Development of a Virtual Near-Wellbore (WNWB) mathematical model for CSG
Constructing mathematical models
The VNWB constructs mathematical models of the different processes at a model scale representing a radius of about a metre from the wellbore with a vertical section of between one and three metres. Understanding the behaviour in this model will assist in the determination of more accurate parameters of the cells in the flow simulation models.
This project aims to improve our understanding of the physical processes close to a producing or injecting wellbore and their interactions.
This appears to be more critical in unconventional petroleum reservoirs such as coal seam gas and shale gas, because the permeability of the producing rocks is significantly lower than conventional reservoirs.
It is important to consider fluid flow in the matrix, fluid flow in fractures, changes in geomechanical properties of the reservoir, and particle transport in the fractures both into and out of the reservoir. There are also chemical effects to complicate matters further.
Measurements may be made on each of these processes in laboratories at small-scales, but it is not immediately obvious how the combined effects of these processes can be quantified and modelled at a larger scale.
Flow simulation is routinely used in the petroleum industry to model the behaviour of fluids through the reservoir and current computing limitations restrict the size of the cells in this model to typical thicknesses of at least 30 centimetres and lateral extents of more than 50 metres. Measurements that are made on rock samples in a lab that are less than 10 centimetres across may not be representative of the larger scale behaviour of these systems.