Patent GB-1491283-A (GB)
Title: Well apparatus
IPC: E21B33/043
Filed: 1975-05-30
Abstract: 1491283 Wells &c. CAMERON IRON WORKS INC 30 May 1975 [19 June 1974 13 Nov 1974] 23642/75 Heading E1F A well seal assembly, for sealing the annulus between a casing hanger 28 and the bore of a casing head 27, includes a body adapted to be landed in the well and which carries an elastomeric sealing ring located between two shoulders, the sealing ring seating on a first cylindrical surface when in its relaxed state and seating on a second cylindrical surface larger in diameter than the first cylindrical surface when in its expanded state in which it seals against the second cylindrical surface and the casing head bore, the sealing ring being moved from the first to the second cylindrical surface by relative movement between the shoulders and the second cylindrical surface. When the sealing ring is in sealing engagement with the second cylindrical surface and casing head bore, the shoulders are sufficiently spaced from the sealing ring so that the sealing engagement of the sealing ring is pressure energised in response to pressure differentials across the sealing ring.  In a first embodiment (Fig. 2) the seal assembly body 33 has a first cylindrical surface 50 and a second cylindrical surface 51  connected by a conical surface. The sealing ring 36 is located between a shoulder formed at the lower end of a first sleeve 37 which is threaded onto the body 33 and a shoulder formed at the upper end of a second sleeve 52. Initially the sleeves 37 and 52 are secured to the body 33 by shear pins 48 and 53 respectively such that the sealing ring 36 is seated on the first cylindrical surface 50.  The seal assembly is lowered into the well by a running tool 21 having spring loaded catches 38 which support the seal assembly and lugs 42 engaging recesses 43 in the sleeve 37 to transmit rotary motion to the seal assambly. When the seal assembly has been lowered to the position shown in Fig. 2, the running tool 21 is rotated so that threads 44 on the seal assembly are screwed into threads 45 on the casing hanger 28. During engagement of the threads 44, 45 seal rings 35 seal the body 33 to the casing hanger 28, and a conical surface 49 on the casing hanger 28 depresses the spring loaded catches 38 so that the running tool 21 may be lifted from the well at a later stage. After the threads 44, 45 are fully engaged and shoulders 46, 47 are in contact further rotation of the running tool 21 shears pins 48 so that sleeve 37 is screwed downwardly on body 33 and forces the sealing ring 36 onto the larger cylindrical surface 51 so that the ring 36 is expanded into sealing engagement with casing head bore. Downward movement of sleeve 37 also forces sleeve 52 downwardly, shearing pins 53. In a second embodiment (Fig. 8) further rotation of therunning tool moves an expansion sleeve- 75 downwardly behind the sealing ring 73 to expand it into sealing engagement with the well head bore. The expansion sleeve 75 is initially fixed to the body of the seal assembly by shear pins 78 and an outer sleeve 90 is initially fixed to the expansion sleeve 75 by a split ring 95. During downward movement of the expansion ring 75 balls 98 force the split ring 95 outwardly to free the outer sleeve 90 so that a shoulder 91 formed on the lower end of the outer sleeve 90 rests on the sealing ring 73.