Deborah,
If you know the legal description of the 200 acres then you can fill out an affidavit of heirship and have it recorded at the county clerk’s office. That is a cheap method of claim, or you could do a probate but I wouldn’t unless it was required by an oil company. Call the Oklahoma Corporation Commission and ask if there are any producing wells. If you need an affidavit of heirship let me know and I’ll send you one.