Research on Stress Sensitivity of Fractured Carbonate Reservoirs Based on CT Technology
Abstract
:1. Introduction
2. Stress Sensitivity Experiment
2.1. The Preparation of the Experiment
2.2. Experimental Conditions and Experimental Apparatus
2.3. Experimental Procedure
- (1)
- First, the core was placed into the core clamping device, and then a CT scan was conducted when the confining pressure was 0 MPa. The relative positions of the CT X-ray source, detector, and sample before scanning were adjusted so that a 3D core image of 0 MPa was obtained [42].
- (2)
- The second step was to assemble the hand pump, pressure gage, valve, pipeline, and clamp holder together as per Figure 4, then increase the confining at the step of 0.2 MPa.
- (3)
- At each pressure point in the case of loading, that confining pressure was maintained for 1 h to allow the load to dissipate through the sample before a scan was taken; all conditions are kept the same as outlined in Step 1.
- (4)
- In the case of unloading, the confining pressure was slowly reduced from the maximum confining pressure of 5.4 MPa to 4.0 MPa, then reduced by a step of 1 MPa down to 0 MPa.
- (5)
- Same as in the loading case; each confining pressure was maintained for 1 h before scanning.
- (6)
- Then we extracted the fracture aperture from all scanned image volumes of 400 × 400 × 400 pixel3. Pre-processing was applied to every image before being segmented. The image was processed, then the pictures were segmented. Finally, the 3D digital core of the fracture was obtained.
- (7)
- The same location of the fractures was found by using the white mineral as the reference in the larger rectangular figure, and by amplifying the two-dimensional (2D) image, as shown in Figure 5. We measured the width of the fracture in loading and unloading cycles.
2.4. Experimental Results and Analysis
3. Pore-Scale Simulations
3.1. Mesh Generation
3.2. Simulations of Fracture in Different Confining Pressures
3.3. Results and Analysis
4. Conclusions
- (1)
- The stress sensitivity experiment of the reservoir showed that a change in fracture width was non-linear in relation to changes in confining pressure through the data and graph. With an increase in confining pressure, the fracture width decreased, and the fracture width decreased more between 0 MPa and 0.6 MPa than at any other stage, which showed that the rock had strong stress sensitivity at a stage of low effective stress. After 0.6 MPa, the change gradient of the fracture width obviously weakened; after 2.6 MPa, there was very little variation, which showed that at a stage of high effective stress, the stress sensitivity of the rock samples weakened. With a decrease in confining pressure, the fracture opening increased, but could not recover its initial condition.
- (2)
- From the results of the pore-scale simulations, it was easy to see that the flow rate and permeability dropped sharply from 0 to 0.6 MPa, which meant that the rock had strong stress sensitivity at a stage of low effective stress. However, after 0.6 MPa, the variation was not obvious, which showed that at a stage of high effective stress, the stress sensitivity of the rock samples weakened tremendously. This finding was consistent with the results in the stress sensitivity experiment.
- (3)
- Exponential fitting was used to fit the relationship curve of k and confining pressure. We thus obtained the fitting equation: = 0.954exp (−/0.203) − 0.009 (R² = 0.9984). The results can provide guidance for the numerical simulations and the production of oil fields of fractured reservoirs.
Acknowledgments
Author Contributions
Conflicts of Interest
References
- Berkowitz, B. Characterizing flow and transport in fractured geological media: A review. Adv. Water Resour. 2002, 25, 861–884. [Google Scholar] [CrossRef]
- Sahimi, M. Flow and Transport in Porous Media and Fractured Rock; VCH Verlagsgesellschaft: Weinheim, Germany, 1995. [Google Scholar]
