Casing corrosion in storage wells is a matter of considerable concern to the gas storage industry. Such wells are typically flowed through the casing rather than through production tubing, to facilitate high flow capacities. When failures occur, gas leakage to surrounding formations, freshwater zones and to the surface can pose a sizable economic loss as well as a serious safety hazard. For these reasons, monitoring corrosion in down-hole casing in gas storage fields has become a major concern of many storage field operators, and the in situ detection and assessment of corrosion damage by means...
Casing corrosion in storage wells is a matter of considerable concern to the gas storage industry. Such wells are typically flowed through the casing rather than through production tubing, to facilitate high flow capacities. When failures occur, gas leakage to surrounding formations, freshwater zones and to the surface can pose a sizable economic loss as well as a serious safety hazard. For these reasons, monitoring corrosion in down-hole casing in gas storage fields has become a major concern of many storage field operators, and the in situ detection and assessment of corrosion damage by means of logging instruments is a significant part of this effort. The study reported in this document has sought to investigate in detail the objectives, methods and results of currently available commercial logging devices as a first step in determining whether down-hole corrosion damage can be more accurately characterized by improved logging methods. Of the several methods potentially capable of meeting the through-wall measurement requirement, only two form the basis for current commercial corrosion logs: the flux leakage, or magnetic perturbation technique, and the remote field eddy current approach. In seeking to provide reasonably short term performance improvements to the industry, it was decided in this project to pursue refinements of magnetic perturbation logs for two reasons: first, the shortcomings evidenced by present logs of this type appear to be amenable to relatively simple improvement, and second, the remote field eddy current approach, while useful as an adjunct to damage assessment, offers little promise of sizing individual corrosion flaws.