A Fracture-Orientation Comparison Between Core-Based and Borehole-Imaging Techniques: Paleomagnetic, Electronic Multishot, and FMI: ABSTRACT

Abstract

Accurate orientation of fractures is crucial to enhanced productivity in low-permeability fractured reservoirs. This study presents results of a rare instance in which three widely different fracture-orientation techniques could be directly compared for orientation accuracy. In a fracture-orientation study of Pardonet/Baldonnel (Upper Triassic) carbonates from the Gwillim field, British Columbia, a 50[degrees] to 60[degrees] fracture-orientation discrepancy was observed in two consecutive core runs oriented by [open quotes]electronic multishot[close quotes] (an electronic version of the conventional [open quote]multishot[close quotes] core- orientation technique) versus Schlumberger's Fullbore Formation MicroImager (FMI). To resolve this discrepancy, the paleomagnetic core-orientation technique was employed as a third fracture-orientation method. The paleomagnetically-determined fracture orientations agreed within 5[degrees] with FMI, and confirmed a systematic error in the electronic multishot orientations of 46[degrees] in Core 1 and 60[degrees] in Core 2. Superimposed on the systematic error was a second-order, oscillatory [open quotes]torsion error[close quotes] of [+-]10[degrees], which probably reflects acquisition of electronic multishot data within a rotating drillstring (unlike conventional multishot where coring is stopped before each [open quotes]shot[close quotes]). The paleomagnetic and FMI data reveal that natural and induced fractures have different orientations at this well location in the Gwillim field. Natural fractures dip 72[degrees] toward N 45[degrees] E,more » nearly orthogonal to bedding which dips 15[degrees] toward S 45[degrees] W. In contrast, induced petal fractures strike N 10[degrees] E, at a 55[degrees] angle to the strike of natural fractures and bedding.« less