A pipe string for separate layering and combined production of tight gas and coal rock gas and a use method thereof

Abstract

This invention discloses a combined production string for tight gas and coalbed methane, and its usage method. The string comprises, from top to bottom, a threaded connection of tubing 1, gas lift valve 1, tubing 2, gas lift valve 2, circulating sleeve, packer, tubing 3, and a bell mouth. Gas lift valve 2, circulating sleeve, and packer are located between the tight gas layer and the coalbed methane layer. This invention enables initial circulating gas lift to induce flow. Gas lift valve 1 reduces the gas lift start-up pressure, preventing pressure surges that could cause wellbore fluid to enter the tight gas layer and create water lock. Tight gas is used to assist coalbed methane drainage and gas production via gas lift valve 2. Sufficient tight gas energy allows for annular single-stage tight gas production. Annular gas injection and circulating gas lift assist coalbed methane drainage and gas production. The circulating sleeve enables reverse circulation well washing, mitigating the risk of sand blockage.

Description

Technical Field

[0001] This invention relates to the field of drainage gas extraction technology, and in particular to a combined extraction string for tight gas and coal rock gas and its application method. Background Technology

[0002] Currently, in the development of two gas layers—tight gas and coalbed methane—two separate development well networks are used, resulting in high drilling costs. Using a single development well network for both layers simultaneously is not feasible, as fracturing each layer individually is difficult and expensive. Conversely, a single development well network can only support the general combined production of two gas layers with identical pressure systems, physical properties, and produced fluid compositions. For coalbed methane and tight gas, which have different pressure systems and high water production, simultaneous production leads to inter-layer interference, and fluids from the high-pressure layer can easily flow back into the low-pressure layer, causing formation contamination, water shrinkage, and gas lock-up, severely impacting production efficiency.

[0003] Patent search results: Publication No. CN109372474A, Application No. CN201811398632.2, Invention Title: A Coalbed Methane and Sandstone Gas Production String and Extraction Method in a Co-production Well. This invention discloses a co-production string for coalbed methane and sandstone gas in a well, proposing a method for achieving separate extraction, gas lift drainage, and combined extraction of the two gases in the same wellbore. However, the string structure involved is complex, including multiple components such as multi-layer coiled tubing, packers, and safety valves. These components require high manufacturing precision and fit, increasing manufacturing costs and technical implementation difficulty. In the initial production stage, coalbed methane and sandstone gas need to be extracted and drained separately, which increases the complexity and time cost of extraction, failing to achieve simultaneous extraction of the two gases. The complex string structure and extraction method may increase safety risks during operation, especially after sand production in the upper sandstone gas layer, which can easily cause packer sand jamming and difficulty in retrieving the string. Summary of the Invention

[0004] To solve the above problems, this invention provides a stratified extraction string for tight gas and coal-rock gas, and a method for its use, enabling interference-free extraction of the two gases.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a combined production string for tight gas and coal-rock gas, comprising, from top to bottom, a first oil pipe, a first gas lift valve, a second oil pipe, a second gas lift valve, a circulating sleeve, a packer, a third oil pipe, and a bell mouth; the second gas lift valve, the circulating sleeve, and the packer are located between the tight gas layer and the coal-rock gas layer.

[0006] Furthermore, the distance between the packer and the top boundary of the coal-rock gas layer is 3-5 meters.

[0007] Furthermore, the funnel-shaped opening is located below the bottom boundary of the coal-rock gas layer.

[0008] Furthermore, the top of the first oil pipe is installed below ground via a hanger.

[0009] Furthermore, the packer's separating sleeve has an upper oil sleeve annulus and a lower oil sleeve annulus.

[0010] Furthermore, oil pipes one, two, and three are corrosion-resistant and scale-resistant oil pipes.

[0011] A method for using a combined tight gas and coalbed methane extraction tubing string includes the following steps:

[0012] Step 1: Install the blowout preventer assembly, well control equipment, and well control manifold, and test the pressure to ensure it passes.

[0013] Step 2: Sand exploration and flushing;

[0014] Step 3: Well cleaning;

[0015] Step 4: Lower the tubing string.

[0016] Further, in step two, if a sandy surface is encountered, sand flushing operation is carried out; otherwise, the sand-exploration tubing is pulled out and well-washing operation is carried out.

[0017] Further, in step three, the well gauge is lowered to the bottom of the artificial well, and the well-connecting tubing is retrieved.

