Natural gas well shaft blockage position calculation method

Abstract

The invention discloses a natural gas well shaft blockage position calculation method, and belongs to the technical field of gas well shaft blockage removal of oil and gas exploitation, and the method comprises the following steps: 1, obtaining the daily gas production q1 during production of a blocked well, closing the blocked well for t1 hours, recording the oil pressure P1 and the wellhead temperature T1 before opening the well, then opening the well for production for t2 hours, the oil pressure P2, the wellhead temperature T2 and the gas production rate q2 after well opening production are recorded; step 2, acquiring a compression factor Z1 of the gas under the conditions of the pressure P1 and the temperature T1, and acquiring a compression factor Z2 of the gas under the conditions of the pressure P2 and the temperature T2; 3, all parameters are substituted into a publicity, and the depth of the shaft blockage position is obtained through calculation. According to the gas state equation, the position of a blockage point is calculated by using data such as oil pressure, wellhead temperature and gas production before and after well opening, so that corresponding blockage removal measures can be carried out in a targeted manner, and great practical significance is achieved for guiding blockage removal of a gas well shaft.

Description

Technical Field

[0001] The invention relates to the technical field of gas well bore unblocking in oil and gas exploitation, and in particular to a method for calculating a blockage position of a natural gas well bore. Background Art

[0002] During the gas well production process, polymers and organic lipids in the well additives will generate long-chain fatty acids, saturated alkanes and other organic substances with a certain viscosity under the high temperature and high pressure conditions of the formation, and gradually return during the gas well production process. These viscous substances are cemented with inorganic substances such as downhole corrosion products and reaction residues of formation rocks after acidification, causing wellbore blockage, severely limiting the gas well production capacity or even making it impossible to produce.

[0003] At present, the main unblocking measures used on site are continuous tubing flushing, acidification, and injection of organic solvents. However, since the specific location of the blockage in the gas wellbore is unknown, it is impossible to carry out targeted unblocking technology, which increases the difficulty of unblocking measures and the unblocking effect is not ideal. Therefore, there is an urgent need for a method for determining the location of the wellbore blockage, which can simply and quickly calculate the location of the wellbore blockage point, efficiently guide the unblocking measures plan, and optimize the gas well production in real time.

[0004] A Chinese patent with publication number CN115434693A and publication date 2022.12.06 discloses a device for measuring and unblocking the position of hydrate blockage in a wellbore, including a gas wellbore unit, a gas tree unit is provided on the gas wellbore unit, a hydrate blockage position measurement unit for measuring the hydrate blockage position of the gas wellbore unit is provided on the gas tree unit, and a microwave transmitting unit for unblocking the gas wellbore unit is also provided on the gas tree unit; and a control unit is also included, and the gas tree unit, the hydrate blockage position measurement unit and the microwave transmitting unit are electrically connected to the control unit respectively. The use of this patent requires the additional resetting of the gas wellbore unit, which has the disadvantage of cumbersome operation. Summary of the invention

[0005] In view of the above-mentioned defects in the prior art, the present invention provides a method for calculating the blockage position of a natural gas wellbore. According to the gas state equation, the blockage point position is calculated using data such as oil pressure before and after well opening, wellhead temperature and gas production, so that corresponding unblocking measures can be carried out in a targeted manner, which has great practical significance for guiding the unblocking of gas wellbore.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A method for calculating a blockage position of a natural gas wellbore comprises the following steps:

[0008] Step 1: Obtain the daily gas production q1 of the plugged well, shut down the plugged well for △t1 hours, record the oil pressure P1 and wellhead temperature T1 before opening the well, then open the well for production for △t2 hours, and record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening the well;

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

[0010] Step 3: Bring all parameters into the public display and calculate the depth of the wellbore blockage location.

[0011] Preferably, the step 1 needs to be performed under standard ground conditions.

[0012] Preferably, in step 2, the compression factor Z1 and the compression factor Z2 are obtained by checking the natural gas compression factor chart based on the oil pressure P1 and the wellhead temperature T1 before well opening and the oil pressure P2 and the wellhead temperature T2 after well opening for production.

[0013] Preferably, in step three, the volume V2 of the gas between the plugging point and the wellhead in the oil pipe after the well is opened for production under standard ground conditions is equal to the volume V1 of the gas between the plugging point and the wellhead in the oil pipe before the well is opened under standard ground conditions plus the volume of gas entering the wellbore from the formation during the well opening period q1*△t2 / 24 minus the gas production q2, and the corresponding expression is established as follows:

[0014]

[0015] Where: V1: The volume of gas between the plugging point in the tubing and the wellhead under standard ground conditions before well opening, m 3 ; V2: The volume of gas between the plugging point in the tubing and the wellhead under standard ground conditions after the well is opened for production for △t2 hours, m 3 ; q1: daily gas production of the plugged well, m 3 ; q2: gas production of the plugged well within △t2 time, m 3 ; △t2: time to start well production, h.

