Photogeologic Mapping as Important Exploration Tool--a 30-Year Analysis

Stephen W. Dart, Jr.

Photogeology has been used as a petroleum exploration tool in the Rocky Mountains for more than 50 years. A measure of the value of the tool is the determination of the correlation between photo-observed structure and production. During the past 30 years, most of the Rocky Mountain sedimentary basins have been mapped photogeologically by IntraSearch Inc. using low-altitude aerial photographs. To test the value of the tool, 14 Wyoming intermontane basins within a 93,000-mi³ area were examined to determine how many areas of current or previous production exhibit surface structural evidence observable on 1/60,000-scale black-and-white aerial photographs. Three types of anticlinal traps were examined: (1) singly plunging, (2) doubly plunging, and (3) faulted nose.< /p>

Of all oil and gas fields, 40% are photogeologically observable. For different basins, this percentage varies from 3% to 30% where production is stratigraphically controlled, 70% to 100% where production is structurally controlled, and 35% to 65% in basins with both stratigraphic and structural controls. For each anticlinal type where there is coincidence with production, the percentage of occurrence varies: singly plunging, 40%; doubly plunging, 50%; and faulted nose, 10%. Sixty percent of all photogeologically observable anticline traps occur in nonproducing areas and are either undrilled or drilled dry.

A comparison of effectiveness of geologic interpretations between 1/60,000-scale aerial photography and 1/1,000,000-scale Landsat imagery (MSS, black and white, band 7) in the structural trap-dominated Big Horn basin of Wyoming in identifying areas of production indicates that aerial photography is 65% more effective than Landsat imagery interpretation. Only 25% of all discovered fields are observable on Landsat imagery.

Photogeologic evaluation is a cost-effective (Landsat = 26¢/mi²; 1/60,000-scale aerial = $4/mi²) and successful exploration tool for generating petroleum prospects. Natural color, 1/24,000-scale photography has increased the effectiveness of the tool. In the Rocky Mountains, a mature region of exploration, many known photogeologic prospects remain undrilled and await renewed activity.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.