Patent Publication Number: US-6659183-B2

Title: Cuttings injection target plate

Description:
This application claims priority of the provisional application Serial No. 60/270,743, filed Feb. 22, 2001. 
    
    
     TECHNICAL FIELD 
     This invention relates in general to disposing of drill cuttings that are generated in the process of drilling oil and gas wells. This is accomplished by injection into the annulus around the well casing. 
     BACKGROUND OF THE INVENTION 
     When drilling a subsea well, cuttings are generated. The cuttings are small pieces of earth formation formed by the drill bit. The cuttings are circulated along with drilling fluid up a riser to the drilling platform, where they are separated. The drilling fluid is circulated back into the well. 
     In the past, it was a common practice to dump the cuttings into the sea. Particularly with oil based drilling fluids, this practice is no longer acceptable. The cuttings would be contaminated with oil and result in pollution. One disposal technique is to inject the cuttings back into a well. The well could be the well that is being drilled or an adjacent well. The cuttings are ground and pumped in a slurry down an annulus between strings of casing and into a porous earth formation. Subsequently, the well receiving the injected cuttings is completed into a producing well. 
     Injection systems normally pump the cuttings slurry through a port in a wellhead housing at the upper end of the well. The wellhead housing contains at least one concentric tubular member, such as a casing hanger and a string of casing extending into the well. An annular clearance is located between the tubular member and the housing, the annular clearance communicating with the casing annulus. The stream of cuttings strikes the wall of the casing hanger or casing and flows down the annular clearance into the casing annulus. 
     The stream of cuttings is abrasive because of the cuttings. Consequently, the stream tends to erode the tubular member where it impinges. 
     SUMMARY OF THE INVENTION 
     The invention comprises a cuttings injection target or deflection plate. The deflection plate is mounted in proximity to the outlet of the injection port for contact by the stream as it discharges from the outlet for protecting the inner tubular member from contact by the stream. Preferably, the deflection plate is on an inner end of a protection sleeve that is mounted in the injection port extending through the wall of a wellhead housing. Exit holes in the sleeve upstream of the deflection plate allow injected cuttings discharge to the annulus. Drill cuttings impact upon the deflection plate and deflect to exit through the holes. This reduces the wear by erosion on the casing hanger by deflecting the impact and allowing the cuttings to escape through the holes. The deflection plate preferably has a wear resistant surface, such as a hardfacing. 
     The sleeve can be periodically removed and checked during cuttings injection operations. Where annulus space is limited, provisions can be made to enlarge the inner end of the passage through the wall of the wellhead housing and shorten the sleeve so that the sleeve outlet holes are inside the enlarged outlet end of the injection passage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical cross-sectional view of a wellhead with an injection system constructed in accordance with this invention. 
     FIG. 2 is an enlarged cross-sectional view of a portion of the wellhead of FIG.  1 . 
     FIG. 3 is a cross-sectional view of an alternate embodiment of an injection system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIGS. 1-2, a tubular inner member such as a casing hanger  15  is landed in a wellhead housing  13 . Wellhead housing  13  is located at the upper end of a well. A string of conductor pipe  12  extends from wellhead housing  13  into the well to a first depth. A first string of casing  14  is supported in wellhead housing  13  and extends into the well to a second depth. A preferred application of the current invention includes use on a land or surface well, but can be extended to other applications. Wellhead housing  13  is illustrated in the drawings to be of a type employed on the surface, such as on a platform, however, it could also be a subsea wellhead housing of various types. In a subsea environment, typically there are two wellhead housings, with an inner or high pressure wellhead housing landing in an outer or low pressure wellhead housing, such as shown in U.S. Pat. No. 5,662,169. 
     A passage or port  11  is located in a side wall of a wellhead housing  13 . In this embodiment, port  11  extends radially through the sidewall of wellhead housing  13  relative to a longitudinal axis of wellhead housing  13 . However, port  11  could also be inclined relative to the axis of wellhead hosing  13 . Port  11  has an inlet on the exterior of wellhead housing  13  and an outlet in the interior of wellhead housing  13 . 
