I found a reference to a structure in Section 15 on a survey from 1948.
Ignoring the newer, cardinally oriented lease roads, you can see the object which looks like angled lines in your favorite mapping software at:
N 31.265480 W 103.415751
Or on Google Maps
A clue to the purpose is the orientation of the lines.
Rancho Boundaries? Did they have those in Texas? A bunch of County lines around San Antonio appear to oriented the same way.
Parallel to the old railroad to the southwest?
My 2 cents.
JA, PLS SoCal
Ancient Anasazi soccer field?
I've heard of concrete arrows in the West Texas desert, to aid wounded long range bombers find their way home in WWI, but I have never seen this.
Airway beacon?
I know that there have been places where sections or quarters have been divided on the diagonal (it's in some of the manuals) so that you might have for instance the NE half and the SW half. This sort of looks like it could be 4 of those.
Or do I perhaps see an old rail bed running NW/SE and maybe they laid off some "squares" oriented to that?
I think what you are seeing as an old railroad bed is actually the original location of the road from Pecos City, Texas to Fort Stockton, and is also shown on the 1948 map as abandoned highway.
Second Clue
N 31.377294 W 103.505980
Second Clue
Ahh yes the original Area 51, due to oil they had to move it.
Answer
One of 4 auxiliary air fields for the Pecos Army Airfield (now Pecos Municipal).
9 miles southeast of the end of the runway.
