Abstract
Efficient well placement profoundly depends on early geo-steering decisions to maximize reservoir contact. In highly undulated thin target zones, this can be more concerning as the formation dip changes abruptly. Such environments present a significant challenge where geo-mapping instruments are placed farther behind the bit in the bottom hole assembly, leading to relatively late decision making and more aggressive well path corrections. This paper presents the advantages of placing geo-mapping tools close to the drilling bit position leading to enhanced reservoir contact (Net-to-Gross) and less tortuous well bores.
Deep and ultra-deep azimuthal resistivity measurements have historically provided a step change for proactive geo-steering, yet the challenge has always been the proximity of the sensors to the bit opposed to other less sophisticated near bit sensors. Well placement with conventional configurations have been regularly utilized to ensure maximum reservoir exposure with varying results due to unforeseen geo-structural changes such as the formation dipping regime (1D environment), lateral boundaries (2D environment) or channels (3D environment). A new tool design was introduced in which the ultra-deep resistivity transmitter was embedded into the rotary steerable system allowing 1D and 3D inversions to be closest to the bit position, offering at-the-bit visualization of the reservoir, hence, earlier, and less aggressive well path corrections could be made to optimize well placement and increase reservoir contact. Geo-mapping formation boundaries while drilling high angle sections with a near bit ultra-deep azimuthal resistivity inversion minimized potential reservoir exits while also minimizing wellbore tortuosity. This is critical for efficient well placement, minimizing drilling risks and smooth completions deployment. Horizontal wells were placed in thin reservoir targets that are successfully resolved by integrating 1D and 3D inversions to improve reservoir mapping, remote lithology and fluid identification to optimize well placement and reservoir evaluation. The accuracy of reservoir visualization from the near-bit resistivity inversion has been validated by other logging while drilling measurements in the drill string, such as triple combo and azimuthal images from several sensors.
This paper presents the global first at-the-bit look-around inversion utilizing an ultra-deep resistivity sensor embedded in a rotary steerable system for horizontal well placement in two target sand packages. The proximity of the ultra-deep sensor to the bit enabled quicker decisions to optimally place the well in the target zone while reducing well tortuosity leading to a higher net-to-gross and a smoother well trajectory. This also facilitated the deployment of the completion equipment saving costly rig time.
