Real time 2D inversion of induction logging data

Tabarovsky, L.; Rabinovich, Michael

doi:10.1016/s0926-9851(97)00034-7

Cited by 26 publications

(8 citation statements)

References 5 publications

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“…This is a critical step for the following inversion of 3DEX data for the vertical resistivity. 4. In deviated wells, we use the separation of modes.…”

Section: Discussionmentioning

confidence: 99%

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Measuring Formation Anisotropy Using Multifrequency Processing of Transverse Induction Measurements

Tabarovsky¹,

Epov²,

Rabinovich³

2001

Proceedings of SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMulti-frequency processing of transverse induction measurements (3D Explorer -3DEX™) allows us to reduce the distortion of interpretation by near-borehole effects. Recently, we have developed a multi-frequency processing technique for determining formation anisotropy in vertical and deviated wells. The method, based on a separation of induction and galvanic modes, provides a fast and stable indicator of anisotropy in real time.We consider a borehole oriented along the Z-axis. Axes X and Y are positioned in a perpendicular plane. The set of measurements under consideration includes XX, YY, and ZZ data. The magnetic field XX is excited by an X-oriented transmitter and measured by an X-oriented receiver. Similar definitions are true for YY and ZZ components.We start processing by performing a multi-frequency skineffect correction on the measured XX, YY, and ZZ data. Correction pre-conditions the data for rotation from the tool coordinate system to the formation coordinate system. As a result of the rotation, we calculate responses XX', YY', and ZZ' where axis Z' is orthogonal to the formation boundaries. Axes X' and Y' belong to the boundary planes. The rotation of multi-frequency processed data does not require knowledge of the full tensor of electromagnetic measurements: the rotation can be done only with the principle components XX, YY, and ZZ.Rotation isolates the induction mode in the ZZ component and removes the dependence on the vertical conductivity. This allows for applying a very fast processing technique to calculate horizontal resistivity of the formation, R h . The technique utilizes a modified geometric factor with the transmitter and receiver shifted horizontally with respect to each other.Next, we produce a synthetic response for XX' and YY' components in an isotropic model with formation resistivity, R h . The calculated synthetic response is used to correct the field data for the horizontal conductivity. If the formation is isotropic, the corrected signal will be equal to zero. A nonzero residual signal indicates the presence of anisotropy.The methodology is illustrated with several examples.

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“…This is a critical step for the following inversion of 3DEX data for the vertical resistivity. 4. In deviated wells, we use the separation of modes.…”

Section: Discussionmentioning

confidence: 99%

“…The background model includes everything except borehole and invasion. With the electric field, E, known, the magnetic field, H, may be expressed as follows (Tabarovsky et al, 1996(Tabarovsky et al, , 1998:…”

Section: Appendix B-multi-frequency Focusingmentioning

confidence: 99%

Measuring Formation Anisotropy Using Multifrequency Processing of Transverse Induction Measurements

Tabarovsky¹,

Epov²,

Rabinovich³

2001

Proceedings of SPE Annual Technical Conference and Exhibition

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“…MFF allows us to reduce environmental effects and simplify the data dependence on the formation parameters. MFF processing is based on an expansion of the measured field into a frequency series (Tabarovsky and Rabinovich, 1998;Tabarovsky et al, 2001). One of the series terms does not depend on the borehole and invasion properties.…”

Section: Txmentioning

confidence: 99%

“…12) is full. The situation becomes different when a multi-frequency focusing is applied to the magnetic matrix to extract terms proportional to ω 3/2 (Tabarovsky and Rabinovich, 1998;Tabarovsky et al, 2001). In a deviated well (non-zero relative dip), the matrix of MFF components looks similar to the magnetic matrix:…”

Section: Processing Multi-component Induction Data For Biaxial Anisotmentioning

confidence: 99%

Biaxial Anisotropy: Its Occurrence and Measurement With Multicomponent Induction Tools

