New procedure for tightness tests (MIT) of salt cavern storage wells: Continuous high accuracy determination of relevant parameters, without the need to use radioactive tools
Hartmut von Tryller, Andreas Reitze, Fritz Crotogino, 2009. "New procedure for tightness tests (MIT) of salt cavern storage wells: Continuous high accuracy determination of relevant parameters, without the need to use radioactive tools", Underground Gas Storage: Worldwide Experiences and Future Development in the UK and Europe, D. J. Evans, R. A. Chadwick
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In performing the mechanical integrity test (MIT) on salt cavern storage wells the most used method worldwide is the In-Situ Balance method (ISB). The principal sources of errors in the execution and evaluation of the test are the depth change of the gas/liquid interface and the surface area of the interface.
In the past, the interface depth has been predominantly determined using radioactive methods, i.e. gamma-gamma, neutron-gamma and neutron-neutron tools. The disadvantages of these methods are the low measurement accuracy and the need to perform several tool runs during the test period, which introduces an additional source of error, because cost factors normally prevent continuous measurements.
A new method (SoMIT) is presented based on ultrasonic techniques in which the interface depth, the temperature and the differential pressure at the interface depth can be measured continuously during the tightness test while achieving much greater levels of accuracy than was previously the case. In the SoMIT method a tool is fixed in place throughout the entire test period such that the problems associated with several tool runs are also avoided. The advantages for users are to be found in the greater accuracy available to verify the tightness of the well and also in the reduced test period.