ABSTRACT: The Reality of the 3-D World
ELAM, JACK G., Independent, Midland, TX
A substantial difference exists in understanding structural style and exploration when rifting is viewed in three dimensions rather than by using two-dimensional visualization.
Examples from AAPG Memoir 46 involve both symmetrical and asymmetrical "rift" basins, and the vastly different productive potential of each. Asymmetrical basins are more abundant; symmetrical basins produce most of the hydrocarbons and are far more worthy exploration objectives.
True rifting, caused by thermal uplift, has to be modeled in three dimensions to be understood. The combination of increasing heat flow and dilational tectonics provides the ideal set of conditions for maturing and entrapping the hydrocarbons, and these conditions are found only in symmetrical rift basins.
Extensional asymmetric basins have different thermal histories, and do not offer comparable advantages. Thus, to call both types of basins rifts is misleading. This problem is the result of the use of planar models, which suggests that extension in all directions (dilation) is mechanically similar to extension. That is true only with planar models and not in the real world.
In addition to trapping oil and gas more efficiently, rifting associated with thermal uplift creates symmetrical traps that are far easier to locate. Furthermore, subsequent cooling and collapse of thermal uplifts drops many traps into what now appears to be inferior structural positions. Thus, half of the fields in the Permian basin remain to be fully exploited, a fact that also should be true for other rift basins.
AAPG Search and Discovery Article #91018©1992 AAPG Southwest Section Meeting, Midland, Texas, April 21-24, 1992 (2009)