A method for sealing abandoned brine wells

Abstract

The present invention belongs to the technical field of well cementing and plugging for abandoned brine wells, and relates to a packer assembly and a well plugging method for abandoned brine wells. An abandoned brine well packer assembly includes a packer nipple and a rubber cylinder, the rubber cylinder is tightly sleeved on the outer wall of the packer nipple, and a threaded joint is provided at one end of the packer nipple. It is possible to plug abandoned brine wells with relatively simplified processes and low costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of well cementing and plugging for abandoned brine wells, and particularly relates to a method for plugging abandoned brine wells. Background Art

[0002] During the exploitation of brine wells, natural gas containing hydrogen sulfide is usually associated. Abandoned brine wells pose safety hazards such as brine pollution of groundwater, natural gas explosion, and hydrogen sulfide poisoning. Therefore, abandoned brine and gas wells need to be plugged and treated.

[0003] Brine wells in Zigong area have a long history of development. In the early days, there were no casings or wooden and bamboo casings were used in brine wells. Later, steel casings began to be used. In order to meet a certain squeezing pressure and ensure the well plugging quality, the current method for plugging and treating abandoned wells without casings and wooden and bamboo casings is to run a steel surface casing after reaming the well, and then carry out well plugging construction after casing cementing. This method permanently seals a section of steel casing in the abandoned well, and the construction procedures for casing cementing of abandoned wells require pre-drilling a floating cement plug, detecting the cement plug, waiting for the cement to set, and drilling the cement plug, etc., which have the disadvantages of high labor intensity, waste of steel casing, and high time cost. Therefore, a method for simplifying the process and saving costs is needed. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for plugging abandoned brine wells, which can plug abandoned brine wells through relatively simplified processes and at low cost.

[0005] To this end, in the first aspect of the present invention, a packer assembly is provided. The packer assembly includes a packer nipple and a rubber cylinder. The rubber cylinder is tightly sleeved on the outer wall of the packer nipple, and a threaded joint is provided at one end of the packer nipple.

[0006] In some embodiments of the present invention, a step is circumferentially connected to the packer nipple near the threaded joint end, and the outer diameter of the step is not less than the outer diameter of the rubber cylinder.

[0007] In some embodiments of the present invention, the rubber cylinder is made of a liquid-expandable material.

[0008] In some embodiments of the present invention, the liquid-expandable material includes a liquid-expandable waterproof rubber made of water-soluble polyurethane prepolymer or sodium acrylate superabsorbent resin and natural rubber or neoprene. Other liquid-expandable materials can also be used without limitation.

[0009] In the second aspect of the present invention, a method for plugging an abandoned brine well is provided, including: reaming the abandoned brine well, directly running a steel casing with the packer assembly described in the first aspect of the present invention connected to the bottom end thereof into the well, injecting cement slurry below the packer assembly, and pulling out the steel casing upward.

[0010] In some embodiments of the present invention, the well plugging method includes the following specific steps:

[0011] S1: Reach the top of the pre-plugging formation through the abandoned brine well, and then perform well logging, cement plugging, waiting for setting, and probing the cement plug surface in sequence;

[0012] S2: Lower a steel casing with a centralizer into the well. The bottom end of the steel casing is connected with a packer assembly through a threaded joint, and a wellhead device is installed;

[0013] S3: Lower a pump injection string into the well above the cement plug, inject cement slurry until it returns below the packer assembly, close the wellhead and then apply pressure for squeezing injection. After pressure testing, pull out the pump injection string;

[0014] S4: Remove the wellhead device, pull out the steel casing upward, wait for setting, and re-inject cement slurry to the ground.

[0015] In some embodiments of the present invention, the pre-plugging formation is the shallowest producing formation.

[0016] In some embodiments of the present invention, the producing formation includes a natural gas layer and a brine layer.

[0017] In some embodiments of the present invention, the setting depth of the packer assembly is the bedrock layer; preferably, the setting depth of the packer assembly is the shallow layer of the bedrock layer; more preferably, the setting depth of the packer assembly is the position with regular well diameter in the bedrock layer.

