Shale Gas-in-Place Calculations Part I: New Pore-Scale Considerations
- Raymond J. Ambrose (Devon Energy) | Robert C. Hartman (Weatherford Labs) | Mery Diaz-Campos (University of Oklahoma) | I. Yucel Akkutlu (University of Oklahoma) | Carl H. Sondergeld (University of Oklahoma)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- March 2012
- Document Type
- Journal Paper
- 219 - 229
- 2012. Society of Petroleum Engineers
- 5.1.1 Exploration, Development, Structural Geology, 5.8.2 Shale Gas, 5.2.1 Phase Behavior and PVT Measurements, 4.3.4 Scale
- Shale, Gas-in-place, Correction
- 24 in the last 30 days
- 4,376 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 10.00|
|SPE Non-Member Price:||USD 30.00|
Using focused-ion-beam (FIB)/scanning-electron-microscope (SEM) imaging technology, a series of 2D and 3D submicroscale investigations revealed a finely dispersed porous organic (kerogen) material embedded within an inorganic matrix. The organic material has pores and capillaries having characteristic lengths typically less than 100 nm. A significant portion of total gas in place appears to be associated with interconnected large nanopores within the organic material.
Thermodynamics (phase behavior) of fluids in these pores is quite different; gas residing in a small pore or capillary is rarefied under the influence of organic pore walls and shows a different density profile. This raises serious questions related to gas-in-place calculations: Under reservoir conditions, what fraction of the pore volume of the organic material can be considered available as free gas, and what fraction is taken up by the adsorbed phase? How accurately is the shale-gas storage capacity estimated using the conventional volumetric methods? And finally, do average densities exist for the free and the adsorbed phases?
We combine the Langmuir adsorption isotherm with the volumetrics for free gas and formulate a new gas-in-place equation accounting for the pore space taken up by the sorbed phase. The method yields a total-gas-in-place prediction. Molecular dynamics simulations involving methane in small carbon slit-pores of varying size and temperature predict density profiles across the pores and show that (a) the adsorbed methane forms a 0.38 nm monolayer phase and (b) the adsorbed-phase density is 1.8 - 2.5 times larger than that of bulk methane. These findings could be a more important consideration with larger hydrocarbons and suggest that a significant adjustment is necessary in volume calculations, especially for gas shales high in total organic content. Finally, using typical values for the parameters, calculations show a 10 - 25% decrease in total gas-storage capacity compared with that using the conventional approach. The role of sorbed gas is more important than previously thought. The new methodology is recommended for estimating shale gas in place.
|File Size||3 MB||Number of Pages||11|
Allen, M.P., and Tildesley, D.J. 2002. Computer Simulation of Liquids,reprint. London: Oxford University Press.
Aukett, P.N., Quirke, N., Riddiford, S., and Tennison, S.R. 1992. Methaneadsorption on microporous carbons—A comparison of experiment, theory, andsimulation. Carbon 30 (6): 913-924. http://dx.doi.org/10.1016/0008-6223(92)90015-O.
Bustin, R.M., Bustin, A.M., Cui, X., Ross, D.J.K., and Murthy Pathi, V.S.2008. Impact of Shale Properties on Pore Structure and Storage Characteristics.Paper SPE 119892 presented at the SPE Shale Gas Production Conference, FortWorth, Texas, USA, 16-18 November. http://dx.doi.org/10.2118/119892-MS.
Comer, J.B. and Hinch, H.H. 1987. Recognizing and quantifying expulsion ofoil from the Woodford Formation and age-equivalent rocks in Oklahoma andArkansas. AAPG Bulletin 71 (7): 844-858.
Cui, X., Bustin, A.M.M., and Bustin, R.M. 2009. Measurements of gaspermeability and diffusivity of tight reservoir rocks: different approaches andtheir applications. Geofluids 9 (3): 208-223. http://dx.doi.org/10.1111/j.1468-8123.2009.00244.x.
