﻿180 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1943 
  

  

  In 
  contrast 
  with 
  the 
  principle 
  of 
  flotation, 
  which 
  requires 
  no 
  lateral 
  

   movement 
  of 
  the 
  fluids 
  in 
  the 
  reservoir 
  but 
  only 
  displacement 
  of 
  indi- 
  

   vidual 
  particles, 
  other 
  theories 
  which 
  are 
  based 
  on 
  the 
  fundamental 
  

   principle 
  that 
  the 
  fluids 
  in 
  the 
  porous 
  bed 
  are 
  in 
  motion 
  have 
  been 
  

   developed 
  to 
  account 
  for 
  oil 
  migration. 
  Munn 
  (1909) 
  announced 
  the 
  

   "hydraulic 
  theory" 
  that 
  moving 
  water 
  under 
  either 
  hydraulic 
  or 
  capil- 
  

   lary 
  pressure 
  has 
  been 
  the 
  direct 
  agent 
  of 
  accumulation 
  of 
  oil 
  and 
  gas 
  

   pools." 
  It 
  was 
  his 
  view 
  that 
  hydraulic 
  pressure 
  was 
  the 
  result 
  both 
  of 
  

   compaction 
  and 
  of 
  invasion 
  by 
  water 
  from 
  surface 
  sources. 
  The 
  causes 
  

   of 
  hydraulic 
  movement 
  were 
  more 
  definitely 
  stated 
  by 
  Rich 
  (1931) 
  to 
  

   be 
  compaction, 
  generation 
  of 
  gas 
  by 
  regional 
  metamorphism, 
  and 
  

   artesian 
  pressure. 
  

  

  Cheney 
  (1940, 
  p. 
  116) 
  has 
  recently 
  suggested 
  a 
  modification 
  of 
  earlier 
  

   views 
  concerning 
  hydraulic 
  movement. 
  He 
  visualizes 
  

  

  * 
  * 
  * 
  the 
  main 
  controlling 
  movement 
  of 
  fluids 
  (except 
  in 
  reservoirs 
  having 
  

   intake 
  greatly 
  elevated 
  above 
  sea 
  level) 
  as 
  occurring 
  updip 
  instead 
  of 
  downdip; 
  

   the 
  time 
  of 
  movement 
  being 
  largely 
  restricted 
  to 
  the 
  early 
  periods 
  when 
  porosity 
  

   was 
  being 
  reduced 
  actively 
  by 
  sedimentary 
  loading 
  or 
  compressive 
  diastrophic 
  

   forces 
  instead 
  of 
  later 
  when 
  erosion 
  and 
  unloading 
  progressively 
  reduce 
  pres- 
  

   sures 
  ; 
  and 
  the 
  source 
  of 
  the 
  migrating 
  water 
  being 
  not 
  meteoric 
  but 
  from 
  the 
  

   compacting 
  sediments 
  of 
  the 
  basin 
  or 
  geosynclinal 
  areas. 
  

  

  A 
  combination 
  of 
  the 
  principles 
  of 
  flotation 
  and 
  hydraulic 
  movement 
  

   seems 
  best 
  to 
  explain 
  the 
  movement 
  of 
  oil 
  and 
  gas 
  to 
  areas 
  of 
  accumula- 
  

   tion. 
  If 
  globules 
  of 
  oil 
  are 
  put 
  in 
  motion 
  in 
  currents 
  of 
  water 
  which 
  

   are 
  passing 
  through 
  porous 
  rocks, 
  they 
  will 
  at 
  every 
  opportunity 
  seek 
  a 
  

   higher 
  position. 
  Because 
  of 
  the 
  difference 
  in 
  specific 
  gravity 
  a 
  definite 
  

   upward 
  pressure 
  is 
  exerted 
  on 
  each 
  oil 
  globule 
  and, 
  if 
  it 
  is 
  in 
  a 
  condition 
  

   of 
  flotation 
  and 
  can 
  move 
  freely, 
  it 
  will 
  tend 
  to 
  move 
  upward 
  with 
  ref- 
  

   ereace 
  to 
  the 
  water 
  by 
  which 
  it 
  is 
  surrounded. 
  It 
  will 
  come 
  to 
  rest 
  when 
  

   it 
  reaches 
  a 
  capillary 
  opening 
  too 
  small 
  to 
  permit 
  its 
  passage, 
  taking 
  

   into 
  account 
  the 
  pressure 
  exerted 
  against 
  it 
  by 
  the 
  moving 
  water. 
  

   Ultimately 
  the 
  decrease 
  in 
  the 
  size 
  of 
  the 
  capillary 
  spaces 
  due 
  to 
  

   compaction 
  will 
  retard 
  and 
  perhaps 
  completely 
  stop 
  hydraulic 
  move- 
  

   ment 
  in 
  a 
  sedimentary 
  basin, 
  bringing 
  about 
  at 
  the 
  same 
  time 
  a 
  cessation 
  

   of 
  oil 
  migration 
  in 
  the 
  carrier 
  bed. 
  

  

  The 
  fundamental 
  cause 
  of 
  the 
  movement 
  of 
  fluids 
  through 
  porous 
  

   beds 
  is 
  differential 
  pressure, 
  and 
  the 
  amount 
  and 
  direction 
  of 
  pressure 
  

   are 
  determined 
  by 
  the 
  geologic 
  conditions 
  in 
  the 
  area 
  at 
  the 
  time 
  the 
  

   movement 
  takes 
  place. 
  

  

  EFFECTIVENESS 
  OF 
  CARRIER 
  BEDS 
  

  

  The 
  extent 
  to 
  which 
  movement 
  of 
  oil 
  from 
  source 
  rock 
  to 
  reservoir 
  

   may 
  occur 
  is 
  largely 
  determined 
  by 
  the 
  effectiveness 
  of 
  the 
  carrier 
  bed 
  

   as 
  a 
  conductor. 
  The 
  capacity 
  of 
  a 
  porous 
  substance 
  to 
  transmit 
  fluids 
  

   is 
  termed 
  permeability. 
  Some 
  of 
  the 
  factors 
  which 
  influence 
  the 
  perme- 
  

  

  