This is a two-part paper consisting of an analysis by an engineer of the costs of obtaining information in exploratory drilling, and a statement by a geologist of the basic information desired.

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The cost of exploratory drilling is usually higher than development drilling because of more unknown factors, such as depth of objectives and incomplete knowledge of structural and stratigraphic conditions. Services are often requested by the geologist that may not evaluate potentially productive zones but aid in the geological interpretation. The cost is charged to the well, nevertheless. In order to drill exploratory holes in the most economical manner the fullest use must be made of those information gathering techniques which obtain information as the drilling progresses, that cause neither slowdown nor shutdown of drilling operations. This information must be closely watched and diligently recorded by the geologist in order to minimize the use of more expensive and more time-cons ming information tools. The practice of exploring in long rat-hole intervals, in particular, appears in analysis to be extremely costly and time-consuming, and recent improvements in formation-testing equipment render it impractical. All operations which increase drilling time and the number of round trips increase drilling hazards as well as direct costs.

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