1. n. [Enhanced Oil Recovery]

The particular arrangement of production and injection wells. The injection pattern for an individual field or part of a field is based on the location of existing wells, reservoir size and shape, cost of new wells and the recovery increase associated with various injection patterns. The flood pattern can be altered during the life of a field to change the direction of flow in a reservoir with the intent of contacting unswept oil. It is common to reduce the pattern size by infill drilling, which improves oil recovery by increasing reservoir continuity between injectors and producers. Common injection patterns are direct line drive, staggered line drive, two-spot, three-spot, four-spot, five-spot, seven-spot and nine-spot. Normally, the two-spot and three-spot patterns are used for pilot testing purposes. The patterns are called normal or regular when they include only one production well per pattern. Patterns are described as inverted when they include only one injection well per pattern.

See: enhanced oil recovery,  injection well,  off-pattern well,  waterflooding