The response of an induction dipmeter and standard induction tools to dipping beds

Gianzero, Stan; Su, Shey-Min

doi:10.1190/1.1442929

Cited by 10 publications

(6 citation statements)

References 2 publications

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“…Following Anderson et al (2001), the uni-axial conductivity tensor with principal axes having strike 𝜙 and dip 𝜃 with respect to bed boundaries is given by…”

Section: Appendix A: Reference Formulasmentioning

confidence: 99%

Limits of three‐dimensional target detectability of logging while drilling deep‐sensing electromagnetic measurements from numerical modelling

Jahani,

Torres‐Verdín,

Hou

2023

Geophysical Prospecting

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Subsurface energy resources are often found in three‐dimensional and non‐spatially continuous rock formations that exhibit electrical anisotropy. Deep‐sensing tri‐axial borehole electromagnetic measurements are currently being used to detect three‐dimensional fluid‐bearing subsurface formations, but borehole environmental, geometrical and instrument‐design factors, together with measurement noise, constrain their practical range of detection and spatial resolution. By understanding the interplay of the above factors on the detectability and sensitivity of borehole deep electromagnetic measurements, one can potentially quantify the uncertainty of both target spatial location (relative to the well trajectory) and electrical resistivity contrast, thereby improving the certainty of three‐dimensional well navigation in real time. We implement a finite‐volume method to numerically solve Maxwell's equations for three‐dimensional electrically anisotropic heterogeneous rock formations in the calculation of magnetic fields measured with deep‐sensing tri‐axial borehole electromagnetic instruments. The calculated magnetic fields at measurement locations are described as the per cent difference between measurements acquired in rock formations with and without conductive or resistive three‐dimensional targets. We quantify the maximum radial distance of detection from the well trajectory and the spatial sensitivity of a commercially available deep‐sensing electromagnetic instrument with respect to environmental factors and measurement acquisition parameters by assuming that the borehole electromagnetic instrument can reliably detect offset three‐dimensional targets if the corresponding per cent measurement difference exceeds the threshold for measurement noise. Results indicate that commercially available tri‐axial deep‐sensing borehole electromagnetic instruments can achieve maximum detection distances between a quarter of and a full transmitter–receiver spacing. In addition, we show that radial detection distances vary from 0.3 to 2 skin depths depending on the geological environment, that is, target conductivity contrast with respect to the embedding background, electrical anisotropy of the background formation and targets and measurement acquisition parameters, that is, frequency and transmitter–receiver spacings. The above findings are not only important for instrument design and measurement‐acquisition planning but also for the effective implementation of real‐time inversion‐based measurement interpretation procedures.

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“…Following Anderson et al (2001), the uni-axial conductivity tensor with principal axes having strike 𝜙 and dip 𝜃 with respect to bed boundaries is given by…”

Section: Appendix A: Reference Formulasmentioning

confidence: 99%

Limits of three‐dimensional target detectability of logging while drilling deep‐sensing electromagnetic measurements from numerical modelling

Jahani,

Torres‐Verdín,

Hou

2023

Geophysical Prospecting

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“…Indeed, past experience has shown that the response of an induction tool calculated in such complex geometries does not depend significantly on the inclusion of the borehole in the model. Analytic solutions developed for dipping bed situations [Gianzero, 1989], [Anderson, 1986], [Shen, 1986] are then directly applicable to this simplified configuration.…”

Section: Dual Inductionmentioning

confidence: 99%

“…The results of the modeling [Gianzero, 1989] are plotted in Figure 2 as a function of the distance separating the axis of the borehole from the horizontal bed boundary. When the dual induction is in the lower formation, far below the boundary, it naturally reads R Iow .... As the sonde approaches the upper resistive formation, both the medium and the deep measurements sense this medium long before it is reached.…”

Section: Dual Inductionmentioning

confidence: 99%

Induction, Resistivity, and MWD Tools in Horizontal Wells

Gianzero

Chemali

1992

International Meeting on Petroleum Engineering

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We shall investigate the applicability of induction and resistivity devices to horizontal wells, where the borehole runs parallel to the bed boundaries.The presence of the borehole may be simply ignored for induction sondes and log response is computed analytically for entire trajectories for the more common radii of curvature used in the drilling process.Since the borehole is an essential part of the problem for focused resistivity devices, the tool respqnse must be evaluated numerically.The modeling results for the resistivity devices indicate that the measurement is more sensitive to conductive than to resistive shoulder beds, whereas, the reverse physical situation is evidenced with induction devices.

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“…Indeed, past experience has shown that the response of an induction tool calculated in such complex geometries does not depend significantly on the inclusion of the borehole in the model. Analytic solutions developed for more general physical situations [Gianzero, 1989], [Anderson, 1986], [Shen, 1986] are then directly applicable to this simplified configuration.…”

Section: Dual Inductionmentioning

confidence: 99%

Induction, resistivity and MWD tools in horizontal wells

Gianzero¹,

Services²,

Chemali³

et al. 1990

BGSM

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Conventional induction and focused resistivity tools ar designed to measure resistivity from a vertical borehole surrounded by a cylindrically invaded zone while minimizing the signal contribution from adjacent horizontal beds. In recent years our understanding of these devices was extended to include beds exhibiting a large dip relative to the borehole as in the case of a highly deviated well. We shall investigate the applicability of induction and resistivity devices to horizontal wells, where the borehole runs parallel to the bed boundaries. The presence of the borehole may be simply ignored for induction sondes and the tool response in computed via an analytic solution. Because of the relative simplicity of the. induction solution, the log response is computed for entire trajectories for the more common radii of curvature used in the drilling process. On the other hand, for focused resistivity devices su,ch as the dual laterolog or the MWD toroid sonde the borehole is an essential part of the problem. The tool response is evaluated using a numerical solution to simulate accurately the complex physical situation. The modeling results for the resistivity devices indicate that the measurement is more sensitive to conductive than to resistive shoulder beds. Typically, for the MWD sonde fIfty percent ofthe resistivity signal comes from the adjacent conductive bed when it is half a foot away from the approaching borehole wall. A similar sensitivity to a resistive adjacent bed is not attained until the borehole has actually penetrated the bed. The reverse physical situation is evidenced with induction devices; resistive adjacent beds are more readily detected than conductive adjacent beds.

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The response of an induction dipmeter and standard induction tools to dipping beds

Cited by 10 publications

References 2 publications

Limits of three‐dimensional target detectability of logging while drilling deep‐sensing electromagnetic measurements from numerical modelling

Limits of three‐dimensional target detectability of logging while drilling deep‐sensing electromagnetic measurements from numerical modelling

Induction, Resistivity, and MWD Tools in Horizontal Wells

Induction, resistivity and MWD tools in horizontal wells

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