Abstract：

　　Both of the structure of logging tools and environmental factors affect the response of LWD (Logging While Drilling) electromagnetic wave resistivity tools. The structures of the receiver coil, coil groove, coil cover and metal mandrel impact on the amplitude of the induced voltage in the receiver coil, and the measurements of resistivity are affected indirectly. In terms of environment factors, the responses of borehole-mud, surrounding rock, drilling fluid invasion, dielectric properties and anisotropy contribute to the real response of logging tools. These responses corresponding to environment factors should be removed to obtain the real response of the undisturbed formation. Thus, it is indeed imperative to study the effects of tool-structure and environments factors for the interpretation and application of logging information. In this paper, an example of numerical simulation of a wave propagation resistivity tool based on a 3D FEM (Three-dimensional Finite Element Model) method is introduced. We have conducted the numerical simulation of the tool-structure and environments factors based on the real structure of the logging tools. The absolute value of the induced voltage rapidly increases with an increase of coil radius, width of coil groove, length of coil slot, and space proportion of cover. The absolute value decreases with an increase of the depth of the coil groove. The shallow mode is more susceptible than the deep mode to the above factors. Moreover, the absolute value has a weak relation with the conductivity of the metal drill collar. In the respect of environmental factors, the apparent amplitude ratio resistivity decreases while the apparent phase shift resistivity increases due to the borehole-mud while the effects of mud become weaker as the mud resistivity increases; both in the apparent amplitude ratio and the apparent phase shift resistivity increase due to the anisotropy. The value difference between the apparent amplitude ratio and apparent phase shift resistivity increases owing to the effects of the mud invasion, surrounding rock, dielectric or anisotropy. The difference of the two above resistivity values increases at first, and then decreases due to the effect of mud. The influence of dielectric properties becomes more significant in high resistivity formations. Apparent phase shift resistivity is more sensitive than the apparent amplitude ratio resistivity for dielectric effects.

Key words：LWD electromagnetic propagation resistivity logging tool structure environment correction finite element model

Received： 06 July 2016

Corresponding Authors：

Cite this article：JIANG Ming,KE Shizhen,LI Anzong, et al. Factors effecting simulation of the response of LWD electromagnetic wave resistivity based on 3D FEM[J]. 石油科学通报, 2016, 1(3): 342-352.

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