Abstract

Gas transport in unconventional shale strata is a multi-mechanism-coupling process that is different from the process observed in conventional reservoirs. In micro fractures which are inborn or induced by hydraulic stimulation, viscous flow dominates. And gas surface diffusion and gas desorption should be further considered in organic nano pores. Also, the Klinkenberg effect should be considered when dealing with the gas transport problem. In addition, following two factors can play significant roles under certain circumstances but have not received enough attention in previous models. During pressure depletion, gas viscosity will change with Knudsen number; and pore radius will increase when the adsorption gas desorbs from the pore wall. In this paper, a comprehensive mathematical model that incorporates all known mechanisms for simulating gas flow in shale strata is presented. The objective of this study was to provide a more accurate reservoir model for simulation based on the flow mechanisms in the pore scale and formation geometry. Complex mechanisms, including viscous flow, Knudsen diffusion, slip flow, and desorption, are optionally integrated into different continua in the model. Sensitivity analysis was conducted to evaluate the effect of different mechanisms on the gas production. The results showed that adsorption and gas viscosity change will have a great impact on gas production. Ignoring one of following scenarios, such as adsorption, gas permeability change, gas viscosity change, or pore radius change, will underestimate gas production.

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Adsorption; Calculation; Chemical Model; Controlled Study; Desorption; Diffusion Flux; Energy Resource; Gas Flow; Gas Production; Mathematical Computing; Mathematical Model; Oil Shale; Porosity; Simulation; Viscosity; Chemistry; Diffusion; Oil And Gas Field; Natural Gas; Adsorption; Diffusion; Models, Chemical; Natural Gas; Oil And Gas Fields; Permeability; Viscosity

International Standard Serial Number (ISSN)

19326203

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2015 Public Library of Science, All rights reserved.

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