iknxioman.]  FLORENCE,  COLO.,  OTL    FIELD.  439 
ing,  might  be  expected  to  open  from  below  upward,  would  communi- 
cate with  the  great  reservoir  of  artesian  water  supposed  to  be  con- 
tained in  the  Dakota  sandstone  is  not  conclusive.  It  may  indeed 
prove  to  be  the  case  that  such  cracks  are  limited  in  their  downward 
extension  by  the  superincumbent  weight  and  that  this  limit  is 
reached  at  a  depth  less  than  that  of  the  Dakota  sandstone.  There 
are  no  data  showing  the  strength  of  the  soft  Benton  shales,  but  it 
is  not  impossible  that  a  burial  approximating  2  miles  might  suffice 
to  bring  them  within  the  zone  of  flowage. 
Behavior  of  wells. — Gas  has  been  found  at  irregular  depths  in 
beds  similar  to  those  containing  oil.  It  may  occur  either  with  the 
oil  or  in  distinct  layers.  There  is  in  this  field  no  phenomenon  of 
gushing,  but  when  the  oil  is  struck  it  commonly  rises  at  least  a  few 
hundred  feet  in  the  hole  and  may  approach  the  mouth  of  the  well. 
The  issuance  of  gas  and  oil  has  at  times  been  violent,  but  such  occur- 
rences have  been  of  brief  duration.  A  moderate  supply  of  gas 
may  continue  during  the  life  of  the  well,  or  may  cease  after  a 
few  days. 
In  general,  but  little  water  is  encountered  below  that  which  is 
classed  as  surface  water.  The  absence  of  a  wTater  supply  in  an  occa- 
sional isolated  layer  of  friable  sandstone  emphasizes  the  fact  that 
such  bodies  are  of  very  limited  lateral  extent.  Their  character  is 
sometimes  such  that  if  continuous  under  large  areas  they  might  well 
be  expected  to  afford  abundant  flows.  A  few  instances  of  salt  water 
nave  been  met  at  considerable  depths.  There  is  nothing  here  to 
Correspond  to  the  relations  of  water  and  oil  in  the  Appalachian  fields, 
where  the  water  forces  the  oil  upward  and  follows  the  oil  in  the  well. 
The  characteristic  phenomenon  in  the  failure  of  a  producing  well 
in  this  field  is  not  the  advent  of  water  taking  the  place  of  the  oil, 
but  only  a  gradual  disappearance  of  the  latter.  In  those  cases 
where  water  has  apparently  failed  to  enter  the  hole  after  the  exhaus- 
tion of  the  oil  there  has  apparently  been  a  sealing  or  gumming  of 
the  pores  by  the  heavier  constituents  of  the  oil. 
Number  of  wells  mid  production. — The  total  number  of  wells 
drilled  in  the  field  approximates  500.  Of  these,  about  175  have  been 
producers;  GO  are  at  present  pumping.  The  line  between  producers 
ind  (for  practical  purposes)  dry  wells  may  be  placed  at  about  7  or 
barrels  a  day.  Despite  the  good  quality  and  price  of  the  oil,  it 
uis  proved  unprofitable  to  pump  wells  yielding  smaller  amounts 
than  this  on  account  of  the  expense  of  labor,  and  the  further  fact 
that  the  wells  are  so  widely  separated  that  several  pumps  can  not 
conveniently  be  operated  from  a  single  source  of  power.  Upon  this 
classification,  therefore,  only  about  three  wells  in  eight  can  be 
regarded  as  producers.     However,  despite  these  adverse  facts,  the 
