Case Histories of Microbial Prospection for Oil and Gas, Onshore and Offshore in Northwest Europe
Manfred Wagner, Martin Wagner, Joachim Piske, Robert Smit, 2002. "Case Histories of Microbial Prospection for Oil and Gas, Onshore and Offshore in Northwest Europe", Surface Exploration Case Histories: Applications of Geoschemistry, Magnetics, and Remote Sensing, Dietmar Schumacher, Leonard A. LeSchack
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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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Surface Exploration Case Histories: Applications of Geochemistry, Magnetics, and Remote Sensing provides an overview of successful applications of surface exploration methods. Through a series of independent case histories, this volume presents clearly documented evidence that demonstrates how surface exploration methods can significantly reduce exploration risk and finding costs: geochemical, magnetic, and remote sensing. The 19 chapters in this volume reflect the broad scope of applications for these methods: frontier basin reconnaissance, prospect development, prospect evaluation, and field development and production. The case histories span the globe: 1. North America 2. Africa 3. South America 4. Europe 5. Middle East 6. Australia. This book will interest explorationists and managers who seek to get the most out of each exploration dollar.