Abstract
In this paper, finite element analysis is conducted to study dynamic responses of a defected drill pipe (DP) under impact loading encountered in working conditions. Longitudinal impact loading such as tensile, eccentric compressive and torsional impact loading and transverse collision loading are considered. A finite element model is firstly developed and validated, and then employed to evaluate the effects of various impact loading on dynamic responses of the defected DP. It is found that the inertial effect due to tensile impact is the most prominent among all the longitudinal impact loadings. In addition, the effect of the transverse collision between the DP and the borehole wall on the driving force of the crack is evaluated. It is concluded that the dynamic effects of the various impact loading frequently exerting on the DP should be taken into consideration for life prediction of DPs. DOI: http://dx.doi.org/10.5755/j01.mech.24.4.19503
Highlights
Drill pipes (DPs) are the main tools for drilling oil and natural gas wells
A few researches on DP failure were reported, for example, fatigue failures of DPs caused by vibration [2], erosion wear generated by drilling fluid containing debris [3], static fracture characteristics studied by a cohesive zone model [4]
Employing the developed finite element (FE) model, dynamic responses of the cracked DP are investigated under each elementary impact load, and the inertial effects of the impact loading on the dynamic stress intensity factor (SIF) are evaluated
Summary
Drill pipes (DPs) are the main tools for drilling oil and natural gas wells. According to statistics, the regions of the DP near the well head and near the bottom hole assemblies (BHA) are more prone to fracture failures. Rotary drilling systems often experience complicated loading in working conditions, such as severe stick-slip vibration, bit bouncing and self-excited vibration with parameters varying in unstable range [1] All these complicated impact loads can be broken down into elementary impacts such as tensile, eccentric compressive, torsional impact loading and transverse collision with well wall. The effects of impact loading on dynamics responses of DPs with cracks and their fracture failure were rarely studied. Guo et al [13] developed a 3-D FE program and investigated thermal-elastic dynamic fracture of a hollow cylinder with a semi-elliptic surface crack under thermal stress and impact inner pressure. A finite element (FE) model is developed and used to capture 3-D dynamic fracture responses of a defected DP under various elementary impact loads, including tension, eccentric compression, torsion and transverse collision between the DP and borehole wall.
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