A New Delta-Transient Method for Real-Time Permeability and Skin Prediction in Multi-Layered Oil Reservoirs Near Sealed Zones

Abstract

Abstract Permeability and skin prediction in multilayered reservoirs near sealed boundaries during production are essential for the appropriate oilfield development. This work proposes a new method for obtaining the transient individual layers’ permeability, k(t) and skin, S(t) data in a well near a no-flow boundary (sealing fault case) by combining a production logging tool (PLT) and a mathematical formulation that deals with equivalent rock and fluid properties, e.g., transmissibility, pressure drop, and oil flow rates. New fault parameters βf and δf arise in the logarithmic approximation of the line-source solution Ei(r, t) to represent the role of the fault on the real-time permeability and skin responses. The mathematical model presented in this paper is based on the equivalent representation of a system composed of a multilayered reservoir near a no-flow boundary that considers each unsteady-state individual layer property for the formulation. A new reservoir layer parameter named Delta-Transient for sealed zones is derived, and it deals with the unsteady-state permeability and skin effect as a function of the equivalent oil flow rate and pressure gauge real-time data. This paper shows that this parameter comprises the sum of the infinite-acting-radial-flow and the well-sealing fault terms. The calibration of the model developed in this study was performed using a numerical simulator named Saphyr, and the results presented convergence. An error analysis was also presented and demonstrated that the method is sensitive to flow rate and pressure variations. The proposed model is applicable to formation evaluation and reservoir engineering to predict unsteady-state permeability and skin behavior on carbonates reservoirs due to the lack of adequate methods to provide reliable information. This practical field application, combined with the model's simplicity, constitutes the advantages of the model addressed in this paper.