RU2110670C1 - Method and device for melting blind hydrateparaffin plug - Google Patents

Abstract

FIELD: oil and gas production industry. SUBSTANCE: this is aimed at removing blind hydrateparaffin plugs in oil and gas wells with high efficiency and in short periods. According to method, heater is lowered into annular space between casing string and pump-compressor pipes. Heater melts out hole in plug, and working agent is pumped through aforesaid hole in plug until complete removal of plug. Method is realized by means of device for removing hydrateparaffin plug in annular space containing obstacles of stepped configuration. Device has tubular body with heating element. Body is curved so that in device conditionally inscribed in ellipsoid of rotation at least three points of body most distant from ellipsoid axis of rotation are found on surface of ellipsoid of rotation. In ellipsoid of rotation, radius of largest cross-section perpendicular to its axis of rotation is larger than dimensions of obstacles of stepped configuration. Lower end of device is located away from axis of rotation at distance which is less than difference between radius of largest cross-section of ellipsoid and thickness of obstacle. EFFECT: higher efficiency. 2 cl, 4 dwg

Description

 The invention relates to the oil and gas industry and can be used to eliminate deaf hydrate-paraffin plugs in oil and gas wells.

 There is a method of dewaxing wells by pumping hot oil to completely eliminate paraffin-tar deposits with subsequent replacement by gaseous medium to a dynamic level of the well [1].

 This method has limited applicability due to the impossibility of pumping a thawing agent into wells with deaf hydrate-paraffin plugs.

 A more universal known method of thermal destruction of the hydrate plug in the well, including the descent of a hollow column, equipped with a hydro-monitor tip and a check valve, into the tubing string, heating the flushing fluid, pumping it into the hollow column and discharging the fracture products [2].

 This method requires a pipe lift and a hollow column equipped with a hydraulic monitor tip and a check valve. Work is carried out only through the tubing string, before which the equipment is lifted from the tubing string, for example, a sucker rod pump, which significantly increases the amount of work, the timing and cost of their implementation.

 Great difficulties with thawing deaf plugs in tubing accommodating various equipment (rods, cable, etc.). This method does not allow to eliminate deaf hydrate-paraffin plugs in the annulus, without first removing the plug from the tubing string, and then the equipment.

 A major drawback of this method is that it is not known the location in the annulus of a significant length of deaf hydrate-paraffin plug, especially if there is a column of liquid above the plug, although in this case, the tubing string is heated for a long time, for example, over 1000-1200 m by pumping a hot agent through a hollow column.

 Thus, the main disadvantages of this method are the low efficiency and the long duration of the elimination of deaf hydratoparaffin plugs.

 To eliminate plugs, a well-known electric heater is known, comprising a housing with a heating element and centralizers placed unevenly on the spiral [3].

 This device is designed to thaw hydrate-paraffin plugs in tubing. For thawing the annulus it is unsuitable due to its obstruction in the annulus. The disadvantage of this device is its surface, made in the form of protrusions, complicated by centralizers and a heating element.

 Known borehole electrode heater, taken as a prototype, containing a housing made in the form of a glass and acting as a first electrode, and a second electrode placed in the housing [4].

 However, this device is intended for heating operations within tubing. Its use for thawing a deaf hydrate-paraffin plug in the annulus is impossible. It either sticks into the sleeve of the tubing, or clamps in the area of the tubing with the casing, which prevents its further descent and thawing of deaf hydrate-paraffin plugs.

 The objective of the invention is to increase the efficiency and accelerate the process of eliminating deaf hydrate-paraffin plugs in the annulus.

 The problem is achieved in that in the known method of thawing a deaf hydrate-paraffin tube, including lowering the heater into the well and thawing the tube, the heater is lowered into the annulus between the casing and tubing, they burn a hole in the tube and the working agent is pumped through this hole until the plug is completely eliminated.

 The method is as follows.

 When the fact of the formation of a deaf hydrate-paraffin plug is established, a lubricator is installed, for example, on an eccentric faceplate, through which the hole in the faceplate is lowered into the annulus between the casing and the tubing using the armored cable of the heating device. After this device abuts against the cork, electric power is supplied to it and they begin to burn a hole in the deaf hydrate-paraffin cork. After passing the cork and the appearance of circulation, the thawing agent is pumped through the formed hole in the cork until it is completely eliminated.

 The method is implemented using a device for thawing a deaf hydrate-paraffin tube in the annulus containing step-shaped obstacles, including a tubular body with a heating element, the body being made curved so that at least three points of the body are conventionally inscribed in the rotation ellipsoid, farthest from the axis of rotation of the ellipsoid, are located on the surface of the ellipsoid of revolution, in which the radius of the largest section perpendicular to its axis of rotation exceeds the size of the mortar obstacles, and the lower end of the device is located from the axis of rotation at a distance less than the difference between the radius of the largest cross section of the ellipsoid and the thickness of the obstacle. The heating element can be of any physicochemical nature (electrode, electromagnetic, electric, etc.).

