Hydraulic Design

Hydraulic Design

A well screen should be designed to minimize friction loss across its surface. This principle is similar to observing water flow through a garden hose - longer hoses deliver less water due to increased friction against the walls, resulting in pressure loss. The same applies to well screens, where pressure drop depends on water volume, screen diameter, and length.

Different screen types offer varying percentages of open area: slotted pipe and pipe base types provide 1-5% open area; louvered and punched types offer 3-15%; while vertical rodded wire wrapped types deliver 12-30% open area. These percentages directly relate to slot size, with finer slots (like 0.010 inch) having lower open areas than larger slots (such as 0.100 inch). The optimal design approach always selects the largest possible slot size that still prevents sand intrusion, thereby maximizing open area.

Three primary factors determine total open area: the percentage of open area, screen length (which is directly proportional to total open area), and screen diameter (where larger diameters increase open area). Screen length faces several constraints including cost considerations, formation thickness, and the need to keep the screen top submerged below anticipated water levels during pumping.

While screen diameter significantly affects open area, its selection typically involves multiple considerations beyond just hydraulic performance. These include pump equipment requirements and other practical installation factors. To effectively minimize friction loss, designers should: maximize the percentage of open area within other design constraints, use the longest feasible screen length, and select the largest appropriate diameter.

The design process offers flexibility to compensate in one area when compromising in another. For instance, using extended lengths of lower-percentage screens (like slotted pipe) can achieve equivalent total open area to shorter, higher-percentage screens (like wire-wrapped types). This balanced approach ensures efficient hydraulic performance while meeting all practical installation requirements and constraints.