Failure Analysis of Tubing Collapse in a Gas Well

Table 4

Hardness test of the failed tubing and the same batch of tubing without failure.

Sample		Hardness test (HRC)
		Quadrant I				Quadrant Ⅱ				Quadrant Ⅲ				Quadrant Ⅳ
		Single value			Average value	Single value			Average value	Single value			Average value	Single value			Average value
Failed pipe body	Outer surface	27.3	27.7	27.6	27.5	27.6	27.4	27.3	27.2	26.0	27.2	27.1	26.8	26.9	27.2	27.1	27.1
	Center	27.8	27.7	27.8	27.8	26.4	27.6	27.5	27.4	27.6	27.7	27.6	27.6	27.2	27.3	27.3	27.3
	Inner surface	27.5	27.8	27.5	27.6	27.8	27.7	27.4	27.6	27.8	27.7	27.6	27.7	27.2	27.5	27.5	27.4
Variation value		0.3				0.4				0.9				0.2
The tubing body in the same batch	Outer surface	25.9	25.7	25.8	25.8	25.4	25.6	26.2	25.7	24.9	25.9	25.5	25.4	25.7	24.9	24.9	25.2
	Center	25.4	26.0	25.7	25.7	25.8	26.3	25.9	26.0	26.3	25.8	26.3	26.1	25.9	26.3	26.3	26.2
	Inner surface	25.4	25.4	25.9	25.6	25.6	23.8	25.4	24.9	25.4	25.3	25.8	25.5	25.9	26.1	26.1	26.0
Variation value		0.2				1.1				0.7				1.0
Requirements of ordering technical agreement requirement		Single value ≤28.5 Variation value ≤3.0