Wellsite Interpretation of Multicomponent Induction Log Data in Anisotropic Media

Kriegshäuser, Berthold; Fanini, Otto; Yu, Liming; Gupta, Pankaj; Horst, Juun van der

doi:10.2118/62906-ms

Cited by 2 publications

(1 citation statement)

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“…From the beginning of this century, the need for more information from interbedded sand-shale turbidite sequences prompted the development of the triaxial or multicomponent wireline induction tool, with nine coupling components, that have been successfully used to determine formation anisotropy and bedding dip angle (Kriegshäuser et al, 2000). Currently, besides being the main location tool of finely laminated reservoirs, triaxial sources and sensors are also applied in many situations of asymmetric geometry, such as locating dissolution cavities (vugs) in carbonates and fractured zones in the vicinity of the wells, and monitoring invasion fronts in horizontal wells (Omeragic et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Borehole Effects on Coaxial and Coplanar Logs of Triaxial Tools in Laminated Formations with Anisotropic Shale Host

Carvalho

Régis²,

Silva³

2022

Braz J Geophys

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This paper studies the borehole effect in the triaxial induction logs within sand-shale laminated models with isotropic and anisotropic shale laminae with transverse isotropy. This study compares results from a 3D Vector Finite Element program (with borehole) and a 1D-Analytic code (no borehole). In comparison with the coaxial configuration, the vertical coplanar logs show a stronger horning effect in front of the laminated pack boundaries; a more intense skin effect to the conductivity media; and a more prominent oscillation within the laminated formation. In addition, feature changes (angular or smooth shapes) occur on the coaxial and coplanar responses as the dipping angle varies. The sensitivities of the logs to the anisotropy and borehole are opposite, i.e., for small angles where the coaxial is least sensitive, the coplanar is most sensitive, and for large angles where the coaxial is most sensitive, the coplanar is least sensitive. The main physical cause of these opposite behaviors to the anisotropy and borehole effect is the same: the weight of the horizontal magnetic component of the horizontal dipole contribution on the coaxial and coplanar dipping logs since it is the only one of the four magnetic field components that has anisotropy sensitivity and strongest skin effect.

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Section: Introductionmentioning

confidence: 99%

Borehole Effects on Coaxial and Coplanar Logs of Triaxial Tools in Laminated Formations with Anisotropic Shale Host

Carvalho

Régis²,

Silva³

2022

Braz J Geophys

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Well-site Resistivity Anisotropy Interpretation: A 2-D Method and a Case Study from the Gulf of Mexico

Frenkel

2002

SPE Annual Technical Conference and Exhibition

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A novel rapid inversion method has proved to be one of the fastest methods designed for accurate, multi-dimensional interpretation of array resistivity logs. In this paper, we discuss the development of this method as a basis for future well-site anisotropy interpretation, using data recorded with the 3D ExplorerSM multi-component induction instrument (3DEXSM). The new method demonstrates the feasibility for a substantial reduction of computing time by partitioning the two-dimensional (2-D) inverse problem into a sequence of smaller one-dimensional (1-D) problems (radial inversion). It rapidly converges to a true earth model. In the case of a vertical well (2-D), the method requires multiple 1-D, yet only a few 2-D forward model calculations. To achieve this substantial extra increase in computing speed, 1-D forward responses are pre-calculated and stored as look-up tables to be consulted at inversion time. The computations required for a full 2-D interpretation process is thus reduced to a set of four to five 2-D forward response calculations at a limited number of observation points. As a result, the proposed method allows the entire spectrum of measurements to be combined as a part of an interpretation scheme suitable for well-site processing. The method is capable of providing a consistent and accurate picture of formation resistivity anisotropy. The potential for the technique is presented and illustrated by anisotropy interpretation results from 3DEX data acquired in a vertical well in the Gulf of Mexico. These results are shown to be in excellent agreement with what is inferable directly from the raw 3DEX logs. They are also in good agreement with results from an independently performed anisotropy interpretation based on a rigorous 2-D inversion technique. A field example confirms the capability of the proposed technique to deliver comparable quality results now achievable with standard log analysis center processing in run times comparable to run times for other familiar well-site deliverables. Introduction The recently introduced multi-component induction logging technology, 3D ExplorerSM (3DEXSM), allows the log analyst to obtain a comprehensive picture of the formation resistivity distribution around the borehole, including formation anisotropy. The 3DEX tool yields five magnetic field components acquired at ten distinct frequencies.1 Due to near-borehole and shoulder-bed effects, such measurements produce merely apparent resistivities. Consequently, they must be further interpreted to yield the required true horizontal and vertical formation resistivities. This paper describes an inversion process that has been developed for this purpose. The inversion of multi-component induction logging data can be described in terms of a process to map a data space into a formation parameter space. The inversion process thus furnishes a distribution of horizontal and vertical resistivities surrounding the borehole, whose synthetic tool responses match the observed data within a given range of uncertainty. The use of inverted 3DEX data in petrophysical interpretation results in a more accurate reservoir description, as well as in a much improved hydrocarbon saturation determination. By now, the industry has developed numerous fast resistivity logging data interpretation techniques. These are mainly based on either an approximate solution to an inverse problem,2 or on focusing concepts.3 The results of the application of a very fast, so-called ‘turbo boost’ method4 to multi-component induction data have not yet been published.

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Wellsite Interpretation of Multicomponent Induction Log Data in Anisotropic Media

Abstract: TX 75083-3836, U.S.A., fax 01-972-952-9435.

Cited by 2 publications

References 3 publications

Borehole Effects on Coaxial and Coplanar Logs of Triaxial Tools in Laminated Formations with Anisotropic Shale Host

Borehole Effects on Coaxial and Coplanar Logs of Triaxial Tools in Laminated Formations with Anisotropic Shale Host

Well-site Resistivity Anisotropy Interpretation: A 2-D Method and a Case Study from the Gulf of Mexico

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