RU2576538C1 - Method of production string section sealing - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: while implementing the method losses of sealing are identified, a shutter is run in at the tubing string and fixed place of sealing loss, to this end mineral and polymer compound is used with properties of cold welding. The shutter is represented by a pipe or a group of in-series pipes with outer diameter less than inner diameter of the production string with total length exceeding the length of damaged section per at least 20%. Grooves with depths of at least 2 mm and width of at least 20 cm are lathed at the pipe beginning and ending; the above grooves are filled in with a layer of material having properties of cold welding, at that material shall protrude from the grooves per 2-10 mm, moreover this material is glued with glue layer to the groove bottom. Before running in of the shutter its mounting site at inner surface of the string is cleaned with scraper, length of the area for cleaning is selected on the basis of the shutter length with reserve of 5-10% above and below the mounting site. Upon running in of the shutter with applied material long sections in the area of groves are spread outward thus activating cold welding and ensuring fixture of the shutter to the production string.

EFFECT: improved efficiency of sealing, reduced water cut, increased oil flow rate.

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Description

The invention relates to the oil industry and may find application in eliminating leaks in the walls of the production casing of wells by means of installation in these sections of overlappers.

A known method of isolating the zones of complications in the well with a profile cutter, including profiling its constituent pipes, making internal threads on the coupling ends and external threads on nipple ends, or calibrating the profile ends with chamfering for welding, tightly screwing sections of the profile pipes together or welding, lowering the shutter into the necessary pre-extended interval of the well, radial expansion of the profile pipes by creating hydraulic pressure in them, flaring to a tight tight pressing them to the walls of the well. The profiling of its constituent pipes is carried out from cylindrical pipes, the inner diameter of which is 5-8% greater than the internal diameter of the wellbore, the installation interval is expanded to a diameter at which the full expansion of the profile pipes occurs while they are pressed against the walls of the well, before lowering into the well the end of the overlapper is equipped with a flare mill with a mill for breaking the shoe and an expanding flare, and the lower end has an easily drilled shoe, and the expanding flare has a diameter of still on duty position, which allows the inner diameter is expanded in the most Perekryvatel bottlenecks to a diameter surpassing the diameter of the borehole at least 1.5% (RF Patent 2418151, cl. E21V29 / 10, publ. 10.05.2011).

The closest in technical essence to the proposed method is a method of installing a shutoff of profile and cylindrical pipes in the well, including the implementation of internal tapered threads on the sleeve ends of the pipes and external - on the nipple, connecting the pipes to each other with the application of sealant on the threads, lowering the shutter to the previously required extended interval of the borehole, radial expansion of profile pipes by creating hydraulic pressure in them, calibration of profile pipes and expansion of cylindrical pipes ub before pressing their walls to the walls of the well. Before threading, the nipple and sleeve ends of the pipes are formed to form a taper corresponding to the taper of the thread, and after cutting the threads on the outer surfaces of the sleeve and inner surfaces of the threaded pipe ends, grooves are made to form annular protrusions at the ends of the surfaces opposite the threaded ones, and before connecting the thread pipes coated with a mineral-polymer composition having the properties of "cold welding" (RF patent No. 2265115, class Е21В29 / 10, Е21В33 / 10, publ. 11/27/2005 - prototype).

A common disadvantage of the known methods is the lack of sealing efficiency in relation to casing strings, a slight decrease in water cut in production wells and, as a result, low oil production rates.

The invention solves the problem of increasing the efficiency of sealing casing or production strings, reducing water cut in produced products and increasing oil production rates of producing wells.

The problem is solved in that in a method of sealing a section of a production casing, including determining the location of a leak in the production casing, lowering into the well on the string of pipes of the overlap and fixing it at the place of failure, using a mineral-polymer composition with cold welding properties, expanding the overlap according to the invention is lowered into the well a shutter, which is a pipe or a group of series-connected pipes of any section with an external diameter smaller than the inner the diameter of the production casing, with a total length exceeding the leaking section by at least 20%, at the beginning and at the end of the overlap pipe, grooves with a depth of at least 2 mm and a width of at least 20 cm are pre-machined into which a layer of material is placed with the properties of cold welding, protruding from the grooves of 2-10 mm, and this material is fixed with a layer of glue to the bottom of the groove, before the shutter is lowered, the place of its installation on the inner surface of the production casing pipes is cleaned with a downhole scraper, the length of the cleaning zone they are selected based on the length of the overlap with a margin of 5-10% above and below the installation location of the overlap, after lowering the overlap with the applied material, these sections are expanded in the groove region, thereby activating cold welding and securing the overlap to the production casing.

