A Petrographic Study of the Three Forks Formation (Upper Devonian), Williston Basin, North Dakota: Based on Thin Section Analysis, XRD and SEM

Table 2

Summary of Bulk and Clay XRD Analysis.

Facies ID	Type of analysis	Wt.%	Qtz	Plag	K-Feld	Cal	Dol	Hem	Sider	←Clays→			Total clay
										Kaol	Chl	Ill
1	Bulk	91.27	16	2	2	1	65	1	0	2	1	10	13
	Clay	8.73	8	1	1	0	12	0	2	12	10	54	76
	Bulk + clay	100	15	2	2	1	60	1	TR	3	2	14	19
3	Bulk	93.50	17	1	2	1	61	0	0	3	3	12	18
	Clay	6.50	8	1	2	0	7	1	3	12	16	50	78
	Bulk + clay	100	16	1	2	1	58	TR	TR	3	4	15	22
4	Bulk	95.15	15	2	3	2	58	1	0	3	3	13	19
	Clay	4.85	4	1	1	0	6	1	1	10	25	51	86
	Bulk + clay	100	14	2	3	2	56	1	TR	3	4	15	22

Bulk fraction: greater than 3 microns size fraction.
Clay fraction: less than 3 micron size fraction.
Bulk and clay: mathematical recalculation including the bulk and clay fraction representing the whole sample.
Total clay: sum of the clay minerals (may include authigenic and matrix clays plus clays in rock fragments).
Dol: dolomite; Olivine: olivine; Plag: plagioclase feldspar; Hem: hematite; Ill: illite; Hema: hematite; Kaol: kaolinite; Sider: siderite; Chl: chlorite; K-feld: potassic feldspar; Cal: calcite; Qtz: quartz.
Tr: trace; detectable, but not measurable (0-1%).