WO2022177464A1 - Method of forming an underground reservoir in a stratum of rock salt - Google Patents

Abstract

The invention relates to forming underground reservoirs by dissolving rock salt via a vertical and a vertical/horizontal borehole. In an initial step, a working pipe string consisting of two suspended strings is installed in the vertical borehole, a nonsolvent is injected into the borehole, and a preparatory opening is created having dimensions that allow the linking of the vertical and vertical/horizontal boreholes. The point at which water is fed into the opening under formation is periodically changed by means of installing a packer in the working string of the vertical/horizontal borehole and subsequently perforating said string ahead of the packer. The level of the nonsolvent in the vertical borehole is periodically raised in order to prevent exposure of the roof of the salt stratum in the vicinity of the shoe of a casing string. The invention makes it possible to increase the efficiency with which a reservoir is formed and to provide for high reservoir capacity.

Description

METHOD FOR CONSTRUCTING UNDERGROUND TANK IN ROCK SALT LEVEL

Technical field

The proposed technical solution relates to the construction of underground reservoirs through wells in rock salt by dissolving it and can be used in the oil, gas and chemical industries to create underground storage facilities and to extract salt through wells.

State of the art

A known method of constructing an underground tunnel reservoir in a bed of rock salt of limited power, involving the drilling of vertical and directional (vertical-horizontal) wells with the output of a directional (vertical-horizontal) well in a horizontal position near the bottom of the salt reservoir, installation of casing and technological pipe strings in the wells, shutdown of wells in a salt reservoir, injection of a non-solvent, dissolution of rocks by supplying water through the process pipe string of a directed well with brine extraction along the process pipe string of a vertical well (RU 2258652, publ. 20.08.2005).

The disadvantage of this method is the uneven dissolution of salt along the length of the tunnel tank, since the most intensive dissolution occurs above the shoe of the technological pipe string of a directional (vertical-horizontal) well, and the least intensive - near the vertical well, which leads to incomplete use of the formation thickness. In addition, the disadvantage of this method is the download non-solvent into a directional well and creating a development near the casing shoe of the directional well. While there are no technical means to control the level of non-solvent in directional wells, the absence or unreliable control does not allow maintaining the required level of non-solvent near the directional (vertical-horizontal) well, which can lead to the dissolution of salt near the casing shoe of the directional (vertical-horizontal) wells, exposure of the roof of the salt layer with its possible collapse and loss of tightness of the underground reservoir. In addition, the method can be implemented only with a strictly horizontal roof of the salt reservoir, since a necessary condition for its implementation is to maintain the non-solvent-brine interface in a vertical well at or above the level of the non-solvent-brine interface in the development working or the horizontal part of the working working being constructed, moreover, the fixation of the moment of completion of construction is carried out by the flow of the non-solvent from the horizontal part of the mine to the vertical well.

Closest to the claimed technical solution is the method adopted for the prototype of constructing an underground tunnel tank in a rock salt formation of limited power, which involves drilling vertical and vertical-horizontal wells with the latter in a horizontal position near the bottom of the salt formation, installation of casing and technological pipe strings in wells with the location of the shoes of technological columns of pipes at the sole salt reservoir, shutting down wells, dissolving salt by supplying water through the technological column of pipes of a vertical-horizontal well and withdrawing brine along the technological column of pipes of a vertical well, changing the point of water supply to the constructed working during the transition to the next stage of dissolution (V.A. Mazurov "Underground gas and oil storage facilities in rock salt deposits". M., "Nedra", 1982, pp. 129-132).

The disadvantage of this method is the uneven dissolution of salt along the length of the tunnel reservoir, since the salt is predominantly dissolved near the vertical well, where the dissolution process is longer, as a result of which the salt reservoir will be mined to its full height, exposing the casing shoe of the vertical well before sufficient salt dissolution occurs. along the length of the tank. In addition, the method involves moving the technological column of pipes of a vertical-horizontal well, which is technically difficult and can lead to a break in the string.

Disclosure of the essence of the invention The problem to be solved is to increase the efficiency of the construction of an underground tunnel reservoir in rock salt by controlling the process of its formation:

In comparison with the prototype, the proposed solution has the following advantages: the ability to control the formation of an underground reservoir through the use of a non-solvent injected into a vertical well;

- obtaining an underground reservoir with a large geometric volume and capacity at a given thickness of the salt reservoir; - ensuring the reliability and continuity of the technological process of creating a reservoir due to a controlled change in the point of water supply to the constructed working.

