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Book Chapter

Case Histories of Microbial Prospection for Oil and Gas, Onshore and Offshore in Northwest Europe

By
Manfred Wagner
Manfred Wagner
MicroPro GmbH Gommern, Germany
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Martin Wagner
Martin Wagner
MicroPro GmbH Gommern, Germany
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Joachim Piske
Joachim Piske
Erdöl-Erdgas Gommern GmbH Gommern, Germany
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Robert Smit
Robert Smit
VEBA Oil Nederland B.V. The Hague, Netherlands
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Published:
January 01, 2002

Abstract

This paper presents the Microbial Prospection for Oil and Gas (MPOG) method, which uses microbiological techniques to explore for oil and gas. These techniques are based on the principle that light hydrocarbons from oil and gas fields escape to the earth’s surface, and this increased hydrocarbon supply above the fields creates conditions favorable for the development of highly specialized bacterial populations that feed on the hydrocarbons. This leads to significant increases in the microbial cell numbers and cell activity of these specialized microbes.

By developing methods to establish the separate activities of methane-oxidizing bacteria (a gas indicator) and those bacteria that oxidize only ethane and higher hydrocarbons (oil indicators), it is possible to differentiate between oil fields with and without a free gas cap, and gas fields.

This microbial method of surface prospection has been applied in Germany since 1961. The technique has also been used offshore in the North Sea since 1995. The total area that has been investigated to date is 6000 km2, most of which has undergone wildcat prospection.

To investigate the influence of geologic structure on the results of microbial prospection, model investigations were carried out, with the close cooperation of exploration geologists, on fields that had already been developed. Investigations were conducted on an unfaulted field, on fields with faults within salt, on fields with faults in the supra- or subsalt, and on a completely destroyed field. The case histories presented here support the following conclusions. (1) In microbial prospection, the results do not show a fault-related dependence. (2) The microbial anomalies occur vertically above the respective field. (3) Thick salt seals (Zechstein salt as thick as 800 m) have no effect on microbial prospection. (4) Tectonically destroyed fields without hydrocarbons do not create any microbial anomalies. (5) Recent biogenic methane formation in marsh areas does not lead to significant MPOG anomalies.

To date, a total of 17 oil and gas fields, as well as several seismically identified structures without hydrocarbons—both onshore and offshore—has been confirmed subsequently by the results of 220 wells drilled in the area. The success rate of microbial surface prospecting has therefore reached 90%; i.e., the probability is about 90% that MPOG can indicate the occurrence or absence of hydrocarbons. Seven case histories will be discussed in this paper.

In unexplored areas, MPOG represents a cost-effective method for preliminary exploration work. In mature areas, the method is helpful for ranking seismically defined geologic structures by indicating possible infill locations, as a contribution to reservoir characterization.

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Contents

AAPG Studies in Geology

Surface Exploration Case Histories: Applications of Geoschemistry, Magnetics, and Remote Sensing

Dietmar Schumacher
Dietmar Schumacher
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Leonard A. LeSchack
Leonard A. LeSchack
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American Association of Petroleum Geologists
Volume
48
ISBN electronic:
9781629810591
Publication date:
January 01, 2002

GeoRef

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