A Model of Gas Transport Through Shale Reservoirs Including the Effects of Real Gas, Gas Adsorption and Stress Dependent Permeability
- Nan You (National University of Singapore) | Hon Chung Lau (National University of Singapore)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil and Gas Conference and Exhibition, 23-25 October, Brisbane, Australia
- Publication Date
- Document Type
- Conference Paper
- 2018. Society of Petroleum Engineers
- Gas transport, gas slippage, Surface Diffusion, Knudsen Diffusion, Shale Reservoir
- 4 in the last 30 days
- 82 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 8.50|
|SPE Non-Member Price:||USD 25.00|
Shale reservoirs contain predominantly micro and mesopores (<50 nm), within which gas is stored as free or adsorbed gas. Due to the ultra-small pore size, multiple transport mechanisms coexist in shale reservoirs, including gas slippage, Knudsen diffusion of free gas and surface diffusion of adsorbed gas. In this work, we propose a new transport model, valid for all ranges of Knudsen number, which combines all transport mechanisms with different weighting coefficients. To quantify the effects of influence factors, we introduce the compressibility factor for real gas effect and effective pore radius for gas adsorption and stress dependence. The model is proven to be more accurate than existing models since the deviation of the analytical solution of our model (3%) from published molecular simulation data is lower than that of existing models (10~20%). Based on this model, we compare (1) the contribution of each transport mechanism to gas transport in pores of different radii, (2) shale permeability measured in laboratory and at reservoir conditions, and (3) permeability of nanopores and natural fractures. It is found that gas transport is dominated by gas slippage and surface diffusion when the pore radius is over 10 nm and below 5 nm, respectively. Knudsen diffusion only becomes significant when the pore radius is between 2 and 25 nm and pore pressure is below 1000 psi. Furthermore, laboratory measurements usually over-estimate shale permeability. We also propose a promising enhanced gas recovery method, which is to open and prop up closed natural fractures using micro size proppants.
|File Size||2 MB||Number of Pages||20|
Azom, P. N. and Javadpour, F. 2012. Dual-continuum modeling of shale and tight gas reservoirs. Proc., SPE annual technical conference and exhibition, San Antonio, Texas, USA, 8-10 October. SPE-159584-MS. https://doi.org/10.2118/159584-MS.
Chen, Y. D. and Yang, R. T. 1991. Concentration dependence of surface diffusion and zeolitic diffusion. AIChE Journal 37 (10): 1579–1582. https://doi.org/10.1002/aic.690371015.
Civan, F., Devegowda, D., and Sigal, R. F. 2013. Critical Evaluation and Improvement of Methods for Determination of Matrix Permeability of Shale. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, USA, 30 September. SPE-166473-MS. https://doi.org/10.2118/166473-MS.
Civan, F., Rai, C. S., and Sondergeld, C. H. 2011. journal article. Shale-Gas Permeability and Diffusivity Inferred by Improved Formulation of Relevant Retention and Transport Mechanisms. Transport in Porous Media 86 (3): 925–944. https://doi.org/10.1007/s11242-010-9665-x.
Cui, X., Bustin, A. M. M., and Bustin, R. M. 2009. Measurements of gas permeability and diffusivity of tight reservoir rocks: different approaches and their applications. Geofluids 9 (3): 208–223. https://doi.org/10.1111/j.1468-8123.2009.00244.x.
Darabi, H., Ettehad, A., Javadpour, F.. 2012. Gas flow in ultra-tight shale strata. Journal of Fluid Mechanics 710: 641–658. https://doi.org/10.1017/jfm.2012.424.
Do, H. D., Do, D. D., and Prasetyo, I. 2001. On the surface diffusion of hydrocarbons in microporous activated carbon. Chemical Engineering Science 56 (14): 4351–4368. https://doi.org/10.1016/S0009-2509(01)00051-3.
Dong, J.-J., Hsu, J.-Y., Wu, W.-J.. 2010. Stress-dependence of the permeability and porosity of sandstone and shale from TCDP Hole-A. International Journal of Rock Mechanics and Mining Sciences 47 (7): 1141–1157. https://doi.org/10.1016/j.ijrmms.2010.06.019.
Ertekin, T., King, G. A., and Schwerer, F. C. 1986. Dynamic gas slippage: a unique dual-mechanism approach to the flow of gas in tight formations. SPE formation evaluation 1 (01): 43–52. SPE-12045-PA. https://doi.org/10.2118/12045-PA.
Hwang, S.-T. and Kammermeyer, K. 1966. Surface diffusion in microporous media. The Canadian Journal of Chemical Engineering 44 (2): 82–89. https://doi.org/10.1002/cjce.5450440206.
Javadpour, F. 2009. Nanopores and Apparent Permeability of Gas Flow in Mudrocks (Shales and Siltstone). PETSOC-09-08-16-DA. https://doi.org/10.2118/09-08-16-DA.
