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C. Richard Liu - One of the best experts on this subject based on the ideXlab platform.
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Induction and Logging-While-Drilling Resistivity Tool Response in a Two-Dimensional Isotropic Formation
Theory of Electromagnetic Well Logging, 2017Co-Authors: C. Richard LiuAbstract:In the previous chapters, we discussed the induction and LWD Tool responses in a homogenous and a one-dimensional formations including horizontally layered and cylindrically layered formations. In well logging, formations with both cylindrical and planar boundaries are often encountered. In general, this case is a three-dimensional (3D) problem and analytical method is difficult to apply. However, if the Tool is centered and the borehole is vertical, the system will be axially symmetrical, in which case an analytical solution can be found. In this chapter, we will discuss the solutions of the induction and logging-while-drilling (LWD) Resistivity Tool response in a vertically and radially layered formation without eccentricity. Many simulation methods to model the induction and LWD logs in such formations have been developed. If we assume the vertically layered formation has axial symmetry, the 3D problem is simplified to a two-dimensional problem. Due to the absorption of electromagnetic waves in the formation, the waves propagating in the formation decay exponentially. A forward computation method may be unstable if the wave propagation is not treated properly. In this chapter, we present a stable algorithm to solve this problem by using a horizontal eigenmode expansion method. This method was first discussed by Chew and Pai.
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Triaxial Induction Tool and Logging-While-Drilling Tool Response in a Transverse Isotropic-Layered Formation
Theory of Electromagnetic Well Logging, 2017Co-Authors: C. Richard LiuAbstract:In Chapter 4, Triaxial Induction and Logging-While-Drilling Resistivity Tool Response in Homogeneous Anisotropic Formations, we discussed the induction and logging-while-drilling (LWD) Resistivity Tool response in anisotropic homogenous formations. However, as pointed out in Chapter 1, Introduction to Well Logging, the earth formations mostly contain layers with different resistivities. The layers will greatly affect Tool response, especially when layers are relatively thin, as in the case of sand-shale formations. Generally the axis of the logging Tool or the borehole is deviated from the normal direction of the formation layers, resulting in a dipping angle of the Tool with respect to the formation layers, which must be considered in the discussions. In this chapter, we will discuss the induction and LWD Resistivity Tool responses in a layered formation with dipping angles for the transverse isotropic formations. For the simplicity, the discussions in this chapter assume that there is no borehole and mandrel in the formation. In other word, there is no change in the formation in the radial direction, so that one-dimensional analysis can be applied. For the cases where vertical layers exist, please refer to the later chapters of this book (see chapters: Induction and Logging-While-Drilling Tool Response in a Cylindrically Layered Isotropic Formation; and Induction and Logging-While-Drilling Resistivity Tool Response in a Two-Dimensional Isotropic Formation). For the formations that are layered and biaxially anisotropic, the Tool response will be analyzed in Chapter 6, Triaxial Induction and Logging-While-Drilling Logging Tool Response in a Biaxial Anisotropic-Layered Formation.
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Triaxial Induction and Logging-While-Drilling Resistivity Tool Response in Homogeneous Anisotropic Formations
Theory of Electromagnetic Well Logging, 2017Co-Authors: C. Richard LiuAbstract:In this chapter, we will study the response of induction and logging-while-drilling (LWD) Resistivity logging Tools in homogeneous lossy formations. As we know, in induction and LWD Resistivity logging Tools, the transmitter and receiver coils are of finite dimensions. However, compared with the skin depth, these antennas are electrically small. To simplify the solutions, in the analysis below, we use a magnetic dipole to replace the antennas. Therefore the coil antennas can be simplified as equivalent magnetic dipoles without much loss of accuracy. Therefore the solutions to the response of induction or LWD logging Tools in homogeneous lossy media is converted to the electromagnetic field generated by magnetic dipoles in homogeneous lossy media.
