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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 9. (September)

First Page: 1446

Last Page: 1446

Title: Mapping of Fracture Zones by Helium Emanometry and Possible Relationship of Helium Anomalies to Hydrocarbon Reservoirs in Western Pennsylvania: ABSTRACT

Author(s): Alan A. Roberts, John B. Roen

Article Type: Meeting abstract

Abstract:

Helium is ubiquitous within the earth's crust. Local helium concentrations in the subsurface are observed in association with ores containing uranium and thorium, oil and gas reservoirs, and thermal fluids. In addition, permeable fracture zones tend to intensify local concentrations of helium because of its relative ease of migration along these conduits. A survey of helium in soil-gas samples was conducted across a previously mapped fault zone and a drilling-defined hydrocarbon reservoir in Greene and Fayette Counties, southwestern Pennsylvania, to demonstrate the utility of such surveys for mapping fracture zones and for locating hydrocarbon reservoirs. In the study area, a northwest-trending fracture zone cuts across both an area of hydrocarbon accumulation and an area thought to be relatively barren of hydrocarbons. The survey indicated that the helium content of the soil was anomalously high in a 30-m wide zone above the mapped fault and fracture system. Similar results were obtained from traverses made across both the accurately mapped fault zone and the hypothesized extensions of that zone. These data support the concept that helium can be used to locate fault and fracture zones where location is precluded by more conventional mapping procedures. Although helium surveys have delineated known hydrocarbon reservoirs in other areas, this preliminary survey, which consisted of a few traverses rather than an extensive grid pattern, failed to produce a significant anomaly above a known reservoir in southwestern Pennsylvania. This may be due to the low de sity of sample distribution and the high average background helium value for these traverses.

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