Design of a Testing Facility for Investigation of Drill Pipes Fatigue Failure

Abstract

Drillstring and down-hole tool failure usually results from failing to control one or more of the vibration mechanisms. The solution starts with the ability to measure different modes of vibration, hence identifying different vibration mechanisms. Lateral, torsion and axial are vibration modes that take place when drill pipes run into problems downhole. Due to the three modes of vibration mechanisms such as bit bounce, stick-slip, lateral shocks, bit and bottom hole assembly (BHA) whirl, parametric and torsional resonance occur. Understanding the causes of the destructive loads is the main step towards developing approaches to prevent or reduce their effects, hence improving drilling performance. Vibration modes and mechanisms lead to failure of the drill pipes, BHA and drill bits. Drill pipes fatigue failure is very common due to capability of producing all vibration modes and mechanisms. Drill pipe and downhole tool assembly failure usually result from failing to have power over one or more of these vibration mechanisms. A novel in house experimental setup has been developed to mimic downhole axial, lateral and torsional vibration modes and mechanisms in drilling operations. In this paper, we focus on the design and construction of the testing facility. A number of tests were conducted to validate the capability and performance of the test setup. Drill pipe fatigue failure due to lateral cyclic stresses induced in the drill pipe has also been investigated and presented in this paper. The results show that operating on a rotation speed higher than 90% of the drillstring critical speed leads to yielding in the drillstring.

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