Basic Theory of Induction Logging and Application to Study of Two‐coil Sondes

Moran, J. H.; Kunz, Karl S.

doi:10.1190/1.1439108

Cited by 123 publications

(37 citation statements)

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“…Moran & Kunz (1962) define a "coaxial complex conductivity" by dividing Eq. (5) by the coaxial array constant K/4.…”

Section: Homogeneous Isotropic Mediamentioning

confidence: 99%

Revisiting Some Old Unexplained Effects in Induction Logs Within Laminated Formations With the Triaxial Induction Tool

Carvalho¹,

Régis²

2016

Rev. Bras. Geof.

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ABSTRACT. Modern induction triaxial or multicomponent well logging tools provide resistivity anisotropy logs, and estimates of the electrical resistivity of sand laminae in thinly laminated formations. In this paper, coaxial and coplanar vertical logs were modeled in one-dimensional (1D) laminated packages and in their equivalent anisotropic beds, neglecting the presence of the borehole and the invasion zones, to simulate geological environments of hydrocarbon reservoirs with resistivity anisotropy. The objective of this paper is twofold: to perform a quantitative analysis of the anisotropy level of a thinly laminated reservoir as compared to an equivalent anisotropic bed, and, in doing so, to revisit some old and unexplained effects that appear on the triaxial induction logs. These subtle effects may have only a faint influence on the logs themselves, but their study contribute to our understanding of the electromagnetic phenomena involved in the induction logging. The results show that the coaxial logs in the laminated formation converge to the equivalent anisotropic bed response much sooner than the coplanar logs. They also show that there is a considerable difference between the anisotropy index obtained by the triaxial induction tool within laminated formations and the anisotropy coefficient of its equivalent anisotropic bed, even for extremely thin laminae thicknesses.Keywords: well logging, multicomponent induction tools, laminated reservoirs, electrical anisotropy. RESUMO.As atuais ferramentas de perfilagem em poço por indução eletromagnética, denominadas triaxias ou multicomponentes, fornecem perfis de anisotropia elétrica e permitem estimar a resistividade de lâminas de areia em ambientes finamente laminados. Neste artigo, os perfis dos arranjos coaxial e coplanar de bobinas foram simulados em modelos unidimensionais (1D) de sequências laminadas e de suas respectivas camadas anisotrópicas equivalentes, negligenciando o poço e as zonas de invasão, visando simular ambientes de reservatório de hidrocarbonetos com anisotropia elétrica. Os objetivos deste trabalho são basicamente dois: fazer uma análise comparativa do grau de anisotropia de reservatórios laminados com relação a uma camada anisotrópica equivalente e, no desenrolar deste estudo, reavaliar alguns antigos e ainda não explicados efeitos presentes nos perfis de indução. Estes efeitos têm apenas uma sutil influência nos perfis, embora sejam importantes para uma clara compreensão dos fenômenos eletromagnéticos envolvidos na perfilagem. Pelos resultados pode-se verificar que ao reduzir progressivamente as espessuras das lâminas, os perfis do arranjo coaxial convergem para os da camada anisotrópica equivalente bem mais rápido do que os perfis do arranjo coplanar. Pode-se verificar também que, mesmo para lâminas extremamente finas, existe uma considerável diferença entre oíndice de anisotropia, obtido com as ferrramentas triaxiais, com relação aoíndice de anisotropia da camada equivalente.Palavras-chave: perfilagem de poço, ferramentas multicomponente...

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“…Moran & Kunz (1962) define a "coaxial complex conductivity" by dividing Eq. (5) by the coaxial array constant K/4.…”

Section: Homogeneous Isotropic Mediamentioning

confidence: 99%

Revisiting Some Old Unexplained Effects in Induction Logs Within Laminated Formations With the Triaxial Induction Tool

Carvalho¹,

Régis²

2016

Rev. Bras. Geof.

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“…An estimate of the influence of the invaded zone is given in Figure 4. This diagram shows the responses of the coaxial (Moran & Kunz, 1962) and coplanar arrays as a function of the coil spacing. The conductivity of the noninvaded formation is σ t = 1,000mS/m, corresponding to a skin depth of appro- In one of these, the conductivity of the invaded zone is also taken as σ i = 1,000mS/m, corresponding to a homogeneous medium.…”

Section: Radial Investigationsmentioning

confidence: 99%

Fundamentals of coaxial and coplanar coil arrays in induction tools

Carvalho¹,

Santos²,

Régis³

2010

Rev. Bras. Geof.

