Schwartz's 1969 correlation for optimal gravel size depends on uniformity of the formation and velocity through which component?

Schwartz's 1969 correlation for optimal gravel size depends on uniformity of the formation and velocity through which component?

• A. The borehole
• B. The screen
• C. The formation
• D. The casing

Answer: (B)

In gravel-pack design, choosing the right gravel size hinges on how sand is transported and bridged near the screen. Schwartz’s 1969 correlation links the optimal gravel size to two factors that directly control this behavior: how uniform the formation sand is and the velocity of the fluid moving through the screen. The uniformity of the formation grain sizes determines how easily grains can be sorted, bridged, or carried, which affects how the gravel must pack to stop fines. The velocity through the screen sets the forces that push or pull grains toward and through the screen openings; higher flow through the screen increases the risk of fines migration or gravel washout, so the gravel size must be adjusted accordingly. Therefore, the screen—specifically the flow through the screen—controls the balance Schwartz identified, with formation uniformity modulating how the gravel interacts with the formation.

In gravel-pack design, choosing the right gravel size hinges on how sand is transported and bridged near the screen. Schwartz’s 1969 correlation links the optimal gravel size to two factors that directly control this behavior: how uniform the formation sand is and the velocity of the fluid moving through the screen. The uniformity of the formation grain sizes determines how easily grains can be sorted, bridged, or carried, which affects how the gravel must pack to stop fines. The velocity through the screen sets the forces that push or pull grains toward and through the screen openings; higher flow through the screen increases the risk of fines migration or gravel washout, so the gravel size must be adjusted accordingly. Therefore, the screen—specifically the flow through the screen—controls the balance Schwartz identified, with formation uniformity modulating how the gravel interacts with the formation.