Subterranean Screen with Varying Resistance to Flow

摘要

A screen section is made with variable resistance to flow in the screen material to balance the flow along the screen length. In one variation different discrete zones have screens configured for different percentages of open area while all have the same particle filtration capability. In another variation discrete portions have differing amounts of overlapping screen portions so as to balance flow without affecting the particle size screened. The cross-sectional shape of a wire wrap underlayment for the screen is made closer to trapezoidal to decrease the angle of opening for the incoming flow paths toward the base pipe. In this manner flow resistance is reduced and flow is increased due to reduced turbulence.