RU2190754C2 - Method to strengthen well and device for its implementation - Google Patents

Abstract

FIELD: construction of wells, strengthening of oil and gas wells when presence of penetrable formations is proved. SUBSTANCE: scrapers are put on drill pipe string. Casing is attached to lower part of drill pipe string. Centralizer and centralizer-turbolizer are positioned on casing. Scrapers are set between them. Drill pipe string is run into well to setting. Clay coating is removed and well is gauged. Shaft of well is flushed. Centralizers and scrapers are mounted on casing string. Well is cased and scrapers are set close to penetrable formations. Reinforced cement stone is obtained in points of their setting. Device for implementation of method has drill pipe string, scraper for removal of clay coating prior to cementing, casing string with centralizers and scrapers put on it. Casing to gauge shaft of well is attached to lower part of drill pipe string. Scrapers to remove clay coating are put on casing between centralizer and centralizer-turbolizer. Scrapers of casing string are mounted for setting near penetrable formations, cavern pockets or between oil- and water-bearing beds and for obtainment of cement stone there. Scrapers have tubular body. Pairs of holes are drilled in body along its generating line. Scrapers are passed through these holes. Body of scrapers is fixed with the help of fixing member that comes in the form of hollow cylinder made interference fit inside body. EFFECT: simplified technology and enhanced reliability of device with use of simpler technical aids. 2 cl, 3 dwg

Description

 The invention relates to the field of well construction and can be used for fastening oil and gas wells in the presence of permeable reservoirs.

 A technical solution is known under the name "Method of securing the well and a device for its implementation" / 1 /, including the removal of clay cake from the walls of the well using a cleaning device, lowered on the pipe string, lowering the production string with centralizers, filling the annular space with grouting mortar. At the same time, in the process of cementing, the upper and lower sections of the reservoir are disconnected by devices containing sealing elements.

 There is also known a method of securing a well and a device for its implementation / 2 /, including removing clay cake from the walls of the well with scrapers that are lowered on the drill pipe string before attaching, flushing the wellbore and securing the well using centralizers that casing pipes are provided with.

 In this case, the device for securing the well includes a drill pipe string, scrapers to remove clay cake before cementing, a casing with centralizers and scrapers on it, the casing of which is fixed by a fixing element.

 Known technical solutions - the method and device is closer to the proposed one and can be adopted as a prototype.

 The disadvantage of this method is low technology, which is associated with a large expenditure of time and labor, while the device for its implementation does not provide sufficient reliability of fastening in complicated sections of the wellbore.

 The technical task of the invention is to simplify the mounting technology and ensure its reliability using simpler technical means.

 The problem is solved by the described method, including the removal of clay cake from the walls of the borehole with scrapers that are lowered on the drill pipe string before mounting, flushing the borehole and fixing the borehole using centralizers that supply the casing pipes.

 What is new is that the wellbore is simultaneously patterned in the process of removing the mud cake, by attaching a casing to the bottom of the drill string with scrapers installed on it between the centralizer and the centralizer-turbulator, and when fastening the well, they are placed between centralizers installed near permeable formations , to obtain reinforced cement stone.

 The device for implementing the method includes a drill pipe string, scrapers to remove clay cake before cementation, a casing with centralizers and scrapers on it, the casing of which is fixed by a fixing element.

 What is new is that casing scrapers are designed to be installed near permeable formations, caverns or between oil and aquifers and to receive reinforced cement stone there, and the body of the scrapers is tubular and with holes pairwise located along its generatrix through which the scrapers are passed, while the fixing element is made in the form of a hollow cylinder, placed tightly inside the body, and on the drill pipe string, a casing pipe is fixed to its lower pipe to template the shaft important, on which between the centralizer and the centralizer-turbulators placed scrapers to remove clay cake.

 Patent studies on the novelty of the claimed object were carried out according to the patent fund of the TatNIPIneft Institute to a depth of 20 years. The research results showed that similar methods and devices used in fixing wells, characterized by such a combination of essential features as the proposed facility, are absent. Therefore, we can assume that the claimed technical solution has a novelty and inventive step, and its industrial applicability is confirmed by a description of the technology for its implementation.

 In FIG. 1 shows a drill string, to which a casing is attached through an adapter, equipped with scrapers, centralizers and turbulator centralizers.

 Figure 2 - casing for the implementation of the method in General form before attaching the well.

 Figure 3 is a section along aa in figure 2, where the scrapers are visible, passed through the pairwise located openings of the housing and fixed by a hollow cylinder located inside the housing.

