Weld County Lease -- what's fair value?

Hi - Apologies if this question has been asked and answered elsewhere. My family holds mineral rights in Weld County, CO, on a small section. Five years ago we leased the rights in a 5-yr lease. That has expired, and we're being offered $100/min-acre for a new lease, for 2015-2020. Our offer is from Contex Energy. The section is:

Section 18; Township 11 North, Range 57 West; E2SW, SE
Royalty 1/6

Is this a competitive offer? Offers in recent years appear to have been much higher than this.

Appreciate any feedback on this.

-HB

I know the area pretty well.