Down hole drilling assembly with independent jet pump

摘要

A Down Hole Drilling Assembly (DHDA) that induces artificial lift to remove the drilling fluid from a well bore using a jet pump attached to a casing string. The DHDA includes a drill string that passes through the jet pump assembly. The power fluid is separated from the drilling fluid until after it has passed through the nozzle of the jet pump. The jet pump assembly is joined to a concentric casing string. The jet pump also contains a bladder element that expands to redirect the flow of the drilling fluid from the inner annulus into the jet pump assembly. The jet pump assembly lifts the drilling fluid, lowering the fluid level within a well bore to a point where the hydrostatic pressure near the bottom of the well is lower than the pore pressure of the formation being drilled thereby creating under balanced conditions.