Fig. 1—3D view of pipe in borehole. Microdoglegs are a natural effect of any vertical or directional well that can explain a wide variety of downhole problems. A trajectory-prediction model able to calculate the inclination and azimuth approximately every 12 in. has been developed to estimate microdoglegs using standard surveys, bottomhole-assembly (BHA) data, and steering parameters. This new methodology combining downhole data measurements with drillstring-modeling analysis highlights the potential for drilling optimization and wellbore placement. Standard Surveys. Surveys are generally taken at an interval of every 95 ft, the length of one stand. While the general recommendation is to decrease the survey interval when building faster than 3°/100 ft, this is often neglected because there is no advantage seen in wellbore-positioning-uncertainty models. The well path between each survey point typically is calculated using the minimum-curvature approach, which assumes a curve of equal angle along the surface of a sphere with only one radius in a 3D plane. Looking at the well as a whole, this approach appears logical and yields reasonable-looking trajectories; however, when examining more-frequent survey data, it becomes obvious how this method can mislead users to think that the well path is much smoother than it actually is. Continuous-survey measurements have enabled the industry to take a closer look at what is happening between survey points, in highlighting microdoglegs quite often undetected by standard surveys. This article, written by Special Publications Editor Adam Wilson, contains highlights of paper , “Microdogleg Detection With Continuous Inclination Measurements and Advanced BHA Modeling,” by SPE, and SPE, DrillScan, and SPE, Nabors, prepared for the 2016 SPE Eastern Regional Meeting, Canton, Ohio, USA, 13–15 September. The paper has not been peer reviewed. ... This article is reserved for SPE members and JPT subscribers. If you would like to continue reading, please , or
A computer model has been developed that can help to detect micro-doglegs in drilling operations, which can cause problems of torque and drag in directional wells. Current standard surveys take measurements only every 95 ft, and can miss doglegs. The new method uses measurements taken from bottom hole-assembly (BHA) data, and feeds this into a 3D model to predict the path taken by the bit.