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Triaxial Induction and Logging-While-Drilling Logging Tool Response in a Biaxial Anisotropic-Layered Formation
Theory of Electromagnetic Well Logging, 2017Co-Authors: C. Richard LiuAbstract:In Chapter 4, Triaxial Induction and Logging-While-Drilling Resistivity Tool Response in Homogeneous Anisotropic Formations, the triaxial induction Tool performance was discussed in a homogeneous biaxial formation. In Chapter 5, Triaxial Induction Tool and Logging-While-Drilling Tool Response in a Transverse Isotropic Layered Formation, we studied an analytical method to solve the problem of triaxial logging Tools in a layered transverse isotropic (TI) formation. In many cases, the formation gets more complicated. For example, in a layered TI formation, if cracks present as discussed in Chapter 4, Triaxial Induction and Logging-While-Drilling Resistivity Tool Response in Homogeneous Anisotropic Formations, the formation can be considered to be a biaxial anisotropy. It is important to study the Tool response in a biaxial-layered formation. Due to the complexity of the environment, the mathematic formulations become more involved. Fortunately, if we ignore borehole effect and eccentricity, analytic solutions can be found to the problem. Even though numerical solutions can be applied, the analytical solutions are always advantageous in terms of computation speed and ease of use. The analytical solution may be a good approach for inversion. In this chapter, we will derive the full magnetic field response of a triaxial induction sonde in a layered biaxial anisotropic medium. The derivation of the triaxial induction Tool response in a layered biaxial anisotropic formation is divided into four steps. The source is assumed to be a magnetic dipole with three components. The first step is to find the solutions to the Maxwell’s equations in a homogeneous biaxial anisotropic media based on the electric field. Using this solution, the second step observes the wave-propagation characteristics in an unbounded biaxial anisotropic formation. The third step brings the boundary into the consideration and transmission and reflection coefficients are found using the concept of generalized transmission and reflection matrix, with which the fields can be obtained in any layer. Final step is to derive the expressions of the magnetic fields by substituting the electric field obtained in the previous steps into the Maxwell’s equations with tensor conductivities.
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Theory of the Through-Casing Resistivity Logging Tool
Theory of Electromagnetic Well Logging, 2017Co-Authors: C. Richard LiuAbstract:Conventional laterolog, logging while drilling, or induction Resistivity Tools log a formation before the borehole is cased. As the oil and gas prices increase and the improvements of the drilling technology, many oil fields are reevaluated and thinner layers of reservoir that were considered less profitable are reopened for production. Many oil fields are now in the process of second or third production period. To locate the oil- or gas-bearing zones accurately, it becomes necessary to evaluate the formation in the previously cased holes. It is relatively easy to use radiation Tools or acoustic Tools through-casing metal. However, using electrical ways is rather difficult due to the shielding effect of the metal casing. When a metal casing is applied, conventional Resistivity logging Tools are not operative because the electrically conductive casing practically shields electromagnetic signals from the Tools and prevents any electrical or electromagnetic energy from entering the formation. However, there are many instances when Resistivity logging through the casing is needed. For example, measuring formation Resistivity profile change during the years of production is critical to assess the oil or gas reservoir for further exploration in an old oil field. Therefore the application of through-casing Resistivity Tool becomes important for secondary production of old reservoirs.
L.f. Demkowicz - One of the best experts on this subject based on the ideXlab platform.
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Simulation of multifrequency borehole Resistivity measurements through metal casing using a goal-oriented hp finite-element method
IEEE Transactions on Geoscience and Remote Sensing, 2006Co-Authors: D. Pardo, C. Torres-verdintorres-verdin, L.f. DemkowiczAbstract:The authors simulate multifrequency through-casing Resistivity Tool measurements operating at different frequencies in a borehole environment for the assessment of rock-formation properties. Rock formations are assumed to exhibit axial symmetry around the axis of a vertical borehole. The simulations are performed with a goal-oriented hp-adaptive finite-element method that delivers exponential convergence rates in terms of the quantity of interest (for example, the second vertical difference of the electric potential) against the CPU time. Numerical results confirm the efficiency and accuracy of the method, allowing for high-accuracy and reliable simulations of borehole logging measurements in the presence of highly conductive steel casing. The study of different Tool configurations shows the advantages of using calibrated instruments with toroid antennas located on the borehole wall. The agreement between the numerical and analytical results, when the latter is available, is quantified. Errors on the simulations are consistently below 0.1%
Zhang Zhao-qi - One of the best experts on this subject based on the ideXlab platform.
