Case Study of Active Resistivity Ranging With Ultradeep Azimuthal Resistivity Measurements While Drilling
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Active resistivity ranging with an ultra-deep azimuthal resistivity (UDAR) tool has the potential for the real-time detection and spatial tracking of a nearly parallel target well, either cased or open filled with conductive fluid, during the drilling of a new borehole. Real case studies are presented with postmortem field data to illustrate and evaluate this novel ranging while-drilling technology.
It has been previously demonstrated that the measured data of ultra-deep harmonic anisotropic attenuation (UHAA) channels of the UDAR tool can be used while-drilling to estimate the distance to the target well using the corresponding simulated tool response table. Moreover, the measured angles of the second harmonics of the UDAR tool can be used to derive the azimuthal orientation of the respective target well. Motivated by the successful initial results, this ranging technology was applied to distinct scenarios, with potential application of collision avoidance, i.e., steering the new borehole towards a safe direction to prevent it from accidentally colliding with an existing well. The other possible ranging application would consist of well interception, by purposedly drilling into a cased well or an open hole to control its fluid flow. The first field study occurs at the kick-off stage, where both wells are close to vertical in terms of survey inclination. The other case involves the scenario of high-angle wells. The performance of active resistivity ranging is evaluated for both scenarios with postmortem field data.
In the vertical well case, the formation layers are nearly perpendicular to the wells in the zone of interest. The formation effect is primarily due to inhomogeneity and its impact is relatively moderate in the measurements since the harmonic anisotropic attenuation essentially represents the ratio of second harmonic coupling voltages between transversely polarized magnetic dipoles. Consequently, we can accurately obtain the distance to the target cased well with the ranging workflow. However, in the high-angle well scenario, the measurements of the UHAA channels are very sensitive to both the casing and the formation layers. Thus, an additional step in the ranging workflow is applied to first remove the formation-only response from the measured data, and only then the distance of the target well is computed. This formation-only response can be calculated while-drilling with formation model created with the shallow resistivity measurements that are not affected by the casing. The respective resistivity model incorporates both the horizontal resistivity and anisotropy. Upon removal of the formation-only effect from the UHAA measurements, improved ranging results in terms of distance accuracy were observed.
The results of the case studies demonstrated what can be expected from the novel active resistivity ranging, by using the UHAA measurements of the UDAR tool, in near-parallel scenarios between the wells. As a comparative analysis, the processed ranging distances and the azimuthal orientation from the field studies were shown to effectively agree with the results obtained directly from the well survey data of the borehole trajectories, especially for the vertical well case. For the high-angle well scenario, the formation effect on the ultra-deep harmonic anisotropic measurements must be first removed to improve the well distance estimation. Besides the formation effects caused by resistivity anisotropy, other subsurface features, such as bed boundaries proximity, high formation dip, and discontinuities (e.g., faults), which are more common to be encountered in high-angle wells, must be considered when deploying the respective active resistivity ranging while-drilling.
Your Instructor
Diogo Salim is the Reservoir Mapping Integration Group (RMIG) Lead in the SLB Engineering department of Houston Formation Evaluation (HFE), based in Sugar Land, Texas - USA. He is currently working on novel LWD technologies and digital applications in the domain of geosteering and reservoir mapping, well ranging and reservoir characterization while drilling. He is a Principal petro-technical expert, who joined SLB in 2004 and has worked in the wireline and drilling areas holding various job positions across research, engineering, all the way to operations. He received an MSc. degree in Petroleum Engineering from Federal University of Rio de Janeiro (Brazil) with emphasis on reservoir engineering and numerical simulation. He has contributed to various patent applications and authored/co-authored over 40 papers and articles in different professional societies and external conferences in the energy industry.