Casing Inspection and Cement Evaluation on Drillpipe: Logging in Parallel with Existing Intervention Runs

Abstract The oil and gas industry is in a state of continually challenging the way to improve the efficiency and safety of well construction activities. An interesting path has been followed in the last 30 years in the development and use of logging while drilling tools. The measurement quality and reliability of these tools for open hole formation evaluation and geosteering has propelled an entire sequence of highly complex and highly deviated wells with enormous improvements in productivity from existing fields. You would be hard pressed to find any wells, particularly in the offshore domain, that do not utilize logging while drilling measurements that were once the province of wireline tools only. This development of technologies and tools has, as stated above, largely focused on open hole and while drilling applications only. The same cannot be said for cased hole evaluation tools in general, and for well integrity tools that measure the condition and properties of the casing and cement in particular. This paper will demonstrate the development of a new drillpipe conveyed tool that can both measure the casing condition and what is in the annular space behind the casing. We will show examples from around the world of the tools and how this was qualified versus the existing wireline deployed technology. We will then show a case history from the deepwater West Africa area where the tools were run in parallel with existing intervention operations across a sequence of wells to both increase the efficiency of operations and to de-risk the operation. The basic premise of the tool is that a drill collar is fitted with three circumferential pulse echo ultrasonic transducers. This allows for a full azimuthal image of the casing and annular space behind the casing if the tool is rotated, either from a downhole device such as a mud motor, or by surface rotation through the rig rotary table or top drive. The tool can be run in real-time and also in memory mode, in either case data is both processed downhole and the raw waveforms can be recovered from the tool when back on surface. Analysis of the acquired data allows for interpretation of internal caliper, the thickness of the casing, the location of casing collars and an evaluation of the material in the annular space behind the first casing string. The need to provide oriented images means the tool has magnetometers, accelerometers and a basic gyro measurement device that can be used for orientation of downhole devices such as whipstocks or oriented perforations.