RU2181830C1 - Method of well swabbing - Google Patents

Abstract

FIELD: oil and oil-gas industries; applicable in completion of wells in process of their operation. SUBSTANCE: method consists in reduction of pressure of killing fluid onto producing formation by periodic withdrawal of fluid from flow string and its lifting to surface, at least, by two swabs. Motion of each swab in tubing string located parallel to flow string is effected in synchronism or asynchronism in one or in opposite directions. In this case, formed in fluid on bottom hole are pair pulses of depression with regulated interval of their production: from zero during simultaneous lifting of swabs in two tubing strings, up to half of swabbing cycle period in motion of swabs in two tubing strings in opposite direction. EFFECT: production of smooth, regulated depression on producing formation. 2 cl, 5 dwg

Description

 The invention relates to the field of oil and gas industry and can be used in the development and in the process of operating wells.

 A known method of inducing oil flow by lowering the liquid level in the well by compression. According to this method, lowering the liquid level in the well is achieved by displacing it into the tubing string with high pressure gas supplied to the annulus.

 The disadvantages of the method: high labor and energy costs for implementation; the displacement of liquid by compressed gas leads to mixing of the kill fluid with the formation products, which necessitates its regeneration or complete replacement. In addition, the air compression method is classified as forbidden in terms of safety and environmental impact [see Safety regulations in the oil industry. - M .: Nedra, 1993].

 There is also known a method of swabbing a well, in which a depression on the formation and, accordingly, drainage of the well is created as a result of lifting a column of fluid into the tubing string using a swab moved therein. Technologically, the method is a process of periodic descent of the piston element (swab) in the tubing string under the dynamic level of the killing fluid and its subsequent rise to the wellhead [see E.P. Soldatov, I.I. Kleschenko, V.N. Dudkin. Swabbing is a resource-saving technology. NTZH "Construction of oil and gas wells on land and at sea." 6-7. 1997.S. 27-29]. Swabbing a well in this way is carried out without a packer or with a packer.

 The disadvantages of swabbing a well without a packer are the very small depression on the formation (0.6-0.8 MPa) and the need to produce a significant number of (8-12) swab cycles, which is comparable in time to the duration of well development using the compression method.

 When swabbing a well with a packer, on the contrary, high (7-8 MPa), very sharp depressions on the formation are created, which negatively affects the state of the bottomhole zone of the well when the inflow from weakly cemented reservoirs, oil-saturated formations, etc. In all cases, the swab performance increases with increasing frequency and stability of the swab descent.

 In the present invention, the task is to create a method of swabbing a well, providing an increase in the intensity of the operations of lowering and raising the swab and the implementation of the swab mode, which best meets the conditions for creating a smooth, regulated depression on the reservoir.

 The problem is achieved by the fact that the proposed method of swabbing the well, which consists in lowering the pressure of the killing fluid on the reservoir by periodically taking fluid from the production casing of the well and raising it to the surface with at least two swabs, each of which is moved in the tubing string, placed parallel in the production casing, produce synchronously or asynchronously, in one or in opposite directions.

And also the fact that:
- in a well separated by a packer unit installed below the static fluid level, the fluid is taken from the production string by at least one of the swabs moved in the tubing string in the sub-packer region, with fluid supply to the super-packer region, and fluid withdrawal from the overpacker region and feeding it to the surface is carried out by another swab moving in the tubing string located in the overpacker region;
- the selection of fluid from the overpacker region and its supply to the surface is carried out continuously (by pump, airlift, etc.).

The invention is further illustrated by a description of its essence, a statement of its advantages and the accompanying drawings, which show:
in FIG. 1 is a diagram of the swabbing of a well by two swabs moved in opposite directions;
in FIG. 2 is a diagram of a well swabbing by two swabs moving in opposite directions, with the installation of a packer unit;
figure 3 - scheme of swabbing wells with asynchronous movement of swabs in one direction;
figure 4 - scheme of swabbing wells with simultaneous movement of swabs in one direction;
5 is a diagram of a two-stage swabbing of a well.

 The invention consists in the following. In a liquid medium, at the bottom of the well, not single depression pulses with a long time interval between them are created, as is the case when swab is lifted in one tubing string, but at least paired depression pulses to the formation with an adjustable interval of their creation: from zero (while lifting swabs in two tubing strings) to half the period of the swab cycle (when moving swabs in two tubing strings in opposite directions). As a result, it is possible to regulate the depression on the formation and increase the stability of the fluid flow caused from the productive formation, and therefore, intensify the process of cleaning the formation filtration zone from mechanical particles.

 The implementation of the proposed method is associated with appropriate equipment of the well, different from equipping the well with one tubing string and one swab.

 When swabbing a well with two swabs without installing a packer, the following equipment scheme takes place (see Figs. 1, 3 and 4). Fountain fittings 2 and a lubricator 3 are planted on production casing 1, which provide the possibility of receiving fluid from two columns of tubing 4 and 5 and the passage of traction elements 6 and 7, to which are connected swabs 8 and 9 with weighting weights or devices 10 and 11 The tubing columns also have inlet valves and restriction couplings (not shown). A logging cable, cable or steel tape is used as a traction element, and, accordingly, a logging hoist, a tractor hoist winch, mobile units with winches based on a car are used as a drive element.

