Pressure Transient Analysis of Wells with Finite Conductivity Vertical Fractures in Double Porosity Reservoirs Available to Purchase

This paper presents the results obtained in the study of the transient behavior of a well intersected by a finite conductivity vertical fracture in a double porosity reservoir. Two models are considered to take into account the fluid transfer between matrix blocks and fractures: the pseudo-steady-state matrix flow model and the transient matrix flow model.

A general semianalytical model and simplified fully analytical models are presented. It is demonstrated that these systems exhibit the basic behavior of a well with a finite conductivity fracture: that is bilinear flow, pseudolinear flow and pseudoradial flow in addition to the transition flow periods. Each of these flow periods is under the influence of the different states of the fluid transfer between matrix and fractures; that is fracture dominated period, transition period and total system dominated period.

It is shown that correlating parameters are the dimension-less fracture conductivity (k_fb_f)_D, the fracture storativity coefficient ω and the interporosity flow parameter λ_f(or the dimension-less matrix hydraulic diffusivity η_maD).

It was found, for the transient matrix flow model, that the pressure behavior exhibits 1/8 slope in a log-log graph during the bilinear flow dominated by the transition period of the fluid transfer. Hence a graph of pressure versus t^1/8 yields a straight line passing through the origin.

During the pseudolinear flow, and if the fluid transfer is in the transition period, a log-log graph of the prerssure versus time exhibits 1/4 slope straight line. This means that a graph of p versus t^1/4 yields a straight line. Hence it is concluded that bilinear flow is not the only type of flow that exhibits the one quarter slope type of behavior.

Type curves are presented to analyze data falling in the bilinear – pseudolinear flow regions. The effect of wellbore storage are also included. The general semianalytical models yields simultaneous the constant flow rate and the constant pressure solutions as well as the pressure derivative function for the constant rate case.