SPWLA Glossary

The undesirable process of creating a distortion in the gas-liquid or oil-water isosaturation surfaces at the well bore by the withdrawal of oil at an excessive rate. Production of oil produces pressure gradients in all directions from the depth of withdrawal. Therefore. there is a tendency to draw fluids from above and below (as well as laterally) to the level of withdrawal. That tendency is counterbalanced by the tendency of gas to stay above oil because of its lighter density and water to stay below oil because of its heavier density. Thus, when the pressure gradient required to bring oil to the well bore exceeds the pressure gradient to the gas or water-bearing levels, coning will occur and gas will be drawn down and water will be lifted up toward the withdrawal level.