Martin County Working Interest Value

Hello All, I hope this is not too redundant but I’ve seen a lot of talk about Royalty Interest as opposed to working interests so here goes… I’ve received an offers for my working interest in Martin County Hartley County School Land League 247- Abstract 599 and League 250 - Abstract #602. These offers came unsolicited and completely out of the blue so I expect they are somewhat below market value :). I’ve found this land on the TRRC Public GIS viewer and it appears that there is a drilling campaign ready to embark on this property. How do I determine what a reasonable value of this land is? I have next to no knowledge of the oil and gas industry (these were inherited). Thanks for any help that you can provide. -John