PETROLEUM,  NATURAL  CAS.  AND  ASPHALT. 
THE  FLORENCE.  COLO..  OIL  FIELD. 
By  N.  M.  Fennemak". 
Previous  work, — In  1891  Mr.  George  IT.  Eldridge  made  a  Uriel' 
but  very  satisfactory  examination  of  this  field  and  published  a  report 
on  it.a  Xot  much  detailed  knowledge  of  the  field  has  been  added 
since  this  study  was  made.  There  were  at  that  time  but  82  wells. 
At  present  there  are  about  500.  In  so  far  as  later  drilling  has  added 
to  our  knowledge,  it  seems  generally  to  have  confirmed  the  conclusions 
drawn  by  Mr.  Eldridge.  A  careful  study  of  the  500  Avells  ncm 
drilled  might,  however,  add  to  our  understanding  of  the  detailed 
distribution  of  the  oil. 
A  brief  examination  of  the  economic  conditions  of  the  field  was 
made  by  the  writer  during  the  summer  of  1904.  At  the  same  time 
some  observations  were  made  on  smaller  folds  which  may  prove  to 
be  of  importance  in  the  determination  of  the  laws  of  the  distribution 
of  the  oil. 
Location. — The  field  is  located  in  and  south  of  the  city  of  Florence, 
Fremont  County.  Colo.,  the  city  itself  being  on  the  Arkansas  River 
30  miles  northwest  of  Pueblo,  on  the  lino  of  the  Denver  and  Rio 
Grande  and  Santa  Fe  railroads.  In  area  the  field  covers  from  10  to 
20  square  miles. 
General  structure. — The  location  here  defined  is  on  the  east  side  of 
a  triangular  structural  basin  about  15  miles  in  length  from  north  to 
south  and  having  a  maximum  width  of  perhaps  10  miles.  This  basin 
is  limited  on  the  southwest  by  the  foothills  of  the  AVet  Mountain- :  on 
the  north  by  the  foothills  of  the  southern  end  of  the  Front  Range.  Its 
eastward  limit  is  determined  by  an  uplift  of  the  strata  which  underlie 
the  plains.     The  basin  is  thus  seen  to  be  contained  within  the  reen- 
aTroc.  Am.  Inst.  Min.  Eng.,  vol.  20,  1892,  pp.  442-162. 
436 
