Development of a new compositional model with multi-component sorption isotherm and slip flow in tight gas reservoirs

Abstract Natural gas in unconventional gas reservoirs typically contains multiple gas components. Existing models incorporate either the unique flow mechanisms in tight and shale gas reservoirs (slip flow) or multi-component sorption isotherm without combining them. In this work, we developed a compositional flow code incorporating slip flow and multi-component sorption using the extended Langmuir isotherm (EL). The model was discretized using finite volume method based on unstructured Perpendicular Bisection (PEBI) grids for their local orthogonality and flexibility in handling irregular shaped domain. The code was verified using ECLIPSE-CBM for multi-component sorption and using ECLIPSE with modified transmissibility for slip flow calculation. The model was further validated by reproducing the pressure build up data during well shut-in period in a tight gas reservoir in Xinjiang, China. The developed code was used to understand and quantify the importance of multi-component EL isotherm and slip flow. The evolution of the bottom-hole pressure (BHP), sorption volume, and gas composition was also simulated under various reservoir conditions including different initial gas compositions, sorption capacities, and reservoir sizes. The deviations caused by representing shale gas as pure methane using single-component Langmuir isotherm can reach as much as 90% for BHP and 45% for sorbed volume if the initial methane composition was 80%. The predicted produced gas composition with the EL isotherm showed a unique constant composition (CC) stage before the gas flow reached the domain boundary, indicating the potential use of gas composition as another type of data to infer reservoir boundary and flow regimes. The developed code offers a powerful tool to understand gas flow and sorption, as well as an analyzing tool to identify reservoir boundary and flow regimes compared to traditional well test method, which requires expensive measurements of BHP.

[1]  The kinetic theory of gases and the gas laws , 1978 .

[2]  Khalid Aziz,et al.  Use of Voronoi Grid in Reservoir Simulation , 1994 .

[3]  K. Thomas,et al.  Methane Adsorption on Shale under Simulated Geological Temperature and Pressure Conditions , 2013 .

[4]  J. Wilcox,et al.  Molecular simulation of methane adsorption in micro- and mesoporous carbons with applications to coal and gas shale systems , 2013 .

[5]  H. Kazemi,et al.  Analysis of Production Data From Hydraulically Fractured Horizontal Wells in Shale Reservoirs , 2010 .

[6]  Michael J. Economides,et al.  The state of natural gas , 2009 .

[7]  Erdal Ozkan,et al.  Productivity and Drainage Area of Fractured Horizontal Wells in Tight Gas Reservoirs , 2008 .

[8]  Rui Wang,et al.  Influence of Engineering Measurements on the Desorption and Production of CBM Wells by Eclipse , 2013 .

[9]  R. Marc Bustin,et al.  Impact of mass balance calculations on adsorption capacities in microporous shale gas reservoirs , 2007 .

[10]  Jianfang Li,et al.  A Generalized Framework Model for Simulation of Gas Production in Unconventional Gas Reservoirs , 2013, ANSS 2013.

[11]  Faruk Civan,et al.  Effective Correlation of Apparent Gas Permeability in Tight Porous Media , 2010 .

[12]  R. C. Earlougher.  Advances in Well Test Analysis , 1977 .

[13]  John Lohrenz,et al.  Calculating Viscosities of Reservoir Fluids From Their Compositions , 1964 .

[14]  George J. Moridis,et al.  Modeling and Performance Interpretation of Flowing Gas Composition Changes in Shale Gas Wells with Complex Fractures , 2013 .

[15]  F. Javadpour.  Nanopores and Apparent Permeability of Gas Flow in Mudrocks (Shales and Siltstone) , 2009 .

[16]  C. A. Mora,et al.  Analyst and Verification of Dual Porosity and CBM Shape Factors , 2006 .

[17]  Boming Yu,et al.  Mechanism model for shale gas transport considering diffusion, adsorption/desorption and Darcy flow , 2013 .

[18]  S. A. Schaaf,et al.  Flow of rarefied gases , 1961 .

