Commenced in January 2007
Paper Count: 30835
Sphere in Cube Grid Approach to Modelling of Shale Gas Production Using Non-Linear Flow Mechanisms
Abstract:Shale gas is one of the most rapidly growing forms of natural gas. Unconventional natural gas deposits are difficult to characterize overall, but in general are often lower in resource concentration and dispersed over large areas. Moreover, gas is densely packed into the matrix through adsorption which accounts for large volume of gas reserves. Gas production from tight shale deposits are made possible by extensive and deep well fracturing which contacts large fractions of the formation. The conventional reservoir modelling and production forecasting methods, which rely on fluid-flow processes dominated by viscous forces, have proved to be very pessimistic and inaccurate. This paper presents a new approach to forecast shale gas production by detailed modeling of gas desorption, diffusion and non-linear flow mechanisms in combination with statistical representation of these processes. The representation of the model involves a cube as a porous media where free gas is present and a sphere (SiC: Sphere in Cube model) inside it where gas is adsorbed on to the kerogen or organic matter. Further, the sphere is considered consisting of many layers of adsorbed gas in an onion-like structure. With pressure decline, the gas desorbs first from the outer most layer of sphere causing decrease in its molecular concentration. The new available surface area and change in concentration triggers the diffusion of gas from kerogen. The process continues until all the gas present internally diffuses out of the kerogen, gets adsorbs onto available surface area and then desorbs into the nanopores and micro-fractures in the cube. Each SiC idealizes a gas pathway and is characterized by sphere diameter and length of the cube. The diameter allows to model gas storage, diffusion and desorption; the cube length takes into account the pathway for flow in nanopores and micro-fractures. Many of these representative but general cells of the reservoir are put together and linked to a well or hydraulic fracture. The paper quantitatively describes these processes as well as clarifies the geological conditions under which a successful shale gas production could be expected. A numerical model has been derived which is then compiled on FORTRAN to develop a simulator for the production of shale gas by considering the spheres as a source term in each of the grid blocks. By applying SiC to field data, we demonstrate that the model provides an effective way to quickly access gas production rates from shale formations. We also examine the effect of model input properties on gas production.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1314863Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 529
 Alexander, T., Baihly, J., Boyer, C., Clark, B., Waters, G., Jochen, V.... . Toelle, B. 2011. Shale Gas Revolution. Oilfield Review Autumn, Schlumberger, pp. 40-41.
 Javadpour, F., Fisher, D., Unsworth, M., 2007. Nanoscale gas flow in shale gas sediments. Journal of Canadian Petroleum Technology, 46 (10).
 Berawala, D. 2015. Modelling of Gas Production from Tight Shale Formations: An Innovative Approach (Master Thesis, University of Stavanger, Norway). Retrieved from https://brage.bibsys.no/xmlui/handle/11250/301296
 Langmuir, I., 1916. The constitution and fundamental properties of solids and liquids. Journal of the American Chemical Society, 38 (11): 2221–2295.
 Forchheimer, P., 1901. Wasserbewgung durch Boden‖. Zeitschirift des Vereines Deutscher Ingenieuer, 45 edition.
 Grathwohl, P. 2006. Diffusion II, HGC II. Retrieved from http://www.uni-tuebingen.de/zag/teaching/HGC/DiffusionII_2006.pdfJ.
 Moghanloo, R. G., Javadpour, F., & Davudov, D. 2013. Contribution of Methane Molecular Diffusion in Kerogen to Gas-in-Place and Production. Paper SPE 165376 presented at the SPE Western Regional & AAPG Pacific Section Meeting, Joint Technical Conferene, Monterey, California, USA, 19-25 April.
 Wang, C. 2013. Pressure Transient Analysis of Fractured Wells in Shale Reservoirs. Master Thesis. Colorado School of Mines. Colorado.
 Shi, J. and Durucan, S. 2005. Gas Storage and Flow in Coalbed Reservoirs: Implementation of a Bidisperse Pore Model for Gas Diffusion in a Coal matrix. SPE Reservoir Evaluation & Engineering Journal 8(2): 169-175. Paper SPE 84342-PA. doi: 10.2118/84342-PA.
 Swami, V., Settari, A., Javadpour, F. 2013. A Numerical Model for Multi-Mechanism Flow in Shale Gas Reservoirs with Application to Laboratory Scale Testing. Paper SPE 164840 presented at the EAGE Annual Conference & Exhibition incorporating SPE Europec, London, UK, 10-13 June.
 Firoozabadi A. 2012. Nano-Particles and Nano-Pores in Hydrocarbon Energy Production. Research talk delivered at University of Calgary, Dec 7.
 Loucks, R. G., Reed, R., Ruppel, S., Jarvie, D. 2009. Morphology, Genesis, and Distribution of Nanometer-Scale Pores in Siliceous Mudstones of the Mississippian Barnett Shale. Journal of Sedimentary Research, v. 79, 848-861.
 Nobakht, M., Clarkson, C., Kaviani, D. 2011. New and Improved Methods for Performing Rate-Transient Analysis of Shale Gas Reservoirs. Paper SPE 147869-MS presented at SPE Asia Pacific Oil and Gas Conference and Exhibition, Jakarta, Indonesia, 20-22 September.
 Espevold, I., Skoglund, L.K. 2013. Shale Gas Production – fluid flow towards wellbore. Bachelor Thesis. I. Espevold, L.K. Skoglung. Stavanger.