Schlumberger

Technical Paper: Geosteering Horizontal Wells using Resistivity Anisotropy Obtained in an Offset Vertical Well

Society: SPE
Paper Number: 81137
Presentation Date: 2003
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Abstract

Traditional resistivity logging instruments, when logged in vertical wells through horizontal beds, evaluate the horizontal resistivity (Rh) of the formation. The response of the laterolog tool in the same environment, however, is also sensitive to the vertical resistivity component (Rv). Used alone neither tool is able to resolve the thin beds or evaluate resistivity anisotropy. However, with computer inversion software, data from both tools can be combined to quantify zones of resistivity anisotropy, as well as accounting for various environmental effects such us invasion and shoulder beds improving bed boundary definition.

This paper proposes a new approach, combining NMR logs data with the above technique, in order to obtain improved geological and petrophysical models, using field data. The models, with more accurately parameterized vertical, horizontal, true and invaded zone resistivity values (Rv, Rh, Rt, Rxo), as well thin bed boundary definition, are coherent across a range of reservoir formation types, and are then applied to help drill more precisely (and evaluate more accurately), a horizontal well in the same formation.