Heat-Induced Fractures in Type I Oil Shale Source Rock
Abstract/Contents
- Abstract
- In this report we further understanding of the behavior of kerogen in source rock while undergoing pyrolysis. Source rock being a sedimentary rock with hydrocarbon potential is crucial to understand fully. Being able to predict source rock evolution and the underlying mechanisms it undergoes during geological maturation aids various applications. Those applications include but are not limited to in-situ upgrading, conventional resources, tight oil and gas, basin modeling and exploration. The source rock studied here is in its raw state as oil shale. Oil shale is composed of a very fine-grained sedimentary rock containing immature oil in the form of kerogen. The USGS has estimated 4.2 trillion barrels of oil shale resources in Utah, Wyoming, and Colorado. The few pilot projects that were led by top-tier operators in those regions have yielded interesting results, some of which have been used to validate multiple in-house flow simulators attempting to simulate kerogen pyrolysis. This thesis delves into investigating experimentally the fracture evolution and other related phenomena with lab-simulated maturation as a means to deepen our knowledge of source rock characteristics so that we can effectively develop it for various applications. The Uinta basin sample at hand is a representative Type I sample that has similar characteristics to oil shale seen in literature. It is a 16 gal/ton lean sample that has a kerogen density of 1.05 g/cc. The sample has a single digit initial porosity of 6.6% confirmed by the mercury injection and gas pycnometer porosity and image processing techniques. On the kinetics side, the kerogen conversion peaks at heating rates of 1oC/min, 4 oC/min, and 10 oC/min are 410 oC, 432 oC, and 442 oC respectively. All of which are within 1% of literature values. The Backscattered Electron (BSE) SEM revealed mineralogy that is primarily dolomite, calcite and quartz with instances of K-Spar, Na-Spar, Nahcolite, Smectite, and Illite. Moreover, laboratory imaging techniques are reported to study porosity and fracture behavior of oil shale as kerogen is thermally matured. The pyrolysis setup built is fully functional and provides an inert sealing environment up to and exceeding peak pyrolysis temperatures. This setup allows artificial acceleration of the natural burial process into approximately an hour or two to decompose thermally the sample and fracture it. It is found that fractures induced thermally grow parallel to laminations and are apparent in darker laminations that are originally kerogen rich. Those fractures are created at different stages, implying that other thermally driven mechanisms beside kerogen decomposition could fracture oil shale source rock. The mosaic construction technique developed captures a 1” diameter sample with micron-scale resolution. The mosaic does not show overlapping, stitching marks, or changes in contrast or brightness along the sample making it ideal for image processing. Porosity quantification on highly magnified images is not feasible due to the varying grain sizes and its dependence on magnification and bin size. On the other hand, the mosaic technique provides enough representative area to overcome this problem. This technique produced similar initial 2D low density zones to 3D porosity measured previously with helium pycnometer and mercury injection. Also, the interconnected porosity post-heating could be captured using this framework. On the other hand, the poor overlap of porosities between the preheated and post-heated mosaic, coupled with the random scatter of porosity outside the fracture zone in the post-heating mosaic, raises concerns regarding the viability of the post-heated data for further image processing. Also, a more comprehensive comparison technique must be built to be able to compare pre and post heating mosaics on a quantitative level.
Description
| Type of resource | text |
|---|---|
| Date created | June 2016 |
Creators/Contributors
| Author | Elkady, Youssef |
|---|---|
| Primary advisor | Kovscek, Anthony R. |
| Degree granting institution | Stanford University, Department of Energy Resources Engineering |
Subjects
| Subject | School of Earth Energy & Environmental Sciences |
|---|---|
| Genre | Thesis |
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Preferred citation
- Preferred Citation
- Elkady, Youssef. (2016). Heat-Induced Fractures in Type I Oil Shale Source Rock. Stanford Digital Repository. Available at: https://purl.stanford.edu/vt675ww4508
Collection
Master's Theses, Doerr School of Sustainability
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