[0018] Further, in step four, the top of the tubular column is installed below ground via a hanger.

[0019] The beneficial effects of this invention are:

[0020] 1. It can realize initial circulation gas lift induction. The gas lift valve reduces the gas lift start-up pressure to prevent pressure surge from causing wellbore liquid to enter the tight gas layer and cause water lock.

[0021] 2. Tight gas is extracted by auxiliary coal and rock gas drainage through the gas lift valve II;

[0022] 3. The tight gas energy is sufficient for single-source tight gas extraction in the annulus;

[0023] 4. Annular gas injection and circulating gas lift assisted coal and rock gas drainage and gas production;

[0024] 5. The circulating sliding sleeve can achieve reverse circulation well washing, thus solving the risk of sand blockage. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of the present invention.

[0027] The components are: 1. Oil pipe one; 2. Air lift valve one; 3. Air lift valve two; 4. Circulating sleeve; 5. Packer; 6. Bell mouth; 7. Oil pipe two; 8. Oil pipe three. Detailed Implementation

[0028] The following will be combined with the appendix Figure 1 The technical solutions of the present invention have been clearly and completely described. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0030] In the description of this invention, it should be noted that the terms "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used only for distinction and should not be construed as indicating or implying relative importance.

[0031] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Example 1

[0033] A combined production string for tight gas and coal-rock gas layers includes, from top to bottom, a threaded connection of a first oil pipe 1, a first gas lift valve 2, a second oil pipe 7, a second gas lift valve 3, a circulating sleeve 4, a packer 5, a third oil pipe 8, and a bell mouth 6; the second gas lift valve 3, the circulating sleeve 4, and the packer 5 are located between the tight gas layer and the coal-rock gas layer.

[0034] A method for using a combined tight gas and coalbed methane extraction tubing string includes the following steps:

[0035] Step 1: Install the blowout preventer assembly, well control equipment, and well control manifold, and test the pressure to ensure it passes.

[0036] Step 2: Sand exploration and flushing;

[0037] Step 3: Well cleaning;

[0038] Step 4: Lower the tubing string.

[0039] By introducing a gas lift valve, circulating sleeve 4, and packer 5, the packer 5 is used to solve the interference problem between different pressure systems; the gas lift valve is used to initiate gas lift and induced flow to start the production capacity of the two layers after well completion; and the circulating sleeve 4 is used to achieve backwashing and sand flushing. This enables functions such as surface-assisted gas lift, natural energy gas lift, and combined production of two gases.

[0040] Example 2

[0041] A combined production line for tight gas and coal-rock gas layers includes, from top to bottom, threaded connections of: tubing 1, gas lift valve 2, tubing 7, gas lift valve 3, circulating sleeve 4, packer 5, tubing 3, and bell mouth 6. The top of tubing 1 is installed below ground level via a hanger. Gas lift valve 3, circulating sleeve 4, and packer 5 are located between the tight gas layer and the coal-rock gas layer. The distance between packer 5 and the top boundary of the coal-rock gas layer is 3-5 meters. Bell mouth 6 is located below the bottom boundary of the coal-rock gas layer. The packer 5's separating sleeve has an upper and lower annular sleeve. Tubing 1, tubing 7, and tubing 3 are corrosion-resistant and scale-resistant tubing.

[0042] A method for using a combined tight gas and coalbed methane extraction tubing string includes the following steps:

[0043] Step 1: Install the blowout preventer assembly, well control equipment, and well control manifold, and test the pressure to ensure it passes the test.

[0044] Step 2: Sand exploration and flushing; if sand is encountered, flush the sand; otherwise, remove the sand exploration string and perform well washing.

[0045] Step 3: Well cleaning; run the well cleaning gauge to the bottom of the artificial well and pull out the well cleaning string.

[0046] Step 4: Lower the tubing column; the top of the tubing column is installed below ground using a hanger.

