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Fracture
Interpretation and Discrimination Between Drilling-Induced and Natural
Fractures Through Integration of Cross-Dipole Acoustic 
Anisotropy
and
Electrical Borehole Images
Zarian, P.1,
R. Reinmiller2, M. Markovic2, M. Kozimko3 (1)
Baker Atlas,
Measurements of
anisotropy directions using cross dipole acoustic logging tool provide valuable
information about stress orientations within the borehole. Calibration of the
fracture data identified from electrical borehole images with cross dipole
acoustic anisotropy and Stoneley wave permeability data, leads to a more
precise classification of fracture types. This approach is particularly useful
in structurally complex areas, such as the one presented in this study, where
discrimination between the natural open and drilling induced tensile fractures
is ambiguous. The orientation of the fast shear pathway identified from cross
dipole acoustic anisotropy measurements is theoretically parallel to the
orientation of the drilling induced tensile fractures from electrical borehole
images, which helps to constrain the orientation of the maximum in-situ
horizontal stress. Since the cross dipole acoustic tool has a deeper depth of
investigation in comparison to the electrical borehole imaging tool, this
difference in depth of investigation can help in discrimination of the natural
fractures which propagate deeper into the formation from the drilling induced
fractures which are proximal to the borehole wall. The study is conducted on a
near-vertical well from Greater Green River Basin in Rocky Mountain Wyoming
where the morphology of drilling induced fractures on the electrical
borehole
images resembled the natural open fractures, creating uncertainties in fracture
classification. However, the application of the above approach helped in a
successful identification of the natural open fractures which are main contributors
to the reservoir producibility and fluid flow creating a robust framework for
making decisions for well completion purposes.