Gas recovery modelling of South African shale gas reservoir

Ogojiaku, Gertrude Obiageli
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As the production of shale gas increases globally, there are various mechanisms that are displayed through the flow of shale gas to the wellbore, this creates a prompt for the shale reservoir behavior to be developed for a better comprehension on the complexities of the shale layer. Shale gas cannot be produced naturally as they exist in tight pores. Therefore, to increase productivity, shale gas is extracted through the means of horizontal drilling or hydraulic fracturing, commonly known as fracking. The triple porosity model in this paper considers three different but consecutive flows in the shale layer from the Matrix, Natural Fracture and Hydraulic Fracture. This paper discusses the flow properties of shale gas reservoirs, developing mathematical flow models and how these models can be efficient in predicting recovery of shale gas in South Africa in comparison to existing shale gas reservoirs. The flow equations at the systems were developed and solved using the Finite Difference Method. Once solved explicitly, using MATLAB, the algorithm was plotted to illustrate the reservoir pressure distribution with respect to time. In conclusion, the analysis of the results shows that the behavior of the reservoir with regards to pressure and time is in line with previously simulated triple porosity models done by other researchers. This demonstrates the closeness in behavior of the developed model in this research and renders it viable for use in any reservoir to be effective in predicting the production of shale gas.
A research report submitted in partial fulfilment of the requirements for the degree of Master of Science in Petroleum Engineering to the Faculty of Engineering and Built Environment, School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg, 2022