DETAILS OF THE DEVELOPED TERRITORY. 
95 
one log reports “no shell” until the first oil zone is reached. Wher¬ 
ever ‘‘shell” is penetrated accumulations of gas or oil or both are 
generally encountered. The shale seems to be somewhat more sandy 
in this area than farther west' or in the Graciosa-Western Union 
region. 
Three oil zones are recognizable in the area under discussion, 
although practically all the strata from the top of the uppermost 
zone to the bottom of the lowest are more or less petroliferous at 
one point or another. 
The first productive zone (A) is penetrated at a depth of 1,600 
to 2,100 feet, varying according to the position of the well geograph¬ 
ically and relatively to the axis of the anticline. Its top is from 550 
to 700 feet above the top of zone B in this area. Zone A is produc¬ 
tive for a distance in the wells of 20 to more than 500 feet. Of course 
this does not mean that the beds are productive in any one well for 
the whole distance of 500 feet, but that throughout the zone alternat¬ 
ing barren and productive beds occur at such close and as a rule 
irregular intervals as to preclude their practical differentiation. The 
productive measures in this first zone consist both of hard frac¬ 
tured shale or “shell” and more or less porous sandy layers. In at 
least one of the wells the oil accumulates only under the hard “shell” 
layers. Zone A is the only one penetrated by some of the wells 
farthest away from the anticlinical axis. In these wells it appears 
to be much more petroliferous than in wells higher up on the fold. 
The second oil zone (B) is from 550 to 700 feet below the top of 
zone A, and its upper limit is about 300 or 400 feet above the top of 
zone C, although it can hardly be said to be distinct from C in all 
the wells, so rich in oil are some of the intervening strata between 
them. True sands of medium grain, in addition to the productive 
hard shale, yield the oil in this zone. 
The third oil zone (C) is encountered in some of the deeper wells 
nearest the axis of the main anticline. This zone has been pene¬ 
trated for as much as 150 feet, the whole distance being very rich 
in petroleum. It is overlain by a considerable thickness of black 
shale, also more or less petroliferous, between which and the rich 
zone is a thin, hard “shell” layer. The oil-yielding rock is a true 
sand, coarse in places and even becoming pebbly toward its base in 
certain portions of the area. To the coarseness of the material is 
doubtless due the great productiveness of the zone. 
PRODUCT. 
The oil in the Hall-Hobbs-Rice ranch area runs from 26° to 29° 
Baume and is dark brown in eojor. Gas accompanies the oil and also 
occurs isolated under some of the more impervious “shell” layers 
in the shale. No water is reported in any of the wells. 
