CBM System Sheet

The Facts - Formation - Specific Perforating
By Nathan G. Clark
Director of Ballistics

Q What problems are typically associated with perforating coal formations?
A Coal formations present a unique perforation challenge because of the unpredictability of the response to perforation compared to traditional sandstone to carbonate formations.

Solution: With CBM there are significant changes in permeability in response to the absorption and desertion of the component gas, and so designing perforation for best performance in stressed and saturated media is even more important than any other formation. Perforation performance in cement will not be a reliable indication of perforation performance in a CBM formation.

Q Why develop such a charge?
A A charge developed for maximum performance in stressed coal is significantly different from a charge designed for maximum performance in cement.

Solution: With CBM performance gains from 10-15%, increased well production will quickly pay back development costs.

Q Was it a challenge developing a solution to this exercise?
A The testing of shape charges in stressed and pressurized coal required sophisticated new testing techniques in order to correctly isolate charge performance from all of the other factors which affect the performance of coal formations. The current CBM charge is simply the first of its breed. I would say that it typically takes 12-16 weeks of dedicated effort to complete a program of this magnitude.

Q What does the new CBM charge accomplish that others don’t?
A The new CBM system improves the geometry performance of the perforation over the previous system by 18-23%.