Fluid Identification - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 88

Fig. 7.1 Gradiomanometer tool. Courtesy Schlumberger
In deviated wellbores, the pressure difference measured requires a correction
equal to the cosine of the deviation angle in order to convert the measurement to a
fluid density (see Fig. 7.2 ). Since the measurement made is that of a pressure differ-
ence, it is assumed that the only cause of the pressure difference is the hydrostatic
head of the well bore fluid. But this assumption is not valid if fluid flow is restricted
to a small cross-sectional area. In that case, the measured pressure difference will be
the sum of both the hydrostatic component and a friction gradient.
Fig. 7.2 Gradiomanometer measurements in deviated wellbores: ( a ) Vertical wellbore, ( b )
Deviated wellbore