A method for calculating a natural gas well bore plug location

Abstract

The application discloses a kind of natural gas well wellbore blockage position calculation method, belong to the technical field of gas well wellbore deblocking of oil and gas exploitation, comprising the following steps: step one, obtain the daily gas production q1 of blocked well production, blocked well shut-in Δt1 hour, record the oil pressure P1 and wellhead temperature T1 before opening well, then open well production Δt2 hours, record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening well production;Step two, obtain the compression factor Z1 of gas under pressure P1 and temperature T1 condition, obtain the compression factor Z2 of gas under pressure P2 and temperature T2 condition;Step three, all parameters are brought into public, and the depth of wellbore blockage position is calculated.According to gas state equation, the data such as oil pressure, wellhead temperature and gas production before and after opening well are used to calculate the position of blockage point, so that corresponding deblocking measures can be carried out accordingly, and it has great practical significance for guiding gas well wellbore deblocking.

Description

Technical Field

[0001] This invention relates to the field of wellbore unblocking technology in oil and gas extraction, specifically to a method for calculating the location of wellbore blockage in natural gas wells. Background Technology

[0002] During gas well production, polymers and organic lipids in the well feed additives can generate long-chain fatty acids, saturated alkanes, and other organic substances with a certain viscosity under high temperature and pressure conditions in the formation. These substances are gradually returned during the gas well production process. These viscous substances bind with inorganic substances such as downhole corrosion products and reaction residues of acidized formation rocks, causing wellbore blockage, which severely limits gas well production capacity or even prevents production.

[0003] Currently, the main unblocking measures used on-site include coiled tubing flushing, acidizing, and adding organic solvents. However, because the specific location of the blockage in the gas wellbore is unknown, targeted unblocking processes cannot be implemented, increasing the difficulty of unblocking measures and resulting in unsatisfactory unblocking effects. Therefore, there is an urgent need for a method to determine the location of the blockage in the wellbore, which can quickly and easily calculate the location of the blockage point, efficiently guide unblocking measures, and optimize gas well production in real time.

[0004] Chinese patent CN115434693A, published on December 6, 2022, discloses a device for determining and unblocking hydrate blockages in a wellbore. The device includes a gas wellbore unit, a gas production tree unit on which a hydrate blockage location measuring unit is installed. The gas production tree unit also includes a microwave transmitting unit for unblocking the gas wellbore unit. The device further includes a control unit, with the gas production tree unit, hydrate blockage location measuring unit, and microwave transmitting unit all electrically connected to the control unit. Using this patent requires additional setup of the gas wellbore unit, resulting in cumbersome operation. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, this invention provides a method for calculating the location of blockages in natural gas wells. Based on the gas state equation, the method uses data such as oil pressure before and after well opening, wellhead temperature, and gas production to calculate the location of the blockage point, thereby enabling targeted unblocking measures to be implemented. This method has significant practical implications for guiding the unblocking of gas wells.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for calculating the location of blockage in a natural gas wellbore includes the following steps:

[0008] Step 1: Obtain the daily gas production q1 when the blockage well is in production. Close the blockage well for Δt1 hours and record the oil pressure P1 and wellhead temperature T1 before opening the well. Then open the well for Δt2 hours and record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening the well.

[0009] Step 2: Obtain the compressibility factor Z1 of the gas under pressure P1 and temperature T1, and obtain the compressibility factor Z2 of the gas under pressure P2 and temperature T2.

[0010] Step 3: Substitute all parameters into the formula to calculate the depth of the wellbore blockage.

[0011] Preferably, step one needs to be performed under standard ground conditions.

[0012] Preferably, in step two, the compressibility factor Z1 and compressibility factor Z2 are obtained by referring to the natural gas compressibility factor chart using the oil pressure P1 and wellhead temperature T1 before well opening and the oil pressure P2 and wellhead temperature T2 after well opening.

[0013] Preferably, in step three, the volume V2 of the gas between the blockage point in the tubing and the wellhead under standard surface conditions after well opening is equal to the volume V1 of the gas between the blockage point in the tubing and the wellhead under standard surface conditions before well opening, plus the volume q1*Δt2 / 24 of gas entering the wellbore from the formation during well opening, minus the gas production q2. The corresponding expression is as follows:

[0014] (1);

[0015] Where: V1: Volume of gas between the blockage point in the tubing and the wellhead under standard surface conditions before well opening, m³; V2: Volume of gas between the blockage point in the tubing and the wellhead under standard surface conditions after well opening production Δt2 hours, m³; q1: Daily gas production of the blockage well, m³; q2: Gas production of the blockage well during Δt2 hours, m³; Δt2: Well opening production time, h.

[0016] Preferably, the gas volumes V1 and V2 in equation (1) can be calculated by the following formula:

[0017] (2);

[0018] Where: L: Depth of the blockage point inside the wellbore tubing, m; A: Cross-sectional area of ​​the tubing, m² 2 P: Wellhead oil pressure, MPa; T: Wellhead temperature, K; Z: Gas compressibility factor under pressure P and temperature T, dimensionless.

