Improvements in or relating to devices for filling well casings

摘要

844,106. Wells. HALLIBURTON OIL WELL CEMENTING CO. April 29, 1958 [May 10, 1957], No. 13636/58. Class 85. A device for permitting drilling fluid to fill casing as it is lowered into a well comprises a housing 18 connected in the casing, a valve body 38 fired within the housing by shearable means 28 so that passages 24b in the body are in communication with ports 24 in the housing, and a valve means 44 operated by differential pressure to permit or prevent the fluid entering the casing through a passage 40. The valve means comprises a piston 48 urged towards a seat 46 by a spring 56. The device is incorporated in the casing above a float shoe, and both the valve in the shoe and the valve means are closed during the initial lowering of the casing. When the device reaches a level where the hydro-static pressure is 80 p.s.i. the valve means opens and fluid flows through the passage 40 into the casing, some of the fluid flowing into the casing below the device through passage 42. When the pressure outside the casing is 60 p.s.i. greater than the pressure within the casing the valve means closes, and when the pressure differential is 80 p.s.i. the valve means again opens. Cement is then supplied to the casing, a plug being placed on top of the cement in order to displace cement from the casing out through the float shoe. As the plug reaches the body 38 the pressure of the displacing liquid is increased to shear pins 28 so that the body is moved downwardly until snap ring 32 engages a groove 34 in the housing and the ports 24 are closed. After the cement has set the valve body and valve member are drilled out. If during lowering of the casing an obstruction is moved by pumping fluid down through the casing, out of the shoe, and up to the surface outside the casing, the valve means remains closed. If the casing is floated for the last part of its way into the well, a ball is landed on a ring 66 on the body and sufficient pressure is applied above the ball to shear the pins 28 and close the ports 24. An increase in pressure on the ball fractures the ring so that the ball is received in a cavity 42 in the body to permit cement being pumped down the casing and forced out through the valve in the shoe.