[0047] Packer 5 isolates the two gas layers, eliminating interference from different pressures and gas production rates during combined gas extraction; circulating sleeve 4 must be close to packer 5 to ensure sand flushing effect; gas lift valve 2 3 must be placed below the tight layer to ensure the discharge of water from the tight gas layer; to assist in achieving the best lifting effect for coal-rock gas, gas lift valve 2 3 must be placed as deep as possible, and packer 5 must be placed above the top of the coal-rock gas layer, close to the coal-rock gas layer; bell mouth 6 extends to the bottom boundary of the coal-rock gas layer to improve drainage effect; after the tubing is lowered into the wellbore, gas is injected into the annulus through gas lift valve 2, and the liquid in the wellbore is discharged by gas lift and circulating gas lift, putting the tubing into working condition; the working condition is that tight gas is produced through the annulus of the oil casing. Coal-rock gas is produced by self-flowing through the tubing. During production, if the coal-rock gas cannot discharge the associated water on its own (i.e., production decreases and fluid carrying capacity is insufficient), the tight gas production at the wellhead is controlled (i.e., the tight gas production in the annulus is limited or the annulus does not produce gas), so that the tight gas is produced entirely through the gas lift valve 23, which plays an auxiliary role in lifting and draining the coal-rock gas. When the tight gas energy is insufficient in the later stage of production, the normal production of coal-rock gas can be ensured by surface pressurization and circulation gas lift drainage. Before the tubing string is pulled out, in order to avoid the problem of sand blockage in the packer 5 and the inability to pull out the tubing string due to sand in the tight gas layer, the circulating sliding sleeve 4 is opened by dropping a ball to flush the sand and wash the well, thus solving the problem of pulling out the tubing string.

[0048] By introducing a gas lift valve, circulating sleeve 4, and packer 5, the packer 5 addresses interference issues between different pressure systems. The gas lift valve initiates gas lift-induced flow after well completion to activate the production capacity of both layers. Initially, formation energy from the coal and rock gas is used for gas lift and fluid removal. Later, tight gas is used to assist in coal and rock gas lift and fluid removal. In later operations, the circulating sleeve 4 is used for backwashing and sand flushing. This system achieves functions such as surface-assisted gas lift, natural energy gas lift, and combined production of both gases, ensuring smooth gas extraction from coal and rock gas.

[0049] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. For those skilled in the art, any obvious modifications made without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims. Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no technical conflict, the features in the embodiments disclosed in the present invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A two-stage combined production tubing for tight gas and coalbed methane, characterized in that, It includes, from top to bottom, threaded connection of oil pipe 1 (1), gas lift valve 1 (2), oil pipe 2 (7), gas lift valve 2 (3), circulating sleeve (4), packer (5), oil pipe 3 (8), and bell mouth (6); gas lift valve 2 (3), circulating sleeve (4), and packer (5) are located between the tight gas layer and the coal-rock gas layer.

2. The combined tight gas and coalbed methane extraction tubing according to claim 1, characterized in that, The distance between the packer (5) and the top boundary of the coal-rock gas layer is 3-5 meters.

3. The combined tight gas and coalbed methane production tubing according to claim 1, characterized in that, The funnel-shaped opening (6) is located below the bottom boundary of the coal-rock gas layer.

4. The combined tight gas and coalbed methane production tubing according to claim 1, characterized in that, The top of the oil pipe (1) is installed below the ground via a hanger.

5. The combined tight gas and coal-rock gas extraction tubing according to claim 1, characterized in that, The packer (5) has an upper oil sleeve with an annular opening and a lower oil sleeve with an annular opening.

6. The combined tight gas and coalbed methane extraction tubing according to claim 1, characterized in that, The oil pipes 1 (1), 2 (7), and 3 (8) are corrosion-resistant and scale-resistant oil pipes.

7. A method for using a tubing string for combined extraction of tight gas and coalbed methane, characterized in that, A tubular string according to any one of claims 1-6 comprises the following steps: Step 1: Install the blowout preventer assembly, well control equipment, and well control manifold, and test the pressure to ensure it passes. Step 2: Sand exploration and flushing; Step 3: Well cleaning; Step 4: Lower the tubing string.

8. The method of using the combined tight gas and coal-rock gas extraction tubing as described in claim 7, characterized in that, In step two, if a sandy surface is encountered, a sand flushing operation is performed; otherwise, the sand-exploration tubing is retrieved and a well-washing operation is carried out.

9. The method of using the combined tight gas and coal-rock gas extraction tubing as described in claim 7, characterized in that, Step three involves lowering the well gauge to the bottom of the artificial well and then retrieving the well-clearing tubing string.

10. The method of using the tight gas and coal-rock gas dual-gas stratified combined production tubing according to claim 7, characterized in that, In step four, the top of the tubular column is installed below ground using a hanger.

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