Numerical Simulation in Unconventional Reservoirs

Abstract

Non conventional hydrocarbon reservoirs are characterized by their very low permeability and porosity. To allow oil and gas production, the reservoir has to be fractured using different techniques, like fluid injection at high pressures from a well drilled in the formation (fracking). The final goal is to create a fracture network that combines existing natural fractures with the new generated ones.
The changes in permeability and porosity in the saturated porous media due to the fracking procedure will induce changes in the seismic response. The objective of this work is the numerical modeling of multiphase flow and seismic wave propagation in unconventional reservoirs. The multiphase flow through porous media is described by the well-known Black-Oil formulation, which uses as a simplified thermodynamic model, the PVT data: formation volumen factors and gas solubility in oil and water. The numerical solution is obtained using an IMPES (IMplicit Pressure Explicit Saturation) finite difference technique. The propagation of waves in fluid-saturated porous media is described using a viscoelastic model that takes into account the dispersion and attenuation effects due to the presence of heterogeneities in the fluid and solid phase properties. This model is numerically solved applying an iterative finite element domain decomposition procedure. As an example, we analyze a tight gas reservoir. The results of the simulations show the capability of the seismic techniques to detect the presence of fractures.