Monitoring and modeling the elastic and transport properties of organic-rich marl during maturation through pyrolysis experiments
Abstract/Contents
- Abstract
- Organic-rich marl is an important type of shale reservoir because its stiff matrix leads to relatively high permeability and frackability compared to clay-rich shale. However, how the stiff matrix affects the changes in the elastic and transport properties of organic-rich marl during maturation remains poorly understood, obstructing the remote characterization of this reservoir type across different maturity levels. One major cause of the poor understanding is the lack of rock physics a dataset tracking the changes in these properties as a function of maturity. To overcome this obstacle, I induced ex-situ maturation of core plugs from Eagle Ford marl by conducting confined pyrolysis experiments in fine-steps across all maturity windows from the immature through the early-peak oil, late oil, wet gas, and finally the dry gas window. The confined pyrolysis provides a confining pressure during maturation, imitating lithostatic pressure in the subsurface condition. This is a key improvement over previous unconfined pyrolysis experiments in which unrealistically large aperture fractures developed during pyrolysis. After each of my pyrolysis runs, I monitored the changes in microstructure, porosity, velocity, permeability, and geochemical properties. The results show systematically decreasing kerogen volume, increasing porosity, decreasing velocity, and increasing permeability as maturation progresses. These results reveal that secondary porosity from the loss of kerogen volume is the predominant microstructural alteration and the primary driver for decreasing velocity and increasing permeability. Based on these findings, I developed an elastic model for organic-rich marl that incorporates the maturation process. I used the pyrolysis dataset from this study along with previous petrographic and nanoindentation studies to calibrate a few ill-defined parameters in the model—such as kerogen porosity and the moduli of kerogen—as a function of maturity. These parameters cannot be directly measured and their estimated values in the literature are too sparse to be used in the calibration alone. Lastly, I employed the calibrated elastic model to build a rock physics template for characterizing organic-rich marl based on their elastic properties. I tested the applicability of the template against a rock physics dataset from natural (in-situ) maturation. The dataset comprises Bakken, Eagle Ford, and Niobrara core plugs and 11 Eagle Ford well logs across different maturity levels. The test results show that the template is able to map the scatter in the elastic properties of the naturally matured dataset to the variations in maturity, kerogen content, lithology, and fluid saturation. Therefore, this thesis provides a coherent pyrolysis dataset, a rock physics model, and a rock physic template for characterizing the properties of organic-rich marl across different maturity levels
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2020; ©2020 |
| Publication date | 2020; 2020 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Suwannasri, Krongrath |
|---|---|
| Degree supervisor | Vanorio, Tiziana |
| Thesis advisor | Vanorio, Tiziana |
| Thesis advisor | Graham, S. A. (Stephan Alan), 1950- |
| Thesis advisor | Mavko, Gary, 1949- |
| Degree committee member | Graham, S. A. (Stephan Alan), 1950- |
| Degree committee member | Mavko, Gary, 1949- |
| Associated with | Stanford University, Department of Geophysics. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Krongrath Suwannasri |
|---|---|
| Note | Submitted to the Department of Geophysics |
| Thesis | Thesis Ph.D. Stanford University 2020 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2020 by Krongrath Suwannasri
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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