     An inner tubular member has an upper portion or casing hanger  15  concentrically located in wellhead housing  13 . The inner tubular member also includes a string of casing  16  secured to casing hanger  15  and extending to a third depth in the well. An annulus  23  is located between casing strings  14  and  16 . Port  11  communicates with an annular clearance between casing hanger  15  and wellhead housing  13 , the annular clearance being the upper portion of annulus  23 . 
     A sleeve or tube  17  is secured inside port  11 . Sleeve  17  has a closed inner end or deflection plate  19  that has a wear resistant surface. The wear resistant surface may be hardfacing or coatings of various types. Preferably deflection plate  19  is flat and normal to a longitudinal axis of sleeve  17 . One or more outlet apertures  21  are formed in the cylindrical sidewall of sleeve  17  near deflection plate  19 . Deflection plate  19  is shown integrally formed with sleeve  17 , although it could be separately formed and attached. 
     Sleeve  17  has an enlarged outer diameter portion containing a set of external threads  25 . Port  11  has a mating set of threads  27 . A tapered portion  28  is formed between the larger diameter outer portion and the smaller diameter inner portion. Tapered portion  28  engages a tapered portion in port  11 , forming a stop shoulder. Tapered portion  28  also may form a metal-to-metal seal, or elastomeric seals may be employed to seal the exterior of sleeve  17  in port  11 . Sleeve  17  has an outer portion that preferably protrudes past an exterior flat recess  30  on wellhead housing  13 . The outer portion has a plurality of flats in its interior, defining a polygonal recess  29 . Recess  29  is configured to receive a tool for unscrewing and tightening threads  25  in threads  27 . 
     A flange connector  31  connected to an injection line  35  bolts to recess  30  on wellhead housing  13 . A seal  33  seals flange connector  31  to recess  30  around port  11 . Injection line  35  is in communication with the interior of sleeve  17  via polygonal recess  29 . In the embodiment of FIG. 2 the length of tube  17  is greater than the thickness of the side wall of wellhead housing  13 . Deflection plate  19  is positioned farther inward that the inner diameter of wellhead housing  13 . In the embodiment of FIG. 2, deflection plate  19  is shown located in annulus  23  closer to casing hanger  15  than to the inner diameter of wellhead housing  13  and not touching casing hanger  15 , although this precise positioning is not critical. 
     In operation, drill cuttings will be ground and pumped in a slurry through injection line  35 . The slurry flows straight into sleeve  17  and impinges upon deflection plate  19 . The stream of cuttings then flows through apertures  21  down annulus  23 . The drill cuttings flow into the earth formation of the well for disposal. Sleeve  17  can be readily removed and replaced by removing flange connector  31  and inserting a tool into polygonal recess  29  to unscrew sleeve  17 . This could be performed in a subsea environment with a remote operated vehicle. 
     The embodiment of FIG. 3 illustrates a system where the annulus  23 ′ between the casing hanger  15 ′ and wellhead housing  13 ′ may be too narrow to allow tube  17 ′ to protrude inward. Port  11 ′ has a tapered outlet portion  37  on its inner end that converges outward in a radial inward direction. Deflection plate  19 ′ is located approximately at the inner diameter of wellhead housing  13 ′, rather than protruding significantly into annulus  23 ′. Apertures  21 ′ are recessed within tapered outlet portion  25  to allow drill cuttings to exit through hole  21 ′ and flow from tapered outlet portion  25  into annulus  23 ′. Tube  17 ′ has the same structure as tube  17  of the first embodiment, but is shorter in length. Outlet portion  37  could also be an enlarged cylindrical portion rather than a tapered portion. 
     The invention has significant advantages. The deflection plate avoids erosive contact of the cuttings steam on an inner tubular member within the wellhead. This avoids having to hardface portions of the inner tubular member. The plate can be hardfaced for extended life. The plate can be readily removed and replaced. 
     While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention. For example, although the port is positioned adjacent a casing hanger, it could alternately be located adjacent another inner tubular member, such as casing or portions of an inner wellhead housing in the event the port extends through an outer wellhead housing. Also, while the sleeve is shown secured by threads in the port, it could alternately be hydraulically stabbed into the port as shown in U.S. Pat. No. 5,662,169.