Multi-Array and Triaxial Induction Devices

The traditional deep-induction measurement (6FF40, or ILd) discussed in Chapter 7 was developed in 1960 and remained the standard for over 30 years. Indeed it is still being run today, and in the right conditions can still give accurate answers. However, as it has been applied to ever more stringent conditions its deficiencies have become apparent. These were recognized early on but it was not until computer modeling was applied to the problem in the 1980s that the limitations were fully explained and documented. Even then there was a reluctance to change the standard, so that the first new developments kept the same array but used processing to improve the response. Changes in measurements take time to be accepted. From a reservoir manager’s point of view it is often better to live with a measurement that has some shortcomings but is the same in all wells, rather than to have to compare different responses in different wells.