Four-Dimensional Ultrasonic Caliper While Drilling Enables Advanced Wellbore Evaluation in Slim Hole Size

ABSTRACT: Evaluation of hole conditions is a key measurement for safe drilling and completion operations. Acquiring an accurate hole size measurement has been traditionally performed using wireline mechanical calipers deployed after drilling operations have been completed. This paper demonstrates how logging-while-drilling (LWD) ultrasonic sensors can be used to provide a time-lapse (4D) alternative azimuthal measurement of hole size, enabling data acquisition in different phases of drilling and tripping operations. LWD ultrasonic caliper measures the travel time and computes the tool's stand-off to the wellbore wall. Acquiring azimuthal data around the wellbore during different logging passes enables acquisition of 4D caliper information. After being calibrated inside casing, the ultrasonic sensor provides azimuthal travel-time images, based on which minimum, maximum, and average hole sizes can be computed. Data have been acquired in drilling, trip-in, and trip-out modes and compared to wireline-oriented calipers. The data has been evaluated considering time-dependent deterioration, washout, and breakout developments. Recently introduced LWD slim ultrasonic imaging and caliper tools have multiple transducers and fast sampling rates. The hardware and algorithm design improves the hole size computation and wellbore evaluation. The tools provide a viable alternative to wireline mechanical calipers. While field data showed a good match in competent formations, differences between data acquired in multiple LWD logging passes and wireline mechanical caliper runs have provided 4D caliper information for evaluating time-dependent changes in hole conditions enabling future optimization of well construction. This paper illustrates the utilization of LWD ultrasonic sensors integrated as part of the drilling assembly to provide a 4D azimuthal measurement of hole size at different times, during drilling and tripping in and out of the hole. Introduction Maintaining stable and competent wellbores is essential for safe and successful drilling, logging, and completion of oil and gas wells. Wellbore instabilities can also cause unplanned operational delays and unnecessary costs. Well instability can also increase with an increase in well inclination, leading to higher costs in high-angle well operations. which may negate the benefit of horizontal drilling techniques (Aadony and Looyeh, 2010).