Petroleum migration pathways through a basin
are determined by the three-dimensional distribution of discontinuous sealing
surfaces, which are usually parallel to bedding. The petroleum migrates
below the sealing surface, taking the structurally most advantageous route.
The three-dimensional distribution of migration pathways within the petroleum
system can be modeled on a personal computer using a program based on the
parameters discussed in this paper. Application of the model to the Paris
and Williston basins demonstrates that a good correlation between predicted
pathways and discovered accumulations can be made using simple models.
Pathways form a dense network overlying generating
areas in the central parts of basins. Toward the basin margins these routes
commonly become increasingly focused into discrete pathways by the sealing-surface
morphologies. Eventually, these pathways may reach the surface as seepages.
It is important to integrate surface outcrops of migration routes (surface
seepages) into migration modeling.
Deflection of the pathways from the structurally
most advantageous route below the sealing surface may be caused by lateral
sealing barriers due to facies variation in the carrier rock below the
seal, fault juxtaposition, or cross-formational seals such as salt intrusions.
Deflection of pathways also
1997. The American Association of Petroleum Geologists. All rights reserved.
received May 8, 1996; revised manuscript received October 1, 1996; final
acceptance February 20, 1997.
Algeria Corporation, The Atrium, P.O. Box 576, 1 Harefield Road, Uxbridge,
Middlesex UB8 1YH, United Kingdom.
work was undertaken as part-time research at the Open University, Department
of Earth Sciences, Walton Hall, Milton Keynes, England, under the supervision
of R. C. L. Wilson, whose support and advice is much appreciated. Particular
acknowledgment and thanks to J. T. Hindle (Geofocus Limited) for writing
the personal computer program pathways, which forms a central component
of the research. My former employer, Texaco Ltd. is also thanked for their
support of my research, together with the Texaco graphics department for
assisting with the figures. The manuscript benefited greatly from reviews
by the following, who are also acknowledged: G. Hampson, P. Waddams, J.
W. Lloyd, and S. Blake; and AAPG reviewers D. Schumacher, P. K. Webb, and
Elected Editor K. T. Biddle.