Viewing Gas Material Balance

Estimate original gas in-place (OGIP) using single well material balance calculations. Also use material balance to identify the expected recovery factor by specifying the abandonment P/Z value. At least two P/Z points with different cumulative gas values are required for a linear material balance. Three P/Z points with different cumulative gas values are required to create a parabolic material balance.

The following tutorial example well shows a classic, straight-line material balance with the left estimation boundary dragged right to exclude some initial cumulative gas value samples that were taken at the start of production. The Abandonment P/Z has been lifted to increase the recovery factor.

To view material gas balance

With a DataCard for the desired well displayed, click the Gas Material Balance tab.

The Gas Material Balance dialog box appears.

Drag the Left Estimation Bound and the Right Estimation Bound lines that appear on the graph to the right and to the left (respectively) to remove gas samples from early and late production.

At least three gas samples must appear within the left and right estimation bounds in order to plot a material balance trend.

Select either the linear or parabolic method with which to plot the trend.
Specify the Source.

The different sources appear on the DataCard Gas Analysis/Pressure tab.

Drag the horizontal Abandonment P/Z bound that appears on the graph up to estimate the expected cumulative gas and recovery. To enter an exact abandonment P/Z, click the numerical Abandonment P/Z value that appears on the left of the chart, type the desired value, and then press ENTER.