Field data based on volumetric analysis of recovered fluid points to a low recovery efficiency of the fracturing water. Despite decades of hydraulic fracturing treatment, the reason behind the inefficient water recovery and its impact on ultimate recovery remains poorly understood by the industry. Additionally, it is a common practice in the industry to put wells on production shortly after hydraulic fracturing treatment despite evidence from field data suggesting a positive correlation between gas flow rate and shut-in time. This study was conducted to investigate the reason behind low fracturing fluid recovery, effect of extended shut-in on fracture propagation and gas production mechanism in gas shale reservoirs.
The methodology used in this study first sheds light on the low recovery efficiency of fracturing water and the effect of retained water on fracture propagation by subjecting shale samples to cyclic levels of vapor pressure at constant temperature. Two samples with varying degrees of fracturing were then isolated and studied with SEM, EDX and XRD to investigate the relationship between micro fracture generation and shale chemistry. The reactivity of the two samples with water was studied by estimation of the Hayatdavoudi Hydration Index and Gibbs Free Energy. Finally, shale immersion in water enabled characterization of gas flow in hydraulic fractured gas shale reservoirs.
The study identifies the inherently high capillary suction pressure of shale responsible for inefficient fracturing fluid recovery. Also, Dry-wet (adsorption-desorption) cycles have been observed to fatigue shale and propagate micro fractures. Gas production mechanism in shale reservoirs is characterized by faulting, burst flow, shock waves, swarm flow and bubble in bubble flow.
|Commitee:||Boukadi, Fathi, Salehi, Saeed|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 53/01M(E), Masters Abstracts International|
|Keywords:||Fracturing, Gas, Hydraulic, Production, Shale, Shut-in|
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