PETROLEUM RESOUECES ARNOLD. 275 



base, varying in gravity from 27° to 41° Beaume (0.8917 to 0.8187 

 sp. gr.), and is used for refining. It is piped to the Gnlf and also 

 to Indiana and other eastern States. The development in this field 

 has been phenomenal during the past few years, some of the pools 

 being exceedingly productive. The average initial daily production 

 of the wells in 1911 was 119 ban-els; the average daily production 

 8.6 barrels. A fair percentage of the region embraced in this field 

 yet remains to be prospected, the bulk of the untested land lying 

 in Texas. 



Gulf field. — The Gulf field includes the pools lying along the 

 coastal plain of Louisiana and Texas. The oil occurs for the most 

 part in domes or quaquaversals associated with salt and g}'psum 

 deposits. The age of the containing rocks ranges from Cretaceous 

 to Quaternary. The reservoir rock is usually porous dolomitic lime- 

 stone or sandstone. The oil of northern Louisiana occurs in Cre- 

 taceous and Eocene rocks along an uplift or fold. The oils of the 

 Gulf field vary greatly in composition; those in the strictly coastal 

 belt vary from 15° to 27.7° Beaume (0.9655 to 0.8878 sp. gr.) and are 

 of asphalt base; those of northern Louisiana vary from 25° to 43.6° 

 Beaume (0.9031 to 0.8065 sp. gr.) and are of paraffin base. Sulphur 

 usually accompanies the heavy oil. The lighter oils are used for re- 

 fining, the heavier for fuel. Some of the individual wells have been 

 exceedingly productive, a daily flow of 75,000 barrels being recorded 

 for one at least. The pools usually are quite short-lived. In 1911 

 the average initial daily flow for the Gulf coastal pools was 257 

 barrels; for northern Louisiana, 1,176 barrels; the daily average 

 for the field, 60 barrels. Some territory still remains untested in this 

 field. 



Rocky Mountain field. — The Rocky Mountain field embraces pools 

 in Wyoming and Colorado and as yet untested deposits in Utah and 

 New Mexico. The oil occurs in beds of Carboniferous, Triassic (?), 

 and Cretaceous age, nearly always in sandstone interbedded with 

 shale, though occasionally in fracture zones. Typical dome structure 

 is the most favorable location, but occasionally commercial deposits 

 occupy monoclines or interrupted monoclines. The oils from the 

 older formations vary in gravity from 18° to 24° Beaume (0.9459 to 

 0.9091 sp. gr.), are of asphalt base, and are used largely for fuel; 

 those from the Cretaceous vary from 32° to 48° Beaume (0.8642 to 

 0.7865 sp. gi\), are of paraffin base, and are refined, yielding high per- 

 centages of gasoline, kerosene, and distillates. The productivity of 

 individual Avells usually is not large, the average daily yield per well 

 being about 25 barrels in 1913. The potentialities of the Rocky 

 Mountain field are not great, unless the extensive deposits of oil 

 ghalQ of RQi-thwestern Coiora^a ms^. northeastern Utah are taken 



