Adviser ： Loung-Yie Tsai Presenter ： Ling- Szu Wang Date ： 2011/6/9

1. 99學年度第二學期專題討論Influence of carbon dioxide on coal permeability determined by pressure transient methods Siriwardane,H., Haljasmaa, I., McLendon, R., Irdi, G., Soong, Y., Bromhal, G., 2009. Influence of carbon dioxide on coal permeability determined by pressure transient methods. International Journal of Coal Geology, 77, 109–118. Adviser：Loung-YieTsai Presenter：Ling-Szu Wang Date：2011/6/9

2. Outline • Introduction • Objectives • Methods of Study • Results and Discussion • Conclusions

3. Introduction

4. CO2sorption on coal seams induces swelling effect on coal matrix.(Siriwardane et al., 2006; Mazumder et al., 2006; Day et al., 2008) Swelling v.s. Permeability ? CO2 coal seam

5. Coal seams include matrix and fracture areas . • Diffusion is a very slow process that occurs in the coal matrix, and flow of fluids takes place in the fracture system. Fracture v.s. Permeability ? Pressure v.s. Permeability ? Fig. 1. Diagram of matrix and fractures. (Huy et al., 2010)

6. Objectives

7. To investigate the influence of CO2 exposure on coal permeability.

8. Methods of Study

9. Experimental procedure Fig. 2. Helium porosimeter, HP-401. (TEMCO, Inc.) Fig. 3. A typical fractured coal core sample in a rubber jacket.

10. Experimental procedure Fig. 4. Diagram showing the induced fracture through a coal sample. Fig. 5. CT scan of a fractured coal sample.

11. Determining permeability Fig. 6. Autolab 1500, from New England Research, Inc. (NER, 2005)

12. Pressure transient method For measuring permeability of tight rocks. (Brace et al., 1968; Hsieh et al., 1980; Kamath et al., 1990; Evans and Wong, 1992.) Fig. 7. Schematic diagram of the pressure transient method.

13. Results and Discussion

14. Table 1. Porosity and permeability of the coal samples. (CO2 as pore fluid, Confining pressure : 20MPa, Pore pressure : 10MPa.) Porosity and permeability of coals

15. Table 2. Porosity and permeability of the coal samples. (Aras pore fluid, Confining pressure : 6MPa, Pore pressure : 4MPa.) Porosity and permeability of coals • Table 3. Porosity and permeability after increasing in confining pressure. • (CO2 as pore fluid, Pore pressure : 10MPa.)

16. Influence of exposure time on permeability (Arv.s. CO2) 58% Fig. 8. Variation of permeability with exposure time of argon for sample S02. Fig. 9. Variation of permeability with exposure time of CO2 for sample S02.

17. Effects of confining stress on permeability 65% Fig. 10. Influence of confining stress on the coal permeability for sample S04.

18. Influence of CO2 exposure time on permeability of naturally fractured samples 58% 69% Fig. 9. Variation of permeability with exposure time of CO2 for sample S02. Fig. 11. Variation of permeability with exposure time for a naturally fractured sample S11.

19. Conclusions

20. The permeability of fractured coal samplesdecreased significantly with CO2 exposure timedueto the coal swelling. • After long enough exposure to CO2, the fracture is completely closed due to the coal swelling, and CO2 transport in the sample occurs only by diffusion through the coal matrix.

21. The higher confining pressureappears to close internal fractures causing a reduction in permeability.

22. Thanks For Your Attention.