The Compilation and Application of Aeromagnetic Data for Hydrocarbon Exploration in Interior Alaska
John F. Meyer, Jr., Louis J. Racic, Richard W. Saltus, 1998. "The Compilation and Application of Aeromagnetic Data for Hydrocarbon Exploration in Interior Alaska", Geologic Applications of Gravity and Magnetics: Case Histories, Richard I. Gibson, Patrick S. Millegan
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To stimulate interest and provide background information for future petroleum and mineral exploration in interior Alaska, the state of Alaska, Division of Oil and Gas, and the U.S. Geological Survey joined in a cooperative effort to compile and merge all of the publicly available magnetic data throughout interior Alaska. Interior Alaska extends from the Brooks Range in the north to the Alaska Range in the south and from the Peninsula on the west to the Alaska-Canadian border. Budget and time constraints restricted the initial compilation to the area of state-controlled lands within the Alaskan interior, extending from 61°N to 66°N and 144°W to 159°W (Figure 1). The primary sedimentary basins within this area consist of the Copper River Basin, Susitna Basin, Minchumina Basin, Holitna Basin, and Middle Tanana Basin (Kirschner, 1994).
The data processing was performed by Paterson, Grant & Watson Ltd. of Toronto, Ontario, under contract to the state of Alaska. Aeromagnetic maps at a scale of 1:500,000 have been published jointly by the U.S. Geological Survey and the state of Alaska, Division of Oil and Gas (Meyer and Saltus, 1995). In this study, twenty-three magnetic surveys, comprising 280 000 line-kilometers, flown between 1954 and 1982, were merged to produce two digital data grids. The first grid, referred to as the composite grid (Figure 2), was produced to retain the closest resolution to the original data for each survey and was designed to be used for detailed modeling and local depth-to-basement determinations. The second grid, referred to as the merged grid
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The idea for this book came from a perceived lack of recent, instructive examples of exploration-oriented interpretations of gravity and magnetic data. The Society of Exploration Geophysicists two volumes, Geophysical Case Histories, are probably closest in philosophy to this book. Published in 1948 and 1956, many of the examples in the Case Histories are relatively dated and specific to particular areas. We hope this new book provides an update that includes lessons about gravity and magnetic exploration that can be applied to many parts of the world. The Utility of Regional Gravity and Magnetic Anomaly Maps (SEG, 1985, W.J. Hinze, editor) contains some excellent papers dealing with tectonics that have clear bearing on hydrocarbon exploration, but no paper shows the relationships among hydrocarbon accumulations, exploration, gravity, and magnetics. Geophysical texts focusing on gravity and magnetics, including L.L. Nettleton's classics, include only a few (albeit often excellent) case histories, and many are dated.
Thus, this book's target audience is geologists and geophysicists in operations offices, actively involved in exploration at any level from basin analysis to prospect generation. Although most of the papers deal with hydrocarbon exploration, several papers relate to gravity and magnetic data in mining and environmental applications. A final section is included on new developments, the state of the art.
The book is not intended for gravity and magnetics specialists (although we hope they will find it interesting), or for geophysicists interested in theory, acquisition, and processing, unless those aspects are important to the geologic exploration problem and to the decisionmaking process.
We believe that the philosophical approach to interpretation is almost as important as some aspects of a technical interpretation itself. This book reveals the diversity of philosophies that gravity and magnetic interpreters embrace, as well as the common threads to which all interpreters aspire.
This book is not a textbook, although we have tried hard to highlight the exploration lessons inherent in each technical paper. Additional instructional aspects of the book are the glossary of gravity and magnetic terms, provided by Integrated Geophysics Corporation (with assistance from Richard Hansen of Pearson, DeRidder & Johnson) and an annotated bibliography, which has pointers to the rich literature of gravity and magnetics. Other short "lessons" can be found in stand-alone illustrations or short features throughout the book.
We thank Ray Thomasson for continual encouragement, suggestions, and prodding. Reviewers, whose efforts are appreciated greatly, include Dale Bird, Bill Pearson, Mark Odegard, and several anonymous reviewers. We appreciate the help of the AAPG, especially Ken Wolgemuth, in this, the first effort at serious book publication by the coeditors.