Curtis, M.E., Ambrose, R.J., Sondergeld, C.S., and Rai, C.S. 2010.Structural Characterization of Gas Shales on the Micro- and Nano-Scales. PaperSPE 137693 presented at the Canadian Unconventional Resources and InternationalPetroleum Conference, Calgary, 19-21 October. http://dx.doi.org/10.2118/137693-MS.
de Pablo, J.J. and Escobedo, F.A. 2002. Molecular Simulations in ChemicalEngineering: Present and future. AIChE Journal 48 (12):2716-2721. http://dx.doi.org/10.1002/aic.690481202.
Diaz-Campos, M., Akkutlu, I.Y., and Sigal, R.F. 2009. A Molecular DynamicsStudy on Natural Gas Solubility Enhancement in Water Confined to Small Pores.Paper SPE 124491 presented at the SPE Annual Technical Conference andExhibition, New Orleans, 4-7 October. http://dx.doi.org/10.2118/124491-MS.
Dubinin, M.M. 1960. The Potential Theory of Adsorption of Gases and Vaporsfor Adsorbents with Energetically Nonuniform Surfaces. Chemical Review60 (2): 235-241. http://dx.doi.org/10.1021/cr60204a006.
Energy Information Administration (EIA). 2009. Annual Energy Outlook 2009,With Projections to 2030. Annual Report No. DOE/EIA-0383(2009), EIA/US DOE,Washington, DC (March 2009).
Frenkel, D. and Smit, B. 2002. Understanding Molecular Simulation: FromAlgorithms to Applications, second edition, Vol. 1. San Diego, California:Computational Science Series, Academic Press.
Ghoufi, A., Gaberova, L., Rouquerol, J., Vincent, D., Llewellyn, P.L., andMaurin, G. 2009. Adsorption of CO2, CH4 and their binarymixture in Faujasite NaY: A combination of molecular simulations withgravimetry-manometry and microcalorimetry measurements. Microporous andMesoporous Materials 119 (1-3): 117-128. http://dx.doi.org/10.1016/j.micromeso.2008.10.014.
Harris, J.G. and Yung, K.H. 1995. Carbon Dioxide's Liquid-Vapor CoexistenceCurve And Critical Properties as Predicted by a Simple Molecular Model. J.Phys. Chem. 99 (31): 12021-12024. http://dx.doi.org/10.1021/j100031a034.
Haydel, J.J. and Kobayashi, R. 1967. Adsorption Equilibria in theMethane-Propane-Silica Gel System at High Pressures. Ind. Eng. Chem.Fundamen. 6 (4): 564-554. http://dx.doi.org/10.1021/i160024a010.
Jenden, P.D., Drazan, D.J., and Kaplan, I.R. 1993. Mixing of ThermogenicNatural Gases in Northern Appalachian Basin. AAPG Bulletin 77 (6): 980-998.
Kang, S., Fathi, E., Ambrose, R.J., Akkutlu, I.Y., and Sigal, R.F. 2010.Carbon Dioxide Storage Capacity of Organic-rich Shales. Paper SPE 134583presented at the SPE Annual Technical Conference and Exhibition, Florence,Italy, 19-22 September. http://dx.doi.org/10.2118/134583-MS.
Krishna, R. 2009. Describing the Diffusion of Guest Molecules Inside PorousStructures. J. Phys. Chem. C 113 (46): 19756-19781. http://dx.doi.org/10.1021/jp906879d.
Loucks, R.G., Reed, R.M., Ruppel, S.C., and Jarvie, D.M. 2009. Morphology,Genesis, and Distribution of Nanometer-Scale Pores in Siliceous Mudstones ofthe Mississippian Barnett Shale. Journal of Sedimentary Research 79 (12): 848-861. http://dx.doi.org/10.2110/jsr.2009.092.
Luffel, D.L. and Guidry, F.K. 1992. New Core Analysis Methods for MeasuringRock Properties of Devonian Shale. J Pet Tech 44 (11):1184-1190. SPE-20571-PA. http://dx.doi.org/10.2118/20571-PA.
Luffel, D.L., Hopkins, C.W., and Schettler, P.D. Jr. 1993. MatrixPermeability Measurement of Gas Productive Shales. Paper SPE 26633 presented atthe SPE Annual Technical Conference and Exhibition, Houston, 3-6 October. http://dx.doi.org/10.2118/26633-MS.
