Characteristics and Controlling Factors of the Chang 8 Oil Reservoir in the Yanchi Area of the Ordos Basin: A Case Study of Well G20

Table 1

The trace elements and paleodepths of 8 mudstones from the Yanchang formation in the Yanchi area.

Number	Well	Top depth of the well (m)	Element (mass fraction)																	Ancient water depth (m)
			Pb	Co	Ni	V	Be	Sr	Ba	Th	U	La	Ce	Pr	Mn	P	Ca	Mg	TFe
			10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–6	10^–2	10^–2	10^–2
1	C51-1	2541.1	20.5	6.10	25.5	138	2.06	380	128	12.2	3.78	35.5	69.9	8.50	352.4	141	0.45	1.11	3.42	10.4
2	C51-2	2575.6	18.6	13.4	34.7	138	1.88	326	401	10.9	3.39	28.3	58.3	7.32	587.7	1311	1.17	1.48	4.84	33.9
3	C93	2532.8	10.6	11.6	34.9	163	3.07	257	311	8.18	4.01	42.3	80.4	9.67	292.8	239	0.47	0.85	2.95	27.3
4	F2	2436.7	32.0	17.2	42.3	126	2.73	174	417	9.59	7.07	42.5	79.6	9.19	405.8	413	0.52	1.19	4.08	49.2
5	H36	2787.2	19.8	16.0	47.1	130	1.87	199	451	10.9	3.45	29.2	65.5	8.90	509.6	1278	1.65	1.56	5.33	44.2
6	H39	2677.8	14.0	8.11	30.0	84	3.45	84.4	279	3.90	3.64	13.6	29.0	3.96	66.1	154	0.19	0.35	1.22	15.9
7	H51	3014.2	31.8	15.0	39.6	140	2.55	346	118	12.1	3.63	33.0	55.8	6.21	197.5	354	0.21	1.40	3.97	40.1
8	H54	2547.5	95.3	15.1	67.1	104	1.38	185	451	9.06	4.09	20.1	36.7	4.29	101.5	220	0.12	0.74	18.33	40.5
9	H73	2623.6	19.7	15.1	42.8	149	2.96	284	329	9.15	4.11	23.8	47.1	5.68	25.6	392	0.29	1.39	4.14	40.5
10	H83	2663.0	33.6	17.7	44.5	166	2.11	178	458	12.5	4.02	38.9	53.7	6.26	277.3	275	0.32	1.47	4.43	51.4