 In FIG. 1 shows a heating device, curved in shape, inscribed in an ellipsoid of revolution, in which the axis of rotation of the ellipsoid passes through a straight line connecting the ends of the device, side view; in FIG. 2 - the same in which the axis of rotation of the ellipsoid does not coincide with the straight line connecting the ends of the device; in FIG. 3 - the same, a top view when the bends are located in two planes; in FIG. 4 is the same top view when the bends are located in more than two planes, for example, the device is curved in the form of a spiral.

The heating device (Fig. 1) comprises a tubular housing 1 with upper 2 and lower 3 ends and a heating element 4 located inside the housing. The upper end 2 of the device is mounted through the head 5 with a terminal connection and descends on the armored cable 6 into the annular space between the casing 7 and the tubing 8 with obstacles 9 of a step shape, for example, a coupling. The device is conventionally inscribed in an ellipsoid of revolution 10 with an axis of rotation 11. In FIG. 1 axis of rotation 11 coincides with the line connecting the upper 2 and lower 3 ends of the device. In FIG. 2, the line 12 connecting the ends of the device does not coincide with the axis of rotation of the housing 11. The housing 1 is made so that at least three of its points, for example 13-15, farthest from the axis of rotation 11, lie on the surface of the ellipsoid, in contact with the walls of the casing 7 and tubing 8, the lower end 3 of the device is located axis 11 of rotation at a distance less than the difference between the radius of the maximum section R _m perpendicular to the axis of rotation of the ellipsoid and the thickness h of the stepped obstacle 9 (couplings or pipes of large diameter).

 The proposed device shown in FIG. 1 and 3, it has proven itself for thawing the annulus, in particular, in which the body is made with very gentle bends with a length not less than the length of a stepped obstacle, for example, a coupling.

The device shown in FIG. 2 and 4, is made in the form of spiral bends of a corkscrew type with an end face 3 that is located from the device’s rotation axis 11 at a distance less than the difference between the radius of the maximum cross section R _m perpendicular to the rotation axis of the ellipsoid and the thickness h of the stepped obstacle 9, in particular, in our case, when the axis of rotation 11 does not coincide with the line 12 connecting the ends of the device. When the step (distance) between the spiral bends exceeding the length of the obstacles 9, this device has a minimum passage opening comparable with its thickness at the maximum possible radius R _{m of} spiral bends.

 Such a device provides patency in the annulus filled with deaf hydrate-paraffin plugs. Bends made on the device’s casing prevent the device from getting pinched in the adjoining zone of tubing and casing and allow the lower end of the casing to be placed so that it is removed from the walls of these pipes by a distance exceeding the size of the step obstacles so that the device does not touch during the descent and would not stick into them, but slip. There is no need to lift the pumps (SHGN, ESP).

 Example. A heating device with a regular straight pipe-like shape was lowered into well No. 1567 of the Kogalym field, equipped with a sucker rod pump. After passing 110 m of the vertical section, it stuck into the sleeve or into the contact angle of the tubing and casing. Numerous attempts to continue the dive have failed. The thawing of the deaf hydrate-paraffin plug was discontinued.

 After giving the heating device the proposed curved shape, the work to eliminate the deaf hydrate-paraffin plug was continued.

 The heater easily passed in the annulus through a deaf hydrate-paraffin plug at a speed of 16-21 m / h. In order to more completely remove all residues of the plug into the annulus, a hot agent was pumped through the hole. At the end of the heating operations, circulation was restored, and this well returned to its previous mode of operation. At the same time, there was no need for laborious overhaul of the well. To increase the service life of the device and reduce the amount of abrasion, it is desirable to make the sliding sections of the device within the three main bends of the sliding of extra strong materials.

 A positive point is that this method of thawing can be implemented in the process of oil production and before overhauling wells that have deaf hydratoparaffin plugs in the tubes and annulus. Thawing the hole in the annulus also allows killing the well for repair work, which greatly facilitates the work and increases labor safety, and pumping a hot killing solution through the hole in the annulus reduces the time for overhaul of wells associated with lifting equipment stuck with a hydrate-paraffin plug.

Claims (2)

 1. A method of thawing a deaf hydrate-paraffin plug in oil and gas wells, including lowering a heater into a well and thawing a hydratoparaffin plug, characterized in that the heater is lowered into the space between the casing of the column and tubing, the hole in the plug is burned through the heater through an opening in the working agent is pumped to the cork until the cork is completely eliminated.  2. A device for thawing a deaf hydrate-paraffin plug in the annular space containing step-shaped obstacles, including a tubular body with a heating element, characterized in that the body is made curved so that at least three points of the body are conventionally inscribed in the rotation ellipsoid, farthest from the axis of rotation of the ellipsoid, are on the surface of the ellipsoid of revolution, in which the radius of the largest section perpendicular to its axis of rotation exceeds the size of the stepped obstacles and the lower end of the device is located from the axis of rotation at a distance less than the difference between the radius of the largest cross section of the ellipsoid and the thickness of the obstacle.

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