Shale oil and gas production have provided a massive boost to the United States in its quest for energy independence. These previously deemed uneconomical formations, for their low permeability and low porosity, are now being exploited, not only in the United States but around the globe. Despite many wells drilled in shale formations, much is yet to be understood about the characteristics and behavior of these formations. Hydraulic fracturing in several stages, a well stimulation technique, is often applied to horizontal wells drilled in shale formations to extend the productive life upon finishing drilling.
To evaluate a laboratory scale of "shut-in" equivalent time, this experiment was conducted to determine the effects of cyclic temperature, water vapor and exposure time in the development and propagation of micro fractures in shale. The author believes that during the "shut-in" exposure time, a great number of micro fractures develop at the faces of the main hydraulic fractures. The micro fractures increase the productive life of the shale gas wells.
A laboratory experiment was conducted, using 22 small Pierre shale samples, which were subjected to the aforementioned conditions. The samples were analyzed using a microscope to see if micro fractures developed. The results of this study show that micro fractures developed in 19 samples. Micro fracture propagation in shale is non-uniform.
Coefficient of thermal expansion of shale was estimated by conducting a Retort experiment, heating a shale sample to over 520 °F, measuring the volume of the sample before and after the experiment to determine change in volume as well as amount of water expelled from the sample.
Shale samples developed micro fractures after being subjected to cycles of varying temperature, water vapor and exposure time. However, high temperature and high water vapor created the most number of micro fractures at the sample surfaces.
|Commitee:||Boukadi, Fathi, Salehi, Saeed|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 54/04M(E), Masters Abstracts International|
|Keywords:||Eagle ford, Micro fracture, Pierre, Shale, Temperature, Water vapor|
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