勘探开发的相应要求。特别是对于该时期古环境特征和沉积演化规律的认识不足, 影响了该地区的勘探部署, 因此需要加大这方面的研究力度, 为姬塬地区长6油层组油藏的高效勘探提供依据和指导。文中依据元素地球化学分析, 剖析姬塬地区长6油层组沉积特征, 以期明确该地区沉积演化规律, 对进一步勘探开发提供参考。

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	图 1 鄂尔多斯盆地姬塬地区位置(a)及井位分布Fig.1 Location(a)and wells distribution(b)in Jiyuan area, Ordos Basin

2 样品与测试

较细的沉积物更能近似地代表物源区的岩石矿物组成, 并会保留下该时段完整而丰富的地球化学记录(Nesbitt and Young, 1982)。因此, 此次研究采集的样品均来自于姬塬地区24口井的泥岩, 共计30块。

测试前, 先将样品进行清水冲洗、烘干、研磨; 然后, 使用玛瑙球磨机破碎, 保留小于200目的样品; 最后, 将样品分为2份, 分别用于常量元素分析和微量、稀土元素分析。

样品由中核大地公司测试完成。其中, 常量元素分析采用X-射线荧光光谱仪完成, 微量和稀土元素分析使用ICP-MS质谱仪完成。测试步骤参考许中杰等(2010), 具体如下: 将已粉碎样品于105° 烘箱内烘干之后, 称取25mg样品放入高压溶样罐的内罐中, 加入0.5mL氢氟酸于100℃加热蒸干以去除部分Si; 蒸干后加入1mL氢氟酸和0.5mL浓硝酸, 将溶样罐的内罐取出放入钢套中, 旋紧后放入110~120℃的烘箱中加热72h; 然后将溶解样品在100℃蒸干至湿盐状, 加入1mL硝酸, 去除样品中过量的氢氟酸; 再加入5mL浓度为30%的硝酸, 于110℃密封加热4 h, 使样品充分溶解于酸中, 去除残渣; 最后用浓度2%的硝酸溶液稀释到50mL。各标准样品及空白样品所测元素的线性较好, 分析误差小于5%。相同样品的测试结果基本一致。质谱仪测试检出限小于0.5μ g/L。Li、Be、Sc、V、Cr、Co、Ni、Cu、Zn、Ga、Rb、Sr、Mo、Cs、Ba和Pb检测限为0.01~0.2μ g/L; Y、Nb、Hf、Ta和REE检测限为0.001 0.005 μ g/L。各测试样品最终结果取3次测定的平均值, 数据如表 1、表 2、表 3所示。

表 1 鄂尔多斯盆地姬塬地区长6油层组泥岩样品常量元素含量 Table1 Content of main elements of mudstone samples of Chang 6 oil￣bearing interval in Jiyuan area, Ordos Basin%

序号	编号	深度/m	层位	SiO₂	Al₂O₃	Fe₂ ${O_{3}}^{T}$	MgO	CaO	Na₂O	K₂O	P₂O₅	SO₃	MnO	TiO₂	烧失量
1	Y185	2158.8	6₁	58.66	16.30	6.81	3.65	1.22	2.19	3.21	0.20	0.09	0.05	0.73	6.86
2	Y166	2316.9	6₁	57.50	16.66	5.96	3.29	0.82	1.62	4.62	0.21	0.39	0.04	0.64	7.75
3	Y160	2267.5	6₁	57.45	18.54	5.30	3.09	0.84	1.31	3.98	0.21	0.11	0.04	0.58	7.89
4	C83-1	2153.6	6₂	51.10	20.18	8.23	4.26	0.96	1.42	3.52	0.29	0.22	0.05	1.00	8.21
5	C83-2	2153.7	6₂	52.82	23.11	5.90	2.80	0.42	1.24	2.90	0.11	0.03	0.03	0.74	9.21
6	C139-1	2361.0	6₁	56.58	17.76	7.42	3.07	0.59	2.42	3.51	0.17	0.12	0.04	0.77	6.88
7	C139-2	2338.8	6₁	54.76	18.01	6.38	3.89	1.38	1.70	2.92	0.18	0.48	0.05	0.85	8.82
8	C110	2325.7	6₁	54.37	16.12	7.75	3.39	0.95	1.52	4.27	0.41	0.79	0.04	0.77	9.08
9	C169-1	2247.0	6₁	57.10	16.08	8.00	4.09	0.56	2.69	3.73	0.24	0.23	0.05	0.94	6.10
10	C169-2	2281.6	6₂	55.03	18.78	8.22	3.29	0.58	2.17	3.23	0.22	0.54	0.05	0.85	6.40
11	C169-3	2314.0	6₃	57.26	17.63	6.82	3.34	0.56	2.39	3.66	0.21	0.67	0.04	0.77	6.03
12	C76-1	2490.5	6₁	53.43	19.09	5.66	2.73	3.77	0.92	2.57	0.11	0.51	0.05	0.64	9.87
13	C76-2	2481.7	6₁	56.69	18.67	5.84	2.87	0.79	2.33	4.05	0.14	0.14	0.04	0.65	7.10
14	G145	2396.3	6₂	59.00	15.75	6.78	4.18	1.67	2.71	2.65	0.21	0.16	0.06	0.76	6.12
15	A37	1928.1	6₁	45.13	15.84	8.01	3.76	1.55	2.26	3.95	0.57	0.47	0.10	0.71	16.97
16	A44	2171.5	6₂	52.91	19.23	7.22	3.25	0.61	1.53	3.58	0.26	0.43	0.04	0.92	9.33
17	A158	2205.8	6₂	55.69	16.13	6.24	4.16	2.63	1.32	3.43	0.18	0.16	0.08	0.77	8.97
18	H58	2678.6	6₁	57.56	15.89	6.26	2.96	0.89	1.26	3.86	0.17	0.86	0.05	0.71	9.23
19	H89	2498.3	6₂	55.80	16.07	6.40	4.00	2.18	1.47	4.08	0.16	0.30	0.06	0.76	8.35
20	H169	2479.3	6₁	60.76	19.96	—	1.86	0.70	2.95	2.87	0.17	0.24	0.03	0.59	5.11
21	H211	2361.3	6₁	54.06	18.22	6.74	3.01	0.85	0.93	4.21	0.21	0.48	0.09	0.67	9.92
22	H190	2392.6	6₃	57.21	19.51	—	2.69	0.50	2.37	4.02	0.14	0.19	0.03	0.65	7.12
23	L51	2285.5	6₂	59.36	16.31	6.30	2.74	1.05	2.98	3.74	0.19	0.13	0.10	0.64	6.08
24	L17	2608.7	6₃	60.97	16.33	5.78	2.05	1.14	0.53	3.89	0.12	0.39	0.05	0.88	7.61
25	L225-1	2697.8	6₃	53.33	14.96	4.58	4.79	4.00	0.48	4.42	0.14	0.19	0.08	0.75	12.05
26	L225-2	2348.0	6₂	55.54	13.94	5.83	4.10	3.05	0.93	4.02	0.15	0.25	0.09	0.73	11.40
27	Y33	2367.0	6₃	52.92	17.92	6.69	2.97	0.75	1.65	4.07	0.31	0.95	0.03	0.82	10.26
28	Y37	2417.1	6₂	54.73	18.67	8.17	3.35	0.50	2.13	3.07	0.23	0.13	0.04	0.96	7.40
29	H216	2289.2	6₃	59.58	16.42	6.82	3.58	1.09	3.11	3.12	0.28	0.10	0.05	0.82	4.88

