Carol, find a copy of the deed for the purchase of the property and see if it includes language reserving the minerals.  It sounds as if a company is reviewing the public records and finding an Oil, Gas & Mineral Lease in the name of the deceased prior owner with the old address.  If the minerals were reserved, under LA law that created a mineral servitude which has a prescriptive life of 10 years.  If there is no good faith attempt to drill a well or if a well is drilled and produced that 10 year period is interrupted.  Your question is so general and lacking in specifics it's difficult to know the answer to your question.  It would be helpful to know the location of the property by section-township-range to see what activity may have occurred over the past 10 or 11 years.