Natural Gas Production From Shale Formations

Natural gas shale reservoirs have become an important source of natural gas production North America and are expected to play an increasingly important role in South America and Asia in the near future. This is partly attributed to the foreseeable rise in the global energy demand and the gradual depletion of conventional reservoirs. Although thousands of shale gas wells are actively producing petroleum around the world, factors controlling the permeability in shale gas formations are still poorly understood and lag behind the knowledge amassed from decades of gas production from conventional reservoirs. Hence, a fundamental understanding of the multi-scale flow processes from gas bearing rocks (Fig. 1) and accurate evaluation of gas volume flow are crucial for improving gas production and lowering recovery costs.

Fig. 1 Shale gas reservoir structure at different spatial scales.

In this research, a geometrically accurate model (Fig. 2) based on actual shale formation micro-images has been constructed to investigate gas transport through the rock. The model considers the pertinent rock properties, such as porosity, permeability, and pore geometry as well as the gas properties at the microscopic level. Gas production at the microscopic level is quantified through the solution of the governing equations of mass conservation, momentum conservation and the Navier-Stokes. Preliminary results indicate that pore throats, gas compressibility, reservoir pressure and the gas-water interaction play an instrumental role in gas production.

Fig. 2. Gas shale reservoir SEM image (left) and the computational model (right).

Animations below display the transient variation in pressure (top) and velocity distribution (bottom) when illite (see right model in Fig. 2) is porous. Inlet pressure was 27.58 MPa and temperature 353.15 K. Pressure difference in the model amounted to 1 Pa while the simulation time spanned 1 μs.


Project Commencement Date: Sept. 2016 –

Research Team: Ms. Natalia Kovalchuk and Dr. Constantinos Hadjistassou

Publications:

Kovalchuk N., Hadjistassou C. Fathoming the Mechanics of Shale Gas Production at the Microscale, Journal of Natural Gas Science and Engineering, pp.7, 2020; DOI: https://doi.org/10.1016/j.jngse.2020.103283

Kovalchuk N., Hadjistassou C. New Insights from Shale Gas Production at the Microscopic Scale, European Physical Journal E, 41(134):1-9, 2018; DOI: http://dx.doi.org/10.1140/epje/i2018-11741-5

Kovalchuk N., Hadjistassou C. Laws and Principles Governing Fluid Transport in Porous Media, European Physical Journal E (EPJE), 42(56):1-6, 2019; DOI: http://dx.doi.org/10.1140/epje/i2019-11819-6