Water cut

What is water cut?

Most oil wells produce water along with oil. Water cut expresses how much of the produced liquid is water:

Water cut (%) = water produced ÷ (water produced + oil produced) × 100

A well producing 20 barrels of oil and 80 barrels of water a day has a water cut of 80 percent and an oil cut of 20 percent. The related water-oil ratio compares water directly to oil: in the same example, four barrels of water per barrel of oil.

Why water cut rises

• Waterflooding. As injected water reaches producing wells, water cut climbs; see waterflooding.
• Aquifer influx. Natural water from an underlying or adjacent aquifer moves toward the well as oil is produced.
• Coning and channeling. Water can be drawn up toward the well or travel along high-permeability paths.
• Fracturing fluid. In newly fractured wells, early water cut reflects flowback of the injected fluid.

Why water cut matters

Every barrel of water must be lifted, separated from the oil, treated and disposed of, often by injection into a saltwater disposal well. As water cut rises, those costs grow relative to the oil produced, raising lease operating expense per barrel. Eventually a well reaches its economic limit because of water handling costs rather than a lack of oil. Water cut also affects emulsion formation, scaling and corrosion.

In newly completed shale wells, how quickly water cut falls after fracturing is one indicator of how effectively the well has cleaned up.

Frequently asked questions