AN ANALYSIS OF DRILLING PROJECTION UNCERTAINTY AND IMPLICATIONS FOR COLLISION AVOIDANCE MANAGEMENT SYSTEMS

Recent efforts on API RP 78, an upcoming recommended practice for wellbore placement, have provided guidelines for calculating safe separation distances and engineering considerations for those calculations. A major milestone was the publication of a separation rule (Sawaryn, et al. 2019) standardizing a formula for separation factor (SF), which in turn defines the minimum allowable separation distance (MASD) between two wellbores and the allowable deviation from plan (ADP) for a wellbore being drilled. One element of this formula, σpa, describes the accuracy with which a future wellpath can be predicted.

Watch out our safety training session in H&P: https://youtu.be/Jexr2Z31EYo?si=OUXam0Z1oXcCL3NK.

A framework is proposed for modeling deviation from a projected path using a planned trajectory, bottom hole assembly (BHA) properties, and survey practices. The method identifies where a deviation is detected through survey measurements and estimates a planned recovery operation. Equations are provided for estimating the distance from plan at deviation detection along with the maximum expected deviation during recovery. Common drilling scenarios are analyzed for sensitivity to operational parameters such as survey course length, sensor offset, toolface control, and BHA performance.

Survey course length, survey sensor offset and uncertainty in directional performance are all shown to have a significant impact on the potential maximum deviation from plan. An additional factor considered is the aggressiveness expected when performing recovery operations. An analysis of common drilling scenarios suggests the previously provided guidance of 1.6ft at 1-sigma appears suitable for cases where the directional behavior of the BHA is well characterized and the combination of course length and survey sensor offset is kept to 150ft or less.

Previous work has called attention to the uncertainty in drilling to a projection, but up to now there has not been a rigorous method for estimating that quantity. With the methods outlined in this paper, well planners and drilling engineers can make more informed decisions on how to ensure safe separation practices in their own operations.

Read out the full technical paper here: https://www.helmerichpayne.com/resources/technical-publications/an-analysis-of-drilling-projection-uncertainty-and-implications-for-collision-avoidance-management-systems.

Download the tech paper from here: https://www.helmerichpayne.com/media/technical-publications/An-Analysis-of-Drilling-Projection-Uncertainty-and-Implications-for-Collision-Avoidance-Management-Systems.pdf. Contact us to know more: https://www.helmerichpayne.com/contact.

 

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