24 BEREA GRIT OIL SAND IN CADIZ QUADRANGLE, OHIO. [bull. 198 
Amsterdam pool. — The accumulation from the canoe-shaped basin 
on the western side of the main anticline has been discovered in part 
at Amsterdam. 
The sand at the Amsterdam wells is of such a poor quality that it 
probably would have been reported as all lime had it not been oil- 
producing. The wells are small, but will probably improve when spots 
of better sand are found. The limits of this field have been determined 
across the dip of the sand by a salt-water well, No. 205, and a gas well 
in sec. 19, not located on the map. The lateral extensions along the 
strike are as yet not defined by test wells. The indications are that 
the extensions will be to the southwest in a diagonal line through sec. 
30, and to the east in an almost due east line through the south half of 
sec. 7. 
USE OF THE STRUCTURE MAP. 
To obtain the most valuable result from the use of the map of the 
oil sand, it is necessary to know the true elevation of the mouth of a 
contemplated well. For this purpose the elevations of the surface at 
a great man}^ intersections of roads and other spots have been printed 
on the map. The letters "BM" have been prefixed to two hundred 
of these elevations, and beneath each has been placed one of the num- 
bers of the consecutive series appearing in the first column of the 
bench-mark descriptions on pages 34 to 42. These bench marks have 
been so distributed that it is hoped any point may be reached by not 
over 1 mile of leveling. 
After obtaining the true elevation of the mouth of the proposed 
well, add to it the elevation of the oil sand, as shown by the contour 
map, at the point where the well is to be drilled, disregarding the 
minus sign. The sum will be equal to the depth of well required to 
reach the top of the sand, and by increasing this amount by 40 to 60 
feet the total depth of well will be found. By subtracting 350 feet 
from the computed distance from mouth to top of Berea sand, a very 
close estimate can be made of the casing required to extend through 
the Big Indian sand. 
