Efects of anisotropic changes on the conductivity of sedimentary aquifers, southeastern Niger Delta, Nigeria

• Autorzy: George N. J. , Bassey N. E. , Ekanem A. M. , Thomas J. E.

Identyfikatory

DOI

10.1007/s11600-020-00502-4

• Języki publikacji: EN

Abstrakty

EN

Sundry soils/rocks are characterized by electrical properties with clearly or obscurely expressed anisotropies. These anisotropic efects may be low, moderate or high depending on the coefcient of anisotropy (λ). The vertical electrical sounding technique employing Schlumberger electrode confguration and lithological information from boreholes were deployed to characterize the lithological diversity in homogeneous and anisotropic geologic units that serve as aquifer systems and their overlaying layers in the coastal region of Akwa Ibom State. Based on the λ, the assessed volume of sedimentary formation is classifed into low anisotropy λ<1.2 , moderate anisotropy (1.2 < λ ≤ 1.3) and high anisotropy (λ > 1.3) with alluvium (64.3%), inter-bedded shale and sandstone (14.3%) and shale and slate (21.3%). The estimated percentage of respective compositional coverage indicates that alluvium is dominant, while the blended inter-bedded shale and sandstone as well as the shale and slate are minor geologic units in the Benin Formation. Inferred index of spread of alluvium indicates that the homogeneous and anisotropic units assessed are intrinsic/microscopic in nature as identifed by the impressed current that passed through geologic system. The results showcased that the plot between the strike-dependent resistivity ( ρ_θ ) at arbitrary chosen strike and geometric mean resistivity ( ρ_m ) can be used as a yardstick for inferring the degree of consistency of geologic compositions in homogeneous and anisotropic media. Both the quantitative (graphic) and qualitative (contour) results portend the thin possibility of having anisotropy free geologic units. The finding proposes that ground resistivity measurements and interpretations of geologic structures should be constrained by borehole information in order to frm up the intended plans for obtaining clearer, defendable and well-resolved subsurface structures.

Słowa kluczowe

EN

anisotropy; hydrogeological units; diversity; sensitivity; strike-dependent resistivity

PL

anizotropia; jednostki hydrogeologiczne; różnorodność; wrażliwość

• Wydawca: Instytut Geofizyki PAN ; Springer
• Czasopismo: Acta Geophysica
• Rocznik: 2020
• Tom: Vol. 68, no. 6
• Strony: 1833--1843
• Opis fizyczny: Bibliogr. 38 poz.

Twórcy

autor

George N. J.

• Department of Physics (Geophysics Research Group), Akwa Ibom State University, PMB 1162, Mkpat Enin, Uyo, Nigeria

autor

Bassey N. E.

• Department of Geology, Akwa Ibom State University, PMB 1162, Mkpat Enin, Uyo, Nigeria

autor

Ekanem A. M.

• Department of Physics (Geophysics Research Group), Akwa Ibom State University, PMB 1162, Mkpat Enin, Uyo, Nigeria

autor

Thomas J. E.

• Department of Physics (Geophysics Research Group), Akwa Ibom State University, PMB 1162, Mkpat Enin, Uyo, Nigeria

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