Patent GB-850148-A (GB)
Title: Improvements relating to the drilling of off-shore oil and gas wells
IPC: E21B33/037
Filed: 1959-01-26
Abstract: 850,148. Boring earth &c. BATAAFSCHE PETROLEUM MAATSCHAPPIJ N. V., DE. Jan. 26, 1959 [Jan. 27, 1958], No. 2744/59. Class 85. In off-shore drilling, a well-head housing 1 and caisson assembly 49 is lowered from a drilling platform 65 until the housing is on the sea-bed, the top of the caisson being still above water level, a drive pipe 80 is driven through the bottom of the housing in fluid-tight manner, and the housing is pumped out to enable the top of the drive pipe to be cut off within the housing. The housing 1 is about ten feet in diameter and twenty feet in height, and the pipe 80 is driven through a shoe 5 having sets 31, 32 of packing and, if desired, passages 29 for injecting a plastic for sealing after the pipe 80 has been fully driven. The shoe 5 has jetting holes 30 in the sides and in a plastic bottom 33 which is disrupted when the pipe 80 is driven. The housing 1 is connected at 7, 8, 9 with service conduits 75, 74, 73; and 74 or 73 may be connected with a pump for jetting the housing into the sea-bed. The pipe 80 is guided into the shoe 5 by a removable taper guide. The drilling platform 65 is preferably supported from a submersible barge 68 having a throughway 64 for the housing and caisson. The housing is floated beneath lifting tackle which is connected to eyes 11, and is then positioned to receive caisson sections 49 which are attached as the assembly is lowered. The housing 1 has a cylindrical access tube 2 secured at its top end in eccentric relation to the axis of the shoe 5 so that the drive pipe 80 and, subsequently, the drill pipe string may pass through the tube 2, to one side thereof, and at the same time, men may pass through the tube into the housing 1, ladder rungs 13a being provided for this purpose. The caisson sections 49 are divided by longitudinal partitions 50 to separate the personnel passage from the drill string passage. The bottom of the tube 2 is closable by a hinged door 4, which may be in two parts, and is bolted fluid-tightly to the tube 2. A man-hole opening 25 is closed by a bolted cover. The first section 49 of the caisson has bolted to its lower end a landing fitting 39 which has a flared guide 44 for guiding it on to the tube 2 which latter is provided with an upwardly directed removable tripod-like guide for guiding the fitting 39 to the tube 2. A seal 41 inflatable at 43 excludes water from the caisson until the flanges 46, 3 are bolted together, the bolt holes being aligned by the engagement of a V-projection and a V-recess 45. When the pipe 80 has been cut off, the top of the shoe 5 and pipe 80 are sealed by welding on a cover plate 14, and the annulus between the drive pipe 80 and the well casing 83 is covered by a welded plate 16. A casing head 17 is installed after the casing 83 has been run into the well and cemented, and any desired Christmas tree arrangement may be fitted. The cover 4 may have a hole for the passage of a tubing extension from a swabbing valve 23 to permit swabbing when the door is closed. A relief valve 12 is provided on the housing 1. When the well is completed, the caisson assembly together with the landing fitting 39 are withdrawn upwardly, after the tripod-like guide has been re-attached to the tube 2 to secure a marker buoy.