The geologist that created this structure map is engaged in wishful thinking, I suspect. Don’t hold that against him as oil is first discovered in the minds of men engaged in lots of wishful thinking. The north/south line you see is indeed a fault as he is hypothesizing, but good structure maps will always identify the well control that identifies the fault, where it cuts that well, and what the “throw” or displacement of that fault is. I see no such identification on this map.
In other words, on the west side of the fault the sediments you reference are lower, marked D, than on the upthrown side to the east, marked U. Most good structure maps will contour on both sides of the fault; this one does not. There is one upthrown control point across the fault so there is likely a fault present. (This is hard to explain, sorry.) There is well control (old wells that were logged give geologists lots of information) to the south, on the downthrown side of the fault that implies the possibility of a structure, but no control to the north on the downthrown side so I would seriously question the viability of this idea. If there is structural closure, it is wishful thinking. The well location is spotted at the very top of the structure, naturally. It makes for a pretty map. If you are looking at this from the standpoint of investment, you should be concerned.
This will be really hard to explain but think of things in three-dimensional terms, like bumps that were formed in the subsurface for any number of reasons that were later cut in two pieces by a tectonic event like a fault. One side stayed up, the other broke down. Remember to map the subsurface you must know the measured depth to the top of the formation (by well logs) you are mapping on, but then discount that by how the surface relates to that.
In other words, a well that is drilled to the top of the Palo Pinto on top of a hill on the surface is going to be deeper than a well that was drilled to the Palo Pinto in a valley. So geologists must know the elevation of the surface and make allowances. By example, the top of the Palo Pinto by well logs is 2900 feet, less the surface elevation of 1000 feet above sea level, so the actual datum to be used in contouring the top of the Palo Pinto on the subsurface map is -1900 feet. So your 1500 foot question is probably the subsea datum of the Palo Pinto, not 1500 ft. but -1500 ft. If you get all that, you are doing well.
This operator is filing a proposed TD that might cover the Palo Pinto and the Strawn on the basis of this hypothetical structure map. It will be able to produce anything it might find going down, above 3900 feet. If it were to stumble onto something shallower, like the Caddo (this is not my country), it could produce that by filing new discovery forms, etc.
Thus endeth the geology lesson of the day. Whew!