Gravel packing is used in wells under which condition?

• A. When the rock is igneous
• B. When the formation is unconsolidated, to prevent sand or fine material from entering the well, and to enhance water flow by stabilizing the borehole
• C. To increase water yield
• D. When the formation is consolidated

Answer: (B)

Gravel packing is used when the formation is unconsolidated or poorly consolidated, where sand and fines would otherwise flow into the well. The gravel pack around a screen acts as a permeable filter that stops the formation solids while still allowing water to pass, so sand production is prevented and the borehole remains stable. This stabilization helps maintain consistent flow and protects the pump from sanding and screen damage. In consolidated formations, the rock holds together well and sand production isn’t the same concern, so a gravel pack isn’t typically needed. The primary purpose is preventing solids entry and keeping production stable, not increasing the formation’s inherent water yield.