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Homework Help: Water-Oil Pressure

  1. Jan 30, 2008 #1
    1Assume that below the surface of the earth there is a connection between all of the ground water, and the water is static (the pressure profile is hydrostatic, you should know what this means in terms of water head). A hole is drilled (which fills with water) to a depth of 2000 m, where oil is found.
    a) Call the surface of the earth to be z=0 and assume this is the top of the water column. Find the water pressure (Pw) at a depth of 2000m.
    b) Assume that at the reservoir, the water pressure is equal to the oil pressure (Po). Write down the oil pressure at z=2000 m.
    c) Now assume that the well bore has its water displaced by the reservoir oil (density = 800 kg/m3), and then it is capped (we now have a column of static oil instead of a column of static water). Find the oil pressure at the top of the well bore (z= 0 m) and compare it to atmospheric pressure. (This is the simplest reason why there are gushers).

    2. Relevant equations
    Ptotal = Patmosphere + Pfluid

    3. The attempt at a solution

    for a) I got Ptotal= 1.01 * 10^5+ 1000*9.8*2000=1.9701*10^7 kpa = pw

    b) I'm kind of confused here, so does this mean pw=poil so poil is the same answer as above

    c) I don't have a clue.

    I'm having a hard time understanding the question. Could somebody please clarify it for me? I'd appreciate your help. Thanks in advance.
  2. jcsd
  3. Jan 31, 2008 #2


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    Science Advisor
    Homework Helper

    b) yes, it's the same. c) do the same thing you did in a) but use the density of oil instead of the density of water. Note that atmospheric pressure is much smaller than the other two. You can probably ignore it.
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