[19]  Bernhard M. Krooss,et al.  Geological controls on the methane storage capacity in organic-rich shales , 2014 .

[20]  Robert A. Wattenbarger,et al.  Analysis and Verification of Dual Porosity and CBM Shape Factors , 2006 .

[21]  G. David,et al.  Gas productive fractured shales; an overview and update , 2000 .

[22]  C. Brand,et al.  Modeling reservoir geometry with irregular grids , 1991 .

[23]  Luke D. Connell,et al.  Experimental study and modelling of methane adsorption and diffusion in shale , 2014 .

[24]  Kamy Sepehrnoori,et al.  Simulation of gas desorption and geomechanics effects for unconventional gas reservoirs , 2014 .

[25]  Junhua Fang,et al.  Shale gas reservoir characterisation: A typical case in the southern Sichuan Basin of China , 2011 .

[26]  Mita Das,et al.  Modeling of Transport Phenomena and Multicomponent Sorption for Shale Gas and Coalbed Methane in an Unstructured Grid Simulator , 2011 .

[27]  A. Settari,et al.  A Numerical Model for Multi-mechanism flow in Shale Gas Reservoirs with Application to Laboratory Scale Testing , 2013 .

[28]  Cheng-shu Chang.  The kinetic theory of gases , 1970 .

[29]  Y. Gensterblum,et al.  High-Pressure Methane Sorption Isotherms of Black Shales from The Netherlands , 2012 .

[30]  Xiaoqi Wu,et al.  Tight gas in China and its significance in exploration and exploitation , 2012 .

[31]  Tongwei Zhang,et al.  Effect of organic-matter type and thermal maturity on methane adsorption in shale-gas systems , 2012 .

[32]  H. Cinco-Ley,et al.  Transient Pressure Analysis for Fractured Wells , 1981 .

[33]  A. Alzaydi.  Flow of gases through porous media , 1975 .

[34]  R. M. Bustin,et al.  Measurements of gas permeability and diffusivity of tight reservoir rocks: different approaches and their applications , 2009 .

[35]  Dongxiao Zhang,et al.  A Fully Coupled Multiphase Multicomponent Flow and Geomechanics Model for Enhanced Coalbed-Methane Recovery and CO2 Storage , 2013 .

[36]  Jingjing Guo,et al.  Pressure Transient Analysis for Multi-stage Fractured Horizontal Wells in Shale Gas Reservoirs , 2012 .

[37]  George Em Karniadakis,et al.  REPORT: A MODEL FOR FLOWS IN CHANNELS, PIPES, AND DUCTS AT MICRO AND NANO SCALES , 1999 .

[38]  Y. Saad,et al.  GMRES: a generalized minimal residual algorithm for solving nonsymmetric linear systems , 1986 .

[39]  Danial Kaviani,et al.  Production Analysis of Tight-Gas and Shale-Gas Reservoirs Using the Dynamic-Slippage Concept , 2012 .

[40]  Stanley M. Walas,et al.  Phase equilibria in chemical engineering , 1985 .

[41]  Shahab D. Mohaghegh,et al.  Reservoir modeling of shale formations , 2013 .

[42]  Geoff Wang,et al.  A case study on the numerical simulation of enhanced coalbed methane recovery , 2006 .

[43]  Detang Lu,et al.  Generation and application of adaptive PEBI grid for numerical well testing(NWT) , 2013, Proceedings 2013 International Conference on Mechatronic Sciences, Electric Engineering and Computer (MEC).

[44]  George J. Moridis,et al.  A Numerical Study of Microscale Flow Behavior in Tight Gas and Shale Gas Reservoir Systems , 2011 .

[45]  Raymond Joseph Ambrose,et al.  Multi-component sorbed phase considerations for Shale Gas-in-place Calculations , 2011 .

[46]  Zhixue Sun,et al.  Numerical simulation of gas transport mechanisms in tight shale gas reservoirs , 2013, Petroleum Science.

[47]  Ebrahim Fathi,et al.  Matrix Heterogeneity Effects on Gas Transport and Adsorption in Coalbed and Shale Gas Reservoirs , 2009 .