[0018] In some embodiments of the present invention, in step S1, a cement plug is placed in the caprock at the top of the pre-plugging formation.

[0019] In some embodiments of the present invention, in step S4, when the steel casing is pulled out upward, the packer joint and the rubber cylinder of the packer assembly are separated, and the rubber cylinder remains in the well.

[0020] In some embodiments of the present invention, the thickness of the cement plug is 55 - 65 m. In some examples, the thickness of the cement plug includes but is not limited to: 55 m, 56 m, 57 m, 58 m, 59 m, 60 m, 61 m, 62 m, 63 m, 64 m or 65 m. In some other embodiments, the thickness of the cement plug is set according to the specific situation of the abandoned brine well, without strict limitation.

[0021] In some embodiments of the present invention, in step S1, the waiting time for setting after cement plugging is 48 - 60 h. In some examples, the waiting time for setting after cement plugging in step S1 includes but is not limited to: 48 h, 50 h, 52 h, 55 h, 58 h, 59 h or 60 h.

[0022] In some embodiments of the present invention, the outer diameter of the steel casing is 130 - 150 mm. In some examples, the outer diameter of the rubber cylinder includes, but is not limited to: 130 mm, 132 mm, 135 mm, 138 mm, 140 mm, 142 mm, 145 mm, 148 mm or 150 mm. In some other embodiments, the outer diameter of the steel casing is set according to the specific conditions of the abandoned brine well, without strict limitation.

[0023] In some embodiments of the present invention, the length of the rubber cylinder is 1.8 - 2.2 m. In some examples, the length of the rubber cylinder includes, but is not limited to: 1.8 m, 1.85 m, 1.9 m, 1.95 m, 2 m, 2.1 m, 2.15 m or 2.2 m. In some other embodiments, the length of the rubber cylinder is set according to the specific conditions of the abandoned brine well, without strict limitation.

[0024] In some embodiments of the present invention, in step S3, when injecting the displacement fluid under pressure, the pressure is 4 - 8 Mpa. In some examples, the pressure of injecting the displacement fluid under pressure in step S3 includes, but is not limited to: 4 Mpa, 4.5 Mpa, 5 Mpa, 5.5 Mpa, 6 Mpa, 6.5 Mpa, 7 Mpa, 7.5 Mpa or 8 Mpa.

[0025] In some embodiments of the present invention, in step S3, when pressure testing, if the pressure drop is less than 0.5 Mpa within 30 min, then stop injecting.

[0026] In some embodiments of the present invention, in step S4, wait for setting for 48 - 72 h. In some examples, the setting in step S4 includes, but is not limited to: 48 h, 55 h, 60 h, 65 h or 72 h.

[0027] Advantages of the present invention:

[0028] (1) The abandoned brine well sealing assembly provided by the present invention, by tightly sleeving the rubber cylinder on the outer wall of the sealing short section, and the rubber cylinder is a material that expands when encountering liquid; when sealing the well, the sealing assembly is connected to the bottom end of the steel casing and lowered into the well together with the steel casing. After injecting the cement slurry, the rubber cylinder expands when encountering liquid and the friction force with the well wall increases. When the steel casing is lifted upward, the sealing short section connected thereto is lifted together, and the rubber cylinder is left in the well, and then subsequent well sealing is carried out, avoiding the permanent fixation of the steel casing in the well and saving the well sealing cost.

[0029] (2) The present invention utilizes a packer assembly with a liquid-expandable rubber cylinder and a centralizer to establish a temporary wellbore structure with a surface casing, assisting in the well sealing construction of abandoned brine wells. The rubber cylinder of the packer assembly expands upon contact with liquid to seal the annulus between the steel casing and the formation, eliminating the need to cement the casing and preventing pressure leakage during pressurization, reducing casing cementing procedures such as drilling a floating cement plug, probing the cement plug, waiting for cement setting, and drilling the cement plug. At the same time, after the injection is completed, the surface casing can be removed, avoiding waste of steel casing and saving well sealing costs. Brief Description of the Drawings

[0030] Figure 1 It is a front view sectional view of a packer assembly for abandoned brine wells provided by the present invention.

