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AAPG Bulletin
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AAPG Bulletin; Year: 2020; Issue: February DOI: 10.1306/05091918193
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Figure 10. Wire-line and formation microimager (FMI) log through a 27-m (88-ft)-thick igneous intrusion located within the Faroe–Shetland Basin (213/27-2). Clear fractures can be observed within the intrusion on the FMI log. We interpret the subvertical fractures, which extend more than 30° around the circumference of the hole, to be primary cooling fractures and not drilling induced because no subvertical fractures are seen in the weaker shales horizons above and below the intrusion and no change in mud weight occurred while drilling from the shale through to the intrusion. Note the increased separation of the deep and medium resistivity (RES_Deep and RES_Medium, respectively) wireline measurements within the heavily fractured area of the intrusion from approximately 3270 m (∼10,728 ft) to base of intrusion, and how this separation is greatly reduced within the zone of minimal fracturing toward the top of the intrusion and within the claystone sequence.
Figure 10. Wire-line and formation microimager (FMI) log through a 27-m (88-ft)-thick igneous intrusion located within the Faroe–Shetland Basin (213/27-2). Clear fractures can be observed within the intrusion on the FMI log. We interpret the subvertical fractures, which extend more than 30° around the circumference of the hole, to be primary cooling fractures and not drilling induced because no subvertical fractures are seen in the weaker shales horizons above and below the intrusion and no change in mud weight occurred while drilling from the shale through to the intrusion. Note the increased separation of the deep and medium resistivity (RES_Deep and RES_Medium, respectively) wireline measurements within the heavily fractured area of the intrusion from approximately 3270 m (∼10,728 ft) to base of intrusion, and how this separation is greatly reduced within the zone of minimal fracturing toward the top of the intrusion and within the claystone sequence.