The drilling of boreholes in certain geographic regionsis often significantly influenced by the presence of nonhomogeneousin-situ stress fields. One commonlyobserved phenomena is the development of breakout inthe axis of the hole parallel to the minimum horizontalstress direction. This typically results in elongated(elliptical) wellbores that are frequently rugose alongthe axis of elongation. Virtually all wireline-conveyedopen hole density logging tools incorporate amechanical caliper to ensure pad contact with theborehole wall. In elongated wellbores, poor density datais often acquired, as this design predisposes the tool torotate into the long (rough) axis of the hole. Variousshort-axis running gear and tool configurations (forexample, 90-degree bowsprings, 90-degree calipersand, more recently, dual or tandem-density toolstrings)have been utilized to improve density acquisition.However, the industry has witnessed a steady increasein the proportion of wells being drilled directionally,and correspondently, the mounting realization that evenfairly low wellbore inclinations (of 10-20 degrees) canrender standard short-axis orientation tacticsineffective.This paper seeks to analyze the behavior of tandemdensity toolstrings in directionally drilled wells,especially when subject to elongation. It also attemptsto present a general methodology, as well as specificrecommendations, for improving the acquisition ofwireline density data in low to moderately inclinedwells, even when they are drilled directionally alongstrike into the breakout or minimum horizontal stressdirection. A number of log examples illustrate howstandard density logging tools were successfullyconfigured in an orthogonal arrangement, with relatedrunning gear, to restore consistent short-axisorientation, maximizing pad contact and increasing theprobability of acquiring usable density data. Assumingthat at least some portion of the wellbore is less rugose,the technique described affords more dependabledensity measurement in deviated wells.
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