A Novel Realtime Well Collision Avoidance Monitoring by Definitive Dynamic Surveys and Passive Magnetic Ranging

Abstract Drilling wells in close proximity to offset wells always involves a collision risk. This could lead to a catastrophic event like a blowout if collision avoidance monitoring techniques fail. None of the existing collision avoidance techniques today include continuous six-axis real-time definitive dynamic surveys to detect the offset well while drilling. Rather, all techniques rely on stationary surveys taken at predetermined intervals to calculate the projection ahead of the bit and to calculate the separation distance from the nearby well. This leads to added rig time and directional drilling complexity from hole washouts. Magnetic surveys rely on magnetometer sensors to measure the wellbore's azimuth. External magnetic interference such as that exhibited by the casing of a nearby well has an adverse effect on this measurement. Passive magnetic ranging (PMR) uses the measurements of the rotating magnetometers and accelerometers while drilling in the presence of this interference. A distance and direction to an offset well casing string can be determined by analyzing the raw data taken from the sensors. PMR techniques have previously required close spaced, stationary surveys to provide suitable data for ranging. This method demonstrates that definitive dynamic surveys can provide accurate ranging data while drilling, avoiding the need to stop and take stationary readings. The selected wells for this study are all drilled from the same platform with a relatively small positional uncertainty in order to have a robust comparison for the new technique's estimates of the position and direction to those same offset wells. The presented study includes six wells in a batch drilling sequence. The PMR was conducted in real time while drilling from the drilling well to the offset well. Results show the successful monitoring of the distance and direction of the offset well. Also, the results are accurate and compare well with the known position of the offset well. The technique introduced in this paper offers a unique way to avoid colliding with offset wells while drilling. This could be of particular help where the positions of the offset wells have poor accuracy and you can avoid them without the need for time-consuming static measurement while drilling (MWD) surveys. This new collision avoidance technique enables an offset well to be ranged continuously, enabling for magnetic range to the offset well while drilling. Enabling the approach and deviation from an offset well to be continuously monitored helps ensure a safer and more efficient well delivery.