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Jumet, Belgium

Hansen B.,Eriksfiord AS | Buczak J.,Petris Technology
AAPG Memoir | Year: 2010

Generating a borehole image from the original measurements of rock properties involves a series of steps. The purpose of this chapter is to explain these steps systematically. For wireline (WL)-based imaging instruments, the measurements may come from sensors placed at different depths and orientations at the borehole imaging tool. When composing the image, the position of each measurement ideally has to be calculated at the size of a pixel, a procedure involving the use of downhole accelerometers and magnetometers, which are also part of the borehole imaging tool. For logging while drilling, the imaging is based on a rotating sensor that is part of the drilling assembly: the measurements are assigned to sectors oriented in relative bearing, and image generation is far simpler. Once the measurements have been oriented in space and placed on a rectangular grid, they have to be mapped to a color scale so features of geological interest become visible. A variety of filters may be applied to remove information of a nongeological nature, and pattern recognition or thresholding methods may be used to quantify imaged rock properties. Guidelines to correct faulty input data and detect defective processing are given. Within the context of a typical image processing and interpretation workflow, data verification and image generation and processing are discussed. Aspects of image interpretation, particularly the mechanics of dip picking, are also briefly considered. Copyright © 2010 by The American Association of Petroleum Geologists.

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