Demonstrating the Performance of a Multi-Tubular Corrosion Inspection Tool in Alloyed Completions

Abstract

With the increased demand for drilling deeper wells in harsh environments involving corrosive, briny waters and more corrosive crudes, completion engineers increasingly adopt more resilient materials for well casings than conventional carbon steel. These materials include alloyed steels, where ferrous steel is mixed with other non-ferrous materials, such as chromium and nickel, for increased strength and durability. Alloyed steel has a lower magnetic permeability than carbon steel and, therefore, generates weaker electromagnetic signatures when logged with electromagnetic pipe inspection tools. This paper demonstrates the performance of an array multi-frequency electromagnetic pipe inspection tool in scenarios involving alloyed completions using a simulated mockup test with known defects. The types of defects considered are circumferential with different combinations of overlapping and non-overlapping defects on well casings. The pipe inspection tool uses the eddy current principle and includes two transmitters and eight receivers. It operates in continuous wave mode at multiple frequencies. Optimized transmitter-receiver spacing configurations and multi-frequency operation provide sufficiently diverse information to help assess metal loss in individual pipes for a wide range of configurations, including those with alloyed completions. The tool uses a sophisticated workflow of data-processing and inversion algorithms to decouple individual thickness information from the measured data. A mockup test was designed to replicate typical alloyed completions used in deep water wells to assess tool performance in different scenarios. The mockup comprises an alloyed tubing and two outer casings, which are standard ferromagnetic steel pipes, with seven combinations of defects on the casings. The tool response is synthetically simulated using a finite element electromagnetic solver and the synthetic data are inverted for metal loss on each one of the pipes. The estimated metal loss for each defect was compared to the actual metal loss to assess the accuracy of the tool. It will be shown that in order to obtain high accuracy of metal loss estimation, the electromagnetic material properties of the pipes, including that of the alloyed tubing, must be estimated with sufficient accuracy. The information provided by this tool will enable regular inspection of deepwater wells for corrosion and other integrity issues with minimal downtime and intervention cost.