(A:  Pretty darn quickly.  Here’s one posting, dated about 20 months ago, which illustrates the quick drop-off of Marcellus Shale gas well production.  Keep in mind:  Fracked-gas fields such as Marcellus, Barnett (see earlier post on this blog) and others are what the White House and the Dept. of Energy are counting on to provide supposedly “50 years of solid gas production cushion” in these United States.)

Gas processing and compression north of Pittsburgh, Pennsylvania (Marcellus Shale region).
“The figures will surprise you. It has been shown that the average productive life of a Barnett Shale well is 7.5 years. From these early production results it looks as though these Marcellus wells may share that same short lifespan. The trend points to a 65-percent drop in production over the first 3 years, with further declines of 8 percent per year after that. Using that model, a Marcellus well’s average productive life would be 8 years. Gas liquids (alternately listed as either condensate or oil) production drops just as fast, if not faster, than the methane production shown in the charts below.

The statistics for wells listed below cover a 48-month period (through 6/30/13) even though many of the wells are so new that production figures may only cover a few months. We have expanded the DEP statistics to show the average Mcf production per day (yellow column) making it much easier to compare the various reporting periods. Further information and photos of each of these drilling units is shown on individual web pages linked on the left navigation bar under “Marcellus Shale Wells.”

Read full story here (warning, it is really really long) –they really did reprint charts for 190 different wells.  You don’t have to read very far to get the point that they’re trying to make, however.