A diagnostic method and device for diagnosing blockage types in deep carbonate gas wells

Abstract

This invention provides a method and device for diagnosing blockage types in deep carbonate gas wells. It utilizes well test data to interpret the test results and obtains the following relationship between the well skin coefficient and production rate: S a =S+Dq g The type of blockage in deep carbonate gas wells is determined by the values ​​of the true skin coefficient (S) and the non-Darcy flow coefficient (D). Larger values ​​of S and D indicate more severe blockage. This diagnostic method utilizes the relationship between the skin coefficient and production rate obtained from well productivity testing. It can accurately diagnose the type of downhole blockage in deep carbonate gas wells, dynamically evaluate the degree and trend of blockage, and guide the development of appropriate unblocking plans.

Description

Technical Field

[0001] This invention relates to the field of gas reservoir development technology, specifically to a diagnostic method and device for diagnosing blockage types in deep carbonate gas wells. Background Technology

[0002] With the continuous development of deep oil and gas theory and technology, deep carbonate gas reservoirs, possessing enormous resource potential, have become a key area for future fossil energy exploration and development. Deep carbonate gas reservoirs are generally buried at depths exceeding 4500m, characterized by strong reservoir heterogeneity, high temperature and pressure, and high acid gas content. Furthermore, in recent years, most have adopted open-hole staged acidizing-testing-production integrated tubing technology, resulting in large acid consumption. During development, this can easily lead to wellbore collapse, excessive acidizing residues, tubing corrosion, scaling, and sulfur deposition, all of which can cause well blockage.

[0003] In recent years, several deep carbonate gas reservoirs in the Sichuan Basin have experienced varying degrees of well blockage during development (such as the Feixianguan Formation and Changxing Formation gas reservoirs in the Puguang Gas Field, Yuanba Gas Field, and Longgang Gas Field, and the Dengying Formation gas reservoir in the Anyue Gas Field). Well blockage has become a major hidden danger affecting the long-term stable production and efficient development of gas reservoirs.

[0004] Existing literature has extensively studied the causes, mechanisms, composition and sources of plugging materials, and unblocking techniques for gas wells, but research on the diagnosis of downhole plugging types is scarce. Downhole plugging can be divided into two categories: formation plugging and wellbore plugging. Formation plugging is caused by near-wellbore reservoir contamination leading to decreased permeability, while wellbore plugging is caused by foreign objects in the tubing causing turbulence / throttling effects. The locations of these two types of plugging differ, their impact on gas well production differs, and their unblocking methods also differ. For carbonate gas reservoirs, when wellbore plugging occurs, an effective unblocking method is to flush out the plugging materials during flowback. When formation plugging occurs, an effective unblocking method is to acidize the near-wellbore area. Failure to accurately distinguish between formation plugging and wellbore plugging will affect the accurate formulation and implementation of unblocking solutions.

[0005] Therefore, it is necessary to develop a diagnostic method and device for deep carbonate gas well blockage types, which can accurately diagnose the downhole blockage type of deep carbonate gas wells and dynamically evaluate the degree and trend of gas well blockage, so as to effectively guide the formulation of reasonable unblocking solutions for gas wells. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a method and device for diagnosing the blockage type of deep carbonate gas wells. By interpreting well test data using gas well productivity data, the following relationship between the gas well skin coefficient and production rate is obtained: S a =S+Dq gThe type of blockage in deep carbonate gas wells is determined by the values ​​of the true skin coefficient (S) and the non-Darcy flow coefficient (D). Larger values ​​of S and D indicate more severe blockage. This diagnostic method utilizes the relationship between the skin coefficient and production rate obtained from well productivity testing. It can accurately diagnose the type of downhole blockage in deep carbonate gas wells, dynamically evaluate the degree and trend of blockage, and guide the development of appropriate unblocking plans.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] One objective of this invention is to provide a method for diagnosing blockage types in deep carbonate gas wells, the method comprising the following:

[0009] Step S1: Use gas well productivity test data to interpret the test results and obtain the following relationship between the gas well skin coefficient and production rate:

[0010] S a =S+Dq g

[0011] Among them, S a S is the apparent skin factor of the gas well (also known as the total skin factor); S is the true skin factor of the gas well; D is the non-Darcy flow factor, in units of (10^6)^2. 4 m 3 / d) -1 ;q g For output, in units of 10 4 m 3 / d;

[0012] Step S2: Determine the type of blockage in deep carbonate gas wells based on the values ​​of the true skin coefficient S and the non-Darcy flow coefficient D; the larger the values ​​of S and D, the more severe the blockage.

