Features of inflow and pressure-buildup curves in porous fractured reservoirs

In the present work, by the methods of mathematical and numerical analysis, the author has investigated the regularities of the infl uence of the processes of mass exchange between rock clusters and fractures in porous fractured media on the form of infl ow and pressure-buildup curves and their time derivatives. It has been shown that in addition to the traditionally used parameter governing the relation of the compressibilities of the fracture space and the rock clusters, it is expedient to take account of the compressibility of the pore and fracture space under the action of the difference of pressures in the clusters and fractures. The author has established the governing parameters of the mass-exchange processes and their infl uence on the dynamics of pressure curves, which is manifested in the nonmonotonicity of the derivatives of pressurebuildup curves with respect to the Horner variable. It has been shown that this derivative reaching asymptotically the limiting value is preceded by the formation of the minimum region of the derivative. It has been noted that the nonmonotonic character of the derivatives may be fully or partially smoothed by the infl uence of the wellbore due to the compressibility of the fl uid in the below-packer zone of the wellbore and the infl uence of the skin factor, i.e., by the change in the permeability and porosity properties of the near-wellbore zone. The obtained results can be used for more correct interpretation of the data of hydrodynamic testing of wells in porous fractured reservoirs.
In the present work, by the methods of mathematical and numerical analysis, the author has investigated the regularities of the infl uence of the processes of mass exchange between rock clusters and fractures in porous fractured media on the form of infl ow and pressure-buildup curves and their time derivatives. It has been shown that in addition to the traditionally used parameter governing the relation of the compressibilities of the fracture space and the rock clusters, it is expedient to take account of the compressibility of the pore and fracture space under the action of the difference of pressures in the clusters and fractures. The author has established the governing parameters of the mass-exchange processes and their infl uence on the dynamics of pressure curves, which is manifested in the nonmonotonicity of the derivatives of pressurebuildup curves with respect to the Horner variable. It has been shown that this derivative reaching asymptotically the limiting value is preceded by the formation of the minimum region of the derivative. It has been noted that the nonmonotonic character of the derivatives may be fully or partially smoothed by the infl uence of the wellbore due to the compressibility of the fl uid in the below-packer zone of the wellbore and the infl uence of the skin factor, i.e., by the change in the permeability and porosity properties of the near-wellbore zone. The obtained results can be used for more correct interpretation of the data of hydrodynamic testing of wells in porous fractured reservoirs.
Author:  A. M. Svalov
Keywords:  hydrodynamic testing of wells, porous fractured rocks, infl ow curves, pressure-buildup curves, derivatives with respect to the Horner variable
Page:  377-383