Gas reserves grew substantially in 2000 partly because of declines in production, but also because of a turnaround in drilling, according to a new report by the American Gas Association. The AGA report shows that based on the behavior of 30 large reserve holders examined, total domestic gas reserve additions are expected to be 24 Tcf or greater for 2000. Because only 19.2 Tcf is estimated to have been produced, reserves for 2000 are expected to have grown from 164.7 Tcf to more than 170 Tcf --- the highest level of reserves since 1987, AGA said. Additions to gas reserves exceeded domestic production by at least 26% in 2000.