Print this pageIntegrative Characterization of Faults’ Hydraulic Function in Hydrocarbon Entrapment
Czauner, Brigitta 1; Madl-Szőnyi
Structural elements generally represent key geological factors in fluid migration and retention. Faults can be conduits for migration of water, hydrothermal fluids, contaminants, and hydrocarbons as well, particularly in low-permeability environments. Consequently, also hydrogeology and petroleum geology pay considerable attention to the investigation of hydraulic role of faults, however the aspects of these two disciplines are different. Although petroleum hydrogeology has already applied hydrogeological principles and techniques to petroleum exploration, there were only scarcely attempts to study the hydraulic role of faults in hydrocarbon entrapment by hydrogeological methods.
Starting from these considerations, the initial purpose of the present work was to investigate the fluid-potential field dependent hydraulic role of faults in groundwater flow and hydrocarbon entrapment through the joint application of different, particularly hydrogeological research techniques. During the integrative study, seismic, lithostratigraphic, well-log, hydraulic, hydrochemical, and temperature data were interpreted simultaneously in order to characterize the tectonics, fluidstratigraphy, and fluid flow systems of the research area, in the Pannonian Basin, Hungary. As a result, upward dissipation of overpressure from the Pre-Neogene basement was identified across the Neogene basin fill with differing rates pending on the heterogeneity (e.g., fault density) of the regionally extensive Algyo Aquitard. As the manifestation of pressure dissipation in a heterogeneous flow field, diagnostic anomalies can be observed in the fluid-potential field, as well as in the geothermal and hydrochemical patterns. These anomalies usually coincide with fault zones and hydrocarbon occurrences as well. On the margin, a simple method was developed for identify fluid-potential (i.e. hydraulic head) anomalies caused by pressure data, which were measured in gas pools. Moreover, direction dependent hydraulic behaviour of high-permeability faults, as well as their role in the development of thermal water reservoirs and hydrocarbon entrapment was also demonstrated. Their flow barrier function transversally is simply due to the configuration of the fluid-potential field, and not to their permeability. Consequently, (1) during hydrocarbon exploration it is not definitely necessary to search for low-permeability faults, and (2) hydrogeological methods can be also effective in hydrocarbon exploration.
AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.