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Method to Calculate Formation True Dip in High Angle / Horizontal Wells Applying 3-Dimensional Approach
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Horizontal Wells 2017, May 2017, Volume 2017, p.1 - 5
Abstract
Currently, true dip computation using borehole images is typically based on the routines developed in the 1960s. This approach was formulated for wireline images in vertical wells where boundaries assumed to be planar surface, and could be presented as a sinusoid on the image log.
A different scenario applies for LWD images in horizontal wells. Boundaries can be observed for tens of meters or greater. Within these distances planar geological boundaries are rarely found. The corresponding image response is not an ideal sinusoid shape. Further, it is unlikely that wellbore has constant inclination and azimuth while penetrating geological boundary, introducing explicit inaccuracy in 2-dimensional true dip calculation. The variable depth of investigation for radioactive LWD tools causes additional uncertainty. Another challenge is the human bias in sinusoids manual definition that is a considerable issue in geological applications.
The developed workflow relies on 3-dimensional approach to determine bedding geometry. Boundaries described with contours on 2-dimensional image, which are then transferred to 3-dimensional coordinates. The method forms set of contours where relevant formation boundaries are selected using fuzzy logic. Special noise removal routine is part of the method. Current study highlights advantages of the proposed method over the conventional dip picking workflow.