With the additional information that you are providing, ask the oil company if a survey was done. I will bet a hot dog that they did and you ended up with 7/8ths of an acre short. Just because the mineral deed says XXX acres, it generally goes on to say, “more or less” to account for lots of things - fences off a bit, increased accuracy of surveying instruments, slight shift of magnetic north, and it goes on and on.