Interpretation of responses of commingled systems with mixed inner and outer boundary conditions using derivatives

This work presents a spectrum of possible derivative responses in wells producing commingled reservoirs. Three issues pertaining to commingled reservoir buildup behavior are addressed: (i) study of derivative responses for special commingled systems with emphasis on unequal layer radii, (ii) study of pressure distributions in layers with a view to understand backflow, particularly the origin of rate reversals during buildup, and (iii) application of the Peaceman probe radius formula to obtain pressure distributions in each layer at shut in. From (i) a number of approaches are developed to estimate the areal extent of the smallest layer. From (ii) some general information which should be useful or at least pertinent to the design of PLT surveys are derived. The work on Peaceman's probe radius concept also has application in miscible flooding for the location of areas below minimum miscibility pressure (MMP). Besides the quantitive conclusions we present, we believe the documentation of the spectrum of possible derivative responses fills a significant gap in the literature.

Interpretation of responses of commingled systems with mixed inner and outer boundary conditions using derivatives Conference Paper