Lee, A. L., Gonzalez, M. H., and Eakin, B. E. 1966. The Viscosity of Natural Gases. SPE-1340-PA. https://doi.org/10.2118/1340-PA.
Liu, G., Bai, Y., Fan, Z.. 2017. Determination of Klinkenberg Permeability Conditioned to Pore-Throat Structures in Tight Formations. 10 (10): 1575–1591. https://doi.org/10.3390/en10101575.
Liu, H. H., Ranjith, P. G., Georgi, D. T.. 2016. Some key technical issues in modelling of gas transport process in shales: a review. Geomechanics and Geophysics for Geo-Energy and Geo-Resources 2 (4): 231–243. https://doi.org/10.1007/s40948-016-0031-5.
Luffel, D., Hopkins, C., and Schettler, P.Jr 1993. Matrix permeability measurement of gas productive shales. Proc., SPE annual technical conference and exhibition, Houston, Texas, USA, 3-6 October. SPE-26633-MS. https://doi.org/10.2118/26633-MS.
Ma, J. and Couples, G. D. 2015. Assessing Impact of Shale Gas Adsorption on Free-Gas Permeability via a Pore Network Flow Model. Proc., Unconventional Resources Technology Conference, San Antonio, Texas, USA, 20-22 July. URTEC-2153743-MS. https://doi.org/10.15530/URTEC-2015-2153743.
Ma, J., Sanchez, J. P., Wu, K.. 2014. A pore network model for simulating non-ideal gas flow in micro- and nano-porous materials. Fuel 116: 498–508. https://doi.org/10.1016/j.fuel.2013.08.041.
Medve’, I. and Cerný, R. 2011. Surface diffusion in porous media: A critical review. Microporous and Mesoporous Materials 142 (2): 405–422. https://doi.org/10.1016/j.micromeso.2011.01.015.
Rahmanian, M., Aguilera, R., and Kantzas, A. 2012. A New Unified Diffusion--Viscous-Flow Model Based on Pore-Level Studies of Tight Gas Formations. 18 (01): 38–49. SPE-149223-PA. https://doi.org/10.2118/149223-PA.
Ross, D. J. K. and Marc Bustin, R. 2007. Impact of mass balance calculations on adsorption capacities in microporous shale gas reservoirs. Fuel 86 (17): 2696–2706. https://doi.org/10.1016/j.fuel.2007.02.036.
Singh, H. and Javadpour, F. 2013. Nonempirical apparent permeability of shale. SPE Reservoir Evaluation & Engineering 17 (03): 414–424. SPE-170243-PA. https://doi.org/10.2118/170243-PA.
Song, W., Yao, J., Ma, J.. 2017. Assessing relative contributions of transport mechanisms and real gas properties to gas flow in nanoscale organic pores in shales by pore network modelling. International Journal of Heat and Mass Transfer 113: 524–537. https://doi.org/10.1016/j.ijheatmasstransfer.2017.05.109.
Sutera, S. P. and Skalak, R. 1993. The History of Poiseuille's Law. Annual Review of Fluid Mechanics 25 (1): 1–20. https://doi.org/10.1146/annurev.fl.25.010193.000245.
Wu, K., Chen, Z., Li, X.. 2016. A model for multiple transport mechanisms through nanopores of shale gas reservoirs with real gas effect–adsorption-mechanic coupling. International Journal of Heat and Mass Transfer 93: 408–426. https://doi.org/10.1016/j.ijheatmasstransfer.2015.10.003.
Wu, K., Li, X., Wang, C.. 2014a. Apparent permeability for gas flow in shale reservoirs coupling effects of gas diffusion and desorption. Proc., Unconventional Resources Technology Conference, Denven, Colorado, USA, 25-27 August. URTEC-1921039-MS. https://doi.org/10.15530/URTEC-2014-1921039.
Wu, K., Li, X., Wang, C.. 2015. Model for Surface Diffusion of Adsorbed Gas in Nanopores of Shale Gas Reservoirs. Industrial & Engineering Chemistry Research 54 (12): 3225–3236. https://doi.org/10.1021/ie504030v.
Wu, Y.-S., Li, J., Ding, D.. 2014b. A generalized framework model for the simulation of gas production in unconventional gas reservoirs. SPE Journal 19 (05): 845–857. SPE-163609-PA. https://doi.org/10.2118/163609-PA.
Xiong, X., Devegowda, D., Civan, F.. 2013. Compositional Modeling of Liquid-Rich Shales Considering Adsorption, Non-Darcy Flow Effects and Pore Proximity Effects on Phase Behavior. Presented at the Unconventional Resources Technology Conference, Denver, Colorado, USA, 12-14 August. URTEC-1582144-MS.