RU2060349C1 - Threaded joint of pipes for production strings of up to 168 mm diameter - Google Patents

Abstract

FIELD: casing string. SUBSTANCE: joint includes casing section 1 and coupling 2 joint through cone threaded section 3. Cylindrical boring 5 with length exceeding 200 mm is originated on section 4 of coupling 2. EFFECT: high efficiency. 2 dwg

Description

 The invention relates to the field of drilling equipment, namely to the design of threaded pipe joints.

Known threaded pipe connection, including, interacting with a conical threaded surface of the pipe end coupling with a cylindrical bore on the inner surface at the ends [1]
The disadvantage of the analogue is that the pipe and the sleeve are not equally stressed and therefore the strength of the threaded joint to break is lower than the potential.

The closest in technical essence to the claimed invention is a threaded pipe connection selected as a prototype, including a coupling interacting with a conical threaded surface of the pipe end with a cylindrical bore on the inner surface at the ends, and the length of the cylindrical bore of the coupling is determined based on the condition of observing mathematical equilibrium [2]
The disadvantage of the prototype is that in the case of loading the column with tensile axial force exceeding the tensile strength of the threaded joint to be strained, the end of the pipe exits the coupling. In conditions of a curved or deviated well, when the end of the pipe exits the sleeve, a radial displacement of them relative to each other inevitably occurs. This leads, firstly, to the jamming of tubing and other underground equipment, and secondly, to the non-passage of the instrument below the site of violation. The exit of the pipe end from the coupling makes repair work difficult, and the radial displacement leads to a complete loss of the well.

 The purpose of the invention to improve the health of wells by preventing radial displacement of the end of the pipe relative to the coupling in the production casing.

 In the oil fields of Western Siberia, more than 3,000 wells have failed due to the violation of production casing, which is formed from pipes with a diameter of 139.7; 146; 168 mm.

 To achieve the goal in a threaded connection of pipes with a diameter of up to 168 mm, containing a coupling interacting with a conical threaded surface of the pipe end with a cylindrical bore on the inner surface at the ends, the length of the cylindrical bore of the coupling is selected from the condition L> 200 mm. The exit of the pipe from the engagement leads to leaks in the production string. To eliminate the leakage, a cement mortar is used, which is pumped into the gap between the column and the coupling, where a cement cup is formed. The experience of repairing leaking wells shows that if the cement cup is less than 200 mm, then the tightness of the cement ring cannot be achieved. Therefore, L the length of the cylindrical bore of the coupling must be at least 200 mm.

 In FIG. 1 shows a threaded connection in a mated state; in FIG. 2 the same, after stragging and moving the end of the pipe along the axis of the well.

 The threaded connection of pipes with a diameter of up to 168 mm includes a pipe section 1 and a sleeve 2, mated along a conical threaded section 3. A cylindrical bore 5 is made inside section 4 of the sleeve 2.

 The assembly of the proposed threaded connection is carried out in the usual manner, namely, when the pipe string (tubing, casing) is lowered into the well, the end of the pipe is lowered into the sleeve and the threaded connection is screwed using a mechanical wrench.

 During the operation of the well, when axial tensile loads occur, exceeding the strength of the threaded joint for straining, the conical surfaces of the pipe and couplings leave the mating state. However, the ends of the pipe do not exit the coupling, since the length of the cylindrical bore is greater than the displacement of the end of the pipe. This prevents radial displacement of the pipe and sleeve relative to each other.

 To determine the length of the cylindrical bore, studies are conducted in wells in which a threaded connection is broken. Using geophysical methods, such as a locator couplings, determine the maximum displacement of the end of the pipe relative to the coupling after stragging.

 PRI me R. At the Samotlor field on Bush 126, several cases of threaded connections of production casing joints at a depth of 400-500 m were discovered. Since all these wells are directional, there was a radial displacement of the pipe ends relative to the couplings (this was determined using lead printing). Wells could not be repaired and were liquidated. Studies by the coupling locator revealed that in the indicated wells the ends of the pipes emerged from the couplings and moved 200-260 mm along the axis of the well. Therefore, if the cylindrical bores of the couplings were more than 200 mm in length, then there were no radial displacements of the ends of the pipes relative to the couplings in the wells of the bush 126, repair work could be carried out in the wells.

 The part of the coupling constituting the cylindrical bore can be manufactured separately in the form of pipes of appropriate sizes and then welded to the coupling.

 The proposed threaded connection of pipes with a diameter of up to 168 mm inclusive will find application in the fields of Western Siberia, where more than 3,000 wells have been abandoned or are awaiting liquidation due to disruption of the production string.

Claims (1)

 A threaded connection of production casing pipes with a diameter of up to 168 mm, including a coupling interacting with a tapered threaded surface of the pipe end with a cylindrical bore on the inner surface at the ends, characterized in that the length of the cylindrical bore of the coupling is selected to be greater than 200 mm.

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