The outline of the producing area which has been superimposed on the reflection seismograph survey contour map, does not coincide with the outline of the Tomball structure. This is due to the fact that the upper or Kobs sand becomes so tight and argillaceous at the north end of the structure that it can not produce oil. Thus, the outline of production follows a structural contour around Tomball field rather closely except at the north end. At this end, the structure continues further north and resembles very closely the reflection seismograph picture. These remarks have been made so one may appreciate how remarkably well reflection geophysical surveying outlined the Tomball structure.