# A new relationship for calculatingthe exponential integralused for constant-terminal-rate solution of diffusivity equation

## Document Type

Article

## Publication Date

2016

## Abstract

The constant-terminal-rate solution of diffusivity equation is an integral part of most transient test analysis techniques, such as with drawdown and pressure buildup analyses. Most of these tests involve producing the well at a constant flow rate and recording the flowing pressure as a function of time. There are two commonly used forms of the constant-terminal-rate solution: the -function solution and the dimensionless pressure solution.

This paper presents a new relationship for calculating the exponential integral with an average error of 0.026% and correlation coefficient of 0.999999999 for the range .

Another new relationship was developed for calculating the exponential integral with an average error of 6.05 and correlation coefficient of 0.999988 for the range .

## Recommended Citation

Gomaa, Sayed, "A new relationship for calculatingthe exponential integralused for constant-terminal-rate solution of diffusivity equation" (2016). *Petroleum Engineering and Gas*. 3.

https://buescholar.bue.edu.eg/pet_eng_gas/3