SUMMARY OF THE INVENTION

The rate of oil recovery from reservoirs depends on the oil production rate of the wells. However, leaky production cores, especially in old wells, where the metal of the pipes is worn out by the corrosive effects of an aggressive environment (for example, high salinity of formation water), can lead to annular flows, water flow from aquifers and, accordingly, very high water cuts of production wells. A high proportion of the water in the flow in the wellbore ultimately reduces the flow rate of the well oil. Existing technical solutions are not effective enough to seal the areas of violations of production casing. The invention solves the problem of increasing the efficiency of sealing production casing with violations, reducing the water content of the produced products and increasing the oil production rate of the producing wells. The problem is solved as follows.

In FIG. 1 is a sectional view of a production casing with a portion of a leak and an isolator for isolation. Designations: 1 - production string, 2 - aquifer, 3 - leakage location of the production string 1, 4 - cement ring, 5 - shutoff, 6 - mineral-polymer composition with cold welding properties, L - violation length 3, A - length to be cleaned along the inner surface of the production casing 1, S is the length of the overlap, Z is the depth of the groove, X is the width of the groove, H is the distance that the material 6 for cold welding protrudes from the grooves.

The method is implemented as follows.

An oil well operating an oil reservoir is watered. Studies reveal that the cause of flooding is leakage in the production (casing) string 1 in the zone of the aquifer 2 (Fig. 1). Determine the place 3 of the leak and its length L. The cement ring 4 may be broken, which leads to the penetration of water from the aquifer 2 into the production casing 1 through violation 3.

The shutter 5 for sealing the zone of violation 3 is selected from the condition of a smaller diameter than the diameter of the production string 1. The shutter 5 is a pipe or a group of series-connected pipes of any shape in cross section. Pipes are connected in series if the length of violation 3 of production casing 1 exceeds the standard pipe length. The total length S of the overlap 5 must exceed the length L of the untight portion 3 by at least 20%.

At the beginning and at the end of the pipe of the overlap 5, grooves with a depth Z of at least 2 mm and a width of X of at least 20 cm are pre-machined. If the overlap 5 consists of several pipes connected in series, then the grooves are made at the beginning of the first pipe and at the end of the last. A layer of mineral-polymer composition 6 with cold welding properties is placed in the grooves, protruding from them at a distance of H = 2-10 mm. This composition 6 with the properties of cold welding is fixed with a layer of glue to the bottom of the groove. The glue allows you to prevent the loss of material 6 from the grooves during the descent of the overlap 5 into the well.

To apply cold welding technology, it is necessary to clean at least the surface of the weld points of paraffins, rust, etc. Therefore, a scraper for casing or production casing is initially lowered into the well. Above and below the leaky section 3 of the production casing 1, the inner surface of the pipes 1 is cleaned of the deposits with a scraper. The length A of the pipe cleaning zone 1 is selected based on the length S of the overlap 5 with a margin of 5-10% in length, i.e. A = (1.05 ... 1.10) · S. The reserve length of the cleaning zone compensates for possible inaccuracy when installing the overlap 5.

According to studies, the indicated dimensions of the overlap 5, grooves with material 6 for cold welding, the surface for cleaning pipes, as well as the volumes of the mineral-polymer composition itself (i.e., sizes S, Z, X, A), allow for the existing sizes and masses of pipes used in wells, to conduct sufficiently reliable and tight fastening of the shutoff to the production casing. The smaller sizes of the volumes of the composition for cold welding in some cases does not provide the required fastening. The distance H is defined as the most optimal from the point of view of the passage of the overlap into the production casing and subsequent flaring. When H exceeds 10 mm, the likelihood of damage to the applied composition for cold welding when lowering the overlap 5 increases.

After lowering the overlap 5 with the applied material 6, it is expanded, which activates cold welding in the groove area, providing a tight fastener of the overlap 5 to the production casing 1.

The result of the implementation of this method is to increase the sealing efficiency of casing or production casing with violations, reduce the water content of the produced products and increase the oil production rate of the producing wells.

