When you say that "production volume is steadily being reduced monthly", is it your understanding that it is being intentionally reduced by Anadarko? That is unlikely, so I probably misunderstood your meaning. If your well is horizontal, it is typical for these wells to have a very steep (i.e., rapid) decline curve. If it is a conventional "straight hole" well and has declined rapidly, that usually is indicative of a very small and/or very low quality reservoir.
How soon or if/when they will drill another well may depend on a number of factors. As "TennisDaze" suggested, your well may have been drilled to hold the acreage with production and they may develop it completely over time and simply have other wells to drill elseehere where circumstances are of a more urgent nature.
I don't know anything about your well, but it could be that year-to-date production is inadequate at current prices to qualify other potential locations on your acreage as "prime locations". Companies like Anadarko make a big deal of concentrating on drilling their "prime locations" to make a good impression on their stockholders. By "prime locations", they mean locations that offer a good chance of resulting in wells that offer a fast payout and very good rate of return on investment at current prices.
Should thus be the case, at higher prices the locations on your acreage could become "prime locations" in short order. Or, even if prices stay flat for a long time, as Anadarko's inventory of "prime locations" gets drilled up, lesser but still good locations will rise to become their new "prime locations".
The preceding are just a few possible contingencies worth considering. There are many, many others.
All the best,