﻿PETROLEUM 
  GEOLOGY 
  — 
  HEROT 
  167 
  

  

  Stated 
  in 
  a 
  few 
  words, 
  it 
  is 
  a 
  theory 
  that 
  oil, 
  being 
  lighter 
  than 
  water, 
  must 
  

   rise 
  to 
  higher 
  levels. 
  If 
  the 
  application 
  of 
  this 
  theory 
  was 
  confined 
  to 
  bottles 
  

   no 
  one 
  would 
  dispute 
  it 
  ; 
  the 
  water 
  in 
  a 
  bottle 
  must 
  collect 
  at 
  the 
  bottom, 
  the 
  

   oil 
  in 
  the 
  middle 
  and 
  the 
  gas 
  on 
  top. 
  But 
  the 
  earth 
  is 
  not 
  a 
  bottle. 
  It 
  has 
  no 
  

   great 
  caverns 
  in 
  it. 
  More 
  than 
  that, 
  the 
  arrangement 
  takes 
  place 
  naturally 
  

   under 
  the 
  pressure 
  of 
  only 
  one 
  atmosphere; 
  while 
  any 
  arrangement 
  of 
  water, 
  

   gas, 
  and 
  oil, 
  made 
  at 
  depths 
  of 
  a 
  thousand 
  or 
  2,000 
  feet, 
  must 
  be 
  made 
  under 
  

   pressures 
  of 
  from 
  100 
  to 
  400 
  pounds 
  to 
  the 
  square 
  inch. 
  * 
  * 
  * 
  It 
  therefore 
  

   seems 
  to 
  me 
  irrational 
  to 
  assign 
  any 
  importance 
  whatever 
  to 
  the 
  extremely 
  

   gentle 
  anticlines 
  of 
  the 
  gas-oil 
  region. 
  

  

  To 
  this 
  I 
  add 
  the 
  important 
  consideration 
  that 
  the 
  movements 
  of 
  oil 
  and 
  

   water 
  have 
  been 
  shown 
  by 
  actual 
  practice 
  to 
  be 
  governed 
  entirely 
  by 
  the 
  char- 
  

   acter 
  of 
  the 
  rock 
  in 
  which 
  they 
  take 
  place, 
  and 
  that 
  they 
  are 
  effectually 
  stopped 
  

   at 
  fixed 
  geographical 
  lines 
  where 
  porous 
  rock 
  changes 
  into 
  sandstones 
  and 
  

   sandstones 
  into 
  shales. 
  And 
  these 
  changes 
  of 
  character 
  in 
  the 
  rock 
  itself 
  have 
  

   no 
  fixed 
  relation 
  whatever 
  to 
  the 
  anticlinal 
  waves, 
  which, 
  on 
  the 
  contrary, 
  cross 
  

   them 
  transversely 
  or 
  diagonally. 
  

  

  White, 
  in 
  replies 
  to 
  these 
  criticisms 
  (1885b 
  ; 
  1886) 
  , 
  again 
  emphasized 
  

   his 
  position 
  that 
  not 
  all 
  anticlines 
  would 
  be 
  gas-bearing, 
  especially 
  

   such 
  subordinate 
  anticlinal 
  folds 
  as 
  occurred 
  within 
  the 
  synclines. 
  He 
  

   pointed 
  to 
  the 
  success 
  which 
  had 
  attended 
  development 
  along 
  eight 
  

   anticlines 
  in 
  the 
  vicinity 
  of 
  Pittsburgh 
  and 
  the 
  failures 
  which 
  had 
  

   resulted 
  from 
  drilling 
  in 
  the 
  intervening 
  synclines. 
  Thus 
  the 
  im- 
  

   portance 
  of 
  structure 
  as 
  a 
  factor 
  in 
  the 
  accumulation 
  of 
  oil 
  and 
  gas 
  

   came 
  to 
  be 
  recognized 
  by 
  the 
  geological 
  profession 
  and 
  by 
  practical 
  

   operators. 
  

  

  With 
  the 
  extension 
  of 
  oil 
  and 
  gas 
  production 
  to 
  areas 
  other 
  than 
  

   western 
  Pennsylvania, 
  it 
  was 
  soon 
  found 
  by 
  the 
  geologists 
  working 
  

   in 
  them 
  that 
  modifications 
  of 
  White's 
  theory 
  were 
  required 
  to 
  explain 
  

   all 
  the 
  structural 
  problems 
  that 
  arose. 
  Minshall, 
  by 
  careful 
  surveys 
  

   along 
  the 
  White 
  Oak 
  anticline 
  in 
  West 
  Virginia, 
  had 
  shown 
  that 
  the 
  

   axis 
  itself 
  was 
  undulating, 
  with 
  pronounced 
  domes 
  or 
  summits 
  at 
  

   some 
  points 
  and 
  sags 
  or 
  depressions 
  at 
  others, 
  and 
  that 
  the 
  commercial 
  

   gas 
  accumulations 
  were 
  confined 
  to 
  the 
  domes. 
  In 
  Ohio, 
  Orton 
  (1888, 
  

   pp. 
  93-95) 
  found 
  that 
  anticlinals 
  were 
  of 
  infrequent 
  occurrence 
  but 
  

   that 
  oil 
  and 
  gas 
  accumulation 
  was 
  controlled 
  by 
  another 
  type 
  of 
  

   structural 
  deformation, 
  which 
  he 
  termed 
  "arrested 
  anticlinals," 
  or 
  

   terraces. 
  

  

  PRESSURE 
  OF 
  GAS 
  

  

  One 
  other 
  major 
  problem 
  in 
  connection 
  with 
  the 
  occurrence 
  of 
  oil 
  

   and 
  gas 
  greatly 
  concerned 
  the 
  petroleum 
  geologists 
  of 
  a 
  half 
  century 
  

   ago 
  — 
  to 
  find 
  a 
  satisfactory 
  explanation 
  for 
  the 
  pressure 
  exerted 
  by 
  

   the 
  gas 
  upon 
  the 
  reservoir 
  within 
  which 
  it 
  was 
  contained. 
  Closed-in 
  

   pressures 
  ranging 
  up 
  to 
  1,000 
  pounds 
  per 
  square 
  inch 
  had 
  been 
  ob- 
  

   served, 
  and 
  the 
  enormous 
  expulsive 
  force 
  of 
  the 
  gas, 
  frequently 
  caus- 
  

   ing 
  the 
  drilling 
  tools 
  to 
  be 
  violently 
  thrown 
  from 
  wells, 
  was 
  well 
  

  

  