Study on Change Rules of Factors Affecting Gas Loss during Coalbed Air Reverse Circulation Sampling

Table 1

Particle size distribution of the original coal sample.

Sample size	≤1 mm	1–3 mm	3–4 mm	4–5 mm	5–6 mm	6–7 mm	7–8 mm
Cone bit	34.61	35.10	8.27	9.10%	4.51%	5.45%	2.96%
PDC bit	30.87	43.29	10.10	5.61%	5.32%	1.25%	3.56%