Dynamic Behavior of the Polished Rod for the Coalbed Methane Pumping Installations | Oil & Gas Science and Technology

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Table 3

The errors in the different approaches to calculating dynamic hanging loads on polished rod in Sanjiao coalfield.

Stroke	Measured total load F′ (kN)	API method		Schafer’s method		Gibbs’s method		The proposed method
Stroke	Measured total load F′ (kN)	Calculated total load F (kN)	Error E (%)	Calculated total load F (kN)	Error E (%)	Calculated total load F (kN)	Error E (%)	Calculated total load F (kN)	Error E (%)
Upstroke	27.12	31.07	−14.56	29.95	−10.41	31.75	−17.06	27.46	−1.25
	27.43	30.04	−9.52	29.45	−7.35	30.96	−12.86	27.69	−0.95
	28.88	29.29	−1.42	29.09	−0.72	30.10	−4.24	28.98	−0.35
	29.11	29.06	0.18	28.97	0.47	29.66	−1.89	29.16	−0.17
Downstroke	9.37	12.47	−33.08	12.58	−34.30	9.24	1.41	9.26	1.17
	10.58	12.96	−22.50	13.02	−23.09	9.48	10.36	10.48	0.99
	11.37	13.31	−17.06	13.34	−17.30	9.75	14.25	11.32	0.45
	11.74	13.42	−14.31	13.43	−14.44	9.89	15.77	11.71	0.30

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