[0031] Figure 2 It is a schematic diagram of a well sealing method for abandoned brine wells provided by the present invention.

[0032] Reference Numerals: 1 - Packer Assembly, 11 - Packer Sub, 12 - Rubber Cylinder, 13 - Threaded Joint, 14 - Step, 2 - Cement Plug, 3 - Steel Casing, 4 - Centralizer, 5 - Pumping String. Detailed Description of the Embodiments

[0033] To make the present invention easier to understand, the following will describe the present invention in detail with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the application scope of the present invention.

[0034] Embodiment 1

[0035] As Figure 1 shown, this embodiment provides a packer assembly. The packer assembly 1 includes a packer sub 11 and a rubber cylinder 12. The rubber cylinder 12 is tightly sleeved on the outer wall of the packer sub 11, and a threaded joint 13 is provided at one end of the packer sub 11. The packer sub 11 facilitates connection to the steel casing through the threaded joint 13.

[0036] In this embodiment, a step 14 is circumferentially connected to the end of the packer sub 11 near the threaded joint 13, and the outer diameter of the step 14 is not less than the outer diameter of the rubber cylinder 12. When the packer sub 11 is lifted upward, the step 14 can prevent the rubber cylinder 12 from sliding upward, thereby realizing the separation of the packer sub 11 and the rubber cylinder 12.

[0037] In this embodiment, the rubber cylinder 12 is made of a liquid-expandable material. The rubber cylinder 12 expands when it encounters liquid, facilitating the sealing of the annulus between the steel casing 3 and the formation.

[0038] In this embodiment, the liquid-expandable material includes a liquid-expandable waterproof rubber made from a water-soluble polyurethane prepolymer or an acrylate-based superabsorbent polymer resin and natural rubber or neoprene. In some other embodiments, other liquid-expandable materials can also be used.

[0039] Example 2

[0040] As shown by Figure 2 this embodiment provides a method for sealing an abandoned brine well, including the following specific steps:

[0041] S1: Reach the top of the pre-sealing layer through the abandoned brine well, conduct logging, drill a 60m-thick cement plug 2 in the caprock, wait for setting for 48h, and then probe the surface of the cement plug 2;

[0042] S2: Connect the bottom of a steel casing 3 with an outer diameter of 140mm to the packer assembly 1, install a centralizer 4 on the outer wall of the steel casing 3 and then lower it into the well, and then install the wellhead device and perform support and reinforcement treatment;

[0043] S3: Lower a small-diameter pump injection string 5 into the well above the cement plug 2, inject cement slurry to return to below the packer assembly 1, lift the small-diameter pump injection string 5 out of the cement slurry surface, close the wellhead and pressurize to inject displacement fluid, the pressurized injection pressure is 5MPa, stop the injection when the pressure drop is less than 0.5MPa in 30 minutes during pressure testing, and open the wellhead to lift out the pump injection string 5;

[0044] S4: Remove the wellhead device, lift out the steel casing 3 upward, wait for setting for 48h, and re-inject cement slurry to the ground.

[0045] Specifically, the cement plug 2 plays a pressure-bearing role. The rubber cylinder 12 of the packer assembly 1 expands when encountering liquid to seal the annular space between the steel casing 3 and the well wall. At the same time, with the assistance of the centralizer 4, a simple wellbore structure is formed, and it is convenient to install the wellhead device and inject cement slurry without casing cementing; since the friction force between the rubber cylinder 12 and the well wall after expansion is greater than the friction force between the rubber cylinder 12 and the packer nipple 11, the steel casing 3 and the packer nipple 11 connected to its lower end can be successfully lifted out after the cement slurry injection is completed, the rubber cylinder 12 is separated from the packer nipple 11, and the rubber cylinder 12 is left in the well, avoiding the waste of the steel casing 3 and saving the construction cost while ensuring the well sealing quality.

[0046] In this embodiment, the pre-sealing layer is the shallowest producing formation, and the producing formation includes a natural gas layer and a brine layer. It is convenient to seal the abandoned brine well with high quality.

