Since decline curve analysis is an empirical curve fitting / trend-line technique, it can also be used for gas reservoirs with no modifications. We assume that the compressible nature of the gas is built into the established trends. When using Arps Decline Curves, the same assumption applies for gas reservoirs: whatever processes that occurred in the past that helped to establish the trend of the data must continue to occur into the future.
As with oil reservoirs, decline curves for gas reservoirs can be used to make reservoir or well forecasts in both the time and domains, estimate the economic cumulative production from the reservoir or well (given the economic abandonment rate), and estimate the EUR (no economic limit) from the reservoir or well.
 Arps, J. J.: “Analysis of Decline Curves,” SPE-945228-G, Trans. of the AIME (1945)