NMR Experimental Study on Dynamic Process of Pore Structure and Damage Mechanism of Sandstones with Different Grain Sizes under Acid Erosion

Table 1

Mineral composition of sandstones with different grain sizes (%).

Sandstone type	Quartz	Feldspar	Muscovite	Kaolinite	Detritus	Cement (mainly calcareous and ferrous)
Fine-grained	72.5	17.6	0.0	1.8	2.4	5.7
Medium-grained	60.3	20.5	5.1	2.4	3.5	7.2
Coarse-grained	43.8	31.6	8.3	4.0	1.7	10.6