注:Fe₂ ${O_{3}}^{T}$ 为全铁含量。

表 2 鄂尔多斯盆地姬塬地区长6油层组泥岩样品微量元素含量 Table2 Content of trace elements of mudstone samples of Chang 6 oil￣bearing interval in Jiyuan area, Ordos Basinμ g/g

序号	编号	Sc	V	Cr	Mn	Cu	Zn	Ga	As	Sr	Zr	Ba	Pb	Rb	Co	Ni	Hf	Ge	Be	Ta	Th	U	Nb	Sn	B	Bi
1	Y185	15.3	117	92.7	388	56.8	114	26.2	1.1	262	124	867	31.8	126	23.0	44.8	3.96	1.85	3.63	1.57	9.74	2.73	17.3	2.24	36.0	0.61
2	Y166	15.1	122	84.4	319	54.8	106	25.9	6.6	227	113	965	34.6	157	20.8	45.2	4.90	1.64	4.09	1.70	13.5	3.07	17.2	3.74	45.2	0.85
3	Y160	15.4	126	75.4	287	51.8	94.1	26.9	2.7	265	106	1007	35.3	184	14.9	33.0	4.64	1.83	3.80	1.33	14.5	3.11	45.8	2.91	54.4	0.91
4	C83-1	20.9	197	135	369	93.9	131	43.1	2.4	245	171	982	35.8	146	20.9	49.3	6.54	2.13	5.78	2.08	16.4	3.90	23.8	3.20	40.0	1.04
5	C83-2	19.0	133	82.4	251	53.9	87.0	31.7	0.5	276	87.5	1311	34.2	127	20.7	38.2	3.74	1.82	5.81	2.23	15.0	4.60	15.3	2.21	25.9	0.57
6	C139-1	16.4	114	84.4	293	45.6	111	27.0	< 0.2	216	120	931	26.0	100	22.4	41.5	3.79	1.82	2.92	2.13	9.59	2.63	15.9	2.90	16.2	0.31
7	C139-2	15.6	141	113	401	51.3	97.7	30.8	4.2	196	186	715	32.9	148	25.7	44.2	5.87	1.60	4.35	2.23	14.9	3.62	20.6	3.67	54.0	0.79
8	C110	16.0	139	93.5	339	54.5	122	25.4	15.1	257	143	943	37.8	129	24.5	49.3	5.48	1.86	3.24	1.43	13.5	3.92	15.2	4.41	39.4	0.74
9	C169-1	16.8	126	102	367	61.8	123	27.6	3.6	266	196	933	29.4	106	23.6	46.8	4.61	1.94	3.63	1.77	12.1	4.01	15.9	3.65	19.7	0.59
10	C169-2	16.8	141	94.6	373	52.1	116	25.2	2.7	275	151	1089	27.6	105	25.4	44.7	3.57	1.71	2.49	1.17	8.63	2.46	14.1	3.26	13.3	0.32
11	C169-3	14.3	120	92.6	313	55.0	100	27.8	5.1	275	159	1073	36.9	120	54.4	72.0	4.85	1.62	3.70	1.88	11.0	3.08	15.8	2.72	23.8	0.47
12	C76-1	15.1	116	94.0	381	37.4	80.0	22.8	4.4	221	189	543	31.9	120	20.6	41.0	7.56	1.57	2.66	2.42	14.0	3.58	17.5	4.06	59.4	0.49
13	C76-2	13.7	119	73.3	299	53.1	110	27.0	0.9	305	102	1097	43.4	123	16.9	35.1	4.23	1.34	2.83	1.12	10.3	3.08	12.8	3.28	42.3	0.64
14	G145	14.1	115	93.2	426	54.9	104	23.5	3.8	270	173	852	30.2	102	23.7	45.0	4.47	1.51	2.77	1.72	10.7	2.94	17.3	2.85	20.2	0.56
15	A37	21.5	157	126	759	104	215	32.0	31.9	316	124	1057	40.9	125	52.8	87.3	4.36	2.42	5.76	1.06	12.0	5.90	27.0	2.95	19.9	0.83
16	A44	19.3	137	98.6	302	57.1	112	30.1	4.9	290	196	1115	30.9	117	28.1	48.8	5.02	1.71	4.94	—	11.8	3.38	—	3.07	20.4	0.47
17	A158	13.4	120	85.0	591	50.1	101	24.1	4.1	305	174	811	30.4	145	19.4	36.9	5.86	1.66	3.73	1.10	16.6	3.80	16.5	3.75	45.5	0.73
18	H58	16.3	120	90.9	401	47.8	93.8	24.0	6.6	164	168	665	29.8	144	17.4	36.8	6.46	1.66	3.20	0.94	14.0	3.76	15.2	3.59	41.7	0.60
19	H89	17.3	124	87.6	495	54.1	102	25.3	4.2	229	148	759	30.9	144	17.9	37.4	5.06	1.62	3.97	1.57	13.7	3.34	12.2	4.16	47.1	0.84
20	H169	10.9	105	71.1	213	37.0	65.9	25.3	3.0	253	142	944	22.4	114	19.2	32.2	3.54	1.26	2.92	1.87	7.46	1.89	13.0	2.03	17.2	0.32
21	H211	18.4	147	93.2	704	47.2	112	26.4	6.8	356	146	991	36.0	163	17.7	40.1	6.26	1.87	3.65	1.79	15.1	3.58	14.1	3.83	55.1	0.75
22	Y176	18.1	128	88.8	284	51.0	105	27.8	0.6	233	131	986	29.4	116	25.4	47.2	3.99	1.58	3.60	2.00	10.1	2.83	14.8	3.06	20.2	0.43
23	H190	14.6	126	72.7	217	48.3	73.9	30.1	1.4	289	103	1088	26.3	139	15.3	33.5	3.57	1.37	4.88	1.47	10.1	3.10	12.9	2.08	30.4	0.50
24	L51	10.6	117	86.7	748	52.8	95.8	23.1	1.4	306	102	1059	29.1	112	20.9	40.9	3.61	1.47	2.49	1.68	8.72	2.28	11.4	3.15	24.4	0.56
25	L17	16.3	143	98.0	355	43.5	78.8	23.1	4.1	147	251	598	30.1	162	18.8	44.2	9.37	1.61	3.09	1.56	19.8	4.90	19.6	4.25	84.9	0.61
26	L225-1	15.5	130	91.3	595	42.7	75.1	22.7	2.4	140	160	643	32.5	174	16.8	38.0	6.64	1.54	2.89	0.65	18.6	3.69	17.8	4.30	66.4	0.56
27	L225-2	17.4	151	96.3	710	44.2	93.6	21.6	5.5	163	187	732	32.3	139	36.2	76.2	6.84	1.56	2.92	1.75	16.1	4.20	15.0	3.82	53.1	0.50
28	Y33	17.6	156	98.4	263	64.2	108	28.4	11.1	239	145	1095	33.3	110	25.9	56.7	5.09	1.94	5.05	1.28	11.5	4.16	16.6	2.66	19.1	0.61
29	Y37	21.4	140	103	317	47.3	107	29.4	1.8	193	226	908	24.1	99.0	25.6	43.0	4.28	1.88	2.94	1.71	9.81	2.58	15.4	3.56	14.7	0.26
30	H216	1127	110	79.9	377	44.0	105	23.6	3.8	311	256	892	26.9	111	18.7	38.0	5.93	1.74	2.62	2.01	14.4	4.55	15.8	3.57	19.6	0.42

表 3 鄂尔多斯盆地姬塬地区长6油层组泥岩样品稀土元素含量 Table3 Content of rare earth elements of mudstone samples of Chang 6 oil￣bearing interval in Jiyuan area, Ordos Basinμ g/g

