Pre-drill estimation of sub-surface pressures and fracture gradient analysis is the cornerstone of the well-planning process. To effectively estimate pre-drill pore pressure, Engineers and Geologist strive to define the underlying fundamental principles that drive pressure generation in a field or basin. In the oil and gas industry today, pressure generation is thoroughly understood, but mostly from mechanical properties perspective, i.e. compaction.
The other piece of the system, which is given less attention, is the thermodynamic properties of such system. The reason may be due to the inability to identify the subtle changes witnessed in the thermodynamics of a system. It is widely understood that overpressure can be generated from aquathermal expansion of pore fluids, yet little is written on when this thermodynamic phenomenon dominates and under what conditions it becomes a source of excess pressure generation.
In this research, the author discusses excess pressure generation in a thermodynamic sense, using a thermodynamic equilibrium approach that governs the system. Focus is on the Abbeville field, located in the Gulf Coast Salt Dome basin in Southern Louisiana. This approach dissects the Abbeville field and exposes the behavior of Thermal Conductivity and Heat Flow when compared with the Pressure vs. Temperature equilibrium plot.
Results show that using the equilibrium approach can help define the subtle thermal changes experienced within the transition zone, which points to temperature playing a selectively dominant role in excess pressure generation under the appropriate sub-surface conditions. Furthermore, more than one system is seen to be responsible for excess pressure generation, divided between aquathermal expansion of pore fluids and compaction.
Future use of this work also suggests a beneficial economic use of thermal equilibrium in locating a potential hydrocarbon bearing zone. This approach is similar to how rock petrophysical properties, such as resistivity, neutron porosity, etc. are being used today.
|Commitee:||Boukadi, Fathi, Seibi, Abdennour|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 54/06M(E), Masters Abstracts International|
|Keywords:||Aquathermal expansion, Overpressure, P - t plot, Pore pressure, Subsurface thermal properties, Thermal equilibrium|
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