As the slope and intercept of the conventional semilog graphing are sensitive to gas and well properties, the calculation of conductivity and skin effect for cases of high velocity flowrate can yield erroneous results.

A sensitivity analysis of the transient response of a well located in an infinite medium while a non-Darcy flow caused by high fluid velocity is presented. A rigorous material balance on the wellbore is included.

The analysis of simulated drawdown tests produced several important conclusions. Gas and formation properties such as gas gravity, initial pressure, temperature, and permeability can lead to significant errors if not considered correctly. The rate-dependent pseudoskin factor is not simply an additive term as are the other skin factor components. The radius of invasion of the damaged region around the well remains a significant factor ëven for long times in cases where turbulence is considered. The effect of high velocity is more pronounced in a production case than in an equivalent injection case, and the slope of the conventional semilog straight line may be greater (production) or less (injection) than 1.151. Although wellbore storage was handled in a rigorous manner, for high pressure drawdown cases the shape of log-log drawdown curves of mD(1,tD) vs tD are similar to the liquid log-log graphs. Thus log-log type-curve matching can be a useful technique for detecting the beginning of the semilog straight line. New correlating groups which consider a variety of possible conditions were found. A correction procedure for analyzing drawdown tests when data for only one flowrate are available is suggested.

You can access this article if you purchase or spend a download.