Abstract: Alternate Geologic Interpretation--Potential Use of Computer Mapping in Field Development

C. R. Johnson

Commercially available to the oil industry are new programs for mapping complex geologic structure which have application to the evaluation and drilling of "proved" prospects. This application allows several alternative interpretations to be considered in both estimating reserves and selecting the order in which locations are to be drilled.

The production geologist always must have in mind alternatives to his "best guess" in case geology doesn't support his theory but, until computer mapping and the mapping of faults in particular came of age, he could not expect to develop fully these alternatives ahead of time. In fact, the extensive labor involved in hand drafting of his pictorial 3-D model commits him to a single interpretation which he must modify to satisfy contradictory data, but would certainly hesitate to abandon. To avoid such a premature commitment, this paper suggests an approach in which the computer provides the geologist with several fully documented alternatives to which he can switch allegiance, if subsequent drilling does not support his first choice.

An example has been selected which consists of a set of simulated seismic profiles on which several stratigraphic horizons are recognized. On each profile a normal fault also has been identified. How one correlates the fault cuts results in four interpretations, each drastically changing the configuration and reserves of the field. Assuming that all four interpretations are equally viable, the talk examines the changing reserves and risks when the well locations are drilled in a different order.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC