Four curves designated as I, II, III, and IV are shown in the figure. \(P_b\) is the bubble point pressure of a crude oil at the given temperature.
Which ONE of the following options correctly depicts the solubility of asphaltene (\(q_a\)) in the crude oil with pressure (\(P\)) at a given temperature?
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Show Hint
- I
- II
- III
- IV
The Correct Option is B
Solution and Explanation
Step 1: Recall asphaltene solubility behavior.
- At high pressures (above bubble point \(P_b\)), asphaltenes are stable and remain dissolved in crude oil. - As pressure decreases towards \(P_b\), solubility decreases, and precipitation risk increases. - Below \(P_b\), gas liberation reduces solvency power, decreasing solubility further. Step 2: Interpret curves.
- Curve I (horizontal) suggests no change with pressure → unrealistic. - Curve II (U-shaped): high solubility at high \(P\), minimum near \(P_b\), then increase again due to lighter fractions vaporizing → matches known behavior. - Curve III and IV do not follow known asphaltene solubility trends. Step 3: Conclusion.
The correct curve is \(II\). Final Answer: \[ \boxed{\text{II}} \]
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For a hydrocarbon reservoir, the following parameters are used in the general material balance equation (MBE):
\[ \begin{aligned} N & = \text{Initial (original) oil in place, stb} \\ G & = \text{Initial volume of gas cap, scf} \\ m & = \text{Ratio of initial volume of gas cap to volume of oil initial in place, rb/rb} \\ S_{wi} & = \text{Initial water saturation} \\ S_{oi} & = \text{Initial oil saturation} \\ B_{oi} & = \text{Initial oil formation volume factor, rb/stb} \\ B_{gi} & = \text{Initial gas formation volume factor, rb/scf} \end{aligned} \]
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