The essence of the proposed method lies in the use of the method of constructing an underground tunnel reservoir in a rock salt formation of limited thickness, which involves drilling vertical and vertical-horizontal wells with the latter in a horizontal position near the bottom of the salt formation, installation of casing and technological pipe strings in the wells with the shoes of technological columns pipes at the bottom of the salt formation, shutting down wells, dissolving salt by supplying water through the technological string of pipes of a vertical-horizontal well and withdrawing brine through the technological string of pipes of a vertical well, changing the point of water supply to the mine under construction during the transition to the next stage of dissolution.

According to the proposed method, a technological pipe string is installed on a vertical well, consisting of two coaxially located hanging strings, a non-solvent is pumped into the annular space of the casing and external hanging strings and a development working is created with dimensions that ensure the shutdown of vertical and vertical-horizontal wells.

Two coaxially located suspended columns in a vertical well, one of which pumps water and the other takes brine, make it possible to create a development working. The injection of a non-solvent into a vertical well makes it possible to control the dissolution of salt in the top of the development working and near the well.

According to the proposed method, a periodic change in the point of water supply to the development under construction is carried out by installing a packer in the technological column of a vertical-horizontal well and subsequent perforation of the column in front of the packer. The packer is installed to exclude the passage of water to the previous point of its supply and uncontrolled salt dissolution. An additional advantage of maintaining the position of the technological column is its fixation in the working, which prevents the loss of stability (uncontrolled movement) during water injection.

When moving to the next stage of dissolution, the level of non-solvent in the vertical well is raised in such a way as to slow down the dissolution of salt in the ceiling of the development working and prevent the top of the salt formation from being exposed near the casing shoe of the vertical well until the construction of the underground reservoir is completed.

To increase the productivity of water injection and brine output after well shutdown, the inner overhead string is removed from the vertical well, and the brine is taken along the outer overhead string.

Brief description of the drawings

The proposed method for constructing a tunnel tank is illustrated by the diagrams in Fig. 1 and 2. In FIG. 1 shows a diagram of the method of construction after the creation of a preparatory development in a vertical well and well shutdown.

In FIG. 2 shows a diagram of the method of construction after the last stage of creating a working.

The images in Fig. 1 and 2 include vertical 1 and vertical-horizontal 2 wells, rock salt formation of limited thickness 3. Vertical well 1 is equipped with a casing string 4 and a technological string consisting of external 5 and internal 6 hanging columns. In the space between the casing string 4 and the external hanging string 5 there is a non-solvent 7, which has an interface with the brine at level 8. For shutting down wells, a development working 9 is created in the lower part of the well 1. The vertical-horizontal well 2 is equipped with a casing string 10 and a technological string 11 The shoe of the technological column of a vertical-horizontal well 2, corresponding to the water supply point before the first stage of creating a working, is set to position 12. Packers 13, 14 and 15, installed at the second, third and fourth stages, and the corresponding water supply points 16, 17 and 18 move away from the vertical well 1. As a result, at the first stage, a working 19 is created, at the second - a working 20, at the third - a working 21, and after the fourth stage - an underground reservoir 22.

EXAMPLES OF CARRYING OUT THE INVENTION

The method is carried out as follows. First, a vertical well is drilled 1. Well 1 is equipped with a casing string 4 and two coaxially located outboard outer 5 and inner 6 columns. The outer hanging string 5 is installed at a depth above the bottom of the salt formation 3, and the inner hanging string 6 is near the bottom of the formation 3. A non-solvent 7 is pumped into the well 1, setting the non-solvent-brine interface 8 to the depth of the mark of the outer shoe. suspension column 5. Water is pumped through the external suspension column 5 and brine is taken along the internal suspension column 6, as a result of which a development working 9 is created. 11, the shoe of which is set at a certain distance from the vertical well to position 12. The level of non-solvent in well 1 is raised, water is pumped through the technological column 11 and brine is taken from the hanging columns 5 and 6 of well 1. To reduce hydraulic friction losses and increase the feed rate water before starting During the dissolution process, the inner suspension string 6 is withdrawn from the vertical well 1, and the brine is taken along the external suspension string 5. After a certain volume of salt has been extracted and a working 19 has been created, the first stage ends. Then, a packer 13 is installed in the technological string 11 and the string 11 is perforated, creating perforations 16. The level of the non-solvent in the well 1 is raised, water is pumped through the technological string 11 and the brine is taken along the overhead string 5. After extracting a certain volume of salt and creating a working 20, the second stage ends. Then packer 14 is installed, perforations 17 are created, lifted level of non-solvent, water is pumped in and brine is taken, extracting a certain amount of salt, creating a development 21 at the third stage. Similarly, operations are carried out at the fourth stage, after which an underground reservoir 22 is created.