[0019] Preferably, substituting equation (2) into equation (1) yields the formula for calculating the depth of wellbore blockage location:

[0020] (3);

[0021] Where: P1: Wellhead oil pressure before well opening, MPa; P2: Wellhead oil pressure after well opening production Δt2 hours, MPa; T1: Wellhead temperature before well opening, K; T2: Wellhead temperature after well opening production Δt2 hours, K; Z1: Compressibility factor of gas under pressure P1 and temperature T1, dimensionless; Z2: Compressibility factor of gas under pressure P2 and temperature T2, dimensionless.

[0022] Preferably, all parameters are substituted into equation (3) to calculate the depth of the wellbore blockage location.

[0023] Preferably, a calculation program is written in the C language of a computer, and the parameters P1, P2, Δt2, T1, T2, Z1 and Z2 are input to obtain the depth of the well blockage location.

[0024] The beneficial effects of this technical solution are as follows:

[0025] I. The present invention provides a method for calculating the location of blockage in a natural gas wellbore. Based on the gas state equation, the method uses data such as oil pressure before and after well opening, wellhead temperature, and gas production to calculate the location of the blockage point, thereby enabling targeted unblocking measures to be taken. This method has significant practical implications for guiding the unblocking of gas wellbores.

[0026] II. The present invention provides a method for calculating the location of blockage in a natural gas well, which fills the gap in the current technology for determining the location of blockage in a well. The present invention is simple to operate, and most of the parameters required by the present invention can be obtained from field monitoring instruments, which is convenient and quick. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0028] Example 1

[0029] A method for calculating the location of blockage in a natural gas wellbore includes the following steps:

[0030] Step 1: Obtain the daily gas production q1 when the blockage well is in production. Close the blockage well for Δt1 hours and record the oil pressure P1 and wellhead temperature T1 before opening the well. Then open the well for Δt2 hours and record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening the well.

[0031] Step 2: Obtain the compressibility factor Z1 of the gas under pressure P1 and temperature T1, and obtain the compressibility factor Z2 of the gas under pressure P2 and temperature T2.

[0032] Step 3: Substitute all parameters into the formula to calculate the depth of the wellbore blockage.

[0033] Example 2

[0034] A method for calculating the location of blockage in a natural gas wellbore includes the following steps:

[0035] Step 1: Obtain the daily gas production q1 when the blockage well is in production. Close the blockage well for Δt1 hours and record the oil pressure P1 and wellhead temperature T1 before opening the well. Then open the well for Δt2 hours and record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening the well.

[0036] Step 2: Obtain the compressibility factor Z1 of the gas under pressure P1 and temperature T1, and obtain the compressibility factor Z2 of the gas under pressure P2 and temperature T2.

[0037] Step 3: Substitute all parameters into the formula to calculate the depth of the wellbore blockage.

[0038] Step one, in particular, needs to be carried out under standard ground conditions (20℃, 0.101MPa).

[0039] In step two, the compressibility factor Z1 and compressibility factor Z2 are obtained by referring to the natural gas compressibility factor chart using the oil pressure P1 and wellhead temperature T1 before well opening and the oil pressure P2 and wellhead temperature T2 after well opening.

[0040] In step three, the volume V2 of gas between the blockage point in the tubing and the wellhead under standard surface conditions after well opening is equal to the volume V1 of gas between the blockage point in the tubing and the wellhead under standard surface conditions before well opening, plus the volume q1*Δt2 / 24 of gas entering the wellbore from the formation during well opening, minus the gas production q2. The corresponding expression is as follows:

[0041] (1);

[0042] Where: V1: Volume of gas between the blockage point in the tubing and the wellhead under standard surface conditions before well opening, m³; V2: Volume of gas between the blockage point in the tubing and the wellhead under standard surface conditions after well opening production Δt2 hours, m³; q1: Daily gas production of the blockage well, m³; q2: Gas production of the blockage well during Δt2 hours, m³; Δt2: Well opening production time, h.

[0043] The gas volumes V1 and V2 in equation (1) can be calculated using the following formula:

[0044] (2);

[0045] Where: L: Depth of the blockage point inside the wellbore tubing, m; A: Cross-sectional area of ​​the tubing, m² 2P: Wellhead oil pressure, MPa; T: Wellhead temperature, K; Z: Gas compressibility factor under pressure P and temperature T, dimensionless.

[0046] Substituting equation (2) into equation (1), we obtain the formula for calculating the depth of wellbore blockage location:

[0047] (3);

[0048] Where: P1: Wellhead oil pressure before well opening, MPa; P2: Wellhead oil pressure after well opening production Δt2 hours, MPa; T1: Wellhead temperature before well opening, K; T2: Wellhead temperature after well opening production Δt2 hours, K; Z1: Compressibility factor of gas under pressure P1 and temperature T1, dimensionless; Z2: Compressibility factor of gas under pressure P2 and temperature T2, dimensionless.

