WELL CASING ASSEMBLY WITH EROSION PROTECTION FOR INNER SCREEN

摘要

Well casing assembly (20) for use in oil and gas wells, and especially deviated or horizontal wells, has an inner pipe member (22) with threaded ends (22') which permit a number of casing assemblies to be joined in a string. The inner pipe (22) has a serie of perforations (40) along a segment (42) of its length which are covered by an elongated screen member (64) which prevents the passage of sand particles. A concentric outer protective cover member (24) is devoid of perforations (50) in regions which are radially opposite the inner screen (64) to prevent damage to the screen. One or more perforated segments (52, 52') of the outer member (24) are axially spaced from the screen member (64) so that inward flow from a formation will have its energy and velocity reduced before it reaches the screen, thereby minimizing erosion of the screen surface. If desired, perforated flow control devices such as annular rings (82) can be located between the inner pipe (22) and outer member (24) at the ends of the screen segment to allow a more uniform flow to the screen, and thus further reduce erosion.