DETAILS OF THE DEVELOPED TERRITORY. 
93 
the latter was followed. In the Fernando formation, which uncon- 
formably overlies the Monterey shale, it was natural to expect vari¬ 
ance with the structure in the Monterey, but even here the surface 
evidence more often supported than contradicted the evidence 
obtained by the drill. 
DIFFICULTIES OF PREPARATION. 
After carefully plotting all the logs on a uniform scale it was found 
that the greatest obstacle to overcome in the preparation of the con¬ 
tour map was the correlation of strata from one well to another and 
from one part of the field to another. The difficulties of such corre¬ 
lations are doubtless familiar to anyone who has tried to work out 
the underground structure of any of the California fields. The Santa 
Maria field offers as much encouragement to successful study and 
mapping of the underlying oil-bearing formations as any other so far 
examined by the senior author, and so the effort has been made to 
delineate on the map all the details of structure furnished by the 
data available, and to supplement these details by showing for the 
untested areas what seem to be the most likely conditions of under¬ 
ground structure. It is very easy to make an ambiguous statement 
which will apply equally well to any conditions exposed by future 
development, no matter what they may be; but it is impossible to 
make an ambiguous map. However, it is deemed advisable to show 
the information in hand, incomplete as it is, on a map. Future 
development will doubtless add much to our knowledge of this field, 
and will show the inaccuracies of the contouring as here presented, 
but it is hoped that the benefits which may accrue to the operators 
from a knowledge of the general structure of the field will compen¬ 
sate in a measure for the errors in detail which are to be expected in 
a map based on data so incomplete. 
THE WELLS. 
AREAS DISCUSSED. 
For convenience of discussion the proved portion of the Santa 
Maria field has been roughly divided into six areas, based largely 
on the geographic position of the wells. The following are the areas 
discussed: Hall-Hobbs-Pice ranch; Pinal-Fox-FIobbs; Pinal-Fol- 
som-Santa Maria Oil and Gas-Escolle; Hartnell-Brookshire; Gra- 
ciosa-Western Union; and eastern Western Union. 
OIL ZONES. 
Although in many instances detailed correlation from one well 
to another is impossible, four fairly well defined oil zones are believed 
to be recognizable in the Santa Maria field. Of these at least two 
are found in practically every part of the field, although all vary 
1784— Bull. 322—07-7 
