The wording of that depth clause is not unusual, but it is not in favor of the mineral owner. The word “penetrated” and “base of the stratigraphic equivalent” stretch it farther than the mineral owner would probably like. If the original well penetrates the top of a reservoir (common source of supply), then it holds the entire reservoir. If they drilled 10’ into it and it is 2000’ thick, then it hold all 2000’ (extra 1990’ was never drilled) plus another 100’ below that. Not optimal wording for the mineral owner but great for the operator.