EVALUATION OF LWD HIGH RESOLUTION ULTRASONIC IMAGING TECHNOLOGY AND APPLICATIONS IN SLIM HOLE SIZE

Abstract

Logging while drilling (LWD) ultrasonic imaging tools have been recently introduced for slim hole size. Due to fundamental differences in data acquisition methodologies with other previously utilized LWD and wireline imaging techniques, field trials have been performed with the objective of validating and evaluating the new ultrasonic tool’s measurement. Ultrasonic imagers have been deployed in multiple wells of different environments and formation characteristics to evaluate the tool’s measurement quality and potential applications. The trials were performed in carbonate and clastic formations, horizontal and vertical trajectories, oil- and water-based drilling fluid systems, and in drilling and wipe operations. An LWD ultrasonic imager has also been deployed back to back with wireline. Multiple passes were performed to evaluate the time dependency and hole deterioration effect. In water-based mud, an ultrasonic imaging tool was run in the same bottomhole assembly with the proven LWD laterolog resistivity imager for the comparison of both technologies. In addition to stratigraphic dips, bed boundaries, fractures, faults, and other geological features usually detected by other imaging techniques, ultrasonic imaging tools also provided high measurement sensitivity for detecting geometric features relating to wellbore shape and wellbore stability. LWD microresistivity-based image comparisons indicated a robust correlation of the fractured zones contributing to lost circulation while drilling. Multiple passes for drilling and wipe images with wireline comparisons logged days after the LWD run clearly illustrated the time-dependency of the image quality due to borehole deterioration, invasion, and progression of geomechanical effects used to benchmark future data acquisition requirements. This paper evaluates the capabilities and performance of ultrasonic imaging tools in comparison with other LWD and wireline high-resolution imaging sensors.