Petrophysical Answers for Producibility of the Bossier Sandstones, East Texas Basin
J. Rick Turner
Barrow-Shaver Resources Company, Tyler, Texas
The Bossier Sandstone is a drilling objective for natural gas on the west flank of the East Texas Basin. Drilling depths range between 10,000 feet and 16,000 feet, with production tests ranging from one million to twelve million cubic feet of gas per day.
Gauging the producibility of the Bossier from open hole logs requires more than calculating the water saturation, cross-plotting methods are necessary. Since the Bossier usually produces insignificant amounts of water, it is assumed to be at irreducible water saturation.
The product of the porosity and the water saturation is the bulk volume water irreducible (BVI). The value is illustrated by plotting lines of constant BVI on a graph with water saturation on the horizontal axis and porosity on the vertical axis. If lines of constant permeability are added to the plot, it can be used as a template. The position of data points on the template yield interpretative information about the producibility of the formation.
In addition to the BVI-PERM cross-plot, a Producibility Index utilizing porosity-derived permeability, formation pressure, and formation temperature can be calculated. When the Producibility Index is plotted against the average BVI for data points above the 10 md permeability line, an estimate of the ultimate recovery for a well can be made.
The cross-plotting methods are not complicated. They provide a powerful method of organizing borehole data to rank wells on the basis of their petrophysical character.
AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004