序号	编号	深度/m	层位	Y	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu
1	Y185	2158.8	长6₁	25.5	50.7	101	11.2	39.2	6.58	1.81	6.27	0.82	3.88	0.93	2.45	0.40	2.63	0.36
2	Y166	2316.9	长6₁	26.8	49.0	97.4	10.7	37.6	6.76	1.80	6.10	0.88	4.10	0.90	2.33	0.39	2.38	0.39
3	Y160	2267.5	长6₁	22.0	50.8	89.0	9.62	32.7	5.72	1.59	5.07	0.76	3.36	0.72	2.05	0.31	2.21	0.36
4	C83-1	2153.6	长6₂	32.6	66.2	129	13.7	48.7	8.57	2.25	7.84	1.06	4.98	1.15	2.90	0.47	3.36	0.52
5	C83-2	2153.7	长6₂	22.0	65.0	120	12.8	41.2	7.09	1.93	5.98	0.86	3.35	0.74	2.03	0.29	1.94	0.27
6	C139-1	2361.0	长6₁	24.1	51.0	107	11.7	40.6	7.43	1.85	6.17	0.86	3.84	0.80	2.32	0.40	2.59	0.37
7	C139-2	2338.8	长6₁	23.8	60.4	112	11.7	40.7	6.92	1.64	5.74	0.78	3.42	0.80	2.31	0.37	2.22	0.43
8	C110	2325.7	长6₁	40.3	59.2	122	13.8	51.1	9.46	2.56	8.68	1.31	5.78	1.29	3.22	0.50	3.11	0.49
9	C169-1	2247.0	长6₁	27.5	62.5	127	13.9	49.2	8.35	2.03	7.12	1.00	4.73	1.05	2.59	0.38	2.64	0.40
10	C169-2	2281.6	长6₂	30.0	61.9	121	13.6	48.0	8.39	2.20	7.60	0.98	4.82	0.98	2.79	0.40	2.50	0.41
11	C169-3	2314.0	长6₃	28.0	66.4	127	13.7	47.2	7.99	2.14	7.08	0.97	4.08	0.96	2.40	0.40	2.80	0.42
12	C76-1	2490.5	长6₁	29.5	48.7	95.6	10.3	36.3	6.87	1.44	6.04	0.91	4.47	0.98	2.47	0.47	2.69	0.40
13	C76-2	2481.7	长6₁	19.5	44.1	86.0	8.98	30.1	5.22	1.56	4.57	0.61	3.11	0.68	1.70	0.30	2.12	0.29
14	G145	2396.3	长6₂	27.6	51.7	103	11.3	40.9	7.76	1.77	6.36	0.86	4.22	0.86	2.32	0.38	2.54	0.39
15	A37	1928.1	长6₁	97.5	81.5	184	21.8	85.0	19.9	5.13	17.2	3.08	14.9	3.30	7.46	1.14	6.65	0.99
16	A44	2171.5	长6₂	25.8	59.6	118	13.0	44.0	7.27	2.26	6.60	0.91	3.81	0.89	2.26	0.39	2.28	0.42
17	A158	2205.8	长6₂	30.7	59.3	118	12.9	44.1	7.65	1.90	7.16	1.05	4.86	1.01	2.77	0.43	2.74	0.42
18	H58	2678.6	长6₁	52.6	90.6	179	19.4	67.8	11.7	3.00	11.2	1.72	8.27	1.93	4.66	0.75	4.95	0.78
19	H89	2498.3	长6₂	31.8	55.1	108	12.4	42.5	7.73	1.89	7.00	1.05	4.74	0.98	2.85	0.44	2.91	0.46
20	H169	2479.3	长6₁	16.0	48.8	90.7	9.69	32.1	5.09	1.80	4.65	0.67	2.31	0.64	1.40	0.23	1.43	0.20
21	H211	2361.3	长6₁	34.7	62.2	122	13.0	47.1	8.15	1.90	7.49	1.10	5.06	1.17	2.89	0.54	3.27	0.50
22	Y176	2392.6	长6₃	24.6	55.2	107	11.8	39.8	6.83	1.78	5.64	0.87	3.81	0.85	2.29	0.40	2.49	0.42
23	H190	2285.5	长6₂	18.9	64.2	125	12.8	43.1	6.37	1.85	6.00	0.72	2.76	0.67	1.92	0.32	2.23	0.34
24	L51	2608.7	长6₃	22.4	43.4	83.5	9.09	32.5	5.90	1.63	4.52	0.69	3.48	0.79	2.04	0.29	2.23	0.27
25	L17	2697.8	长6₃	36.8	61.4	120	13.0	45.4	7.91	1.66	6.68	1.03	5.46	1.24	3.40	0.56	3.50	0.51
26	L225-1	2348.0	长6₂	31.7	56.7	113	12.7	43.1	7.36	1.62	6.09	0.98	4.62	1.08	2.67	0.46	2.80	0.41
27	L225-2	2367.0	长6₃	32.3	52.8	105	11.4	40.0	6.80	1.60	6.37	0.93	4.69	1.13	3.00	0.53	3.19	0.50
28	Y33	2417.1	长6₂	36.8	55.1	114	12.8	46.0	8.29	2.31	6.75	1.04	5.05	1.12	2.94	0.46	3.15	0.50
29	Y37	2289.2	长6₃	26.7	78.1	159	17.4	61.6	9.92	2.30	8.48	1.10	4.31	0.99	2.54	0.44	2.59	0.42
30	H216	2101.5	长6₂	26.2	63.6	128	13.5	48.3	8.69	2.12	6.86	1.00	4.13	0.88	2.40	0.38	2.34	0.38

3 沉积环境特征

3.1 湖泊古盐度

3.1.1 Ca/Mg值

水体中的Ca、Mg元素以钙盐和镁盐的形式存在, 二者溶解度不同, 通常镁盐较钙盐更难沉淀。Ca的沉淀受介质酸碱性影响更为明显。Ca/Mg值变大, 反映古水体盐度增加、pH值升高、Eh值降低、深度加大或沉积物搬运距离增大(Benway et al., 2006; Rohling, 2007)。研究区Ca/Mg平均值从长6₃到长6₁分别为0.37、0.35、0.37, 反映了水体古盐度和pH值先降低后升高的过程(表 4)。

表 4 鄂尔多斯盆地姬塬地区长6油层组泥岩样品主量元素、微量元素、稀土元素比值和古水深计算结果 Table4 Element ratio of main elements, trace elements and rare earth elements, and paleowater depths of mudstone samples of Chang 6 oil￣bearing interval in Jiyuan area, Ordos Basin

