Multiphase and multiscale Modelling of Gas-liquid-particle Transport in CSG Reservoirs and WellsThis project set out to deploy recently-developed computational models to provide new insights into the flow of gases, liquids and particles in unconventional gas reservoirs and wellbores. There were three distinct, but related themes that the project focused on. The first was to extend a new multiphase model developed by the group to fully resolve the simultaneous transport of gas and liquids in unconventional wellbores. This provided new insight on the pressure drop as well as critical transition mechanisms associated with the prominent flow regimes. The second was to utilise a novel, temperature-dependent model for particle suspensions in order to determine the influence of formation temperature on the rheology, and ultimately efficacy, of hydraulic fracturing fluids. The third theme for the project was altered with the departure of a PhD researcher from the team. The new theme was based around fully-resolving the fluid flow past embedded proppant particles. This was used to determine the plausibility of graded proppant injection during a hydraulic fracturing treatment.
Principal investigatorChristopher Leonardi email@example.com
Area of scienceMathematical Sciences, Numerical and Computational Mathematics, Petroleum and Reservoir Engineering
Applications usedTCLB – Open-source code used and developed in by research group, Esys-particle – Open-source discrete element code, Paraview Catalyst
The depletion of conventional reservoirs in Australia along with the demand for natural gas both domestically and internationally has led companies to explore extraction from unconventional resources. This presents a number of technical and social challenges to the industry. This project was designed to solve problems of production efficiency, environmental safety as well as develop fundamental understanding of these systems. The first challenge was modelling the new flow regimes evident in the wellbore when extracting gas from coal seams. In comparison to conventional wells where all fluids are extracted co-currently in a tubular pipe, coal seam gas wells often lead to counter-current extraction in an annular gap. The flow characteristics and pressure gradients seen in such a system vary substantially. These must be better understood to insure feasible and safe extraction. Hydraulic fracturing is a very controversial topic, but is currently the only viable method to allow for extraction of gas from certain reservoirs (shale, tight sands, some coal seams). With its use around the world, understanding how the fracturing fluid is interacting with the reservoir is a critical concern. Questions are raised around its environmental impact with issues such as leak-off as well as its efficiency in terms of the design of fluid and proppant to maximise reservoir permeability
In order to solve the challenges discussed, this project conducted high resolution simulations with novel computational models to gain understanding of the mechanics associated with flow inside of unconventional wellbores and reservoirs. The modelling of simultaneous gas and liquid transport in the wellbore has allowed for the development of closure relations to feed into industry scale simulations. This increases the confidence in predictions made for the amount of expected production as well as provides guidance to operators on the safe and optimal use of downhole pumps.
There are a number of complexities that arise when looking at hydraulic fracturing with physical experiments, the most obvious being the inability to visualise what is going on hundreds of metres below the surface. On the other hand, the fully resolved simulations conducted as part of this project provided key insights into the interactions between proppant particles, the reservoir and the rheological properties of the fracturing fluid. With this improved understanding operators can begin to design frack-jobs with the knowledge of how the particle suspension will behave at reservoir conditions. It is expected that this will lead to safer operations for both personnel and the environment.
There is an intensive computational requirement associated with fully-resolved, three-dimensional computational fluid dynamics simulations. The resources supplied by Pawsey Centre enabled the research group to extend the open-source codes to make full use of the high level of MPI available, allowing the analysis of the physical systems discussed in a practical timeframe. In addition to this, there is a large parameter space associated with the range of flows that could be expected in unconventional gas extraction. The ability to explore this was also very dependent on the resources supplied by the Pawsey Centre. In particular, when looking to upscale high-fidelity simulations to a level applicable to the industry, one needs to consider the parameter space applicable in the field.
List of Publications
Doctoral Thesis Completion:
 Jon McCullough, Numerical investigation of conjugate heat transfer and temperature-dependent viscosity in non-Brownian suspensions with application to hydraulic fracturing, Doctoral Thesis, The University of Queensland, 2018.
 Travis Mitchell, Development of a multiphase lattice Boltzmann model for high-density and viscosity ratio flows in unconventional gas wells, Doctoral Thesis, The University of Queensland, Under examination.
Journal Papers Published:
 G. Gruszczyński, T. Mitchell, C. Leonardi, Ł. Łaniewski-Wołłk, T. Barber, A cascaded phase-field lattice Boltzmann model for the simulation of incompressible, immiscible fluids with high density contrast, Computers & Mathematics with Applications, 2019.
 T. Mitchell, C. Leonardi, M. Firouzi, B. Towler, Towards closure relations for the rise velocity of Taylor bubbles in annular piping using phase-field lattice Boltzmann techniques, 21st Australasian Fluid Mechanics Conference, Adelaide, Australia, 10-13 December 2018.
 T. Mitchell, C. Leonardi, A. Fakhari, Development of a three-dimensional phase-field lattice Boltzmann method for the study of immiscible fluids at high density ratios, International Journal of Multiphase Flow 107, 1-15, 2018.
 McCullough, J.W.S., Aminossadati, S.M., and Leonardi, C.R. (2019) Transport of particles suspended within a temperature-dependent viscosity fluid using coupled LBM-DEM. International Journal of Heat and Mass Transfer. Under review.
 McCullough, J.W.S., Aminossadati, S.M., and Leonardi, C.R. (2019) A 3D LBM-DEM study of sheared particle suspensions under the influence of temperature-dependent viscosity. Powder Technology. Under review.
Figure 4. Leak_example_1: Simulation of continuous particle injection in a T-bifurcation to replicate the injection of 200μm proppant in an idealised fracture channel.
Figure 4. 2. Leak_example_2: Simulation of continuous particle injection in a T-bifurcation to replicate the injection of 400μm proppant in an idealised fracture channel.
Figure 2. DasC_inclined-1: Taylor bubble profiles at t^*=20t_0 with fluid parameters mimicking that of air-water in a 2” outer pipe with a 1” internal creating the annular configuration. The angles are measured from the horizontal for 10≤θ≤45.
Figure 2. DasC_inclined-2: Taylor bubble profiles at t^*=20t_0 with fluid parameters mimicking that of air-water in a 2” outer pipe with a 1” internal creating the annular configuration. The angles are measured from the horizontal for 45≤θ≤80.