Seeing Ahead of the Bit: Avoiding Drilling Hazards Using New Ultra-Deep Resistivity Technology for Proactive Decisions While Drilling Horizontal Wells

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Abstract High-angle and horizontal wells can be drilled laterally into new zones of high uncertainty in petrophysical properties, geological structure, fluid distribution, rock strength and pore pressure regimes. This high level of variations in properties can present significant drilling and wellbore stability management challenges especially for horizontal extended reach drilling applications. The recent developments in logging while drilling (LWD) technologies included far reading sensors that can map resistivity variations around as well as ahead of the well path in horizontal wells. These technologies have been proven to map faults, petrophysical and fluid level variations in the far field away from horizontal wellbore and can hence be used for proactive decision making to plan for, mitigate and avoid drilling and wellbore instability hazards. This paper demonstrates the utilization of ultra-deep resistivity measurements to provide an early indication for sources of drilling hazards before the well intercepts them. Ultra-deep resistivity measurements have been a key enabler for reservoir mapping and well placement applications in horizontal wells. Electromagnetic (EM) signals have been inverted traditionally in one dimension (1D inversion), then evolved to cover the full volume around the wellbore (3D Inversion). Inverting the signal components travelling ahead of the drill bit has been a known challenge and was only possible in horizontal wells due to the fact that the tools have already passed the formations around and behind the ultra-deep resistivity EM antennas. A breakthrough in the inversion technologies has now enabled a new advancement that allowed ahead-of-the-bit EM signal components to be separated from the components around the wellbore. horizontal wells. has been the ability to invert for the signal ahead of the bit. Capitalizing on the new advancements, the ultra-deep resistivity tools were used to detect sharp changes in resistivity ahead of the bit. These were interpreted to be faults or sharp dip changes that can serve as an early warning and enable a more proactive well placement to be made avoiding undesired zones that could induce multiple wellbore instability risks and/or loss of reservoir contact. 3D ultra-deep look-around inversion has proven the ability to map faults and structural displacements at a distance from the wellbore. Investigating several ultra-deep resistivity datasets for the look-ahead capability showed the sensitivity of the data to successfully detect changes in resistivity ahead of the horizontal wells while drilling. These changes were attributed to faults and sharp dip changes detected around 70ft+ ahead of the drill bit. The horizontal wells were actually drilled through the detected zones and confirmed the inversion results. This paper establishes a new workflow for proactively avoiding drilling hazards by capitalizing on ultra-deep resistivity simultaneous look-around and lookahead inversion in real-time.

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