Usually, offshore field development wells will be drilled as highly deviated bore holes and evaluated by a series of logs including dipmeters. Dipmeters run in a deviated bore hole have often been treated with the same respect for validity of accuracy as any regular dipmeter run in a practically vertical bore hole. However, when the formations exhibit small dip magnitudes (from the horizontal) and are penetrated by rather highly deviated bore holes, accuracy of the dipmeter results should be held suspect. Recent work has indicated any small error in any one of several instrument measured parameters can result in an error in the final dipmeter results such that the formation dip magnitude will be erroneous and even the dip direction can be wrong.

Errors in relative bearing and bore-hole diameters (including caliper accuracy and pad depth of investigation) are the most susceptible to causing errors in the final computed results. This could have serious consequences in that erroneous dip vectors would be displayed as valid dip vectors. Unfortunately it is almost impossible, even for an "expert," to visibly determine that wrong dipmeter vectors have been plotted as the result of poor input data.

Several actual and theoretical dipmeter computation results will be presented wherein a controlled amount of error will be deliberately introduced to show its effect upon the computed dip vectors.

Results of these computations indicate that to give consistently good dipmeter results under most conditions encountered in highly deviated bore holes, practically all of the instrumentation must perform at accuracy levels considerably in excess of current instrument capabilities to yield results of the same quality as those obtained in nearly vertical bore holes.

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