[0049] Substituting all parameters into equation (3), the depth of the wellbore blockage location is calculated.

[0050] The computer C language is used to compile a calculation program. By inputting parameters P1, P2, Δt2, T1, T2, Z1, and Z2, the depth of the wellbore blockage location can be obtained.

[0051] Example 3

[0052] A gas well has an inner diameter of 76 mm for its tubing. After the wellbore becomes clogged, the daily gas production q1 is 17.8 × 10⁻⁶ mm. 4 m³, after shutting in the well for 1 hour, the wellhead oil pressure P1 is 40MPa, the wellhead temperature T1 is 25℃, after starting production for 0.5 hours, the wellhead oil pressure P2 is 30MPa, the wellhead temperature T2 is 50℃, and the gas production q2 is 5285m³.

[0053] The cross-sectional area A of the oil pipe can be calculated to be 0.0045m from its inner diameter. 2 Based on the wellhead pressure and temperature before well opening and 0.5 hours after well opening, the natural gas compressibility factor charts were consulted to obtain Z1 as 1.03 and Z2 as 0.92.

[0054] Substituting all parameters into equation (3), the depth of the blockage point in the oil pipe was calculated to be 4261m.

[0055] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: it fills the gap in the current technology for determining the location of well blockage. The technology of the present invention is simple to operate, and most of the parameters required by the method can be obtained from the field monitoring instruments, which is convenient and fast. It can quickly determine the location of the well blockage point, so that targeted unblocking measures can be carried out. It has great practical significance for guiding the unblocking of gas wells.

[0056] Finally, it should be noted that the above embodiments are only for illustration and not for limiting the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for calculating the location of blockage in a natural gas wellbore, characterized in that, Includes the following steps: Step 1: Obtain the daily gas production q1 when the blockage well is in production. Close the blockage well for Δt1 hours and record the oil pressure P1 and wellhead temperature T1 before opening the well. Then open the well for Δt2 hours and record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening the well. Step 2: Obtain the compressibility factor Z1 of the gas under pressure P1 and temperature T1, and obtain the compressibility factor Z2 of the gas under pressure P2 and temperature T2. Step 3: Substitute all parameters into equation (3) to calculate the depth of the wellbore blockage location; Equation (3): （3）； Where: P1: Wellhead oil pressure before well opening, MPa; P2: Wellhead oil pressure after well opening production Δt2 hours, MPa; T1: Wellhead temperature before well opening, K; T2: Wellhead temperature after well opening production Δt2 hours, K; Z1: Compressibility factor of gas under pressure P1 and temperature T1, dimensionless; Z2: Compressibility factor of gas under pressure P2 and temperature T2, dimensionless.

2. The method for calculating the location of blockage in a natural gas wellbore according to claim 1, characterized in that: Step one must be performed under standard ground conditions.

3. The method for calculating the location of blockage in a natural gas wellbore according to claim 2, characterized in that: In step two, the compressibility factors Z1 and Z2 are obtained by referring to the natural gas compressibility factor chart using the oil pressure P1 and wellhead temperature T1 before well opening and the oil pressure P2 and wellhead temperature T2 after well opening.

4. The method for calculating the location of blockage in a natural gas wellbore according to claim 3, characterized in that: In step three, the volume V2 of gas between the blockage point in the tubing and the wellhead under standard surface conditions after well opening is equal to the volume V1 of gas between the blockage point in the tubing and the wellhead under standard surface conditions before well opening, plus the volume q1*Δt2 / 24 of gas entering the wellbore from the formation during well opening, minus the gas production q2. The corresponding expression is as follows: （1）； Where: V1: Volume of gas between the blockage point in the tubing and the wellhead under standard surface conditions before well opening, m³; V2: Volume of gas between the blockage point in the tubing and the wellhead under standard surface conditions after well opening production Δt2 hours, m³; q1: Daily gas production of the blockage well, m³; q2: Gas production of the blockage well during Δt2 hours, m³; Δt2: Well opening production time, h.

5. The method for calculating the location of blockage in a natural gas wellbore according to claim 4, characterized in that: The gas volumes V1 and V2 in equation (1) can be calculated by the following formula: （2）； Where: L: Depth of the blockage point inside the wellbore tubing, m; A: Cross-sectional area of ​​the tubing, m² 2 P: Wellhead oil pressure, MPa; T: Wellhead temperature, K; Z: Gas compressibility factor under pressure P and temperature T, dimensionless.

6. The method for calculating the location of blockage in a natural gas wellbore according to claim 5, characterized in that: A computer C language program is written to calculate the location and depth of well blockage by inputting parameters P1, P2, Δt2, T1, T2, Z1, and Z2.

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