California is a land ripe with many natural resources which result in some of its land being leased out for the sole purpose of harvesting these resources. Some land may be leased from private individuals or corporations while other land may involve leases with the federal government. When the federal government is involved, it may end up paying the state of California royalties.
If someone has approached you with a lease offer for the minerals or the oil on your California land, it is not unreasonable to think the person who is talking with you represents a company that excavates minerals or other natural resources. Sometimes this is the case. However, there is the chance the party you are conversing with is actually farther removed from an actual drilling operation or has no ability to drill at all.