[0013] The diagnostic method described in this invention utilizes the gas well productivity test to obtain the relationship between the gas well skin coefficient and production: S a =S+Dq g It can be seen that the apparent skin coefficient S of the gas well a It can be divided into two parts: one part is unrelated to production, namely the gas well true skin coefficient S, which represents the degree of reservoir stimulation; the other part is related to production, namely Dq. g It represents the additional skin layer caused by the non-Darcy turbulence effect of the gas, which is mainly related to the friction between the gas flow and the tubing wall. This invention determines the type of blockage in deep carbonate gas wells based on the values ​​of the true skin coefficient S and the non-Darcy flow coefficient D. The larger the values ​​of S and D, the more severe the blockage. It can accurately diagnose the downhole blockage type of deep carbonate gas wells, evaluate the degree of blockage and the trend of blockage changes, and guide the rational formulation of gas well unblocking schemes.

[0014] As a preferred technical solution of the present invention, the types of blockage in deep carbonate gas wells in step S2 include the following:

[0015] Type 1: When S > 0 and D > 0, both the formation and the wellbore are blocked;

[0016] Type 2: When S > 0 and D = 0, the formation is blocked, but the wellbore is not blocked;

[0017] Type 3: When S≤0 and D>0, the formation is not blocked, but the wellbore is blocked;

[0018] Type 4: When S≤0 and D=0, there is no blockage in the formation or wellbore.

[0019] As a preferred embodiment of the present invention, the diagnostic method further includes the following:

[0020] Step S3: Obtain the numerical changes of the true skin coefficient S and the non-Darcy flow coefficient D of the gas well at different times before and after, and determine the trend of gas well blockage.

[0021] As a preferred technical solution of the present invention, step S3 includes: conducting a new gas well productivity test in the later stage, and judging the gas well blockage trend based on the changes in the true skin coefficient S and non-Darcy flow coefficient D obtained from the gas well productivity test data at different times before and after.

[0022] As a preferred technical solution of the present invention, step S3 includes: conducting gas well productivity testing in the early stage of the gas well, and only conducting gas well pressure recovery testing in the later stage, based on the effective permeability and apparent skin coefficient S of the gas well at different times. a The changes in the true skin coefficient S and the non-Darcy flow coefficient D of the gas well are obtained to determine the trend of gas well blockage.

[0023] Step S3 of the present invention can be performed using either of the two methods described above to obtain the numerical changes of the true skin coefficient S and the non-Darcy flow coefficient D of the gas well at different times before and after, and to determine the trend of gas well blockage. When the value of S increases with time, it indicates that the formation blockage becomes more severe. When the value of D increases with time, it indicates that the wellbore blockage becomes more severe.

[0024] As a preferred technical solution of the present invention, the gas well production capacity test data is obtained by conducting downhole production capacity test tests on the gas well. Each test involves 3 to 5 different production points, and multiple tests can be conducted at different times, with an interval of 1 to 2 years.

[0025] One of the necessary conditions for the diagnostic method described in this invention is the need for the following test data: gas well production test data and optional gas well pressure recovery test data. Each test involves 3 to 5 different production points (back pressure test, isochronous test, or modified isochronous test are all acceptable), and multiple tests can be conducted at different times with an interval of 1 to 2 years.

[0026] The second objective of this invention is to provide a diagnostic device for the type of blockage in deep carbonate gas wells, the diagnostic device comprising:

[0027] The data acquisition unit is used to acquire well production test data of carbonate gas wells in the research area;

[0028] The well test interpretation unit is used to interpret the well test data based on the gas well production capacity well test data to obtain the relationship between the gas well skin coefficient and the production rate.

[0029] The blockage analysis unit is used to determine the type of blockage in deep carbonate gas wells based on the values ​​of the true skin coefficient S and the non-Darcy flow coefficient D.

[0030] As a preferred embodiment of the present invention, the diagnostic device further includes:

[0031] The blockage trend unit is used to determine the blockage trend of a gas well based on the changes in the true skin coefficient S and the non-Darcy flow coefficient D at different times.

[0032] As a preferred embodiment of the present invention, the diagnostic device further includes:

[0033] The unblocking countermeasures unit proposes targeted unblocking countermeasures after identifying the type of gas well blockage. For wellbore blockage, an effective unblocking method is to flush the blockage in the wellbore during flowback. For formation blockage, an effective unblocking method is to acidize the near-wellbore area.

[0034] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0035] (1) The diagnostic method described in this invention utilizes the gas well production capacity test to obtain the relationship between the gas well skin coefficient and production, and uses quantitative indicators to diagnose the type of downhole blockage in the gas well, clearly distinguishing between formation blockage and wellbore blockage.

