Automatic Estimation of Borehole Shape Using Ultrasonic Data While Drilling

The drilling operation can be complex depending on well trajectory and types of the formation to be drilled. In a highly deviated well, drilling parameters require careful assessment while drilling to minimize risks of serious drilling hazards. Ultrasonic imager provides ability to monitor well bore shape and real-time conditions. Transit time data inversion for high resolution well bore shape is an established technique for wireline logging. This technique is not yet available for while drilling imager due to its dynamic position changes during drilling. A new method is developed to accurately estimate the borehole shape from transit times corrected for tool eccentering. This algorithm invert simultaneously transit time data acquired from four pulse-echo sensors while assuming elliptic borehole shape. The principle consists in constraining the solution to minimize the ellipse surface. This approach was applied to real data and the performance evaluated.