序号	编号	层位	Ca/Mg	Sr/Ba	V/Ni	Rb/K	La_N	Ce_N	Pr_N	δ Ce	Sr/Cu	Fe/Mn	CIA^*	水深/m
1	Y185	长6₁	0.33	0.30	2.61	0.0039	153.6	124.7	101.8	1.00	4.60	136.2	71.12	19
2	Y166	长6₁	0.25	0.24	2.70	0.0034	148.5	120.2	97.3	1.00	4.15	149.0	70.24	16
3	Y160	长6₁	0.27	0.26	3.82	0.0046	153.9	109.9	87.5	0.95	5.12	132.5	75.15	7
4	C83-1	长6₂	0.23	0.25	3.99	0.0041	200.6	159.5	124.5	1.01	2.61	164.6	77.38	13
5	C83-2	长6₂	0.15	0.21	3.48	0.0044	197.0	148.1	116.4	0.98	5.13	196.7	83.52	13
6	C139-1	长6₁	0.19	0.23	2.74	0.0028	154.5	132.1	106.4	1.03	4.75	185.5	73.15	18
7	C139-2	长6₁	0.35	0.27	3.19	0.0051	183.0	138.3	106.4	0.99	3.83	127.6	75.01	22
8	C110	长6₁	0.28	0.27	2.81	0.0030	179.4	150.6	125.5	1.00	4.71	193.8	70.52	20
9	C169-1	长6₁	0.14	0.29	2.69	0.0028	189.4	156.8	126.4	1.01	4.31	160.0	69.73	18
10	C169-2	长6₂	0.18	0.25	3.15	0.0033	187.6	149.4	123.6	0.98	5.27	164.4	75.85	21
11	C169-3	长6₃	0.17	0.26	1.67	0.0033	201.2	156.8	124.5	0.99	5.00	170.5	72.73	86
12	C76-1	长6₁	1.38	0.41	2.82	0.0046	147.6	118.0	93.6	1.00	5.92	113.2	72.45	15
13	C76-2	长6₁	0.28	0.28	3.40	0.0030	133.6	106.2	81.6	1.02	5.75	146.0	72.25	11
14	G145	长6₂	0.40	0.32	2.56	0.0038	156.7	127.2	102.7	1.00	4.91	113.0	69.14	20
15	A37	长6₁	0.41	0.30	1.80	0.0032	247.0	227.2	198.2	1.03	3.04	80.1	67.12	77
16	A44	长6₂	0.19	0.26	2.81	0.0033	180.6	145.7	118.2	1.00	5.08	180.5	77.07	26
17	A158	长6₂	0.63	0.38	3.25	0.0042	179.7	145.7	117.3	1.00	6.09	78.0	68.61	12
18	H58	长6₁	0.30	0.25	3.26	0.0037	274.5	221.0	176.4	1.00	3.44	125.2	72.56	5
19	H89	长6₂	0.55	0.30	3.30	0.0035	167.0	133.3	112.7	0.97	4.23	106.7	67.52	10
20	H169	长6₁	0.38	0.27	3.26	0.0040	147.9	112.0	88.1	0.98	6.84	—	75.38	13
21	H211	长6₁	0.28	0.36	3.66	0.0039	188.5	150.6	118.2	1.01	7.54	74.9	75.26	9
22	Y176	长6₃	—	0.24	2.71	—	167.3	132.1	107.3	0.99	4.57	—	—	22
23	H190	长6₂	0.19	0.27	3.76	0.0035	194.5	154.3	116.4	1.03	5.99	—	73.90	6
24	L51	长6₃	0.38	0.29	2.87	0.0030	131.5	103.1	82.6	0.99	5.79	63.0	67.73	17
25	L17	长6₃	0.56	0.25	3.24	0.0042	186.1	148.1	118.2	1.00	3.38	115.6	74.60	11
26	L255-1	长6₂	0.84	0.22	3.41	0.0039	171.8	139.5	115.5	0.99	3.28	57.3	62.70	9
27	L255-2	长6₃	0.74	0.22	1.98	0.0035	160.0	129.6	103.6	1.01	3.68	64.8	63.54	45
28	Y33	长6₂	0.25	0.22	2.75	0.0027	167.0	140.7	116.4	1.01	3.72	223.0	73.47	23
29	Y37	长6₃	0.15	0.21	3.25	0.0032	236.7	196.8	158.2	1.02	4.07	204.3	76.61	18
30	H216	长6₂	0.30	0.35	2.88	0.0036	192.7	158.0	122.7	1.03	7.08	136.4	69.17	10

* CIA= $[(A L_{2} O_{3}) / (A L_{2} O_{3} + Ca O^{*} + N a_{2} O + K_{2} O)]$ × 100, 其中CaO^*为硅酸盐矿物中的CaO成分(Nesbitt and Young, 1982)。

3.1.2 Sr/Ba值

Sr和Ba的化学性质比较相似, 前者的迁移能力强, 当淡水与咸化湖水混合时, 淡水中的Ba²⁺与咸化湖水(海水)中的S $O_{4}^{2 -}$ 结合生成BaSO₄沉淀, 而Sr²⁺继续迁移到盐湖中央(远海), 通过生物作用生成溶解度较大的SrSO₄沉淀, 因此Sr/Ba值可定性地反映古盐度。高值(> 1)反映高盐度或炎热干旱气候, 低值(< 1)指示低盐度或温暖潮湿气候(王益友等, 1979; Zhang et al., 2014)。姬塬地区长6油层组沉积时期Sr/Ba值主要为0.2~0.5, 属于低盐度环境, 气候相对温暖潮湿。

3.1.3 V/Ni值

随着盐度增高、还原程度增强, V的聚集作用十分明显。V/Ni值越高, 则盐度越大(许中杰等, 2017; Liang et al., 2017)。姬塬地区V/Ni值较低, 基本处于1~4之间, 显示本区盐度较低, 是低盐度和低还原程度的淡水湖泊环境。

3.1.4 Rb/K值

K含量与泥岩中的黏土矿物有关, 特别是与伊利石关系密切。而Rb大部分呈悬浮胶体状态搬运, 在碱性还原条件下, Rb的胶体状因凝絮效应沉淀而易被黏土和有机质吸附, 故水体的含盐度越高, 黏土和有机质对 Rb 的吸附越强, Rb的含量和Rb/K值亦越高, 因此, Rb的含量和 Rb/K值能反映水介质的盐度变化。一般海相Rb/K值大于0.006, 微咸水Rb/K值大于0.004(李进龙和陈东敬, 2003; 文华国等, 2008)。姬塬地区长6油层组Rb的丰度平均值为131μ g/L, Rb/K平均值为0.0036, 亦表明该区为低盐度的淡水湖泊环境。

综上所述, 长6油层组沉积时期整个姬塬地区处于低盐度的淡水湖泊沉积环境。

3.2 氧化还原环境

稀土元素因具特有的地球化学行为且对沉积环境变化十分敏感而被广泛应用于古环境研究。通常, δ Ce> 1为正异常, 指示还原环境; δ Ce< 0.95为负异常, 指示氧化环境(王中刚等, 1989)。姬塬地区长6油层组氧化和还原环境共存。将δ Ce> 1的取样点用灰色于图 3中圈出, 可发现整个研究区中部区域基本为还原环境, 但也具有一定的变化: 从长6₃到长6₂沉积时期, 还原环境范围有所缩小, 且迁移到姬塬以东地区。到了长6₃沉积时期, 还原环境范围进一步缩小, 并向南偏移。

	Figure Option View Download New Window
	图 3 鄂尔多斯盆地姬塬地区长6油层组Ce异常等值线图 a— 长6₃油层; b— 长6₂油层; c— 长6₁油层Fig.3 Ce anomaly contour map of Chang 6 oil￣bearing interval in Jiyuan area, Ordos Basin

3.3 古水深

碎屑岩中Co的来源主要有宇宙沉降和陆源输入, 宇宙沉降每年以8.262× 10⁸t的恒定速率降落于地表, 陆源输入单位体积中的Co含量是宇宙沉降的1/4, 所以陆源物质的加入对宇宙沉降Co含量会产生“ 稀释效应” , 因此Co的含量可以反映其当时的沉积速率, 即Co含量愈高反映其沉积速率愈慢, 反之愈快。因而, 可通过沉积岩中Co的含量来推测当时岩石的沉积速率, 而水深与沉积速率存在一定关系, 也可以进一步推算古水深, 计算公式如下:

