Drill Pipe Dynamic Measurements Provide Valuable Insight Into Drill String Dysfunctions

Abstract

Abstract Recently the oil and gas drilling industry has become increasingly interested in drilling dynamics and vibration as a cause of reduced drilling performance, downhole tool and drill string failures. Historically, vibration data has been captured by an MWD tool incorporated in the lower BHA. Whilst this provides valuable information on the dynamic behaviour of the lower BHA, this approach is not always sufficient for understanding the drill string dynamics of more complex applications. Two case wells are discussed within this paper in which high frequency vibration data was recorded at several strategic and innovative points within the drill string. The acquisition and analysis of this data provided new insights of the dynamic behaviour of drill strings in high angle wells. A large international operator experienced both excessive and erratic surface torque during the first horizontal section of a large development project. The available surface drilling parameters and MWD vibration data were analysed, but the cause for the excessive surface torque could not be explained. To gain an understanding of the dynamic conditions across the drill string and to help identify the cause for the excessive torque, multiple Downhole Dynamics Recorders (DDRs) were included in the drill pipe, at positions up to 2500 metres from the drill bit, for two subsequent wells. The DDR data revealed that during periods of excessive surface torque, severe levels of sustained lateral vibration were present in the drill pipe, but not in the lower BHA, where traditional vibration measurement tools are located. Two drill string failures occurred during the second well and the fracture profile suggested that they were the result of fatigue failure. The DDR tools located in close proximity to the failure points recorded periods of severe and sustained lateral vibration. It is likely that fatigue failure of the drill string was accelerated by the high and cyclic bending stresses generated during these periods of vibration. In conclusion, dynamic dysfunctions can be present at any point in the drill string and these dysfunctions can have severe consequences within a short period of time. Furthermore, it is shown that novel and untraditional downhole measurements are required to understand, and mitigate, these dynamic dysfunctions.