The primary challenge in evaluating a horizontal well is to clearly identify what is needed and what is done with this information. The formation parameters that best define naturally fractured formations are quite different from those associated with matrix permeability reservoirs. The need for logging tools will also be different. And, the difference in the measurement geometry between the vertical and horizontal settings for each type of tool further complicates the evaluation.

This paper is comprised of four parts. The first examines current client needs in horizontal well evaluation for both the naturally fractured and matrix type reservoirs. Next, a basic view of the geometrical considerations in the transition from the vertical to the horizontal depth frame is discussed. This is followed by discussion of the measurement characteristics of the most common openhole tools as they pertain to fractured and matrix reservoirs. The paper concludes with several interpretation case examples.

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