LOG INVERSION METHOD FOR NUCLEAR LOG DATA OF EARTH FORMATIONS

摘要

#$%^&*AU2013200951A120131010.pdf#####ABSTRACT In a method of inverting nuclear log data pertaining to a geological formation surrounding a borehole, nuclear log data is acquired for a portion of the borehole using a moveable 5 nuclear logging tool, and additional log data is also acquired for the borehole a portion using another logging device with superior resolution. Boundaries between adjacent zones of the part of the borehole are identified that exhibit an attribute of the geological formation to a detectably contrasting degree. From pre-acquired data describing one or more characteristics of the nuclear logging tool, a modelled log of the attributes is 10 generated over the borehole portion, and a zone response is calculated from the preacquired data for each zone by using the boundaries to define an initial measure of the depth of each zone and ascribing a value of the attribute in dependence on the depth of each zone. The attribute of each zone is then calculated by deconvolving the nuclear log data using the zone response to minimize the difference between the nuclear log data 15 and the convolution of the zone response and the zone attribute.4/4 64 50 64 F r 58 54 60 5 56 64 62 82 80 Figure 5B 72 NUCLEAR LOG DATA 70 BED BOUNDARY DATA T© IMAGE LOG DATA 76 74 Figure 6