The Evolution of Diagenetic Fluids and Accumulation Characteristics of Tight Sandstone Reservoir in Upper Paleozoic, Southwestern Ordos Basin

Table 2

Electron probe microanalysis of the compositions of sandstone cements in the Upper Paleozoic Erathem in the southwest of study area.

Well number	Depth (m)	Stratum	Sample number	Na2O	P2O5	MnO	MgO	K2O	Cr2O3	Al2O3	CaO	TiO2	SiO2	FeO	NiO	Mineral type
Qingtan 2 well	4731.5	Shan 1	1		0.023	0.535	20.66	0.02		0.088	49.84	0.071		28.75	0.002	Ankerite
He 3 well	4146.62	Shan 2	2		0.004		0.032	0.024	0.002				99.89	0.044		Quartz
Zitan 1 well	3742.50	He 8	3		0.014			0.012				0.026	99.87	0.012	0.058	Quartz
Ling 1 well	3697.14	Shan 1	4	0.026	0.018				0.038		0.011		99.87		0.028	Quartz
Lian 1 well	3470.03	Shan 1	5			0.11	3.14	3.3		33.6	0.19		45.7	11.4		Mixed-layer clay
Qingtan 2 well	4731.5	Shan 1	6				0.015	0.42		37.4	0.066	0.142	48.46			Kaolinite
He 3 well	4146.62	Shan 2	7				0.057	3.98		33.74		0.062	50.29	1.163		Kaolinite