Georgi

Schoen

Rabinovich

2008

SPE Annual Technical Conference and Exhibition

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For years petrophysicists interpreted logs as if all formations were locally homogenous and isotropic. They did this even though they well understood that sedimentary deposition occurs layer by layer, making transversely isotropic, TI, media the rule rather than the exception in sedimentary geology. With the widespread availability of multi-component induction logging technology petrophysicists are more willing to use TI resistivity models (i.e., R h and R v ). Generally, sediments buried a few hundred meters or more are subject to a principal stress aligned with the overburden. In many environments, depending on mechanical properties, this leads to bedding perpendicular fractures, which can give rise to biaxial anisotropy in the macroscopic petrophysical properties.We have developed resistivity models for laminated sand-sale formations in the presence of drilling-induced and natural fractures. The principal resistivities R x , R y , R z are expressed as a function of horizontal and vertical resistivities of unfractured formation, fracture porosity and resistivity of fracture which is the resistivity of mud filtrate in the case of drilling induced fractures or the connate water resistivity and saturation in the case of natural fractures. These models allowed us to study the effect of fractures on the three principal resistivities as a function of laminated shale content and as a function of fracture porosity for both drilling induced and natural fractures. The combined three-step analysis of measured principal resistivities based on the modular concept allows a separation and quantification of the two anisotropy sources: fracturing and lamination. The analysis based on the three principal resistivities provides an estimate of fracture porosity, resistivity of the porous sand fraction (without fractures) and water saturations. We have also developed an inversion algorithm for the biaxially anisotropic formations that reliably determines three principal resistivities from multi-component induction measurements. First, in the least-square inversion the multi-frequency focused magnetic field tensor is rotated to the principal coordinate system. This rotation is characterized by three angles: ϕ, θ, and ψ; and three principal, diagonal magnetic field components H xx , H yy , and H zz . After the three angles and three principal components are determined, we recover principal formation resistivities using a fast inversion algorithm based on a look-up table approach. To validate the theory and algorithms described above, we have simulated the multi-component induction measurements in thick biaxially anisotropic layers for various sets of parameters and used the software to process the data. The new approach was also applied to the real measurements acquired in the well with drilling induced fractures and as a result principal formation resistivities, fracture orientation, and fracture porosity were reliably determined.

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“…Sophisticated processing and interpretation techniques are available for vertical and near-vertical wells. Focusing and inversion algorithms are designed to determine invasion profile, measure resistivity deeply into the formation (up to 10 ft), and provide high vertical (up to 1 ft) resolution [9][10][11] .…”

Section: Hdil Application To Formation Evaluationmentioning

confidence: 99%

Application of Array Resistivity Measurements in Horizontal Wells

Frenkel¹,

Geldmacher²,

Georgi³

et al. 2000

Proceedings of SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWhen interpreting array resistivity measurements in horizontal wells, the objectives are quite different from traditional data interpretation in vertical or near vertical boreholes. While the emphasis for the latter is put on resolving the invasion profile and "true" formation resistivities, the former measurements are aimed at the identification of any nearby geometry, e.g., cap rock or oil-water contacts in the vicinity of the wellbore. In order to accomplish this, new algorithms have been developed ranging from real-time "geosteering" applications to sophisticated inversion-based processing.Early resistivity tools were complex devices that utilized bucking coils and guard electrodes to "focus" the measurement onto a particular region in the formation, for example, shallow and/or deep. These analog focusing methods were designed for and worked well in quasi-horizontally layered formations penetrated by a near vertical well.

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Real time 2D inversion of induction logging data

Cited by 26 publications

References 5 publications

Measuring Formation Anisotropy Using Multifrequency Processing of Transverse Induction Measurements

Measuring Formation Anisotropy Using Multifrequency Processing of Transverse Induction Measurements

Biaxial Anisotropy: Its Occurrence and Measurement With Multicomponent Induction Tools

Application of Array Resistivity Measurements in Horizontal Wells

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