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Recent Advances in Foreign Logging While Drilling Technology
Well Logging Technology, 2008Co-Authors: Zhang Zhao-qiAbstract:Introduced are specialities,structures and parameters of some newly developed Logging While Drilling(LWD)Tools used by eminent well logging companies in the past few years,such as quadrupole shear wave technology,multipole sonic Tools,compact propagation Resistivity Tool,azimuthal focused Resistivity sensor,azimuthal deep Resistivity Tool,etc.Recent development in LWD technologies and Tools can extend measurement range,improve data quality and reduce rig time and cost.Newly advances in this field make LWD technology play more important role in directional drilling and formation evaluation.
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Recent Advances in Foreign Wireline Logging Technology
Well Logging Technology, 2008Co-Authors: Zhang Zhao-qiAbstract:Introduced are specialities,structures and parameters of some newly developed well logging Tools used by eminent well logging companies in the past few years,such as the new 3-D electrode-type logging Tool,the new asymmetrical array induction logging Tool,the new micro-Resistivity pad Tool,the oil-based mud imaging Tool,the novel through-casing Resistivity Tool,the formation tester with an oval pad,the ArmadaTM sampling system and the ConneX perforating system.These technologies and Tools can be used to determine 3-D formation Resistivity distribution in deviated and horizontal wells,acquire clean fluid samples in short period,overcome the deficiency of traditional perforating system and increase oil and gas production.
Tsili Wang - One of the best experts on this subject based on the ideXlab platform.
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A Discovery In The Lwd Resistivity Tool Response In A High-Angle Well - A Case Study Of Spiraled Borehole Respons
2012Co-Authors: Mark Kenneth Dennis, John Rasmus, Dave Kennedy, Tsili WangAbstract:Anomalous" LWD propagation Resistivity log res- ponses were observed in a high angle well. The ano- malous character includes anomalous curve separa- tions, periodic variations with depth, and anticorrela- tion of the phase and attenuation apparent Resistivity curves. In particular, the long-spacing curves show larger depth variations than the short spacing curves. It was also observed that the cyclic variations remain in either compensated or uncompensated logs. The section of the well was drilled with oil-based mud (OBM) in a shale formation. Several possible hypo- theses were tested to explain the log. Numerical modeling showed that Resistivity anisotro- py, Tool eccentering, thin beds or dielectric effects alone could not explain the curve separations and the anticorrelation of the attenuation and the phase dif- ference apparent Resistivity log responses. To test the hypothesis of spiraled borehole effect, a detailed 3D numerical study was performed. Contrary to an earli- er anticipation, a spiraled borehole itself does not necessarily cause significant cyclic log variation. Spirals gouges of reasonable geometrical dimensions failed to reproduce the magnitudes of variations in depth as observed in either the attenuation or phase difference logs, particularly for long spaced arrays. It is discovered that only a combination of a spiraled borehole with Resistivity anisotropy, and optionally including Tool eccentering effect, can explain the ob- served anomalous log responses, consistent with the anisotropic shale lithology. The numerical study fur- ther revealed that the alternation of the maximum and minimum responses in the logs does not depend on the transmitter-to-receiver or receiver-to-receiver spacing, but rather on the spiral period, which ex- plains the long- and short-spaced logs having closely similar period. Simulations in geometrically same spiral models, with and without anisotropy indicate an "amplifica- tion" of the spiral affects with inclusion of anisotropy in the formation model. Formation anisotropy can "amplify" spiral effects, which are normally a minor perturbation for apparent Resistivity responses. This opens the idea that a mixture of various Resistivity affecting environments may be more the norm. The combination of these effects must be corrected for simultaneously, instead of correcting for a single en- vironmental effect, or another, as is now the usual practice in the industry.
