Piceance Basin Lease Information

My uncle owns a small 40 acre tract of land (20 net mineral acres) in Garfield County, Colorado and has been approached to lease his acreage (not sure which company) for $500/acre and an 18% royalty (not sure of the term) and asked if I could help him. I work for a small E&P that works primarily out of the Permian Basin and do not have access to DrillingInfo for Colorado, and am unfamiliar with the area, though I know ExxonMobil has been extremely active in the area and was wondering if these terms fall in line with what other landowners are receiving? If it helps, his land is between Glenwood and Rifle. Any help would be appreciated, thanks.