[0047] In this embodiment, the setting depth of the packer assembly 1 is the well diameter regular position of the bedrock formation. Because the bedrock formation is relatively hard, the well diameter regular position in the bedrock can be found through logging, so that the sealing performance of the rubber cylinder 12 after expansion is better. In some other embodiments, the setting depth of the packer assembly 1 can also be any position or the shallow layer of the bedrock formation.

[0048] In some other embodiments, the thickness of the cement plug 2 can also be 55m, 56m, 57m, 58m, 59m, 61m, 62m, 63m, 64m or 65m. In some other embodiments, the thickness of the cement plug 2 is set according to the specific conditions of the abandoned brine well.

[0049] In some other embodiments, the waiting time for setting the cement plug 2 in step S1 can also be 50h, 52h, 55h, 58h, 59h or 60h.

[0050] In some other embodiments, the outer diameter of the steel casing 3 can also be 130mm, 132mm, 135mm, 138mm, 142mm, 145mm, 148mm or 150mm. In some other embodiments, the outer diameter of the steel casing 3 is set according to the specific conditions of the abandoned brine well.

[0051] In this embodiment, the length of the rubber cylinder 12 is 2m. In some other embodiments, the length of the rubber cylinder 12 can also be 1.8m, 1.85m, 1.9m, 1.95m, 2.1m, 2.15m or 2.2m. In some other embodiments, the length of the rubber cylinder 12 is set according to the specific conditions of the abandoned brine well.

[0052] In some other embodiments, the pressure for pressure squeezing injection in step S3 can also be 4Mpa, 4.5Mpa, 5.5Mpa, 6Mpa, 6.5Mpa, 7Mpa, 7.5Mpa or 8Mpa.

[0053] In some other embodiments, the waiting time for setting in step S4 can also be 48h, 55h, 60h, 65h or 72h.

[0054] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for sealing abandoned brine wells, characterized in that, it includes: Pass through the abandoned brine well, directly lower a steel casing with a packer assembly connected to the bottom end into the well, inject cement slurry below the packer assembly, and lift the steel casing upward; the packer assembly includes a packer nipple and a rubber cylinder, the rubber cylinder is tightly sleeved on the outer wall of the packer nipple, one end of the packer nipple is provided with a threaded joint, a step is circumferentially connected near the threaded joint end of the packer nipple, the outer diameter of the step is not less than the outer diameter of the rubber cylinder, the rubber cylinder is made of a liquid-swelling material, and the liquid-swelling material includes a liquid-swelling waterproof rubber made of water-soluble polyurethane prepolymer or sodium acrylate high molecular water-absorbing resin and natural rubber or neoprene; The method for sealing the well includes the following specific steps: S1: Pass through the abandoned brine well to the top of the pre-sealing layer, and then perform well logging, cement plugging, waiting for setting, and probing the cement plug surface in sequence; S2: Lower a steel casing with a centralizer into the well, the bottom end of the steel casing is connected with a packer assembly through a threaded joint, and a wellhead device is installed; S3: Lower a pump injection string into the well above the cement plug, inject cement slurry and return it below the packer assembly, close the wellhead and then pressurize and squeeze, and lift out the pump injection string after pressure testing; S4: Remove the wellhead device, lift the steel casing upward, wait for setting, and reinject cement slurry to the ground; when lifting the steel casing upward, the packer nipple and the rubber cylinder of the packer assembly are separated, the rubber cylinder is left in the well, and then subsequent well sealing is carried out, avoiding the permanent sealing of the steel casing in the well and saving the well sealing cost.

2. The method for sealing the well according to claim 1, characterized in that, the pre-sealing layer is the shallowest productive layer; and / or, the setting depth of the packer assembly is the bedrock layer.

3. The method for sealing the well according to claim 1, characterized in that, the pressure of the pressurized squeezing injection in step S3 is 4 - 8 Mpa.

4. The method for sealing the well according to claim 1, characterized in that, for the pressure testing in step S3: when the pressure drop is less than 0.5 Mpa in 30 minutes, then stop the squeezing injection.

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