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

[0017]

[0018] Where: L: the measured depth of the plugging point in the wellbore tubing, m; A: the cross-sectional area of ​​the tubing, m 2 ; P: wellhead oil pressure, MPa; T: wellhead temperature, K; Z: compressibility factor of gas under pressure P and temperature T, dimensionless.

[0019] Preferably, by substituting formula (2) into formula (1), the calculation formula for the wellbore blockage position depth is obtained:

[0020]

[0021] Wherein: P1: wellhead oil pressure before well opening, MPa; P2: wellhead oil pressure after well opening and production for △t2 hours, MPa; T1: wellhead temperature before well opening, K; T2: wellhead temperature after well opening and production for △t2 hours, K; Z1: compression factor of gas under pressure P1 and temperature T1, dimensionless; Z2: compression factor of gas under pressure P2 and temperature T2, dimensionless.

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

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

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

[0025] 1. The present invention provides a method for calculating the blockage position of a natural gas wellbore, which aims to calculate the blockage point position based on the gas state equation and using data such as oil pressure, wellhead temperature and gas production before and after well opening, so that corresponding unblocking measures can be carried out in a targeted manner, which has great practical significance for guiding the unblocking of gas wellbore.

[0026] 2. The method for calculating the blockage position of a natural gas wellbore provided by the present invention fills the gap in the current technology for determining the blockage position of the wellbore. The technology of the present invention is simple to operate, and most of the parameters required by the present invention can be obtained from on-site monitoring instruments, which is convenient and fast. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0028] Example 1

[0029] A method for calculating a blockage position of a natural gas wellbore comprises the following steps:

[0030] Step 1: Obtain the daily gas production q1 of the plugged well, shut down the plugged well for △t1 hours, record the oil pressure P1 and wellhead temperature T1 before opening the well, then open the well for production for △t2 hours, and record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening the well;

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

[0032] Step 3: Bring all parameters into the public display and calculate the depth of the wellbore blockage location.

[0033] Example 2

[0034] A method for calculating a blockage position of a natural gas wellbore comprises the following steps:

[0035] Step 1: Obtain the daily gas production q1 of the plugged well, shut down the plugged well for △t1 hours, record the oil pressure P1 and wellhead temperature T1 before opening the well, then open the well for production for △t2 hours, and record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening the well;

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

[0037] Step 3: Bring all parameters into the public display and calculate the depth of the wellbore blockage location.

[0038] Wherein, the step 1 needs to be carried out under standard ground conditions (20°C, 0.101MPa).

[0039] Among them, in the step 2, the compression factor Z1 and the compression factor Z2 are obtained by checking the natural gas compression factor chart based on the oil pressure P1 and the wellhead temperature T1 before well opening and the oil pressure P2 and the wellhead temperature T2 after well opening for production.

[0040] Among them, in step three, the volume V2 of the gas between the blockage point and the wellhead in the oil pipe after the well is opened for production under standard ground conditions is equal to the volume V1 of the gas between the blockage point and the wellhead in the oil pipe before the well is opened under standard ground conditions plus the volume of gas entering the wellbore from the formation during the well opening period q1*△t2 / 24 minus the gas production q2, and the corresponding expression is established as follows:

[0041]

[0042] Where: V1: The volume of gas between the plugging point in the tubing and the wellhead under standard ground conditions before well opening, m 3 ; V2: The volume of gas between the plugging point in the tubing and the wellhead under standard ground conditions after the well is opened for production for △t2 hours, m 3 ; q1: daily gas production of the plugged well, m 3 ; q2: gas production of the plugged well within △t2 time, m 3 ; △t2: time to start well production, h.

[0043] Wherein, the gas volumes V1 and V2 in the formula (1) can be calculated by the following formula:

[0044]

[0045] Where: L: the measured depth of the plugging point in the wellbore tubing, m; A: the cross-sectional area of ​​the tubing, m 2 ; P: wellhead oil pressure, MPa; T: wellhead temperature, K; Z: compressibility factor of gas under pressure P and temperature T, dimensionless.

[0046] Substituting formula (2) into formula (1), we get the calculation formula for the wellbore blockage depth:

[0047]

[0048] Wherein: P1: wellhead oil pressure before well opening, MPa; P2: wellhead oil pressure after well opening and production for △t2 hours, MPa; T1: wellhead temperature before well opening, K; T2: wellhead temperature after well opening and production for △t2 hours, K; Z1: compression factor of gas under pressure P1 and temperature T1, dimensionless; Z2: compression factor of gas under pressure P2 and temperature T2, dimensionless.

[0049] Among them, all parameters are substituted into formula (3) to calculate the depth of the wellbore blockage position.

