Semester

Spring

Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Petroleum and Natural Gas Engineering

Committee Chair

Ebrahim Fathi

Committee Co-Chair

Kashy Aminian

Committee Member

Ali Borujeni

Committee Member

Ebrahim Fathi

Abstract

This study sheds the light on the effect of poroelastic properties of the shale matrix on storage and transportation mechanism in multi-scale organic rich shale gas reservoirs. Over last decades shale gas research widen significantly, however, the behavior and properties of shale formation still need more investigation. Most of our knowledge regarding poroelsctic behavior of shale matrix comes from studies on coalbed methane reservoirs, which is somewhat similar to shale gas reservoirs. The poroelastic effect of coal and shale is a strong function of total organic content (TOC) of these sedimentary rocks. Coalbed methane reservoirs have more than 50% TOC, however, the TOC of shale gas reservoirs are less than 10%, which leads to expect completely different mechanical behavior in shale than coalbed. Therefore, it is important to understand the poroelastic behavior of shale and it is impact on flow and storage within the matrix. In this research, a new model has been developed to study the poroelastic properties of shale using fundamental governing equations.;In order to study the effect of poroelasticity of the shale precisely, multi-continuum approach has been chosen. The governing equations for the model have been developed from the basic fundamentals of mass and momentum conservation equations and transport in naturally fractured porous media. Different continuum has been coupled using mass exchange term in sprit of Warren and Root coupling approach. The model has been used to represent and investigate four different cases. In the first case, the shale has been seen as a dual-porosity, system where matrix has a single porosity and transport in the matrix is governed by the convective and diffusive flow. The second model is an extension for the first model by adding fracture system. In the third model, detailed descriptions of shale matrix is used; shale matrix is assumed to consist of organic and inorganic continuum. In this case, gas transport in organic matter is assumed to be diffusive while gas transport in inorganic material is governed by convection and diffusion. Finally fracture system is added to multi-scale shale gas matrix and poroelatic effect of shale matrix on transport and storage is investigated. Modified Palmer and Mansoori model (1998) has been used to include the pore compression, matrix shrinkage, and adsorption effect of shale organic matter on overall pore compressibility of the shale matrix. For inorganic part of the matrix, on the other hand, relationship between rock mechanical properties and pore compressibility are obtained following Raaen (1993), Fajaer (1992) and Zimmerman (2000). To include the sorption behavior of shale matrix, Langmuir-Henry dualmodel isotherm is used to describe equilibrium sorption dynamics of shale in more details.;The purpose of this research is to develop governing equations describing gas transport and storage in shale gas reservoirs including the multi-scale nature of the shale matrix, gas sorption behavior, and poroelastic effects due to change in effective stress. Governing equations are derived based on mass and momentum conservation at an isothermal condition using analytical techniques and solved using implicit finite difference approach using MATLAB. MATLAB program has also been used for sensitivity analysis of different poroelastic parameters of shale matrix such as Poisson ratio and Young modulus under specified initial and boundary conditions.;Based on our study, impact of the pore compressibility on gas production is significant. Variation of effective stress shows great impact on poroelastic properties of the shale represented by Poisson ratio and Young modulus and thus, highly influence gas storage and transport in shale reservoirs. In conclusion, new governing equations developed and applied successfully to quantify the poroelastic effects on gas transport and storage in shale gas reservoirs. Moreover, any strategic production plan.

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