Abstract
Wellbores drilled on US land today are geosteered predominantly using total gamma ray measurements and periodic survey data. This approach results in a number of ambiguous scenarios whereby not enough data are available to make the correct interpretation decisions. It is for this reason that many horizontal wells are unknowingly in different locations from where they are reported to be both positionally and stratigraphically. Geosteering techniques employing high-quality azimuthal gamma imaging and continuous inclination measurements address some of the main challenges plaguing accurate wellbore placement in the Wolfcamp A and Wolfcamp B of the Southern Midland Basin. Azimuthal gamma image examples of stratified and non-stratified bedding are related to lithofacies observed in core, bringing visibility to internal geometries and demonstrating how depositional environment influences tool response from a gamma radiation standpoint. Azimuthal gamma logged in conjunction with an accurate continuous inclination measurement to reduce TVD error enhances the benefits to geosteering interpretation and bed dip calculation, resulting in higher confidence wellbore placement. Furthermore, azimuthal gamma and continuous inclination MWD tool designs are discussed in the context of the critical elements needed for accurate and high resolution measurements.