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ABSTRACT. Until about ten years ago, all commercial borehole induction devices were built up with the traditional coaxial coil arrays. Since then, those apparatus incorporated the unconventional coplanar coil arrays, in order to investigate thinly laminated reservoirs and to locate axially asymmetrical anomalies like vugs and fractures. In order to comprehend the fundamentals of the coplanar array in induction probes, we present a comparative study with the coaxial array through onedimensional modeling of some borehole environments, like: 1) homogeneous, isotropic and unlimited conducting media; 2) invaded thick bed with annulus; 3) horizontal and dipping multilayer sequences; 4) gradational transition zone between two thick beds; and 5) thinly laminated formations. The comparative study allows us to conclude that: 1) the skin effect is strongest in the coplanar array responses; 2) the coplanar array responses are more sensitive to mud filtrate invasion and annulus zones, which are direct indicators of movable oil; 3) polarization "horns" on the coplanar array profiles can be good bed boundary indicators; 4) coplanar arrays present the greatest sensitivity to detect and delineate thinly laminated reservoirs.Keywords: well logging, induction tools, thinly reservoirs, coplanar array. RESUMO.Por meio século, dede sua criação, todas as sondas comerciais por indução eletromagnética (EM) utilizavam o tradicional arranjo coaxial de bobinas.Somente a partir da virada do século XX que estas sondas passaram a incorporar o arranjo coplanar, devidoà necessidade de investigar reservatórios finamente laminados ou anomalias sem simetrias de rotação (fraturas ou cavidades). Com o objetivo de melhor compreender a aplicação do arranjo coplanar nas sondas de indução, elaboramos um estudo comparativo de suas respostas com as do tradicional arranjo coaxial, através de modelagem unidimensional, em alguns ambientes comunsà geofísica de poço: 1) meios homogêneos, isotrópicos e ilimitados; 2) camadas espessas com invasão de filtrado de lama e formação de annulus; 3) sequências de multicamadas horizontais e inclinadas; 4) transição gradacional entre duas camadas espessas; e 5) formações finamente laminadas. Este estudo comparativo entre os arranjos coaxial e coplanar permite concluir que: 1) o efeito pelicularé mais acentuado nas respostas do arranjo coplanar; 2) as respostas do arranjo coplanar são mais sensíveis a movimentação de fluidos na formação, principalmente nas zonas de annulus; 3) os perfis do arranjo coplanar apresentam picos devidosà polarização nas interfaces, que podem ser bons indicadores das fronteiras entre camadas; 4) o arranjo coplanaré mais sensível para detectar e delinear reservatórios finamente laminados.Palavras-chave: perfilagem em poço, ferramentas de indução, reservatório laminado, arranjo coplanar.

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“…Therefore, the caliper data should be used from the density log to properly correct these electric logs to true formation resistivities. See Lynch (1962), Doll (1949Doll ( , 1951, Moran and Kunz (1962), Tixier et al (1959), and Keller and Frischnecht (1966) for detailed discussions and interpretation precautions.…”

Section: Electric-logging Toolsmentioning

confidence: 99%

Methods for Laboratory measured Physical Properties, Gearhart-Owen Well Logs, and the Uyeda Down-Hole Temperature Probe, Leg 61, Deep Sea Drilling Project

Boyce¹

1981

Initial Reports of the Deep Sea Drilling Project

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In the laboratory, we measured heat conductivity, sound velocity, 2-minute GRAPE wet-bulk density, gravimetric wet-bulk density, wet-water content, and porosity on the same sample, when possible.An attempt was made to obtain an undisturbed sample. This is a serious problem in the upper 200 meters of the hole, where the sediments are soft, as the drill bit is 25 cm in diameter, with the ~ 6-cm-diameter coring hole within this cutting bit. Most soft sediments are literally "squirted" into the core barrel and completely disturbed.Because of this core disturbance, few discrete samples for physical-property measurements were taken in the upper part of the hole; however, the continuousanalog GRAPE was always run. Also as a result of the degree of core disturbance in the upper part of the hole, and stiffness of samples which were not disturbed, vane shear strength could be measured on only a small number of "semi-soft" samples.The criterion for an undisturbed sample is undistorted bedding or laminae in the sample. The obvious problem with this criterion is that a completely homogeneous soft-sediment core would not be sampled, even if it were undisturbed.In general, sediment remained in the core liner for about 2 hours. The core section was split, and samples were selected immediately for heat-conductivity measurement, which was done immediately (2-5 minutes). Then a D-shaped sample was cut for the sound-velocity measurement, and a smear slide was made; this sample was wrapped in plastic and placed in a small plastic box with a wet sponge. The sample was then removed from the plastic wrapper, and its surface cleaned with either a spatula or file. Distilled water was squirted on these surfaces, and the velocities were measured; then the GRAPE 2-minute wet-bulk-density determination was made. Afterward, a sub-sample was cut for gravimetric determination of wet-water content, wet-bulk density, and porosity; this sample was cleaned and wrapped in plastic, then sealed in a plastic vial with a wet towel. The vial was placed in a refrigerator above freezing until it could be processed. Initial Reports of the Deep Sea Drilling Project, Volume 61.Basalt samples were handled differently, because of DSDP's official curatorial process. Basalt was not in a plastic liner; therefore, it was necessary to select soundvelocity samples when the cores arrived on deck and were brought into the laboratory. These core segments were wrapped in plastic until the samples were processed by the DSDP curator and eventually split. After the core segment was split, heat conductivity was measured immediately (2-5 minutes) on the split core. Then a minicore (~2 cm diameter) was drilled out of this 1/2 core segment. This mini-core was wrapped in plastic and placed in a plastic vial with a damp sponge until velocity and a 2-minute GRAPE were measured. Velocity was measured across the axis of the mini-core, and 2-minute GRAPE was measured parallel to the axis of the minicore. The mini-core was then wrapped in plastic and sealed in a vial with a wet sponge...

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Basic Theory of Induction Logging and Application to Study of Two‐coil Sondes

Cited by 123 publications

References 5 publications

Revisiting Some Old Unexplained Effects in Induction Logs Within Laminated Formations With the Triaxial Induction Tool

Revisiting Some Old Unexplained Effects in Induction Logs Within Laminated Formations With the Triaxial Induction Tool

Fundamentals of coaxial and coplanar coil arrays in induction tools

Methods for Laboratory measured Physical Properties, Gearhart-Owen Well Logs, and the Uyeda Down-Hole Temperature Probe, Leg 61, Deep Sea Drilling Project

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