124 
OTL DISTRICTS OF SOUTHERN CALIFORNIA. 
oil is said to come from the upper sands, the lighter from the lower. 
The product of the wells is run to a common tank with a resultant 
gravity of between 21° and 22° B. 
The westerly wells of the Union Oil Company adjoin on the east 
those of the Brea Canyon Company, and the territory in which they 
are drilled, except for a slight undulation of the strike from a few 
degrees north of west to an equal amount north of east, is strati- 
graphically and structurally similar so far as surface exposures indi¬ 
cate. A marked difference in the productiveness of the two areas 
has been revealed by development, however, the many conditions in 
depth familiar to all students of oil occurrence probably being suffi¬ 
ciently variant in the two areas to cause the widely differing results 
obtained. It is unsafe as a general rule to predicate the success of a 
proposed* group of wells upon that of a group already drilled, and, on 
the other hand, it is equally difficult to offer a tenable reason for the 
superior yield of one area over another, the conditions available for 
observation in the two being practically the same. Where there is a 
noticeable variation in surface conditions between two localities 
there is likely to be an equal variation in underground conditions, 
and it would not be unreasonable to expect a marked difference 
in the results of drilling. In illustration of this may be compared 
the eastern part of the Union Oil Company’s tract in Brea Canyon 
and the western part already referred to. In the eastern part the 
strata show a distinct bowing to the south, and, moreover, the area 
is in proximity to a complex of folds that are traceable from the 
Olinda field. The conditions in the western part are more regular, 
the beds dipping rather uniformly toward the south. While in the 
light of experience it would be impossible to predict whether the 
eastern area would be more or less productive than that a mile to the 
west, it would be a fair inference that there would be a material differ¬ 
ence in the yield of the two, and such a difference has been found by 
exploitation. 
The territory of the Menges Oil Company, which adjoins that of the 
Brea Canyon Company on the west, is structurally at variance with 
both productive tracts described above and has so far yielded smaller 
wells. The general horizon at which oil is obtained by the Menges and 
the Brea Canyon companies is the same, but between the two tracts, 
strongly developed at the sharp bend in the canyon, is a compound 
flexure involving the oil-bearing strata, in part at least, of both proper¬ 
ties. The flexure is as local as it is sharp, and disappears within a 
short distance of the stream. In the Menges tract, however, the strata 
are more disturbed than in that of the Brea Canyon Company, show¬ 
ing local and abrupt variations in both strike and dip, at one or two 
points with distinct overturns having a northerly dip. 
The foregoing discussion has been carried to considerable length at 
this point because of the typical example afforded by the Brea Can- 
