A well is sometimes deliberately completed in order to retard or avoid what effect?

• A. Sand production
• B. Formation damage
• C. Water breakthrough
• D. Coning effects

Answer: (D)

Coning effects show up when production creates a strong drawdown that pulls the water (or gas) from the surrounding reservoir toward the wellbore, forming a cone of inflow. This happens most when the well taps near the edge of the water or gas cap and fluids under pressure move preferentially into the well as the oil is produced. By deliberately shaping the completion, you limit direct communication with the unwanted fluid zones and control the pressure drop near the well. Techniques like isolating the water zone with a packer, selecting perforation intervals away from the water contact, or using inflow-control methods help slow or prevent the cone from forming, so oil production stays higher for longer and water or gas breakthrough is delayed.