- Babadagli, T. Scaling of Co-Current and Counter-Current Capillary Imbibition for Surfactant and Polymer Injection in Naturally Fractured Reservoirs. In Proceedings of the SPE/AAPG Western Regional Meeting, Long Beach, CA, USA, 19–22 June 2000; Volume 6, pp. 465–478. [Google Scholar]
- Kantzas, A.; Pow, M.; Allsopp, K.; Marentette, D. Co-Current and Counter-Current Imbibition Analysis for Tight Fractured Carbonate Gas Reservoirs; Petroleum Society of Canada: Calgary, AB, Canada, 1997. [Google Scholar]
- Van Poollen, H.K.; Aguilera, R. Current Status On The Study Of Naturally Fractured Reservoirs. Log Anal. 1977, 18, 1–23. [Google Scholar]
- Xie, W.; Li, X. Research on Fractured Horizontal Wells Productivity and Productivity Influence in Shale Gas Reservoir. In Proceedings of the SPE/EAGE European Unconventional Resources Conference and Exhibition, Vienna, Austria, 25–27 February 2014. [Google Scholar]
- Meng, C.; De Pater, C.J. Acoustic Monitoring of Hydraulic Fracture Propagation in Pre-Fractured Natural Rocks. Key Eng. Mater. 2011, 452–453, 4003–4010. [Google Scholar] [CrossRef]
- Farquhar, R.A.; Smart, B.G.D.; Todd, A.C.; Tompkins, D.E.; Tweedie, A.J. Stress sensitivity of low-permeability sandstones from the Rotliegendes sandstone. In Proceedings of the SPE Annual Technical Conference and Exhibition, Houston, TX, USA, 3–6 October 1993. [Google Scholar]
- Lei, Q.; Xiong, W.; Yuang, J.; Cui, Y.; Wu, Y.-S. Analysis of stress sensitivity and its influence on oil production from tight reservoirs. In Proceedings of the Eastern Regional Meeting, Lexington, KY, USA, 17–19 October 2007. [Google Scholar]
- Vairogs, J.; Hearn, C.L.; Dareing, D.W.; Rhoades, V.W. Effect of Rock Stress on Gas Production From Low-Permeability Reservoirs. J. Pet. Technol. 1971, 23, 1161–1167. [Google Scholar] [CrossRef]
- Davies, J.P.; Davies, D.K. Stress-Dependent Permeability: Characterization and Modeling. In Proceedings of the SPE Annual Technical Conference and Exhibition, Houston, TX, USA, 3–6 October 1999; Volume 6, pp. 224–235. [Google Scholar]
- Geilikman, M.B.; Wong, S.-W.; Karanikas, J.M. Stress-Dependent Permeability Model of Laminated Gas Shale. In Proceedings of the 49th U.S. Rock Mechanics/Geomechanics Symposium, San Francisco, CA, USA, 28 June–1 July 2015. [Google Scholar]
- Fatt, I.; Davis, D.H. Reduction in Permeability With Overburden Pressure. J. Pet. Technol. 1952, 4. [Google Scholar] [CrossRef]
- Ali, H.S.; Al-Marhoun, M.A.; Abu-Khamsin, S.A.; Celik, M.S. The Effect of Overburden Pressure on Relative Permeability. In Proceedings of the Middle East Oil Show, Manama, Bahrain, 7–10 March 1987. [Google Scholar]
- Fatt, I. The Effect of Overburden Pressure on Relative Permeability. J. Pet. Technol. 1953, 5, 15–16. [Google Scholar] [CrossRef]
- Zhang, J.; Bai, M.; Roegiers, J.-C.; Liu, T. Determining stress-dependent permeability in the laboratory. In Proceedings of the Vail Rocks 1999, the 37th U.S. Symposium on Rock Mechanics (USRMS), Vail, CO, USA, 7–9 June 1999. [Google Scholar]
- Liang, B.; Jiang, H.; Li, J.; Gong, C.; Jiang, R.; Pei, Y.; Wei, S. Flow in multi-scale discrete fracture networks with stress sensitivity. J. Nat. Gas Sci. Eng. 2016, 35, 851–859. [Google Scholar] [CrossRef]
- Gangi, A.F. Variation of whole and fractured porous rock permeability with confining pressure. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 1978, 15, 249–257. [Google Scholar] [CrossRef]
- Zhang, Y.; Xu, X.; Lebedev, M.; Sarmadivaleh, M.; Barifcani, A.; lauer, S. Multi-scale X-ray computed tomography analysis of coal microstructure and permeability changes as a function of effective stress. Int. J. Coal Geol. 2016, 165, 149–156. [Google Scholar] [CrossRef]
- Carpenter, C. Digital Core Analysis and Pore-Network Modeling in a Mature-Field Project. J. Pet. Technol. 2015, 67, 97–99. [Google Scholar] [CrossRef]
