George,
I makes a huge difference in how you approach the problem of non-payment as to whether your "interest" is as a lessor or a well participant. If you interest is as lessor/royalty owner documentation and research into the record of non payment before acting could mean a big payday for you if your minerals are located in most areas of Upton County. At this point, the language in the underlying lease is the keystone to future action. Until you know the lease terms it is best to let sleeping dogs lay. To wake the big dog prematurely may cost you a lot of money in the future.
If on the other gand, your interest is a working interest only, take Buddy's advice and demand that the big dog wake up.
Gary L Hutchinson