Examples of specific performance of the method

Example 1. A vertical production well operating an oil reservoir at a depth of 1600 m with a current reservoir pressure of 13 MPa has an oil production rate of 0.2 t / day and a water cut of 97.5% at a bottomhole pressure of 10 MPa. Studies of measuring the density of produced water have established that the cause of watering is the leakage of the production string 1 in the zone of the aquifer 2 (Fig. 1), located at a depth of 1300 m. The diameter of the production string is 146 mm and the wall thickness is 7 mm.

Place 3 of the leakage is determined, its length is L = 10 m. The cement ring 4 is broken, which leads to the penetration of water from the aquifer 2 into the production casing 1 through violation 3.

To install a profile overlap in the casing with a diameter of 146 mm and a wall thickness of 7 mm, a multi-beam profile overlap with six beams and a nominal pipe diameter of 109 mm (i.e., diameter before flaring) is selected. The wall thickness of the profile pipe is 5 mm. After flaring, the outer diameter of the pipe is 133 m with an inner diameter of the casing of 132 mm. Thus, 1 mm of the difference provides a tight pressing of the overlap to the walls of the column after expansion. The overlap 5 is selected with a length of S = 12 m.

At the beginning and at the end of the overlap pipe, grooves with a depth of Z = 2 mm and a width of X = 20 cm are pre-machined. A layer of mineral-polymer composition 6 with cold welding properties is placed in the grooves, for example, Triboplast-9 (in accordance with TU No. 2257-004 -25669359-98), protruding from them to a distance of H = 5 mm. This composition 6 with the properties of cold welding is fixed with a layer of glue (for example, based on epoxy resins) to the bottom of the groove.

Before lowering the shutoff 5 with composition 6, a casing scraper is initially lowered into the well, for example, the hydromechanical type SGM-1M. The inner surface of the pipes 1 is cleaned with a scraper from deposits at the installation site of the overlap 5. The length of the pipe cleaning zone 1 is A = 1.10 · S = 1.10 · 12 = 13.2 m.

After lowering the overlap 5 with the applied material 6, it is expanded and accordingly cold welding is activated.

Example 2. Perform as example 1. Two violations were found in the production casing: 23 m long and located at a different depth, 4 m. A layer of mineral-polymer composition 6 with cold welding properties for 4 m, the violations are applied with a protrusion from the grooves at a distance H = 2 mm, for 23 m disturbances - by 10 mm. Overlappers are lowered sequentially. For 23 m disturbances, several overlap 5 are connected.

As a result of repair work, after the well was put into operation at a similar bottomhole pressure of 10 MPa, the oil production rate was 5.1 tons / day and the water cut was 43.6%. According to the prototype, ceteris paribus, the oil production rate was 2.8 tons / day and the water cut of 68.9%. The increase in oil production by the proposed method is 2.8 tons / day, the decrease in water cut is 25.3%.

The proposed method allows to increase the efficiency of sealing production casing in which there are irregularities, to reduce the water content of the produced products and to increase the oil production rate of producing wells through the use of cold-welded shutoffs and optimization of the repair work technology.

The application of the proposed method will allow to solve the problem of increasing the efficiency of sealing casing or production casing with violations, reducing water cut of produced products and increasing oil production rates of producing wells.

Claims (1)

    A method of sealing a section of a production casing, including determining the location of a leak in the production casing, lowering the shutoff pipe into the well on the column and securing it at the site of violation, using a mineral-polymer composition with cold welding properties, expanding the shutoff, characterized in that the shutter is introduced into the well, consisting of a pipe or a group of series-connected pipes of any section with an external diameter smaller than the internal diameter columns with a total length exceeding the leaky section by at least 20%, at the beginning and at the end of the overlap pipe, grooves with a depth of at least 2 mm and a width of at least 20 cm are pre-machined into which a layer of material with properties is placed cold welding, protruding from the grooves of 2-10 mm, and this material is fixed with a layer of glue to the bottom of the groove, before lowering the shutter, the place of its installation on the inner surface of the pipes of the production casing is cleaned with a downhole scraper, the length of the cleaning zone is selected based on the length p rekryvatelya with a margin of 5-10% above and below the site of installation Perekryvatel after descent Perekryvatel the coated material is expanded data portions in the slots, thereby activating the cold welding and providing Perekryvatel attachment to production tubing.

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