Design to Compare Stehfest’s and Iseger’s algorithms for Laplacian Inversión in Pressure Well Tests Diseño de Software para comparar los algoritmos de Stehfest e Iseger para inversión Laplaciana en pruebas de presión

Abstract

This paper presents a software design with the purpose of comparing two algorithms used for the inverse Laplace transform determination. The comparison was applied to two well-known oil-industry reservoir models in the Laplacian domain, for which the inversión ís made and the results are plotted to establish a comparison. The code is written in Visual Basic 2008 and consists of a graphical interface that displays the inversions made by each algorithm and also generates two output test files which include data of time, pressure and pressure derivative. The graphical interface allows to choose the desired well model or to introduce another model or function to invert using the keyboard. It also offers the option of removing or adding the plot of the derivative and making plots in logarithmic scale.

The study allowed to establish that Iseger’s algorithm handles more efficiently function discontinuiües. It was observed for good tests that fulfilling the conditions relating tune with sanóle number size provides more stable inversions It was also proved that the greater the number of points to invert, the more accurate the solution. Besides, parameter nrp originally set by Iseger to be 8, was found to provide more stable solutions with a valué of 3.