[0050] Among them, the computer C language is compiled into a calculation program, and the parameters P1, P2, △t2, T1, T2, Z1 and Z2 are input to obtain the depth of the wellbore blockage position.

[0051] Example 3

[0052] The inner diameter of the oil pipe of a gas well is 76 mm. After the wellbore is blocked, the daily gas production q1 is 17.8×10 4 m 3 , after shutting in the well for 1 hour, the wellhead oil pressure P1 is 40MPa, the wellhead temperature T1 is 25℃, after opening the well for 0.5 hour, the wellhead oil pressure P2 is 30MPa, the wellhead temperature T2 is 50℃, and the gas production q2 is 5285m 3 .

[0053] The cross-sectional area A of the oil pipe can be calculated from the inner diameter of the oil pipe, which is 0.0045m 2 According to the wellhead pressure and temperature before well opening and 0.5h after well opening, the natural gas compression factor chart was checked and the Z1 was 1.03 and Z2 was 0.92.

[0054] Substituting all parameters into formula (3), the measured depth of the blockage point in the oil pipeline is 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 wellbore blockages. The technology of the present invention is simple to operate, and most of the parameters required for the method can be obtained from on-site monitoring instruments. It is convenient and fast, and can quickly determine the location of the wellbore blockage point, so that targeted unblocking measures can be carried out, which has great practical significance for guiding the unblocking of gas wellbores.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate rather than limit 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 the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for calculating the blockage position of a natural gas wellbore, characterized in that: The following steps are involved: Step 1: Obtain the daily gas production q1 of the plugged well, shut down the plugged well for △t1 hours, record the oil pressure P1 and wellhead temperature T1 before opening the well, then open the well for production for △t2 hours, and record the oil pressure P2, wellhead temperature T2 and gas production q2 after opening the well; Step 2: Obtain the compression factor Z1 of the gas under the conditions of pressure P1 and temperature T1, and obtain the compression factor Z2 of the gas under the conditions of pressure P2 and temperature T2; Step 3: Bring all parameters into the public display and calculate the depth of the wellbore blockage location.

2. A method for calculating the blockage position of a natural gas well according to claim 1, characterized in that: The step 1 needs to be performed under standard ground conditions.

3. A method for calculating the blockage position of a natural gas well according to claim 2, characterized in that: In the step 2, the compression factors Z1 and Z2 are obtained by checking the natural gas compression factor chart based on the oil pressure P1 and wellhead temperature T1 before well opening and the oil pressure P2 and wellhead temperature T2 after well opening for production.

4. A method for calculating the blockage position of a natural gas well according to claim 3, characterized in that: In step 3, the volume V2 of the gas between the plugging point and the wellhead in the oil pipe after the well is opened for production under standard ground conditions is equal to the volume V1 of the gas between the plugging point and the wellhead in the oil pipe before the well is opened under standard ground conditions plus the volume of gas entering the wellbore from the formation during the well opening period q1*△t2 / 24 minus the gas production q2, and the corresponding expression is established as follows: Where: V1: The volume of gas between the plugging point in the tubing and the wellhead under standard ground conditions before well opening, m 3 ; V2: The volume of gas between the plugging point in the tubing and the wellhead under standard ground conditions after the well is opened for production for △t2 hours, m 3 ; q1: daily gas production of the plugged well, m 3 ; q2: gas production of the plugged well within △t2 time, m 3 ; △t2: time to start well production, h.

5. A method for calculating the blockage position of a natural gas well according to claim 4, characterized in that: The gas volumes V1 and V2 in formula (1) can be calculated by the following formula: Where: L: the measured depth of the plugging point in the wellbore tubing, m; A: the cross-sectional area of ​​the tubing, m 2 ; P: wellhead oil pressure, MPa; T: wellhead temperature, K; Z: compressibility factor of gas under pressure P and temperature T, dimensionless.

6. A method for calculating the blockage position of a natural gas well according to claim 5, characterized in that: Substituting formula (2) into formula (1), we get the calculation formula for the wellbore blockage depth: Wherein: P1: wellhead oil pressure before well opening, MPa; P2: wellhead oil pressure after well opening and production for △t2 hours, MPa; T1: wellhead temperature before well opening, K; T2: wellhead temperature after well opening and production for △t2 hours, K; Z1: compression factor of gas under pressure P1 and temperature T1, dimensionless; Z2: compression factor of gas under pressure P2 and temperature T2, dimensionless.

7. A method for calculating the blockage position of a natural gas well according to claim 6, characterized in that: Substitute all parameters into equation (3) and calculate the depth of the wellbore blockage location.

8. A method for calculating the blockage position of a natural gas well according to claim 7, characterized in that: A calculation program is compiled in computer C language, and the parameters P1, P2, △t2, T1, T2, Z1 and Z2 are input to obtain the depth of the wellbore blockage position.

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