- Ghous, A.; Knackstedt, M.A.; Arns, C.H.; Sheppard, A.; Kumar, M.; Sok, R.; Senden, T.; Latham, S.; Jones, A.C.; Averdunk, H.; et al. 3D imaging of reservoir core at multiple scales: Correlations to petrophysical properties and pore scale fluid distributions. In Proceedings of the International Petroleum Technology Conference, Kuala Lumpur, Malaysia, 3–5 December 2008. [Google Scholar]
- Ketcham, R.A.; Carlson, W.D. Acquisition, optimization and interpretation of X-ray computed tomographic imagery: Applications to the geosciences. Comput. Geosci. 2001, 27, 381–400. [Google Scholar] [CrossRef]
- Knackstedt, M.A.; Sok, R.; Adrian, S.; Arns, C.H. 3D Pore Scale Characterisation of Carbonate Core: Relating pore types and interconnectivity to petrophysical and multiphase flow properties. In Proceedings of the International Petroleum Technology Conference, Dubai, UAE, 4–6 December 2007. [Google Scholar]
- Yang, Y.; Yao, J.; Wang, C.; Gao, Y.; Zhang, Q.; An, S.; Song, W. New pore space characterization method of shale matrix formation by considering organic and inorganic pores. J. Nat. Gas Sci. Eng. 2015, 27, 496–503. [Google Scholar] [CrossRef]
- Dunsmuir, J.H.; Ferguson, S.R.; D’Amico, K.L.; Stokes, J.P. X-Ray Microtomography: A New Tool for the Characterization of Porous Media. In Proceedings of the SPE Annual Technical Conference and Exhibition, Dallas, TX, USA, 6–9 October 1991. [Google Scholar]
- Cipolla, C.L.; Lolon, E.; Mayerhofer, M.J.; Warpinski, N.R. Fracture Design Considerations in Horizontal Wells Drilled in Unconventional Gas Reservoirs. In Proceedings of the SPE Hydraulic Fracturing Technology Conference, The Woodlands, TX, USA, 19–21 January 2009. [Google Scholar]
- Geertsma, J.; Klerk, F.D. A rapid method of predicting width and extent of hydraulically induced fractures. J. Pet. Technol. 1969, 21, 1571–1581. [Google Scholar] [CrossRef]
- Yang, Y.; Zhang, W.; Gao, Y.; Wan, Y.; Su, Y.; An, S.; Sun, H.; Zhang, L.; Zhao, J.; Liu, L.; et al. Influence of stress sensitivity on microscopic pore structure and fluid flow in porous media. J. Nat. Gas Sci. Eng. 2016, 36, 20–31. [Google Scholar] [CrossRef]
- Montemagno, C.D.; Pyrak-Nolte, L.J. Fracture network versus single fractures: Measurement of fracture geometry with X-ray tomography. Phys. Chem. Earth Part A 1999, 24, 575–579. [Google Scholar] [CrossRef]
- Wolf, K.H.A.A.; van Bergen, F.; Ephraim, R.; Pagnier, H. Determination of the cleat angle distribution of the RECOPOL coal seams, using CT-scans and image analysis on drilling cuttings and coal blocks. Int. J. Coal Geol. 2008, 73, 259–272. [Google Scholar] [CrossRef]
- Cai, Y.; Liu, D.; Mathews, J.P.; Pan, Z.; Elsworth, D.; Yao, Y.; Li, J.; Guo, X. Permeability evolution in fractured coal—Combining triaxial confinement with X-ray computed tomography, acoustic emission and ultrasonic techniques. Int. J. Coal Geol. 2014, 122, 91–104. [Google Scholar] [CrossRef]
- Watanabe, N.; Hirano, N.; Tsuchiya, N. Determination of aperture structure and fluid flow in a rock fracture by high-resolution numerical modeling on the basis of a flow-through experiment under confining pressure. Water Resour. Res. 2008, 44, 6412. [Google Scholar] [CrossRef]
- Nemoto, K.; Watanabe, N.; Hirano, N.; Tsuchiya, N. Direct measurement of contact area and stress dependence of anisotropic flow through rock fracture with heterogeneous aperture distribution. Earth Planet. Sci. Lett. 2009, 281, 81–87. [Google Scholar] [CrossRef]
- Gao, Y.; Yao, J.; Yang, Y.; Zhao, J. REV identification of tight sandstone in sulige gas field in changqing oilfield china using CT based digital core technology. In Proceedings of the 2014 International Symposium of the Society of Core Analysts, Avignon, France, 8–11 September 2014. [Google Scholar]
- Wang, X.; Yao, J.; Yang, Y.; Wang, X. Visualization Research of the Digital Rock based on Real-time Volume Rendering Methods. Int. J. Pet. Sci. Technol. 2013, 7, 139–145. [Google Scholar]
