The Insignificance of Non-Darcy Flow Pressure Drop

1. The Insignificance of Non-Darcy Flow Pressure Drop Saint-Gobain Proppants Fall 2004

2. Pressure Drops in Gas Wells Every pressure drop reduces the drawdown on the formation and restricts production. Typically, the choke dominates.Every pressure drop reduces the drawdown on the formation and restricts production. Typically, the choke dominates.

3. Sources of Pressure Drops Fracture Darcy & Non-Darcy pressure drop Minimal differences between ceramic proppants Perforations Pressure drop through perfs cannot be avoided Tubing High rate wells can have significant pressure drops Surface Choke Usually the largest of all the pressure drops and it is self imposed

4. Pressure Drop in a Fracture

5. Non-Darcy Flow The pressure drop in a proppant pack is certainly dominated by non-Darcy flow Non-Darcy flow pressure drops can be significant Pressure drop in the fracture simply reduces the drawdown placed on reservoir Pressure drop in the fracture reduces production rate, not reserves.Pressure drop in the fracture reduces production rate, not reserves.

6. Beta factors for three sintered bauxite based materials are very similar.Beta factors for three sintered bauxite based materials are very similar.

7. ELWC denotes �economy lightweight ceramic�. This chart reflects the increase in beta as the ELWC exhibits crushing.ELWC denotes �economy lightweight ceramic�. This chart reflects the increase in beta as the ELWC exhibits crushing.

8. This compares non-Darcy flow effect between Versaprop and ELWC, as shown in the previous chart. This demonstrates that at closure stress above about 6,800 psi, Versaprop has lower non-Darcy flow effect than ELWC.This compares non-Darcy flow effect between Versaprop and ELWC, as shown in the previous chart. This demonstrates that at closure stress above about 6,800 psi, Versaprop has lower non-Darcy flow effect than ELWC.

9. Versaprop has lower non-Darcy pressure drop than ELWC in this case due to the much lower Beta Factor at high stress. However, while the magnitude of the non-Darcy pressure drop is significant, the difference between the two materials is very small.Versaprop has lower non-Darcy pressure drop than ELWC in this case due to the much lower Beta Factor at high stress. However, while the magnitude of the non-Darcy pressure drop is significant, the difference between the two materials is very small.

10. Same demonstration as previous slide, with lower production rate. The magnitude of the pressure drop has declined and the difference between the two materials is even less significant.Same demonstration as previous slide, with lower production rate. The magnitude of the pressure drop has declined and the difference between the two materials is even less significant.

11. This demonstrates lower rate, showing that in many cases, non-Darcy pressure drops are insignificant and the difference between the two proppants even more insignificant.This demonstrates lower rate, showing that in many cases, non-Darcy pressure drops are insignificant and the difference between the two proppants even more insignificant.

12. Slide shows differences in magnitudes of various pressure drops in a producing well system. Note that pressure is on a logarithmic scale. The nDarcy flow difference is the difference between the nDarcy flow pressure drops between Versaprop and ELWC. There will be nDarcy flow effects in a well like this. The choices we have are what proppant to select and therefore only the difference between the proppants is relevant. As you may have experienced, a well producing at 10,000 mcfd would most likely be choked back. If it were choked to a surface pressure of 5,000 psi, then the pressure drop across the choke would be an order of magnitude greater than the difference in nDarcy pressure drop between the two proppants. Also, the pressure drop in the system between 3.5 and 2.875 inch tubing is almost as significant as the pressure drop in the fracture. But we rarely, at least in low permeability reservoirs, consider the frictional flow in tubing effecting our production rate.Slide shows differences in magnitudes of various pressure drops in a producing well system. Note that pressure is on a logarithmic scale. The nDarcy flow difference is the difference between the nDarcy flow pressure drops between Versaprop and ELWC. There will be nDarcy flow effects in a well like this. The choices we have are what proppant to select and therefore only the difference between the proppants is relevant. As you may have experienced, a well producing at 10,000 mcfd would most likely be choked back. If it were choked to a surface pressure of 5,000 psi, then the pressure drop across the choke would be an order of magnitude greater than the difference in nDarcy pressure drop between the two proppants. Also, the pressure drop in the system between 3.5 and 2.875 inch tubing is almost as significant as the pressure drop in the fracture. But we rarely, at least in low permeability reservoirs, consider the frictional flow in tubing effecting our production rate.

13. Same comparison as previous slide, with lower flow rate. At lower rates the choke completely dominates and the difference in nDarcy flow effects between the two proppants is less than 100 psi.Same comparison as previous slide, with lower flow rate. At lower rates the choke completely dominates and the difference in nDarcy flow effects between the two proppants is less than 100 psi.

14. Lower flow rate than previous slide, once again demonstrating relative insignificance of nDarcy pressure drop. Now the nDarcy flow difference is less than 10 psi.Lower flow rate than previous slide, once again demonstrating relative insignificance of nDarcy pressure drop. Now the nDarcy flow difference is less than 10 psi.

15. Summary All sources of pressure drop in a gas well reduce the drawdown to the formation and therefore reduce producing rates Use of a surface choke makes all other pressure drops irrelevant Differences in non-Darcy flow pressure drops between ceramic proppants is insignificant compared to other pressure drops in gas wells