Azimuthal Gamma Images Uncover Stratigraphic Features in a Seemingly Featureless Unconventional Reservoir

This paper discusses the benefits of using an azimuthal gamma ray tool for wellbore placement to better understand the stratigraphy of the formation.

The use of real-time azimuthal gamma images made it possible to determine if the wellbore was moving up or down stratigraphically. Importing the images to borehole imaging software allowed for the calculation of borehole dips and true dips (resulting in a more accurate correlation) dip calculation of the Middle Bakken surfaces, and a better understanding of the stratigraphy surrounding the borehole. A comparison was established with laterolog resistivity images from the same area that were of higher resolution and higher cost, validating the use of azimuthal gamma for dip calculation.

The azimuthal gamma ray measurement provides insight into stratigraphic well placement beyond what can be determined from bulk average gamma ray. Data acquired from the gamma ray image can help to further refine geosteering decisions and reduce uncertainty in wellbore placement.