 When swabbing the well according to the scheme of figure 2, the packer assembly 12, and in some cases a removable check valve 13, enters the borehole layout of the underground equipment.

 When stepped swab well (see figure 3) install the packer 14 together with the tubing string, lowered into the production string to a predetermined depth under the dynamic level. In the case of the descent of the tubing 5 from the surface, a drain device 15 is made in it.

 The method is implemented as follows.

 When swabbing the well with two swabs with moving them in opposite directions when lifting swab 8 in the tubing string 4 (see Fig. 1), fluid is taken from the well, which causes the influx of fluids from the reservoir. When approaching the wellhead of the swab 8, the kill fluid is displaced into the flow line of the collection system connected to the tubing string 4. Simultaneously with the swab 8 of the swab 9 in the tubing string 5, they are lowered from the wellhead to the lowest position, after which the swab cycle of the swab 9 in the string The tubing 5 is carried out similarly to swabbing the swab 8 in the tubing string 4. The synchronization of the lifting and lowering of the swabs 8 and 9 is ensured by the equivalence of their masses, including loads 10, 11, and the movement parameters of the traction elements 6 and 7. The multidirectionality of their movement is It is used using two hoists of the same type, one unit with two winches or a more powerful installation with opposite winding of traction elements on the drum.

 The option of swabbing the well with two swabs 8 and 9 in the case of installing a packer unit (see figure 2) does not differ from the described swab technology without installing it. The peculiarity lies in the fact that the packer unit 12 installed in the production casing 1 isolates the cavities of the tubing strings 4 and 5 from the annulus and when lifting the swab 8 or 9, fluid is sampled only from the corresponding tubing strings from the sub-packer region of the well. As a result, the number of swab lift cycles required to displace fluid from tubing strings to a predetermined level is reduced.

 Swabbing of the well with unidirectional movement of swabs in both tubing strings, but with an outstripping of one of them (see Fig. 3), creates a greater dynamic impact on the formation. When working on this option, both swabs are lowered to the bottom of the well to the same level. Then begin the rise of one of the swabs, for example 8 (see figure 3). When moving it to a certain height (approximately 10-20 m at a swab lift speed of 1-3 m / s), swab 9 is lifted. After displacing the fluid raised by swabs 8 and 9 into the collection system, the cycle of work is repeated in the same order or same with the priority movement of the swab 9. Traction elements are driven by independent drives or by one drive with the corresponding adjustment of the lifting mode.

 The greater efficiency of the "buildup" of fluid in the bottom-hole zone is achieved by coordinating the time interval between the "starts" of the swabs with the frequency of the natural oscillations of the raised fluid. If necessary, the highest level of depression on the formation, both when swabbing a well without a packer and when installing a packer, can be achieved with unidirectional synchronous lifting of swabs 8 and 9 in at least two tubing columns (see Fig. 4). Obviously, the operations of lifting and lowering two swabs simultaneously do not cause difficulties and are carried out by one lifting installation.

 The scheme shown in figure 5, provides the ability to swab a deep well without increasing the duration of the cycle of lifting and lowering the swabs. The gap between the tubing and production casing 1 is separated by the height of the packer 14. One of the swabs, for example 9, is immersed in the tubing string under the dynamic level of the kill fluid, the fluid is lifted into the over-pack area with its supply through the end of the tubing or drain device 15. From the over-pack area liquid swab 8 along the tubing string 4 or in another way (pump, airlift, etc.) is raised to the surface.

The method of swabbing a well with two swabs, each of which is moved in its own tubing string, has several advantages compared to swabbing a single swab, namely:
- reduced time to call fluid flow and well development;
- the intensity of the descent-ascent operations and, accordingly, the productivity of the selection of the kill fluid are increased significantly
- expanding the possibility of choosing a more effective mode of selection of fluid killing and control the magnitude and duration of the depression on the reservoir;
- reduced energy costs for lifting swabs, since the principle of balancing ballast loads on the drive is used;
- ceteris paribus, drive power and strength characteristics of traction elements can be reduced.

Claims (2)

 1. The method of swabbing the well, which consists in lowering the pressure of the killing fluid on the reservoir by periodically taking fluid from the production string and raising it to the surface with at least two swabs, each of which moving in a string of tubing placed in parallel in the production the column is produced synchronously or asynchronously, in one or in opposite directions, while in the liquid medium, paired depression pulses are created at the bottom of the well with an adjustable interval of their creation maneuver: from zero, with the simultaneous rise of swabs in two columns of tubing, up to half the period of the swab cycle, when moving swabs in two columns of tubing in opposite directions.  2. The method according to p. 1, in which in the well, divided in depth by a packer unit installed below the static liquid level, the selection of liquid from the production string is carried out by at least one of the swabs moved in the tubing string in the sub-packer area and the selection of liquid from the overpacker region and its supply to the surface is carried out by another swab moving in the tubing string located in the overpacker region.

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