Relative dip (RDIP) is a critical and widely used parameter in structural characterization and geosteering using image log data and represents the maximum tilt of planar element (e.g., bed, fracture, fault) relative to a wellbore, with relative dip azimuth (RAZIM) being its azimuthal direction as measured clockwise from wellbore high side. Relative strike (RSTRIKE), much like normal strike and dip, is perpendicular to the RAZIM direction and represents the orientation at which the planar element appears horizontal relative to the borehole.

During LWD azimuthal log acquisition, data are acquired as the toolface rotates and are partitioned into sectors around the borehole. For example, a 16 sector dataset has 16 individual log curves, each representing a 22.5 degree section around the borehole. Most commonly, the sector log curves are then processed into the classic image log format, for dip and structural characterization, sedimentological/stratigraphic analysis, and so forth. RSTRIKE analysis, however, represents an additional class of azimuthal log analysis, specifically as a means to extract refined petrophysical data from the azimuthal sectored log curves themselves.

The typical log curve acquired during LWD operations is derived by the average measurement over a specific period of time (time-average period typically seconds) as the toolface rotates arounds the borehole. Relative to a given stratal unit, the majority of azimuthal measurements unfortunately exhibit a “cross-stratal” component, especially with thinner units and as RDIP increases (e.g., running “horizontal”). For example, consider in a typical geosteering configuration, when the toolface is high side, the measurement is essentially looking up into younger strata, and when low side, looking down into older strata. The time-average curve resolution is thus degraded, often severely, because of these cross-stratal aspects. However, the individual log sectors that are oriented closest to the RSTRIKE direction (marked as the inflection points of cosinusoid forms on an image log) have a distinct advantage that their measuring direction (or “look orientation”) is most parallel to the strata. RSTRIKE sector logs exhibit reduced cross-stratal measurement and therefore RSTRIKE logs exhibit significantly better stratal resolution (and thus log resolution) versus the typical LWD log curves.