- Yang, Y.; Wang, C.; Yao, J.; Gao, Y. A new voxel upscaling method based on digital rock. Int. J. Multiscale Comput. Eng. 2015, 13, 339–346. [Google Scholar] [CrossRef]
- Chen, X.; Zhou, Y. Applications of digital core analysis and hydraulic flow units in petrophysical characterization. Adv. Geo-Energy Res. 2017, 1, 18–30. [Google Scholar] [CrossRef]
- Fang, Q.; Boas, D.A. Tetrahedral mesh generation from volumetric binary and gray-scale images. In Proceedings of the IEEE International Symposium on Biomedical Imaging: From Nano to Macro, Boston, MA, USA, 28 June–1 July 2009. [Google Scholar]
- Lorenz, J.C.; Branagan, P.T.; Warpinski, N.R.; Sattler, A.R. Fracture characteristics and reservoir behavior of stress-sensitive fracture systems in flat-lying lenticular formations. J. Pet. Technol. 1989, 41, 615–622. [Google Scholar] [CrossRef]
- Yao, J.; Hu, R.; Wang, C.; Yang, Y. Multiscale Pore Structure Analysis In Carbonate Rocks. Int. J. Multiscale Comput. Eng. 2015, 13, 1–9. [Google Scholar] [CrossRef]
- Wilkins, S.W.; Gureyev, T.E.; Gao, D.; Pogany, A.; Stevenson, A.W. Phase-contrast imaging using polychromatic hard X-rays. Nature 1996, 384, 335–338. [Google Scholar] [CrossRef]
- Cnudde, V.; Boone, M.N. High-resolution X-ray computed tomography in geosciences: A review of the current technology and applications. Earth-Sci. Rev. 2013, 123, 1–17. [Google Scholar] [CrossRef]
- Lomize, G. Flow in Fractured Rocks; Gosenergoizdat: Moscow, Russia, 1951. [Google Scholar]
- Neuzil, C.E.; Tracy, J.V. Flow through fractures. Water Resour. Res. 1981, 17, 191–199. [Google Scholar] [CrossRef]
- Lei, G.; Dong, P.; Wu, Z.; Mo, S.; Gai, S.; Zhao, C.; Liu, Z.K. A Fractal Model for the Stress-Dependent Permeability and Relative Permeability in Tight Sandstones. J. Can. Pet. Technol. 2015, 54, 36–48. [Google Scholar] [CrossRef]
- Xie, S.; Cheng, Q.; Ling, Q.; Li, B.; Bao, Z.; Fan, P. Fractal and multifractal analysis of carbonate pore-scale digital images of petroleum reservoirs. Mar. Pet. Geol. 2010, 27, 476–485. [Google Scholar] [CrossRef]
- Zheng, Q.; Yu, B. A fractal permeability model for gas flow through dual-porosity media. J. Appl. Phys. 2012, 111, 24316. [Google Scholar] [CrossRef]
- Wei, W.; Cai, J.; Hu, X.; Han, Q. An electrical conductivity model for fractal porous media. Geophys. Res. Lett. 2015, 42, 4833–4840. [Google Scholar] [CrossRef]
- Brown, S.R. Fluid flow through rock joints: The effect of surface roughness. J. Geophys. Res. 1987, 92, 1337–1347. [Google Scholar] [CrossRef]
- Velde, B.; Dubois, J.; Moore, D.; Touchard, G. Fractal patterns of fractures in granites. Earth Planet. Sci. Lett. 1991, 104, 25–35. [Google Scholar] [CrossRef]
Confining Pressure (MPa) | 0.0 | 0.4 | 0.8 | 1.2 | 1.8 | 2.6 | 3.4 | 4.2 | 5.4 |
Fracture Width (μm) | 12.21 | 10.63 | 10 | 9.65 | 9.31 | 9.11 | 8.96 | 8.84 | 8.73 |
Confining Pressure (MPa) | 5.4 | 4.0 | 3.0 | 2.0 | 1.0 | 0.0 |
Fracture Width (μm) | 8.73 | 8.83 | 8.94 | 9.1 | 9.43 | 10.00 |
Confining Pressure (MPa) | 0 | 0.2 | 0.4 | 0.6 | 0.8 | 5.4 |
Flow rate (m3·s−1) | 2.36 × 10−9 | 8.77 × 10−10 | 3.33 × 10−10 | 4.99 × 10−11 | 1.88 × 10−11 | 7.62 × 10−12 |
K (mD) | 0.944 | 0.351 | 0.133 | 0.020 | 0.008 | 0.003 |
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Yang, Y.; Liu, Z.; Sun, Z.; An, S.; Zhang, W.; Liu, P.; Yao, J.; Ma, J. Research on Stress Sensitivity of Fractured Carbonate Reservoirs Based on CT Technology. Energies 2017, 10, 1833. https://doi.org/10.3390/en10111833
Yang Y, Liu Z, Sun Z, An S, Zhang W, Liu P, Yao J, Ma J. Research on Stress Sensitivity of Fractured Carbonate Reservoirs Based on CT Technology. Energies. 2017; 10(11):1833. https://doi.org/10.3390/en10111833
Chicago/Turabian StyleYang, Yongfei, Zhihui Liu, Zhixue Sun, Senyou An, Wenjie Zhang, Pengfei Liu, Jun Yao, and Jingsheng Ma. 2017. "Research on Stress Sensitivity of Fractured Carbonate Reservoirs Based on CT Technology" Energies 10, no. 11: 1833. https://doi.org/10.3390/en10111833