Which of the following statement(s) is/are CORRECT about polymer flooding?
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- Viscous fingering in the reservoir decreases.
- Viscosity of the displaced fluid increases.
- Mobility of the displacing fluid increases.
- Mobility ratio decreases.
The Correct Option is A, D
Solution and Explanation
Polymer flooding involves adding high molecular weight polymers to injection water to increase its viscosity. The objective is to improve the mobility ratio and sweep efficiency. Step 2: Viscous fingering.
When the displacing fluid (water) has much lower viscosity than the displaced fluid (oil), viscous fingering occurs, reducing sweep efficiency. By adding polymer, water viscosity increases, thereby reducing fingering. So statement (A) is correct. Step 3: Viscosity of displaced fluid.
The displaced fluid is crude oil. Polymer does not affect oil viscosity. Hence, statement (B) is incorrect. Step 4: Mobility of displacing fluid.
Mobility is defined as \[ \lambda = \frac{k}{\mu}, \] where \(k\) = permeability, \(\mu\) = viscosity. Since polymer increases viscosity of injected water, mobility of displacing fluid decreases (not increases). Hence, statement (C) is incorrect. Step 5: Mobility ratio.
Mobility ratio is \[ M = \frac{\lambda_{\text{displacing}}}{\lambda_{\text{displaced}}}. \] If \(\mu_{\text{water}}\) increases, \(\lambda_{\text{water}}\) decreases, and hence \(M\) decreases. A smaller mobility ratio improves sweep efficiency. Hence, statement (D) is correct. Final Answer: \[ \boxed{\text{Statements (A) and (D) are correct.}} \]
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