Evaluation of structural integrity of tubulars in directional wellbores: A case study in north-eastern parts of India

Abstract Severe fatigue and excessive load transmissions on drill strings during rotary drilling may lead to unexpected drill string failure. And if the driller within the stipulated time-bound did not control these load forces, the situation might increase NPT. To achieve the same by driller in real-time, the structural integrity of the tubular was monitored with a workflow that estimates the overall stresses acting along the drill string. In actual operating conditions, the drill string is subjected to both internal and external pressures, and it can be well explained in terms of true tension and effective tension. The estimation of these tensional forces and other load forces acting on the drill string is important for efficient drilling operation and the selection of optimum operational parameters. In addition, these forces are further utilized to estimate the neutral point and load acting at the deadline. The conventional rigs are subjected to numerous uncertainties that affect the precision of the hookload measurement at the deadline. Therefore, the factors affecting the hookload measurement at the deadline are summed up to a quantifiable metric labeled as Rig Uncertainty Compensation (RUC) factor. Further, the estimated hookload is compared with the actual hookload to detect the upcoming complications and prevent it from aggravation. And, to confirm the upcoming anomaly, the wellbore secondary drilling parameters are monitored in the real-time drilling operation. Additionally, all the forces acting along the drill string were also determined and monitored dynamically such that stress exposure in all the sections of the drill string is below a threshold value. To determine the efficacy of the developed model, the model was integrated with a Decision Support System (DSS) tool and tested in the actual field conditions. The tool was able to detect the upcoming complication successfully, and a field case study was presented in brief.