V_S=V_O× N_Co/(S_Co-t× T_Co)

H=3.05× 10⁵/( ${V_{S}}^{1.5}$ )

其中, Vs代表某样品沉积时的沉积速率; Vo代表当时正常大洋沉积速率(0.15~0.3mm/a), 本次研究取值0.25mm/a; N_Co代表正常大洋沉积物中Co的丰度(20μ g/g); S_Co代表样品中Co的丰度; t为样品中La含量/陆源碎屑中La平均丰度(La/38.99); T_Co代表陆源碎屑中Co的丰度(4.68μ g/g)(吴智平和周瑶琪, 2000; 张才利等, 2011; 庞军刚等, 2012)。

笔者通过微量元素Co含量, 分小层开展长6油层组古水深定量计算, 结果列于表 4。其中, 长6₃油层沉积时期水体最深, 集中于10~30m, 汇水区位于研究区西南部, 湖盆底型较陡; 长6₂油层沉积时期水体变浅, 范围缩小, 主要为10~20m, 汇水区位于研究区中部; 长6₁油层沉积时期水体范围变化不大, 相对深水区范围明显变小, 湖盆底型明显变缓, 汇水区向研究区东南迁移(图 4)。

	Figure Option View Download New Window
	图 4 鄂尔多斯盆地姬塬地区长6油层组古水深等值线图 a— 长6₃油层; b— 长6₂油层; c— 长6₁油层Fig.4 Paleowater depth contour map of Chang 6 oil￣bearing interval in Jiyuan area, Ordos Basin

3.4 古气候特征

3.4.1 Sr/Cu值

通常, Sr/Cu值介于1.2~5.0之间指示温湿气候, 而大于5.0则指示干热气候(王随继等, 1997)。姬塬地区长6油层组的Sr/Cu值介于2.61~7.54之间, 平均值为4.79, 为温湿气候的表现。

3.4.2 Fe/Mn值

湖水中Mn常以Mn²⁺形式稳定存在, 但当湖水强烈蒸发时, Mn²⁺的浓度饱和, 大量沉淀, 从而在岩石中显示高值。Fe在湖水中易以Fe(OH)₃胶体快速沉淀, 因而沉积物中Fe/Mn值高值对应温湿气候, 低值是干热气候的响应(王随继等, 1997)。姬塬地区长6油层组中Fe/Mn值最小为57.3, 最大为223.0, 平均为134.5。Fe/Mn值整体较高, 是长6沉积期姬塬地区温湿气候的表现。

3.4.3 化学蚀变指数

沉积物的风化强度指标可用不稳定的元素氧化物(Na₂O、CaO、MgO、K₂O)和相对稳定元素氧化物(Al₂O₃、ZrO₂、TiO₂)确定, 沉积物源区岩石的化学风化程度, 可以通过化学指数, 即化学蚀变指数(CIA)进行定量研究。CIA=[(Al₂O₃)/(Al₂O₃+CaO^*+Na₂O+K₂O)]× 100, 其中CaO^*为硅酸盐矿物中的CaO成分(Nesbitt and Young, 1982)。化学蚀变指数在研究沉积岩的物源和判断沉积岩化学风化或蚀变程度上应用广泛(Fedo et al., 1997)。通常CIA介于50~100之间, 50代表未经化学风化岩石, 100代表完全化学风化的岩石。经过风化搬运后沉积物的不同CIA值, 是对当时气候条件的记录。CIA值介于80~100之间表示是在炎热的热带气候条件的沉积产物, 介于70~80之间表示是温暖湿润气候条件下的产物, 而介于60~70之间是寒冷干燥气候条件下形成的冰碛岩和冰碛黏土。姬塬地区长6油层组CIA值介于62.70~83.52之间, 平均值为72.03, 且由下至上没有明显的变化, 显示多处于温暖湿润气候下。

综上所述, 长6油层组沉积时期姬塬地区为温暖湿润气候。

4 沉积特征及其演化

4.1 沉积特征

长6₃油层呈现明显的反旋回, 自下而上粒度为粉细砂岩至细砂岩, 沉积构造为平行/交错层理— 块状层理, 主要发育河口坝和远砂坝沉积微相。自然电位和自然伽马曲线呈漏斗型, 单层砂体厚度一般在5~10m之间(图 5)。

	Figure Option View Download New Window
	图 5 鄂尔多斯盆地姬塬地区长6油层组岩心特征 a— H169井, 2485.3m, 长6₂, 波状层理; b— H216井, 2198.6m, 长6₂, 块状构造细砂岩; c— L17井, 2687.4m, 长6₃, 交错层理; d— C139井, 2455.5m, 长6₁, 块状构造; e— H58井, 1670.8m, 长6₁, 平行层理Fig.5 Core characteristics of Chang 6 oil￣bearing interval in Jiyuan area, Ordos Basin

长6₂油层以粉细砂岩— 细砂岩为主, 沉积特征呈现明显的反旋回, 自下而上依次发育波状层理— 细平行层理— 大平行层理— 块状层理, 自然电位和自然伽马曲线呈明显的反旋回, 单层砂体厚度一般为10m左右。砂体以河口坝沉积微相为主, 局部发育水下分流河道微相。

长6₁油层砂体岩性以块状、平行层理细砂岩为主, 泥岩为深灰色、灰黑色, 以水下分流河道微相为主, 测井曲线表现为呈锯齿状的钟型和箱型, 多为多期水下分流河道的叠加, 叠加厚度多为10~30m。中部多发育河口坝微相, 反旋回沉积序列明显。

4.2 沉积演化

姬塬地区长6沉积时期处于温暖湿润的气候条件下, 总体为低盐度的湖泊环境。氧化和还原环境共存, 还原环境逐步减小并有所迁移。笔者仅对姬塬的岩相古地理相关图件进行简单展示(图 6), 具体内容将另文发表。

	Figure Option View Download New Window
	图 6 鄂尔多斯盆地姬塬地区长6油层组沉积相 a— 长6₃油层; b— 长6₂油层; c— 长6₁油层Fig.6 Sedimentary facies of Chang 6 oil￣bearing interval in Jiyuan area, Ordos Basin

在长6油层组沉积早期, 继承长7油层组沉积末期的湖盆沉积特征, 长6₃油层沉积时期湖泊范围较大, 湖岸线分布在大水坑— 古峰庄— 定边— 安边一带, 在南部的樊学— 乔川一带发育半深湖沉积, 砂体主要为河口坝和远砂坝微相沉积, 半深湖发育浊积砂体。

随着湖平面的下降, 长6₂油层沉积时期湖盆范围比长6₁明显缩小至麻黄山— 白儿庄— 杨井一带, 半深湖基本不发育, 仅在乔川一带出现, 砂体主要为河口坝沉积微相。

与长6₂油层沉积时期相比, 长6₁油层沉积时期湖盆范围略有缩小, 且向北东偏移, 位于耿湾— 史家湾— 波罗池— 安边一带, 砂体厚度明显增大, 在湖盆范围内发育多期河道叠加及河道— 河口坝叠加成因的砂体。

这些变化特征与前文中以地球化学数据得到的相关结论是一致的。

5 结论

1) 利用Ca/Mg值、Sr/Ba值、V/Ni值、Rb/K值对鄂尔多斯盆地姬塬地区长6油层组古盐度特征进行了定量判定, 利用Sr/Cu值、Fe/Mn值和化学蚀变指数(CIA)对姬塬长6油层组沉积时期古气候特征进行了定量判定。结果表明, 姬塬地区长6油层组沉积时期整体为低盐度的淡水湖泊环境和温暖湿润气候。

2)利用铈异常(δ Ce)对姬塬地区长6油层组古氧化还原环境进行了定量判定。姬塬地区长6油层组沉积时期氧化和还原环境共存, 从长6₃到长6₁还原环境范围逐渐缩小, 且由西向东偏移。

3)利用Co含量变化对姬塬地区长6油层组沉积时期古水深进行了定量判定, 同时利用传统的岩相古地理成图方法, 对整个长6油层组的沉积演化特征进行了分析。姬塬长6油层组总体为三角洲相和湖相沉积, 具有岸线后退的趋势, 且半深湖范围逐渐缩小。

致谢感谢吉林大学许中杰副教授、杨浩博士在成文过程中给予的指导和帮助!感谢审稿专家给出的建设性意见!

