Dissertation/Thesis Abstract

Comparative Study of Petrophysical and Elastic Properties of Marl and Interbedded Limestone Layers within Eagle Ford Formation
by Jiang, Shuxian, Ph.D., University of Louisiana at Lafayette, 2018, 136; 10981113
Abstract (Summary)

The Eagle Ford Formation in Texas, USA is composed of marl and interbedded limestone sequences. To optimize hydrocarbon recovery from such a heterogeneous formation, it is necessary to have a better understanding of the petrophysical and mechanical properties of the marl and limestone layers. To characterize and quantify properties of marl and limestone layers, more than 15 m of Eagle Ford Shale samples were analyzed using X-ray Fluorescence (XRF), X-ray diffraction (XRD) and rock-eval pyrolysis. XRF results show that concentrations of Al 2O3, Fe2O3, and Mo in marl layers were more than 40% higher than in the interbedded limestone layers. Limestone layers contain calcite content ranging from 55%–90% and clay content ranging from 5%–30%, while marl layers contain 30%–70% calcite and around 20%–50% clay. Marl layers have better generative potential than the limestone layers in the Eagle Ford Formation.

Pyrite is a common mineral with a higher density than most other minerals in the Eagle Ford Shale formation. Hence, it may lead to errors in the TOC estimation based on density logs if pyrite is not considered. So we propose an updated petrophysical model including organic pores, solid organic matter, inorganic pores, pyrite, and inorganic rock matrix without pyrite. What’s more, Passey’s method does not work well in the Eagle Ford well within condensate gas and dry gas window. Thus Passey’s method with a correction factor was proposed. The updated models were validated with the Eagle Ford field data and was proved to have better estimation results than previous models.

To build a mechanical model in layered rock and optimize fracture treatment design, the elastic properties of marl and limestone layers were evaluated in two Eagle Ford wells. Similar positive linear relationships were developed between shear velocity and compressional velocity in two Eagle Ford wells. Correlations between dynamic mechanical properties and gamma ray intensity or clay content were proposed for different layers in the Eagle Ford Formation and the adjacent Austin Chalk and Buda Limestone. Among all the Eagle Ford layers, marl layers in the lower Eagle Ford have the lowest compressional velocity, shear velocity, and dynamic Young’s modulus.

Indexing (document details)
Advisor: Mokhtari, Mehdi
Commitee: Boukadi, Fathi, Guo, Boyun, Hayatdavoudi, Asad, Saidian, Milad, Zhang, Pengfei
School: University of Louisiana at Lafayette
Department: Petroleum Engineering
School Location: United States -- Louisiana
Source: DAI-B 80/08(E), Dissertation Abstracts International
Subjects: Engineering, Petroleum engineering
Keywords: Eagle Ford Formation, Elastic properties, Marl, Petrophysical properties
Publication Number: 10981113
ISBN: 9781392042045
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