| Popis: |
Most recently, the oil industry has focused on drilling dynamics management as a critical process to maximize drilling system energy for an optimum rate of penetration (ROP). The goal is to maintain the physical integrity of the drill string avoiding nonproductive time associated with twistoff events. The process becomes more complex while drilling in total mud loss scenarios which is called blind drilling. The downhole drilling dynamic in total mud losses is quite complex because of the constant fluctuation of the wellbore buoyancy factor, which gives the string an extra induced drilling motion, plus the lack of fluid support above the dynamic fluid level. This harsh drilling environment becomes tougher while drilling the tophole section because of the high clearance between the tubular and the borehole. The clearance gives extra room to the string to experience a high level of shock and vibration, which negatively affects the drilling performance, the physical integrity of the drillstring, and can lead to twistoff events. To overcome this challenging scenario, a complete suite of real-time high-frequency drilling dynamic data tool was added to the drillstring. The addition of this tool increased the understanding of the primary sources of fatigue encountered while drilling the tophole section. Taking into consideration the total mud losses, it was important to determine the predominant drilling motions and level of vibration. To make this determination, it was necessary to perform a drilling dynamic modeling for optimum bottom hole assembly (BHA) design, considering available tubulars, and defining drilling parameter guideline with the mechanical specific energy (MSE) footprint for proper shock/vibration prevention and mitigation. During the downhole data capture stage, it became apparent the magnitude of the harsh drilling condition experienced while drilling could not be identified using surface parameters. However, the MSE can alert when harsh drilling conditions are present because of the energy loss observed. Additionally, the following drilling motions and level of vibrations were identified: BHA chaotic whirl, high torsional and lateral vibration, lateral and torsional vibration directly proportional to surface revolutions per minute (RPM), and whirl severity affected by surface parameters and proximity to the loss zone within a 900 ft from the bit area of influence. To reduce the risk of BHA whirl and high-level vibration, the BHA stiffness ratio was improved incorporating 6 5/8-in heavy-weight drill pipe and standardizing the BHA stabilization, reinforcing with a drilling parameters road map and MSE footprint for shock/vibration prevention and mitigation. This new engineering approach using high-frequency drilling dynamic data reduces the number of twistoff events per year by 67%. This reduces the average from 15 to five events annually with no compliance issues found based on the recommended guidelines for those events. As a result, the number of twistsoff events per 100 runs was reduced by 59%, demonstrating the potential to completely eradicate twistoff events on tophole section. |
