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[[file:production-problems_fig1.png|thumb|300px|{{figure number|1}}Wave coning.]]

[[file:production-problems_fig1.png|thumb|300px|{{figure number|1}}Wave coning.]]

When water underlies an oil column or a gas cap exists above, the phenomenon of ''coning'' can occur when the oil is produced. Muskat<ref name=pt09r18>Muskat, M., 1949, Physical principles of oil production: New York, McGraw-Hill, chap. 5.</ref> noted that coning is most likely to occur when a wellbore only penetrates a portion of the formation or when the perforations are placed only in the oil zone ([[:file:production-problems_fig1.png|Figure 1]]). The horizontal and vertical pressure gradients created by the production of oil causes a deformation of the [http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=oil-water%20contact oil-water] (or oil-gas) contact. When the vertical pressure gradient exceeds the hydrostatic gradient down to the water zone, the water is pulled toward the well, resulting in a cone-shaped distortion of the oil-water contact. If a well is produced too hard, water breakthrough can occur. The same basic principles apply to the downward coning of gas from a gas cap.

When water underlies an oil column or a gas cap exists above, the phenomenon of ''coning'' can occur when the oil is produced. Muskat<ref name=pt09r18>Muskat, M., 1949, Physical principles of oil production: New York, McGraw-Hill, chap. 5.</ref> noted that coning is most likely to occur when a wellbore only penetrates a portion of the formation or when the perforations are placed only in the oil zone ([[:file:production-problems_fig1.png|Figure 1]]). The horizontal and vertical pressure gradients created by the production of oil causes a [[deformation]] of the [http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=oil-water%20contact oil-water] (or oil-gas) contact. When the vertical pressure gradient exceeds the hydrostatic gradient down to the water zone, the water is pulled toward the well, resulting in a cone-shaped distortion of the oil-water contact. If a well is produced too hard, water breakthrough can occur. The same basic principles apply to the downward coning of gas from a gas cap.

To minimize the production of unwanted gas or water, flow rates from the well must be maintained so that the pressure gradients around the wellbore will not cone in the unwanted fluids. Flow performance calculations or reservoir models can be used to help predict the optimum production rates. However, because of pressure depletion within the oil zone, a pressure differential will eventually develop between the water and/or gas zones, such that encroachment will eventually occur. After this point, the well may soon become uneconomical due to the production of these unwanted fluids.

To minimize the production of unwanted gas or water, flow rates from the well must be maintained so that the pressure gradients around the wellbore will not cone in the unwanted fluids. Flow performance calculations or reservoir models can be used to help predict the optimum production rates. However, because of pressure depletion within the oil zone, a pressure differential will eventually develop between the water and/or gas zones, such that encroachment will eventually occur. After this point, the well may soon become uneconomical due to the production of these unwanted fluids.