Cubic Spline and Graphical Techniques for Determining Unsteady State Relative Permeabilities in Field Cores

Abstract

Relative permeability is one of the key factors in reservoir engineering calculations to simulate multiphase behavior in porous media. The relative permeabilities calculated from established models do not perfectly characterize the reservoir without a known trend or history. This necessitates the need to use a reliable and globally accepted technique based on Niger Delta field production data for calculating relative permeabilities from the fields so that the models derived from the relative permeability curves could be tamed and domesticated in the region for better reservoir characterization and evaluation. The Johnson, Bossler and Neumann (JBN) method is the industry standard for measuring relative permeabilities from field cores. In order to eliminate the need of using numerical differentiation, and therefore reduce the overall numerical error in this method, a graphical technique was proposed and implemented during late 70s. However, with splines, the numerical differentiations are still done but with improved results. The current study presents the results from the comparative analysis of two approaches employed to avoid the traditional numerical differentiation required by the JBN method. Production data from field cores in the Niger Delta were used. The graphical method and cubic spline numerical modeling were both used to calculate the individual relative permeabilities from the pressure/production history of the displacements. the results were analyzed and compared. The results of both methods show a very good match over a fairly small saturation range and also differ. However, cubic spline results are closer to the traditional numerical differentiation results because is a modeling approach in which the numerical differentiation is incorporated with improved accuracy.

A Connectionist Model for Dynamic Economic Risk Analysis of Hydrocarbons Production Systems

“…The analyzed dynamic risk is space‐ and time‐dependent to replicate the reservoir flow system. It is a complex, porous, permeable, and saturated subsurface geologic structure/entrapment with hydrocarbons under a distinct pressure gradient (Mamudu, 2016; Mamudu & Olafuyi, 2016; Olafuyi & Mamudu, 2015; Umar, Gholami, Shah, & Nayak, 2019). The economic risks/losses assessment is evidence‐based.…”