Beyond Dual-Porosity Modeling for the Simulation of Fluid
Flow in Unconventional Reservoirs
In fractured shale reservoirs, hydraulic and natural fractures serve as highways for hydrocarbon flow globally while most of fluid is stored in an extremely tight organic-rich matrix. In the fine scale, the stagnant matrix domain can be further subdivided into inorganic and organic porosities with significantly different attributes. Since there exist massive micro- and nano- pore systems in shale matrices, the actual flow mechanisms in shale reservoirs are considerably more complex than can be simulated by conventional Darcy flow. Those complexities make conventional dual porosity/permeability models intractable to directly simulate fractured shale reservoirs.
The necessity of capturing the connectivity hierarchy and distinctive fluid storage/transport characteristics has motivated us to simulate unconventional reservoirs in a novel approach. In this micro-scale model, inorganic and organic portions of shale matrix are treated as sub-blocks. In particular, several porosity systems in the model may be tied to each other through arbitrary transmissibilities.
Pressure and water saturation distribution in shale matrix at different times
Simulation of Fluid Flow in Fractured Carbonate Reservoirs
Significant hydrocarbon resources exist in fractured reservoirs in the world, such as shale gas, CBM, and vuggy carbonate reservoirs. Generally these reservoirs behave in a different manner from conventional homogeneous reservoirs: the matrix mainly provides the fluid storage with little flow capacity and the fracture acts as a highway for global fluid flow with good fluid conductivity but little porosity. Therefore, to simulate the fluid flow in such reservoirs presents a challenging and interesting problem that has been the subject of much research.
In spite of the advances accomplished so far, there still remains a significant obstacle to the accurate simulation of fractured carbonate reservoirs at the reservoir and field levels. A unified theory is required to allow this transition which forms the basis of this research.
This is achieved by developing different techniques for the simulation of fractured carbonate reservoirs which far-exceed current capabilities and to apply these techniques to the relevant reservoirs all over the world. The results of micro-models will be extended to field-scale models through a unifying technique which allows the rigorous upscaling of the the micro-model results.
Outcrop of fractured carbonate showing the potential reservoir complexity