作者声明没有竞争性利益冲突.

参考文献

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2010

0.0

公繁浩, 鲍志东, 刘丽, 伍星. 2010. 鄂尔多斯盆地姬塬地区长6油层组沉积微相特征. 世界地质, 29(4): 614-621.

[Gong F

, Bao Z

, Liu

, Wu

. 2010. Sedimentary microfacies characters of Chang 6 oil-bearing formation in Jiyuan area of Erdos Basin. Global Geology, 29(4): 614-621]

Utilizing core logging，grain size analysis and thin section analysis，the authors identified front delta as the major sub-facies type of Chang 6 oil-bearing formation，including the microfacies of subaqueous distributary channel，river mouth bar，subaqueous interdistributary bay，subaqueous crevasse splay，and subaqueous natural levee． The planar distribution regulation of each layer and the control action of sedimentary microfacies to reservoirs have been analyzed，which show that the high quality reservoirs of Chang 6 oil-bearing formation were mainly hosted in subaqueous distributary channel sand and combination sand between subaqueous distributary channel and mouth bar． In general，the high quality reservoirs of Chang 621 ，Chang 612 and Chang 622 were wider distributed with better continuity in plane and superimposition in vertical，which are the target layers for the next work．

1． College of Earth Sciences，China University of Petroleum，Beijing 102249，China; 2． State Key Laboratory of Petroleum Resources and Prospecting，China Unviersity of Petroleum，Beijing 102249，China

利用岩心测井、粒度分析和薄片鉴定等资料综合分析，揭示出研究区长6 油层组以三角洲前缘亚相沉积为主，可细分为水下分流河道、河口坝、水下分流间湾、水下决口扇和水下天然堤5 个沉积微相，并分析了各小层沉积微相的平面展布规律和沉积微相对储层的控制作用。结果表明，长6 油层组的优质储集体主要赋存于水下分流河道砂体及水下分流河道与河口坝组合砂体中，总体上长621 、长 612 和长622 期优质储层展布范围较广，平面上连片分布，垂向上相互叠置，是下一步工作的主要目标层位。

... 公繁浩等,2010 ...

2008

0.0

郭彦如, 刘化清, 李相博, 完颜容, 郑希民. 2008. 大型坳陷湖盆层序地层格架的研究方法体系: 以鄂尔多斯盆地中生界延长组为例. 沉积学报, 26(3): 384-391.

[Guo Y

, Liu H

, Li X

, Wanyan

, Zheng X

. 2008. Method system on studying sequence stratigraphic framework of large sagged lacustrine basin: A case study from Mesozoic Yanchang Formation, Ordos Basin. Acta Sedimentologica Sinica, 26(3): 384-391]

Abstract The study about sequence stratigraphy in big sagged lacustrine basin have made a quiet great progress, but the study about sequence stratigraphy in Ordos big sagged lacustrine basin have made less progress. The reasons as follow: the trait of seismic data on Loess Plateau is bad; the logging data may be interpreted variedly; contrast in isochronous is difficult; and right method system has not been found. In this paper, authors put forward a new method system of studying sequence stratigraphic framework of big sagged lacustrine basin which include six parts: establishing standard from outcrop profiles, confirming grade of sequence from wavelet analysis, ascertaining sequence cycles from lake level changes, affirming mode from borehole logs, notarizing framework from seismic interpretation, and proposing scheme from the integration of outcrop profiles, borehole logs and seismic interpreted profiles. This method system has been applied to the projects about petroleum prospecting of Ordos Mesozoic Basin. Finally, we have established the sequence stratigraphic framework which adapts to divide and contrast stratigraphy in Ordos Mesozoic basin.

Ordos Branch, Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083

摘要大型坳陷湖盆层序地层学研究有很大进展，但鄂尔多斯大型湖盆层序地层研究进展缓慢，主要原因是黄土塬地震资料品质差，钻井资料多解性强，横向等时对比困难，尚未找到合适的研究方法体系。本文通过三年攻关研究，总结出适于这种湖盆层序地层格架建立的方法体系，笔者称之为“六定”方法体系：“露头剖面定标准、小波变换定级次、湖平面变化定旋回、测井曲线定样式、地震解释定格架、三者结合定方案”。通过“六定”方法体系的系统应用，建立了可以在全盆地范围内进行地层划分与对比的三级层序地层格架。

2001

0.0

... 10⁴km²(图1),横跨陕、甘、宁、蒙、晋等5省区(郝蜀民,2001) ...

2003

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... 004(李进龙和陈东敬,2003 ...

1988

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梅志超, 彭荣华, 杨华, 刘国江, 曾少华. 1988. 陕北上三叠统延长组含油砂体的沉积环境. 石油与天然气地质, 9(3): 261-267.

[Mei Z

, Peng R

, Yang

, Liu G

, Zeng S

. 1988. Sedimentary environment of the oil-bearing sand bodies in the upper Triassic Yanchang formation of northern Shaanxi. Oil and Gas Geology, 9(3): 261-267]

Oil-bearing sandbodies in the upper Triassic Yanchang Formation of north Shaanxi are mainly channel deposits related to lacustrine delta. The delta was builted by the river which discharged into a large freshlake. At that time, north Shaanxi was located on a vast shallow platform of the north flank of the lake basin, the water depth of which ranges from several metres to more thanten metres. In this setting, the river waters often flowed in by a density underflow, so that it was very difficult to form river-mouth bar. Even though thin progradational facies could be formed, it would have been scoured intensely by advancing river waters. As a consequence,channel sandbodies are commonlyin contact with lacustrine mudstone by scouring. The platform deltas are characterized by widespread banded sandbodies, the distribution map of which mainly reflects fluvial and distributary channel de-posits. These channel sandbodies are subdivided into three types according totheir sedimentary characters: sand-rich low-sinuosity channel, mud-rich low-sinuosity channel and mixed load meandering channel deposits, in which the mixed load meandering channel deposits occurred in upper delta plain are the most important reservoirs.

1. Geological Department of Northwest University; 2. Research Institute of Changqing Oilfield

陕北上三叠统延长组的含油砂体主要是与湖泊三角洲相关的河道沉积。本区的三角洲是河流注入到克拉通盆地的大型淡水湖泊中建造的。当时的陕北位于湖盆北翼的浅水台地。因此,三角洲前缘河口坝沉积不发育,且多为后继的河水强烈冲刷,以致河道砂体常常与浅湖泥岩直接呈冲刷接触。因此,河道砂体是该区的主要储集层,其中发育在上三角洲平原的曲流河道砂体是最有利的储集相带。

... 上三叠统延长组是鄂尔多斯盆地重要的含油层位(梅志超等,1988 ...

2012

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... 庞军刚等,2012) ...

2010

0.0

... 王昌勇等,2010) ...

1997

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... 0则指示干热气候(王随继等,1997) ...

