Torsional vibration is the main bottleneck which leads to low efficiency of rock breaking. According to the characteristics of torsional dysfunctions performance, the paper defines three main types of stick-slip, and analyzed the relationship between ROP and energy from bit. Based on Newton’s equations of motion, established frequency domain, single degree of freedom, damped and forced drill string torsional vibration prediction model, with more accuracy for downhole drill string mechanical state description. On this basis, semi-analytical transfer matrix method is adopted to establish drill string response relationship between internal force wave and surface parameters changes in the condition of vibration, which greatly reduce the number of discrete elements and the associated computing time, enabling rapid screening of a large number of design alternatives on a PC. In addition, the response parameters for drillstring stick-slip are integrated into an index (Vibration Strength Estimate, VSE), which is used to quantitatively evaluate downhole stick-slip severity. A three-week pilot test has been conducted in deep wells in Yumen Oilfield in China, with 25% increase of the average ROP and 40% enhancement of the average bit footage compared with offset wells. Validation of field application shows that the downhole torsional vibration evaluation technology is an effective method for further excavate the potential of ROP and reduce drilling cost.
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