 The device for securing the well includes a casing string 1 with scraper 2 made between centralizers 3 and 4 installed near permeable layers 5, caverns or between oil and aquifers 6 and 7, respectively. The housing 8 of the scrapers 2 is made tubular and with holes pairwise located along its generatrix, through which the scrapers are passed, the fixing element of which in the housing is made in the form of a hollow cylinder 9, placed with an interference fit inside the housing. In this case, the length of the scrapers along the radius is taken with a certain margin, for example, 10 mm longer than the radius of the centralizers 3 and 4 in order to be able to clean the clay crust and in the caverns of the walls of the well 10 and form a reinforced cement stone there.

 The device also includes a drill pipe string 11 with a casing 12 fixed to its lower pipe for patterning the wellbore 10 (see FIG. 1), on which scrapers 15 of the same design as scrapers 2 are placed between the centralizer 13 and centralizer-turbulators 14 installed on the casing string 1, and are used to remove clay cake from the walls of the well before its attachment.

 The method is carried out in the following sequence.

 First, the clay crust formed in the intervals of the location of permeable and productive formations during the course of the well sinking is removed from the walls of the well 10, and at the same time, the wellbore is patterned.

 To do this, when lowering the drill pipe string 11, a casing 12 with scraper 15 placed between the centralizer 13 and the centralizers-turbulators 14 is connected to its lower pipe by means of an adapter 16, as shown in Fig. 1. Then, using one of the known methods, for example, by rotating the pipe string 11, clay cake is removed from the intervals of the location of permeable formations by means of scrapers 15, while simultaneously providing borehole template. Then, by creating a circular circulation of the process fluid, the wellbore is washed, and after lifting the pipe string with snap-in to remove clay cake and template, the well is cemented.

 Before the casing is lowered into the well, the pipes 17 and 18, which are planned to be installed near the permeable layers 5, cavities or between the oil and aquifers 6 and 7, are respectively equipped with scrapers, placing them between the centralizers 3 and 4, rigidly fixed to the casing pipes 17 and 18, as shown in FIG. 2. When the casing string is lowered into the well along the downward direction, the scrapers additionally clean the walls of the well of the clay cake remaining there, especially in the caverns, going there and straightening.

 After the casing string reaches the required depth of the well, it is cemented using the traditional method using cementing aggregates. In the cementing process, cement mortar, falling from the pipe space into the annular space and passing between the centering ribs of the lower centralizer, receives a rotational movement. At the same time, the effect of turbulization is enhanced by the passage of cement between the scrapers and the upper centralizer, which ensures the formation of cement stone around the production string pipes of equal thickness without stagnant zones and local voids, which ultimately leads to an increase in the quality of formation separation. This is also facilitated by the receipt of cement stone reinforced with scrapers in the range of centralizers and scrapers.

 Thus, the scrapers placed between the centralizers play a role in this case as a cleaner of the borehole walls, the role of a turbulizer and, finally, provide reinforced cement stone in the interval of their installation, which will protect against the destruction of cement stone during perforation during the second opening of the reservoir and during crimping .

 The technical and economic advantage of the invention is as follows.

 The method is technological, when it is used, high quality of reservoir separation, operational reliability of the well are ensured, and the anhydrous period of oil production increases. The method was tested in the fields of OAO Tatneft. The test results are positive.

Sources of information
1. RF patent 2057905, published April 10, 1996

 2. RF patent 2144609, published on January 20, 2000.

Claims (2)

 1. A method of attaching a well, including removing clay cake from the walls of the well with scrapers lowered on the drill pipe string before attaching it, flushing the wellbore and securing the well using centralizers that supply the casing pipes, characterized in that the wellbore during clay removal the crusts are simultaneously patterned by attaching a casing to the bottom of the drill pipe string with scrapers placed on it between the centralizer and the centralizer-turbulator, and when attaching the well they are placed between centralizers installed near permeable formations to obtain reinforced cement stone.  2. The device for securing the well according to claim 1, comprising a drill pipe string, mud cake scrapers prior to cementing, a casing with centralizers and scrapers on it, the casing of which is fixed with a fixing element, characterized in that the casing scrapers are made with the possibility of installation near permeable formations, caverns or between oil and aquifers and obtain reinforced cement stone there, and the body of the scrapers is made tubular and with holes pairwise located along its generatrix, h Through which the scrapers are missing, the fixing element is made in the form of a hollow cylinder, fitted with an interference fit inside the housing, and a casing pipe is fixed to its lower pipe to the bottom pipe to template the wellbore, on which scrapers are placed between the centralizer and centralizer-turbulators to remove clay peel.

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