Linear geological structure, traverse orientation and structure resolution and characterisation using 1D and 2D resistivity images

Abstract

ABSTRACT This paper presents results of previous investigations involving 1D and 2D resistivity imaging of linear geological structures with varying traverse orientations relative to the structure azimuth with a view to determining the effect of such variation on the resolution of the structures. It observed that the orientation of 2D traverse relative to a fault azimuth significantly determines the resolution of the structure while the alignment of 1D vertical electrical sounding (VES) relative to the structure azimuth defines the form of the VES curve and leads to inconsistency in resistivity and thickness estimates and overall depth estimates at deep depth. 2D structures were best resolved with 2D resistivity images when the traverses were established normal (in-line) to the structure azimuth. Structures delineated by in-line 2D images are corroborated by in-line VES interpretation models and confirmed by drillers’ logs, whereas the resolution of such structure is impaired on parallel (cross-line) 2D resistivity images/maps with distorted and disjointed image of the investigated fault at deep depth. For two orthogonal VES alignments (in-line and cross-line) to the azimuth of an investigated fault, deviations in layer resistivity values were generally ˂17% while thickness/depth estimates deviated by as much as 30–78%, at deep depth.