In a previous paper, Parabolic Projection of Four Assessments of Canadian Conventional Natural Gas Resources, North American conventional gas production over the last decade (including that from Mexico) was found to approximate a flat, drawn-out peak termed here a 'plateau peak' (Web: pages.ca.inter.net/~jhwalsh/wngcanada.html). There is evidence Canadian production taken by itself will also approach such a peak probably at levels between seven and eight trillion cubic feet per year. This note focuses on overall decline rates ranging from three to five per cent per year that may be expected as conventional natural gas production matures in Canada. This approach thus complements the parabolic technique used in the companion paper that does not deal explicitly with the decline period. Taken together, the two papers provide additional insight into the Canadian conventional natural gas situation.

The dates of the onset of decline in conventional Canadian natural gas production estimated from the plateau peak approach employed in this note are reasonably close to those obtained from the parabolic technique in the companion paper for decline rates of 5% per year but less so for lower rates. These dates are in closer agreement when plateau production is eight TCF per year rather than seven.

It is somewhat counter-intuitive that the higher the decline rate, the longer the prior plateau period but this is an inevitable consequence of the mathematics involved. There is an implied warning that higher decline rates lead to a 'cliff' after which production falls more rapidly that at lower rates. Because the plateau period is extended in time at higher rates, this danger may be compounded by the complacency fostered by this longer period at full production.