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An Efficient 2.5D Algorithm for Logging-While-Drilling Resistivity Measurements ModelingNormal access

Authors: Z. Wu, Y. Fan, L. Wang, R. Zhang, X. Yuan and Q.H. Liu
Event name: 81st EAGE Conference and Exhibition 2019
Session: WL & LWD Processing and Interpretation
Publication date: 03 June 2019
DOI: 10.3997/2214-4609.201901660
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 854.99Kb )
Price: € 20

Fast and accurate modeling of Logging-While-Drilling (LWD) resistivity measurements is important for the real time geosteering and reservoir navigation. Different from the 1D solver which is only applicable to limited formation scenarios and the time consuming 3D algorithm, 2.5D simulators can model the tool responses in complex scenarios, e.g. faults, unconformities, and pinch-outs, very efficiently. Among various 2.5D algorisms, the finite difference method (FDM) has been widely used in controlled source electromagnetic due to its easy implementation. When implementing the 2.5D FDM in LWD modeling, two issues should be taken into account to guarantee the accuracy and efficiency: (1) how to impose the magnetic dipole sources in spectral domain accurately? (2) how to reduce the sampling points for the inverse Fourier transform? In this paper, we present an efficient and accurate 2.5D finite-difference frequency-domain algorithm to model the LWD resistivity measurements. The incident fields in spectral domain are used to replace the magnetic dipoles to avoid the singularity. Efforts are also made to improve the inverse Fourier transform by truncating the integral limits of Gauss-Hermite quadrature. Finally we use a fold model to show that the 2.5D algorithm is more accurate than the 1D solution in complex scenarios.

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