Deployment of Novel Wide Dynamic Range Through-The-Bit OBM Borehole Imager Enables Logging in Challenging Environment-Implications for the Ordovician and Silurian Siliciclastic Facies Characterization

Abstract

Abstract Acquiring borehole resistivity image logs on drill-pipe conveyance operations has some operational and data quality challenges especially in challenging hole conditions and complex well trajectories. These challenges include operation efficiency, sticking issues, proper pad contact and pads overlapping which significantly affect the produced image quality and accordingly the geological interpretation reliability. To address these, a new through-the-bit imaging technology in oil-based Mud (OBM) is introduced, the new technology design has been proven to be reliable and effective in challenging hole conditions. This deployment technique allows acquiring high-definition micro-resistivity images in conditions where conventional wireline conveyance techniques cannot be used, such as unstable boreholes, tortuous or rugose wells, loss zones, or severe washouts. The distinctive operational advantage of the through-the-bit imaging technology is deploying the tool through the drill-pipe and reaming bit while performing a wiper trip, which saves rig time and significantly reduces fishing risk through the avoidance of cable and tool sticking. Moreover, it improved operations with full well control and the ability to retrieve logging tools at any time. In addition to the high-resolution images produced with the new technology, an inversion workflow has been developed to quantitatively interpret images. The interpretation results are compared with the analysis performed on the images acquired on tough logging conditions (TLC) operations in the same hole. This paper evaluates the outcome of deploying two electrical borehole imaging technologies through two different conveyance techniques. The innovative through the bit micro-resistivity OBM images are proven reliable in low- and high-resistivity formations, significantly reduced sticking and eliminated the overlapping of pads towards the bottom of the logged interval due to the lighter weight of the through-the-bit technology. The evaluation included the comparison with the existing conveyance method and covered a full range of well profiles from vertical to deviated, including highly deviated wells and long laterals. The high-resolution image produced allowed identifying various sedimentary and structural features within the target formations. These sedimentary features included thin laminations, cross bedding, soft sediment deformation and structural elements such as natural fractures and faults. Additionally, with inverted standoff images, open and closed natural fractures were identified and utilized in the fracture modeling of the field. All the forementioned identified features have been incorporated into the facies and the structural model of the studied area. The models are more reliable and can be used with confidence for well trajectories optimization and stimulation designs.