Sealed and hydrostatically lockable retrievable mwd landing system

Abstract

A sealed mule shoe assembly for use in directional drilling, comprising an outer mule shoe and an inner housing for containing a directional measurement tool which is slidably insertable in the outer mule shoe. The mule shoe assembly advantageously has half-moon mating surfaces which advantageously allow use circumferential seals to thereby prevent ingress of abrasive materials into the landing area between the outer mule shoe and the inner housing, thereby greatly prolonging the life of the mule shoe assembly. Such seals further make use of hydrostatic forces downhole which cause locking landed engagement of the inner tool within the outer mule shoe. Cup seals or a check valve are used to allow escape of fluid when the inner tool is inserted within the outer mule shoe, and similarly prevent ingress of abrasive fluids and drill cuttings into the area of landed engagement.

1 . A mule shoe assembly for use in directional drilling of wells, which mule shoe assembly is adapted to lockingly secure a directional measurement tool therein and further resists ingress into an interior of said mule shoe assembly of abrasive substances such as drilling fines, comprising:
 (i) an outer mule shoe member, having:
 (a) a longitudinal bore, a portion of which is cylindrical; 
 (b) a half member located within said cylindrical portion of said longitudinal bore, fixedly secured to a circumferential portion of said longitudinal bore about at least a portion of a circumference thereof; 
   (ii) a cylindrical housing for containing a direction-indicating tool, said housing adapted for insertion in said longitudinal bore of said outer mule shoe member, comprising:
 (a) a half member situated on an circumferential portion of an outer surface of said housing, extending longitudinally along said portion of said outer surface and protruding radially outwardly about said portion of said outer surface of said housing, adapted to matingly engage said half member located within said mule shoe member so that, when matingly engaged, angular rotation of the housing within the mule shoe member is prevented; and 
   (iii) a pair of circumferential seals, respectively situated proximate mutually opposite ends of said mule shoe member and said housing when said housing is inserted in said longitudinal bore, adapted to reduce ingress of drilling fines and fluids containing drilling fines into an interstitial area bounded by said pair of circumferential seals.   
     
     
         2 . A mule shoe assembly as claimed in  claim 1 , wherein each of said half members comprise half-moon members. 
     
     
         3 . A mule shoe assembly as claimed in  claim 1  or  2 , further comprising:
 a check valve situated in said outer mule shoe member, adapted to allow egress of fluid from within said mule shoe member upon insertion of said housing in said longitudinal bore, and configured to prevent ingress of fluid into said longitudinal bore. 
 
     
     
         4 . A mule shoe assembly as claimed in  claim 1 , wherein said circumferential seals comprise a pair of ‘o’ ring seals, and said half members respectively each comprise half-moon members. 
     
     
         5 . A mule shoe assembly as claimed in  claim 4 , wherein said check valve is a ball-type check valve situated in said outer mule shoe between said pair of ‘o’ ring seals, having a ball resiliently biased over an aperture in said outer mule shoe member and which said aperture extends therethrough to said longitudinal bore. 
     
     
         6 . A mule shoe assembly as claimed in  claim 5 , wherein said check valve is positioned directly above said aperture, and said aperture in said outer mule shoe member further extends through said half-moon member situated therein into said longitudinal bore. 
     
     
         7 . A mule shoe assembly as claimed in claim in  claim 3 , further comprising a pair of check valves situated in said outer mule shoe member intermediate said pair of ‘o’ ring seals, adapted to allow egress of fluid from within said mule shoe member upon insertion of said housing in said longitudinal bore, and configured to prevent ingress of fluid into said longitudinal bore. 
     
     
         8 . A mule shoe assembly as claimed in  claim 1 , wherein said at least one of said circumferential seals comprises a “flapper” type seal adapted to allow egress of fluid from within said mule shoe member upon insertion of said housing in said longitudinal bore, and to prevent ingress of fluid into said longitudinal bore. 
     
     
         9 . A mule shoe assembly as claimed in  claim 8 , wherein said at least one “flapper” type seal is located in said mule shoe assembly at an end thereof most closely proximate an extremity of said housing when said housing is inserted within said longitudinal bore.