Mancini, E. A., Goddard D. A., Barnaby R., and Aharon P.2006. Basin Analysis and Petroleum System Characterization and Modeling,Interior Salt Basins, Central and Eastern Gulf of Mexico. Phase 1 Final Report,Project No. 422, Contract No. DE-FC26-03NT15395, US DOE/NETL, AlabamaUniversity, Tuscaloosa, Alabama.
Mavor, M.J. and Nelson, C.R. 1997. Coalbed Reservoir Gas-In-Place Analysis.Report GRI-97/0263, Gas Research Institute, Chicago, Illinois.
Mavor, M.J., Hartman, C., and Pratt, T.J. 2004. Uncertainty in SorptionIsotherm Measurements. Paper No. 411 presented at the International CoalbedMethane Symposium, Tuscaloosa, Alabama, 14-16 May.
Menon, P.G. 1968. Adsorption at high pressures. Chem. Rev. 68(3): 277-294. http://dx.doi.org/10.1021/cr60253a002.
Ming, L., Anzhong, G., Xuesheng, L., and Rongshun, W. 2003. Determination ofthe adsorbate density from supercritical gas adsorption equilibrium data.Carbon 41 (3): 585-588. http://dx.doi.org/10.1016/S0008-6223(02)00356-1.
Nath, S.K, Escobedo, F.A., and de Pablo, J.J. 1998. On the simulation ofvapor-liquid equilibria for alkanes. J. Phys. Chem. 108(23): 9905-9911. http://dx.doi.org/10.1063/1.476429.
Ozawa, S., Kusumi, S., and Ogino, Y. 1976. Physical adsorption of gases athigh pressure. IV. An improvement of the Dubinin—Astakhov adsorptionequation.Journal of Colloid Interface Science 56 (1):83-91. http://dx.doi.org/10.1016/0021-9797(76)90149-1.
Pollastro, R.M. 2007. Total petroleum system assessment of undiscoveredresources in the giant Barnett Shale continuous (unconventional) gasaccumulation, Fort Worth Basin, Texas. AAPG Bulletin 91(4): 551-578. http://dx.doi.org/10.1306/06200606007.
Reynolds, M.M. and Munn, D.L. 2010. Development Update for an Emerging ShaleGas Giant Field—Horn River Basin, British Columbia, Canada. Paper SPE 130103presented at the SPE Unconventional Gas Conference, Pittsburg, Pennsylvania,USA, 23-25 February. http://dx.doi.org/10.2118/130103-MS.
Sondergeld, C.H., Ambrose, R.J., Rai, C.S., and Moncrieff, J. 2010.Micro-Structural Studies of Gas Shales. Paper SPE 131771 presented at the SPEUnconventional Gas Conference, Pittsburg, Pennsylvania, USA, 23-25 February2010. http://dx.doi.org/10.2118/131771-MS.
Sweatman, M.B. and Quirke, N. 2001. Characterization of Porous Materials byGas Adsorption: Comparison of Nitrogen at 77 K and Carbon Dioxide at 298 K forActivated Carbon. Langmuir 17 (16): 5011-5020. http://dx.doi.org/10.1021/la010308j.
Todorov, I.T. and Smith, W. 2008. The DLPOLY_3 User Manual. Cheshire, UK:Science & Technology Facilities Council (STFC).
Tomutsa, L., Silin, D., and Radmilovic V. 2007. Analysis of ChalkPetrophysical Properties by Means of Submicron-scale Pore Imaging andModeling. SPE Res Eval & Eng 10 (3): 285-293.SPE-99558-PA. http://dx.doi.org/10.2118/99558-PA.
Tsai, M.C., Chen, W.N., Cen, P.L., Yang, R.T., Kornosky, R.M., Holcombe,N.T., and Strakey, J.P. 1985. Adsorption of gas mixture on activated carbon.Carbon 23 (2): 167-73. http://dx.doi.org/10.1016/0008-6223(85)90008-9.
Wang, F.P. and Reed, R.M. 2009. Pore Networks and Fluid Flow in Gas Shales.Paper SPE 124253 presented at the SPE Annual Technical Conference andExhibition, New Orleans, 4-7 October. http://dx.doi.org/10.2118/124253-MS.