... Fe在湖水中易以Fe(OH)₃胶体快速沉淀,因而沉积物中Fe/Mn值高值对应温湿气候,低值是干热气候的响应(王随继等,1997) ...

1979

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... 1)指示低盐度或温暖潮湿气候(王益友等,1979 ...

1989

0.0

... 95为负异常,指示氧化环境(王中刚等,1989) ...

2008

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... 文华国等,2008) ...

2000

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吴智平, 周瑶琪. 2000. 一种计算沉积速率的新方法: 宇宙尘埃特征元素法. 沉积学报, 18(3): 395-399.

[Wu Z

, Zhou Y

. 2000. Using the characteristic elements from meteoritic must in strata to calculate sedimentation rate. Acta Sedmentologica Sinca, 18(3): 395-399]

In the study of sedimentology,one of the most fundamental quantities that geoscientists seek to measure is the sedimentation rate,and it is crucial to a complete understanding of depositional process. The meteoritic dust is a kind of extraterestrial material with high abundance of iridium and cobalt.Most people think that the deposition quantity of meteoritic dust per year is almost constant on earth surface,and the average abundance of some characteristic elements such as Ir and Co in meteoritic dust are fixed,so there is a correlation between sedimentation rate and Ir (or Co) concentration.The abundance of Ir (or Co) in the sedimentary sample with low sedimentation rate is higher than in the sample with high sedimentation rate.According to this,the abundance of the element Ir or Co in sediment can be used to measure the deposition rate as a dating tool.Based on the previous work,the theory and method of using characteristic element from meteoritic dust ot calculate sediment rate have been suggested,and the formulae can be pariticularly expressed as follows: V s= V (Co)/｛ ρ ×[ A (Co)- w (Co)× A ”(Co)] ｝ where V s is the sedimentation rate of the sample which we want to calculate, V (Co) is the deposition rate of Co from meteoritic dust (6.48×10 -7 g/cm 2a), ρ is the density of the sample, A (Co) is the total abundance of Co in the sample, A ”(Co) is the abundance of Co in the source rock and w (Co) is contribution coefficient of Co from the terrigenious sources. Using this method,the sedimentation rates of the Eogene-Neogene section in Linqu County of Shandong Province has been measured as a case in this paper. Comparing with common methods,the method of using characteristic element from meteoritic dust to calculate sedimentation rate is more practical and accurate.

Department of Resources Science,University of Petroleum,Dongying Shandong 257062

地球每时每刻都在接受宇宙尘埃的沉降,且其年沉降量相对稳定,加之宇宙尘埃中的Ir、Co等特征元素的平均含量较恒定,因此沉积物中宇宙尘埃特征元素Ir、Co的丰度值能够体现出沉积物的沉积速率。当沉积速率较慢时,沉积物中宇宙尘埃特征元素的丰度值较大,反之,则较小。本文在前人工作的基础上,对利用宇宙尘埃特征元素计算沉积速率的方法和原理进行了探讨,并运用该方法对山东临朐N/E界线地层的沉积速率进行了实例研究。与传统方法相比,依据宇宙尘埃特征元素在地层中的分布特征计算沉积速率具有更好的实用性和准确性。

... g/g)(吴智平和周瑶琪,2000 ...

2010

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许中杰, 程日辉, 王嘹亮, 张莉, 李飞. 2010. 广东东莞地区中侏罗统塘厦组凝灰质沉积物的元素地球化学特征及构造背景. 岩石学报, 26(1): 352-360.

[Xu Z

, Cheng R

, Wang L

, Zhang

, Li

. 2010. Elemental geochemical characteristics of tuffaceous sediments and tectonic setting of Tangxia formations of middle Jurassic in Dongguan, Guangdong Province. Acta Petrologica Sinica, 26(1): 352-360]

The Tangxia Formation of Middle Jurassic in Dongguan, Guangdong Province, is a kind of lacustrine sediments in rich of tuffaceous materials. The changes of Sr/Ba, B/Ga and Ca/Mg have a positive correlation with the changes of paleosalinity. The result of the ratios is based on the whole rock analysis and ICP-MS trace element analysis of the samples. The characteristics of those shows that sediments of Tangxia Formation ares salty lacustrine sediments. The paleosalinity of Tangxia Formation descends gradually from bottom to top, and the lake depth reduces as well. The value of δ Ce and the ratio of (La/Yb) N to the samples are got through the ICP-MS trace element analysis. The value of δ Ce is between 0.81 and 1.31.The ratio of (La/Yb) N is obvious larger than 1 or smaller than 1.The value of δ Ce and (La/Yb) N reflects that the depositional rate of lake sediments was slower during the main stage of development of Tangxia Formation except the initial and final stages with a relatively faster rate. The values of P and Sr/Cu reflect their enrichment and migration, controlled by the climate. The average of P is 0.205×10 -2 and the average of Sr/Cu which achieved lowest value 1.42×10 -6 in middle and late stages is larger than 4.0×10 -6 . The averages are caused by the climate of Tangxia Formation, which was mainly hot-arid climate and the warm-humid climate only in middle and late stages. The Tangxia Formation is salty lacustrine sediments with slow depositional rate and hot-arid climate. The discrimination diagrams of Zr-Th and La-Th-Sc, REE and the regional tectonic analysis show that the tectonic setting of Dongguan area of Middle Jurassic was back-arc basin of active continental margin. Affected by the extension, Dongguan area developed into the rift lake basin in the back-arc. La/Yb-∑REE source rock discrimination diagram of the mudstones shows that source rock were basalt, granite and sedimentary rocks.

东莞地区中侏罗统塘厦组为富含凝灰质的湖泊沉积。对样品进行全岩分析和ICP-MS微量元素分析,并计算Sr/Ba、B/Ga和Ca/Mg比值,其比值变化与古盐度变化成正相关,特征显示塘厦组为咸水湖泊沉积,由下至上古盐度逐渐降低,水体深度也逐渐变浅。对样品进行ICP-MS稀土元素分析,计算各样品 δ Ce值和(La/Yb) N 比值, δ Ce值介于0.83 ~ 1.31之间,(La/Yb) N 值均明显大于1或小于1,其特征反映湖泊沉积物沉积速率较低,只在塘厦组底部和上部出现相对高的沉积。元素P和Sr/Cu值反映其富集与迁移,受到气候的控制。元素P平均值在0.205×10 -2 ; Sr/Cu平均值大于4.0×10 -6 ,在中晚期出现最低值1.42×10 -6 ,这是塘厦组以干热气候为主,中晚期出现了短暂温湿气候所造成的。塘厦组为干热气候下缓慢沉积的咸水湖泊沉积。Zr-Th、La-Th-Sc判别图解、稀土元素特征及区域构造分析,显示中侏罗世东莞地区构造背景为活动大陆边缘的弧后盆地。受伸展作用影响,本区发育弧后裂谷型湖盆。泥岩La/Yb-∑REE源岩判别图解显示,源岩为玄武岩、花岗岩和沉积岩。

... 测试步骤参考许中杰等(2010),具体如下: 将已粉碎样品于105#cod#x000b0 ...

2017

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... V/Ni值越高,则盐度越大(许中杰等,2017 ...

2013

0.0

... 姚泾利等,2013),自上而下共划分出长1至长10等10个油层组(郑荣才和柳梅青,1999),每个油层组又可细分为若干小层 ...

2011

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张才利, 高阿龙, 刘哲, 黄静, 杨亚娟, 张艳. 2011. 鄂尔多斯盆地长7油层组沉积水体及古气候特征研究. 天然气地球科学, 22(4): 582-587.

