New 2-MHz Multiarray Borehole-Compensated Resistivity Tool Developed for MWD in Slim Holes

Abstract

To address the increasing number of slim holes being drilled in the range of 5.75 in. to 6.75 in., a mixed-boreholecompensated (MERC) 2-MHz array resistivity tool with a 4.75-in. collar diameter is described for resistivity measurement-while-drilling (MWD) applications. MERC is a unique technique developed to minimize the effects of borehole rugosity. The new MWD array resistivity tool makes multiple MERC phase shift and attenuation resistivity measurements using five transmitter-to-receiver spacings.Five independent MERC phase shift and attenuation measurements are made at 2 MHz. The five phase shift resistivities have similar vertical responses but with increasing radial depths of investigation. The five attenuation resistivities are also vertically similar but coarser and are radially deeper than the phase shift resistivities. This new array resistivity tool effectively exploits the technology and the interpretation methodology recently developed for wireline induction resistivities and the benefits of multispacing probes for formation evaluation. Most of the petrophysical applications developed in conjunction with the wireline resistivity AlT· Array Induction Imager Tool are illustrated from MWD array resistivity logs acquired while drilling.

Fast 1D inversion of logging-while-drilling resistivity measurements for improved estimation of formation resistivity in high-angle and horizontal wells

“…In conventional LWD instruments, the above results are further post-processed to obtain apparent resistivities. The main ideas used to perform this operation are delineated in the works of Bonner et al (1995) and Clark et al (1988). First, we compute the z B -component of the magnetic field excited by a z B -oriented dipole at two different receivers RX 1 , and RX 2 .…”

Methods

“…F5B) measures propagation resistivity. Electromagnetic waves are both attenuated and phaseshifted when they propagate in an electrically conductive medium; the degree of attenuation and phase shift depends on the resistivity of the formation (Bonner et al, 1995(Bonner et al, , 1996. Phase-shift resistivity has relatively high vertical resolution and a shallow depth of investigation, whereas attenuation…”

Methods

“…The arcVISION tool (array resistivity compensated) measures propagation resistivities. Electromagnetic waves are attenuated and phase-shifted when they propagate in an electrically conductive medium, and the degree of attenuation and phase shift depends on the resistivity of the formation (Bonner et al, 1995(Bonner et al, , 1996. Phase-shift resistivity has relatively high vertical resolution and a shallow depth of investigation, whereas attenuation resistivity has lower vertical resolution and a greater depth of investigation.…”