Page 217 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

186 Reservoir Engineering

Sandstone, 7- to 9-in. Casing, 12-in. Borehole, Fresh Water Cement, Tool Eccentered

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10 20 30 40 50
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Flgure 5-110. Chart for determining porosity and apparent water salinity from
Zlog and ratio curves in 7- to 9-in. casing and a 12-in. borehole [199].

appareqt water salinity, and Zw, using this combination. By selecting the chart
for the appropriate borehole and casing diameter, these values are easy to
determine. Simply enter the proper axes with the log-derived values, and find
porosity and Zw at the intersection of the two lines. If water salinity and
formation temperature are known, use Figure 5-111 to find xw.
is
Estimating LY another matter. You must first know if the hydrocarbons are
oil, methane, or heavier hydrocarbon gases (Le., propane, butane, pentane). For
oil, solution gas-oil ratio and oil gravity ('API) are needed. If the gas is methane,
reservoir pressure and temperature are required. For gases other than methane,
the specific gravity of the gas can be converted to equivalent methane using