Experimental Study on the Effect of Long-Term Water Injection on Micropore Structure of Ultralow Permeability Sandstone Reservoir

Table 5

Comparison of characteristic parameters between the initial state and after-LTWF state.

Cores	C9-1	C9-2	Change (%)	C11-1	C11-2	Change (%)
Type	Unimodality		/	Bimodality		/
State	Initial	After	/	Initial	After	/
Average pore radius (μm)	0.54	0.599	10.93	0.532	0.675	26.73
Median pore radius (μm)	0.296	0.344	16.22	0.402	0.492	22.52
Mainstream pore radius (μm)	1	1	0	0.63	1	58.73
Proportion of mainstream pore (%)	13.607	16.547	21.61	18.97	18.337	-3.34
Structural coefficient	11.553	14.164	22.6	12.045	19.345	60.6
Tortuosity	3.399	3.764	10.72	3.471	4.398	26.73
Relative sorting coefficient	5.476	4.794	-12.45	5.619	4.404	-21.62
Kurtosis	0.882	0.896	1.59	0.687	0.771	12.17