The flow apertures of a perforated mandrel are temporarily sealed by plugs which are made of a sacrificial material, for example, zinc, aluminum and magnesium. The sacrificial plugs prevent dirty completion fluid from passing through and in and out of the screen as it is run into the hole, thereby protecting the screen from plugging. During the time the screen mandrel is temporarily sealed by the sacrificial plugs, cleaning fluid is circulated through a work string and is returned through the annulus between the screen and the open well bore for removing filter cake, drilling debris and lost circulation material. After the annulus has been cleaned, the annulus is filled with an acid solution or caustic solution, which dissolves the sacrificial plugs. In an alternative embodiment, each sealing plug has a body portion and a stub portion which project into the mandrel bore. The sealing plug body portion is intersected by a vent pocket which is sealed by the stub portion. The screen mandrel flow apertures are opened by mechanically shearing the stub portion of each sealing plug with a milling tool run on a concentric tubing string.
展开▼
