134 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
The yield of most wells becomes less with the lapse of time. This 
decline is generally more marked during the first few months of the 
well’s life than later, when the conditions governing the flow appear 
to become more stable. PL XVII, giving the average daily yield 
by months of a group of wells in the Puente Hills district, illustrates 
graphically the common variations in the yield. The minor fluctua¬ 
tions in the curves are usually traceable to the sanding up or clean¬ 
ing out of the wells or to other local causes. 
ASSOCIATED HYDROCARBONS. 
Brea and gas are the only hydrocarbons associated with the oil 
in the formations of the Puente Hills district. Brea (sand or soil 
impregnated with oil from seepages, the volatile substances having 
evaporated) is found in all of the fields. The largest deposits in 
the district are in Brea Canyon, on the south slope of which are 
considerable areas covered by the material. No practical use has 
been made of it except locally for road dressing. 
Nearly all the wells in the territory under discussion yield more 
or less gas, especially in the earlier stages of their existence. In 
some localities the gas contains a considerable percentage of hydro¬ 
gen sulphide, to judge by the odor encountered in the vicinity of 
certain wells; in others the gas is of such a quality as to be used 
profitably both in the generation of power by gas engines and for 
domestic purposes. Among the companies making use of the gas 
derived from their wells are the Santa Fe, in the Olinda field, and 
the Murphy, in the Whittier field. The Santa Fe Company is said 
to use gas entirely for all purposes requiring the generation of heat 
and light on its property. Some years ago a well yielding gas 
under strong pressure was struck south of Whittier, in the western 
extension of the Coyote Hills anticline. This well never furnished 
any oil, and as the gas gave out the hole was abandoned. 
STORAGE AND TRANSPORTATION. 
With the exception of the oil in the Olinda field, much of which is 
stored in open earthen reservoirs, most of the oil of the Puente Hills 
district is stored in circular metal tanks. These tanks are usually 
covered, and vary in capacity from 5-barrel settling tanks to stor¬ 
age tanks holding about 55,000 barrels. The tankage of the Whit¬ 
tier field is something over 200,000 barrels; that of the Puente 
field, including the Chino refinery, over 100,000 barrels; that of Brea 
Canyon approximately 85,000 barrels, and that of the Olinda field 
possibly 200,000 barrels. In addition to this, the Union Oil Com¬ 
pany has a storage capacity of about 150,000 barrels at Norwalk, 
the center of its pipe-line system, and of 37,500 barrels at San Pedro, 
its shipping point by boat. 
