Well Completion Methods

Abstract

Methods for improving the bonding of a cement sheath to a tubular body in a subterranean well involve anchoring elements mounted on the outside surface of the tubular body—in the annular space between the tubular body and the borehole wall. The cement contains an expansive agent that causes the cement to expand after it sets. The anchoring elements are mounted such that an angle exists between the elements and the tubular-body surface, thereby providing resistance to cement sheath movement away from the tubular-body surface.

1 . An apparatus for improving bonding of a cement sheath in an annulus of a subterranean well having a borehole wall, comprising:
 (i) a tubular body; and   (ii) at least one anchoring element, the element comprising a stem and a hook;   wherein the stem protrudes from the outer surface of the tubular body by at least 2 mm, but does not protrude farther than about 0.5 times the width of the annulus; and the hook is attached to a portion of the stem that is distal to the tubular body, such that the hook and the stem are not collinear.   
     
     
         2 . The apparatus of  claim 1 , wherein the tubular body is casing, liner or coiled tubing or a combination thereof. 
     
     
         3 . The apparatus of  claim 1 , wherein the stem has a circular cross-sectional diameter of a rectilinear cross-sectional length, and the length or the diameter does not exceed 20 mm. 
     
     
         4 . The apparatus of  claim 1 , further comprising at least one weld that attaches the apparatus to the tubular body. 
     
     
         5 . The apparatus of  claim 1 , further comprising at least one clamp that attaches the apparatus to the tubular body. 
     
     
         6 . The apparatus of  claim 1 , wherein the apparatus is fabricated from steel, titanium, aluminum, a composite material, a plastic or a combination thereof. 
     
     
         7 . The apparatus of  claim 1 , wherein the apparatus is fabricated from steel, and the cross sectional thickness of the stem is between 1 mm and 20 mm. 
     
     
         8 . A method for improving bonding of a cement sheath in an annulus of a subterranean well having a borehole wall, comprising:
 (i) installing in the wellbore at least one apparatus comprising a tubular body and at least one anchoring element, the element comprising a stem and a hook, wherein the stem protrudes from the outer surface of the tubular body by at least 2 mm, but does not protrude farther than about 0.5 times the width of the annulus; and the hook is attached to a portion of the stem that is distal to the tubular body, such that the hook and the stem are not collinear;   (ii) preparing a cement slurry comprising at least one expansive agent;   (iii) placing the cement slurry in an annular space between the outer surface of the tubular body and the borehole wall, such that the slurry flows along the outer surface of the tubular body and surrounds the anchoring elements; and   (iv) allowing the cement slurry to set and expand.   
     
     
         9 . The method of  claim 8 , wherein the tubular body is casing, liner or coiled tubing or a combination thereof. 
     
     
         10 . The method of  claim 8 , wherein the stem protrudes from the tubular body surface by at least 2 mm, but does not protrude farther than 0.5 times the width of the annulus. 
     
     
         11 . The method of  claim 8 , wherein the anchoring elements are arranged in a helicoidal pattern around the outer surface of the tubular body. 
     
     
         12 . The method of  claim 8 , wherein the stem has a circular cross-sectional diameter or a rectilinear cross-sectional length, and the length or the diameter does not exceed 20 mm. 
     
     
         13 . The method of  claim 8 , wherein the stem comprises a sheet-like material, and an angle q between the larger dimension of the stem and the direction of slurry flow along the outer surface of the tubular body is less than about ±45° or greater than ±135°. 
     
     
         14 . The method of  claim 8 , wherein the cement comprises Portland cement, calcium aluminate cement, fly ash, blast furnace slag, lime/silica blends, cement kiln dust, magnesium oxychloride, chemically bonded phosphate ceramics, zeolites, geopolymers, and combinations thereof. 
     
     
         15 . The method of  claim 8 , wherein the expansive agent comprises sodium chloride, calcium sulfate, aluminum sulfate, iron (II) sulfate, magnesium oxide, calcium oxide, aluminum metal, zinc metal, magnesium metal, swellable particles in emulsified oils or combinations thereof.