Influence of Structural Deformation on Temperature Distribution Through Time – Is Palinspastic Reconstruction Worthwhile?

Fausto Mosca, Ana Krueger, and Ed Gilbert
Devon Energy Corporation 1200 Smith Street, 77072 Houston Texas, USA

The basic factor affecting generation of hydrocarbons in a sedimentary basin is the burial history, expressed through depth, temperature, and time. However, the temperature regime of a basin is affected by many other geological processes throughout the history of the basin. These includes processes related to basin geometry (such as rifting processes), structural evolution of the basin (vertical and lateral translation of sediment masses during trap formation), deposition and erosion of sediments linked to intra-basin tectonism, physical processes related to compaction, as well as heat and fluid flow. Tectonism not only plays an important role by providing traps for hydrocarbon accumulations in the sedimentary basin, but the effects on the thermal regime, and consequently upon hydrocarbon maturation, can be significant.

With increasing geological complexity of sedimentary basins, it is important not only to properly represent the present geometry of the basin, but to be able to reconstruct a realistic description of the evolving structural geometry over long periods of geological time. Large errors can be introduced into the maturation model by inappropriate approximation of past structural geometries, rendering simulations of basin temperature history unreliable.

At Devon we have developed work flows for combining tectonic modeling with sedimentological history and temperature history that profoundly affect hydrocarbon generation and migration. Two-dimensional fluid flow/compaction models not only allow for both conduction and convection of heat, but illustrate the effects of vertical and lateral movements of large sediment bodies, as well as their constantly changing geometry.

A detailed comparison and critical review of various ways to restore structures, and their impact on variations in the thermal regime through time, are provided. Within individual basins there may be significant lateral temperature contrasts between sediment masses, and significant vertical or lateral movements will affect source rock maturity in both space and time. Thus the magnitude of thermal anomalies depends not only upon simple thickness (burial history), but upon the constantly evolving sediment body geometry. We conclude that the modeled results provide more accurate estimates of the influence of structures as effective oil generation/migration migration pathways from various source intervals.

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands