SEISMIC CHARACTERIZATION OF THE EAGLE FORD SHALE BASED ON ROCK PHYSICS
Zavala-Torres, Ricardo 1974-
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The findings of this dissertation on seismic characterization of the Eagle Ford Shale based on rock physics using actual well-log data from productive and unproductive wells in Mexico can be immediately and effectively applied to avoid future failures and can be corroborated with current and new locations for exploration and production. It was found that basic sequence stratigraphy techniques developed for unconventional reservoirs can be applied to the case of the Eagle Ford Shale in Mexico. Using well log correlation and petrophysical techniques to estimate reservoir properties, it was concluded that the zone where the horizontal well was drilled at Montanes-1 was located above the condensed sequence, bypassing the pay zone below the maximum flooding surface in the transgressive system track. It is verified that the productive well Emergente-1 was drilled in the correct zone with hydrocarbon saturation at the transgressive system track below the maximum flooding surface. It was found that using mineral assessment methods to compute brittleness, and the proper geosteering analysis is a consistent approach for placement of future horizontals. Based on that, it is concluded that any estimation of rock physics and anisotropic parameters derived from well logs at the source rock interval will be deceiving and will give a false estimation. It was concluded that the isotropic rock physic model known as friable-sand or modified friable-shale (unconsolidated sand or unconsolidated shale), or most recently called “soft-sand model”, was proved to match the data better than any other rock physic model tested to predict velocity and density. The term “non-source rock model” will be used instead for the rock physic model because it is more consistent with the Eagle Ford Shale case analyzed here. For the orientation of maximum horizontal stress, it is concluded by integrating VSP, microseismic and borehole data, that a straight north-south orientation of future horizontals is needed in order to generate the fractures in the straight east-west azimuth correlating with the maximum horizontal stress orientation.