Question:

In Water-Alternating-Gas (WAG) injection, the purpose of the injection is to \(\underline{I}\) \(\underline{\hspace{2cm}}\) the "relative permeability" of gas and to \(\underline{II}\) \(\underline{\hspace{2cm}}\) the "mobility" of the gas.

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WAG injection controls gas mobility and permeability by alternating water and gas injections, improving oil recovery efficiency.
Updated On: Jan 9, 2026
  • I = reduce, II = enhance
  • I = reduce, II = reduce
  • I = enhance, II = reduce
  • I = enhance, II = enhance
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The Correct Option is B

Solution and Explanation

Water-Alternating-Gas (WAG) injection is a widely used method in Enhanced Oil Recovery (EOR). This technique alternates between injecting water and gas into the reservoir. The main objective of this process is to improve the efficiency of oil displacement from the reservoir. The two key concepts in WAG injection are the relative permeability of the gas and the mobility of the gas. 1. Relative Permeability of Gas: The relative permeability of gas refers to the ease with which gas can flow through the porous medium of the reservoir. In WAG injection, water is injected first, and it displaces oil while reducing the relative permeability of gas. This means that the gas flow is restricted when water is injected, helping to control the movement of gas and ensuring it does not bypass the oil, which could lead to inefficiency in oil recovery. Therefore, the purpose of the injection is to reduce the relative permeability of gas. This addresses option I = reduce. 2. Mobility of the Gas: Gas mobility refers to how easily gas moves through the reservoir's pore network. In WAG injection, water is used to control the mobility of gas. The water injection decreases the gas's mobility by increasing the capillary pressure and reducing the likelihood of gas channeling through the reservoir. This helps maintain a more uniform displacement of oil and prevents the gas from escaping too quickly. Hence, the goal is to reduce the mobility of the gas, which aligns with option II = reduce. Thus, the correct answer is option (B) I = reduce, II = reduce.
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