[Zhang C

, Gao A

, Liu

, Huang

, Yang Y

, Zhang

. 2011. Study on character on sedimantary water and palaeoclimate for Chang 7 oil layer in Ordos basin. Natural Gas Geoscience, 22(4): 582-587]

Based on Sr concentration,the ratios of Sr/Br and Th/U,and biogliph fossil,we discuss the water condition and paleoclimate for the deposition of Chang7 oil layer in the Ordos basin.The results show that the ratio of Sr/Br and Th/U is from 0.19 to 0.65,and 0.36 to 5.03,respectively,indicating the water during the Chang7 Period was continental freshwater.The V/Ni ratio of 1.75-5.53 is fallen into the score of the reducing environment.The element assemblage,biogliph fossil,and Co quantitative match indicate that the water depth at the Chang7 Period was half-deep to deep lake,with the maximum depth of 50\|120m.The paleoclimate was confirmed as warm and humid climate by sporopollen assemblage.

1.Research Institute of Exploration and Development,Changqing Oilfield Company,PetroChina,Xi′an 710021,China; 2.National Engineering Laboratory for Low\|permeability Petroleum Exploration and Development,Xi′an 710021,China; 3.No.3 Oil Recovery Plant of PetroChina Changqing Oilfield Company,Yinchuan 750006,China; 4.Department of Exploration,Changqing Oilfield Company,PetroChina,Xi′an 710021,China

以Sr含量、Sr/Ba值和Th/U值等地球化学指标及生物遗迹化石作为判识标志，对鄂尔多斯盆地延长组长7油层组沉积环境水介质条件与古气候进行了分析：结果表明长7油层组沉积期古水介质Sr/Ba值为0.19～0.65、Th/U值为0.36～5.03，属陆相淡水环境；V/Ni值为1.75～5.53，属于还原环境；通过元素组合及生物遗迹化石、钴元素定量计算显示水体深度介于半深湖—深湖之间，最大古水深为50～120 m；孢粉组合分析古气候属较温暖潮湿气候。

... 张才利等,2011 ...

1999

0.0

郑荣才, 柳梅青. 1999. 鄂尔多斯盆地长6油层组古盐度研究. 石油与天然气地质, 20(1): 20-25.

[Zheng R

, Liu M

. 1999. Study on palaeosalinity of Chang-6 oil reservoir set in Ordos basin. Oil and Gas Geology, 20(1): 20-25]

Take the geochemical indicators of boron,equivalent boron,adsorptive K + +Na + ,Sr and the ratio of Sr/Br etc.as palaeosalinity indicators,the palaeosalinity of Chang6 oil reservoir set in Ordos Basin is analysed and calculated by using the formula advanced by T.D.Adams and E.L.Couch.The results indicate that the Late Triassic Ordos Basin is not an inland fresh water lake as recognized for a long time,but a brackish water to semisalt water marginal lake caused by intermittent seawater ingression.The paleosalinity of water body of the reservoir set was 0.940%～01.016% during its deposition.The contents of K + +Na + and the ratio of K/Na in the above mentioned paleosalinity do not correspond with that of Chang 26 reservoir set;the contents of boron,equivalent borom, adsorptive K + +Na + ,Sr and Sr/Ba ratio are reliable identifying indicators of the paleosalinity.After the regression analysis of the identifying results of various indicators,it is suggested that the results calculated by E. L. Couch formula are more reliable.The identificatin of paleosalinity could not only distinguish the water type of paleolake,but also could know the evolution of source rock.

1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploiation, Chengdu College of Technology, Chengdu, Sichuan; 2. Goelogical Institute, Southwest Bureau of Petroleum Geology, CNSPC, Chengdu, Sichuan

以硼、“相当硼”、K+Na含量、K/Na比值、吸附K′+Na′、锶含量以及Sr/Ba比值等地化指标作为古盐度的判识标志,运用亚当斯和科奇古盐度计算公式,对鄂尔多斯盆地长6油层组沉积环境的古盐度进行分析和计算,结果表明长6油层组沉积时湖泊水体的古盐度为0.940%～1.016%,属富钠的微咸-半咸水环境。经分析比较,上述古盐度判识标志中,K+Na含量及K/Na比值与长6油层组的古盐度无明显对应关系,不能作为判识标志;而硼、”相当硼“、吸附K′+Na′、锶含量及Sr/Ba比值等地化指标较为灵敏,对古盐度的判识较为可靠。将多种指标判识的结果作回归分析后,认为科奇公式计算的结果最为可靠。古盐度的确定不仅可以判断湖泊水体类型,而且对了解生油岩系的发育情况和分析浊沸石化作用的钠组分来源都大有帮助。

... 姚泾利等,2013),自上而下共划分出长1至长10等10个油层组(郑荣才和柳梅青,1999),每个油层组又可细分为若干小层 ...

2008

0.0

郑荣才, 王海红, 韩永林, 王成玉, 牛小兵, 王昌勇. 2008. 鄂尔多斯盆地姬塬地区长6段沉积相特征和砂体展布. 岩性油气藏, 20(3): 21-26.

[Zheng R

, Wang H

, Han Y

, Wang C

, Niu X

, Wang C

. 2008. Sedimentary facies charateristics and sand body distribution of Chang 6 member in Jiyuan area of Erdos Basin. Lithologic Reserviors, 20(3): 21-26]

Based on the core observation and logging analysis, it is believed that fluvial’dominated delta and shallow lacustrine sedimentary system developed well during Chang 6 period in Late Triassic in the north and west of Jiyuan area which is located in the Midwest of Ordos Basin. The lithofacies and paleogeography mapping based on high resolution sequence analysis show the sandbody distribution clearly. The paleoshoreline in this area is defined by paleosalinity recovery. Deltaic front subfacies mainly developed in the study area, with small(scale of deltaic plain in northeast. The reconstruction of lithofacies and paleogeography, especially the definition of paleoshoreline of Chang 6 member in Gengwan)Shijiawan area is significant for the further exploitation in this area.

姬塬地区位于鄂尔多斯盆地中西部,通过岩心观察和测井资料分析,认为晚三叠世长6时期该区北、西两侧都发育有河控型三角洲—浅湖沉积体系*。基于高分辨率层序地层学分析的岩相古地理编图结果非常清晰地显示了研究区长! 段砂体展布特征!同时通过古盐度恢复!首次确定了该区湖岸线的位置!，从而确定研究区主要发育三角洲前缘亚相!，三角洲平原只在东北一隅有小范围分布。耿—史地区长!6段不同沉积时期岩相古地理面貌，特别是古岸线的确，!对于指导该区长! 油藏下一步的开发具有极其重要的意义。

... 前人研究认为,姬塬地区长6油层组沉积时期存在北东、北西两大物源,且主要为三角洲相和湖相沉积(郑荣才等,2008 ...

2012

0.0

2006

0.0

... Ca/Mg值变大,反映古水体盐度增加、pH值升高、Eh值降低、深度加大或沉积物搬运距离增大(Benway et al ...

1997

0.0

... 化学蚀变指数在研究沉积岩的物源和判断沉积岩化学风化或蚀变程度上应用广泛(Fedo et al ...

2017

0.0

... Liang et al ...

1982

0.0

... 2 样品与测试较细的沉积物更能近似地代表物源区的岩石矿物组成,并会保留下该时段完整而丰富的地球化学记录(Nesbitt and Young,1982) ...

... 为硅酸盐矿物中的CaO成分(Nesbitt and Young,1982) ...

2007

0.0

... Rohling,2007) ...

2014

0.0

... Zhang et al ...