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A fast modeling method to solve Maxwell's equations in 1D layered biaxial anisotropic medium
GEOPHYSICS, 2011Co-Authors: Sofia Davydycheva, Tsili WangAbstract:A fast 1D electromagnetic modeling method has been developed and tested. It allows simulating triaxial responses of induction and propagation Resistivity logging Tools for both logging-while-drilling and wireline applications. An important new feature of the method is its ability to model Resistivity Tool responses in 1D biaxial anisotropic medium, whose anisotropy tensor has up to three different principal values. This feature is particularly useful to evaluate fractured formations. A few possible implementations of the method have been suggested. The modeling code has been extensively tested versus three other independent modeling methods. The new method demonstrates a high sensitivity of transverse and cross couplings of triaxial tensor measurement to all three principal values of the conductivity tensor.
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Modeling of electromagnetic logs in a layered, biaxially anisotropic medium
SEG Technical Program Expanded Abstracts 2011, 2011Co-Authors: Sofia Davydycheva, Tsili WangAbstract:A fast 1D electromagnetic (EM) modeling method has been developed and tested. It allows simulating triaxial responses of induction and propagation Resistivity logging Tools for both logging-while-drilling and wireline applications. An important new feature of the method is its ability to model Resistivity Tool responses in 1D biaxial anisotropic medium, whose anisotropy tensor has up to three different principal values. This feature is particularly useful to evaluate fractured formations. A few possible implementations of the method have been discussed. The modeling code has been extensively tested versus three other independent modeling methods. The new method is used to demonstrate a high sensitivity of transverse and cross-couplings of triaxial tensor measurement to all three principal values of the conductivity tensor.
A.q. Howard - One of the best experts on this subject based on the ideXlab platform.
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Petrophysics of magnetic dipole fields in an anisotropic earth
IEEE Transactions on Antennas and Propagation, 2000Co-Authors: A.q. HowardAbstract:Measurement-while-drilling (MWD) Resistivity log data are often acquired in highly deviated or horizontal holes. The loop sensors are located on the drill collar and are approximated as magnetic dipoles. The conductivity of the earth in the vertical direction /spl sigma//sub v/ and horizontal direction /spl sigma//sub h/ are almost always different. When an MWD Resistivity Tool enters a new bed, the response is compared with the precomputed logs to aid in the determination of the location of the drill bit. The MWD Tool response, however, is sensitive to Resistivity anisotropy. An alternative method is used to derive analytical expressions for the Sommerfeld-type integrals. Numerical results give typical MWD Tool response as a function of the inclination angle /spl theta/ the Tool makes with respect to the axes of anisotropy and also as a function of the anisotropy index /spl kappa/=(/spl sigma//sub h///spl sigma//sub v/)/sup 1/2/.
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Electromagnetic fields of loop antenna with axis parallel to planar interface
Journal of Applied Geophysics, 1997Co-Authors: A.q. HowardAbstract:Abstract Wireline Resistivity Tools in vertical or near vertical holes are run with centralizers to keep the Tool near the center of the borehole. In this environment the borehole signal usually behaves in a predictable manner and is not difficult to compensate. An MWD Resistivity measurement Tool is now often run in highly deviated or horizontal well completions. The rotation of the drill pipe produces continuous lateral as well as axial motion of the Resistivity Tool. A Resistivity Tool measurement is a function of the Tool standoff distance x s from the borehole wall. When x s is small and the Tool surface is near the borehole wall, the effect can be large. In this regime, the magnetic dipole mathematical model, particularly for short array spacings, is not adequate. This paper formulates and computes the finite-size loop electromagnetic response near an idealized interface. Graphical results compare the proximity effect predicted by loop and dipole theories.