An example of using the method.

During the construction of an underground storage of natural gas, an underground reservoir 22 with a volume of 350 thousand m3 is constructed in the depth interval of 1150-1200 m of the salt reservoir 3. A vertical well 1 is drilled 1 m deeper than the sole of the salt reservoir 3, a casing string 4 is installed to a depth of 1150 m, then into the well hanging columns 5 and 6 are lowered to a depth of 1198 and 1199.5 m, respectively. Non-solvent 7 is pumped to the level of 8 - 1198 m. controlled by geophysical methods through a vertical well 1 using downhole tools on a cable. Cylindrical developmental working 9 is eroded with a height of 2 m and a radius of 2 m. a depth of 1150 m and a technological column 11, the shoe of which is located at a distance of 60 m from the vertical well 1. The level of non-solvent in the development working 9 is set 10 m above the mark at which the wells 1 and 2 failed. Water is supplied to the technological column 11 at a flow rate 250 m ³ / hour, and the resulting brine is taken along the technological column of the vertical well along the suspended columns 5 and 6. After the extraction of 30 thousand tons of salt, the first stage is completed, a working is formed 19. A packer 13 is installed in the technological column 11 at a distance of 150 m from the vertical well. Then the column 11 is perforated in front of the packer 13 in such a way that the total area of the perforations was twice the flow section of the column 11. As a result, a new water supply point 16 is created. The level of non-solvent in the development working 9 is raised by 10 m. hour, and the resulting brine is taken along the technological column of the vertical well 1 along the hanging columns 5 and 6. After the extraction of 70 thousand tons of salt, the second stage is completed, a working 20 is formed. A packer 14 is installed in the technological column 11 at a distance of 240 m from the vertical well. column 11 before the packer as well as after the first stage. As a result, a new water supply point 17 is created. The level of non-solvent in the development working 9 is raised by 10 m. Water is supplied to the technological column 11 at a flow rate of 250 m ³ /hour, and the resulting brine is taken along the technological column of a vertical well along suspended columns 5 and 6. After the extraction of 200 thousand tons of salt, the third stage is completed, a working 21 is formed. A packer 15 is installed in the technological string 11 at a distance of 300 m from the vertical well. Then the string 11 is perforated in front of the packer as after the first stage. As a result, a new water supply point is created 18. The level of non-solvent in the development working 9 raise by 15 m. Water is supplied to the technological column 11 at a flow rate of 250 m ³ /hour, and the resulting brine is taken along the technological column of the vertical well 1 along the hanging columns 5 and 6. After extracting 340 thousand tons of salt, the fourth stage is completed. This construction of the development of the underground reservoir 22 ends.

Industrial Applicability

The proposed technical solution was implemented when creating an underground tunnel reservoir in a rock salt seam of limited capacity at one of the underground gas storage facilities in the Russian Federation.

Claims

Claim 1. A method for constructing an underground tunnel reservoir in a rock salt bed of limited thickness, which involves drilling vertical and vertical-horizontal wells with the latter going into a horizontal position near the bottom of the salt bed, installing casing and process pipe strings in the wells with the shoes of the process pipe strings at the bottom of the salt bed. formation, shutdown of wells, dissolution of salt by supplying water through the technological column of pipes of a vertical-horizontal well and the selection of brine along the technological column of pipes of a vertical well, changing the point of water supply to the development under construction during the transition to the next stage of dissolution, characterized in that a technological well is installed on the vertical well a pipe string consisting of two coaxially located external and internal hanging strings, a non-solvent is pumped into the annular space of the casing and external hanging strings and a development working is created with dimensions that provide After shutting down vertical and vertical-horizontal wells, at the transition to the next stage of dissolution, changing the point of water supply to the development under construction is carried out by installing a packer in the technological column of a vertical-horizontal well and subsequent perforation of the column, and the level of non-solvent is raised. 2. The method according to p. 1, characterized in that the inner suspension string is removed from the vertical well after well shutdown.