the pipe curve w represents the water volume fraction profile curve o the oil volume fraction profile and curve f the fluid velocity profile there are also model equations to describe hold up profiles but it can be easily understood that the water hold up is higher at the lower side of the pipe a very simple separator as shown in fig2 can be made that will take advantage of this behavior it is basically no more than a deviated pipe 21 of length l l 1 l 2 fed at the middle by the mixture the two phase outlets being at the two ends upper and lower of the pipe 21 one such outlet 22 o is the inlet mouth of an internal conduit 23 o positioned at the top end of the pipe 21 while the other 22 w is the inlet mouth of a second internal conduit 23 w positioned extending right down to the bottom end of the pipe 21 these conduits are to carry the oil and water respectively up to the surface or to some other place as required as will be apparent a mixture of oil the black circles o and water the white circles w seeps out of the oil producing formation 24 through which the pipe 21 passes through perforations 25 in the formation and the borehole casing not separately shown into the borehole itself there it exists first as a mixture in a mixture zone but gradually it begins to separate under gravity into two parts the lighter oil part tending to rise to the upper side of the deviated pipe 21 the heavier water part tending to sink to the.