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Title Mineral, fluid, and elastic property quantification from well logs and core data in the Eagle Ford shale play : a comparative study
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Publication Date
Date Accessioned
Degree MSin Engineering
Discipline/Department Petroleum Engineering
Degree Level masters
University/Publisher University of Texas – Austin
Abstract Organic shales have become one of the greatest sources of hydrocarbon thanks to novel production techniques such as hydraulic fracturing. A successful hydraulic fracturing job, however, is dependent on several rock properties such as mineralogy and elasticity. A reliable estimation of such properties is therefore necessary to determine ideal rocks for horizontal well placement. In this study, rock types within the Eagle Ford shale that would be suitable for hydraulic fracturing are identified through interpretations of available well logs and core data. A comparative study of petrophysical properties such as mineral content, kerogen type and maturity, porosity, and saturation in six wells is performed to characterize the Eagle Ford shale. Two of the wells studied are within the wet gas window of the shale while the remaining four are in the oil window. Based on the calculated petrophysical properties, rock typing was performed using k-means clustering. Two rock types (RT1 and RT2) were identified and their compositions compared in each well. Elastic properties for the various rock types identified were then estimated using the differential effective medium (DEM) theory and were validated through simulation of slowness logs. The final rock type assessment was then performed to identify ideal rocks for hydrofracturing. Results indicate that the Eagle Ford mineralogy varies greatly with depth and with geographic location relative to the San Marcos Arch, a geological arching prominence across the shale. Northeast of the arch, the Eagle Ford shale is clay-rich. Preferred rocks for hydrocarbon production, RT1, are characterized by volumetric concentrations of ~0.44 carbonate, ~0.09 kerogen, ~0.07 porosity, and ~0.42 clay; RT1 also exhibits high sonic velocities (> 3400 m/s and > 1500 m/s compressional and shear, respectively) and high apparent electrical resistivity (> 2 ohm-m). In the Southwest region, on the other hand, the Eagle Ford shale is mostly calcareous. Ideal rocks in the region, RT1, are rich in kerogen (~0.1) with carbonate content of ~0.56, ~0.1 porosity, ~0.19 clay content, and resistivity > 20 ohm-m. In both regions, porosity and pore aspect ratio displayed substantial effects on elastic properties. For example, over 80% decrease in Young’s modulus was quantified when pore aspect ratio approached zero; high pore aspect ratio is preferred for stiff rocks. Poisson’s ratio estimates were not always reliable therefore fracturability was assessed based on Young’s modulus estimates. The study shows that depth intervals exhibiting Young’s moduli above 18GPa and 21GPa in the Northeast and Southwest region, respectively, are suitable for hydrofracturing.
Subjects/Keywords Eagle Ford shale; Mineral composition; Elastic properties; Kerogen; San Marcos Arch
Contributors Torres-Verdín, Carlos (advisor)
Language en
Country of Publication us
Record ID handle:2152/22369
Repository texas
Date Indexed 2020-10-15
Grantor The University of Texas at Austin
Note [] text; [department] Petroleum and Geosystems Engineering;

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…mineralogy varies greatly with depth and with geographic location relative to the San Marcos Arch, a geological arching prominence across the shale. Northeast of the arch, the Eagle Ford shale is clay-rich. Preferred rocks for hydrocarbon production, RT1, are…

…and resistivity > 20 ohm-m. In both regions, porosity and pore aspect ratio displayed substantial effects on elastic properties. For example, over 80% decrease in Young’s modulus was quantified when pore aspect ratio approached zero; high pore aspect…

…Classification of Reservoir Rocks ....................................21 3.3 Estimation of Elastic Properties and Final Rock Typing ........................22 3.3.1 Rock Physics Model ...................................................................22 3.3.2…

Elastic and Petrophysical Rock Typing ......................................24 Chapter 4: Synthetic Cases ....................................................................................26 4.1 Case 1: Effect of Kerogen and Porosity on Formation…

…43 5.2.2 Mineralogy Results and Discussion ............................................50 5.3 Rock Typing............................................................................................59 5.4 Elastic Property Estimation…

…60 5.4.1 Logs and Mineral Correlations ...................................................60 5.4.2 EF Elastic Model.........................................................................67 5.4.3 Results and Discussion concerning Elastic Properties…

…region. CLA: clay group; CARB: carbonate group; KER: kerogen; RT: Rock type; NE: Northeast; SW: Southwest. ...............................................................59 Table 5.6. Summary of elastic properties and pore aspect ratio used to simulate…

…sonic velocities in six EFS wells. Shear modulus of hydrocarbon and water is 0. Densities of hydrocarbons and water are the same as those listed in Tables 5.3 and 5.4, respectively. Elastic moduli and density of kerogen, carbonate, and quartz-feldspar…

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