GB728197A - Method of and apparatus for sealing a casing in a bore hole - Google Patents

Abstract

728,197. Wells. ZANDMER, S. M. July 14, 1953, No. 19591/53. Class 85. A method of sealing a casing in a borehole traversing a porous producing stratum comprises the steps of lowering a casing into the borehole, moving duct-forming devices laterally from the casing into engagement with the stratum, forcing fluid sealing material downwardly through the casing and then upwardly between the casing and the wall of the bore hole and around the duct-forming devices, and after the sealing material has set, opening a passage through the duct forming devices to provide communication between the interior of the casing and the porous stratum. As shown, a casing 12 is positioned in a bore hole so that an annular space exists for filling by a sealing material 13. Opposite oil or gas-producing strata 14 the casing 12 is provided with ductforming devices 15. Each device comprises a bushing 16 screwed into a hole in the casing 12, the bushing being provided with a closure 18 formed with an orifice for a spring-pressed valve 20. Within the bushing is a sleeve 24 in two parts 26, 27 press-fitted together, the part 27 having a shoulder 28 by means of which in association with shear pins 45 the sleeve is prevented from being moved outwardly while the pins are unbroken. The part 26 is provided with a gasket 32 of resilient material. The interior of the sleeve is filled with a perforated disc 46 and with material 44 which is readily dissolvable in acid or chemical used for treating the strata 14. The disc 46, the closure 18, and the part 27 of the sleeve 24 are made of metal or alloy also readily dissolvable in the acid or chemical. The casing 12 with the duct-forming devices attached, is lowered into the bore hole and fluid under pressure is pumped past the ball valve. When the pressure is sufficient the shear pins 45 break and the sleeve 24 is pressed against the wall of the bore. By the provision of balls 34 resiliently pressed against a ramp 33, backward movement of the sleeve is prevented. Sealing material under greater pressure is then supplied to the casing, the pressure eventually forcing downwardly a closure 41 to uncover ports 42 through which the sealing material passes to the annular space around the casing 12. When the sealing material has set, strata-treating acid or chemical for example hydrochloric acid is pumped into the casing, the acid dissolving the closure 18, sleeve part 27, disc 46 and material 44, to open a passage to the stratum. A modified form of duct-forming device is described in which the sleeve is in one piece wholly dissolvable to the acid or chemical.