Page 185 - Standard Handbook Of Petroleum & Natural Gas Engineering

170 General Engineering and Science

Example 2-12

Consider a 1,000-ft-deep hole. What will be the absolute pressure at the bottom
if (a) it is filled with pure water or (b) it is filled with air at a constant temperature
of 85"F?

(a)
P = P, + dh-h,)

h, = 0
h = 1,000 ft

y = 62.4 lb/ft3

P = 2,116.8 + 62.4(1,000 - 0) = 64,516.8 lb/ft2
P = 448 psi

(b)

s=l
Assume

z=l
T = 85 + 460 = 545"R
1( 53.3)( 545) 1
P = 2,116.8exp (1'000-0)1 = 2,190.941b/ft2

P = 15.21 psi
In a case where Z # 1, it is practical to assume Z = 1, perform Calculation (b), and
then, based on the resultant, estimate for Pavg = (P + P,)/2, find the value of Z, and
repeat the calculation. Three iterations are generally sufficient. If T varies, it is usually
sufficiently accurate to use an estimate of Tavg such as Tavg = (T + TJ2.
Fluid Dynamics

When fluids are in motion, the pressure losses may be determined through the
principle of conservation of energy. For slightly compressible fluids this leads to