[0036] (2) The diagnostic method described in this invention can dynamically evaluate the degree and trend of blockage during the gas well production process, and can predict the risk of gas well blockage in advance, providing a basis for formulating reasonable unblocking solutions for gas wells. Attached Figure Description

[0037] Figure 1 This is a flowchart of the method for diagnosing blockage types in deep carbonate gas wells as described in this invention;

[0038] Figure 2 This refers to the fitted pressure and output q in April 2022 in Example 1. g A curve graph;

[0039] Figure 3 The yield q obtained in April 2022 in Example 1 is... g With visual epidermal coefficient S a Relationship curve;

[0040] Figure 4 These are the pressure recovery double logarithmic curves obtained from the pressure recovery tests conducted in April 2022 and September 2023 in Example 1;

[0041] Figure 5 This is the production curve of well A in Example 1. Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] This invention provides a method for diagnosing the blockage type of deep carbonate gas wells. Figure 1 A flowchart illustrating the diagnostic method is shown, including the following:

[0044] Step S1: Use gas well productivity test data to interpret the test results and obtain the following relationship between the gas well skin coefficient and production rate:

[0045] S a =S+Dq g

[0046] Among them, S a S is the apparent skin factor of the gas well (also known as the total skin factor); S is the true skin factor of the gas well; D is the non-Darcy flow factor, in units of (10^6)^2. 4 m 3 / d) -1 ;q g For output, in units of 10 4 m 3 / d;

[0047] Step S2: Determine the type of blockage in deep carbonate gas wells based on the values ​​of the true skin coefficient S and the non-Darcy flow coefficient D, including the following:

[0048] Type 1: When S > 0 and D > 0, both the formation and the wellbore are blocked;

[0049] Type 2: When S > 0 and D = 0, the formation is blocked, but the wellbore is not blocked;

[0050] Type 3: When S≤0 and D>0, the formation is not blocked, but the wellbore is blocked;

[0051] Type 4: When S≤0 and D=0, there is no blockage in either the formation or the wellbore;

[0052] Among them, the larger the values ​​of S and D, the more severe the blockage;

[0053] Step S3: Obtain the numerical changes of the true skin coefficient S and the non-Darcy flow coefficient D of the gas well at different times before and after, and determine the trend of gas well blockage.

[0054] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0055] Example 1

[0056] This embodiment provides a method for diagnosing blockage types in deep carbonate gas wells, the method including the following:

[0057] Step S1: Using gas well productivity test data, interpret the test results to obtain the following relationship between the gas well skin coefficient and production rate: S a =S+Dq g ;

[0058] Well A is a deep carbonate gas well that began production in November 2021. A production test was conducted in April 2022, and the test was used to interpret the fitted pressure. Figure 2 The fitted pressure and output q are shown. g The curve can be used to obtain the gas well's output at different production rates q. g Apparent skin coefficient S under certain conditions a The data are summarized in Table 1. The yield q can be obtained by fitting the data in Table 1. g With visual epidermal coefficient S a Relationship curves, such as Figure 3 As shown, the relationship between the skin coefficient and production of well A can then be obtained: S a =-2.343+0.506q g That is, the true skin coefficient S of the gas well is -2.343, and the non-Darcy flow coefficient D is 0.506×(10) 4 m 3 / d) -1 ;

[0059] Table 1

[0060] <![CDATA[Output q g (10<s 4 m 3 / d)]]> 28.80 38.35 48.52 58.06 <![CDATA[Apparent skin factor S a > 12.9 16.0 22.3 27.3

[0061] Step S2: Determine the type of blockage in deep carbonate gas wells based on the values ​​of the true skin coefficient S and the non-Darcy flow coefficient D.

[0062] In April 2022, the true skin coefficient S of well A was negative, indicating that the reservoir stimulation effect was good, the reservoir was uncontaminated, and there was no formation blockage. The non-Darcy mobility coefficient D of well A was 0.506 × (10⁻⁶). 4 m 3 / d) -1 There is a significant turbulence effect, at 58.06×10 4 m 3 / d production rate of gas well skin coefficient S a The value is approximately 27.3. Based on the comprehensive judgment, since S≤0 and D>0, it satisfies type three, indicating that there has been no formation blockage since well A was put into production, but there is a certain degree of blockage in the wellbore.

[0063] Step S3: Obtain the numerical changes of the true skin coefficient S and the non-Darcy flow coefficient D of the gas well at different times before and after, and determine the trend of gas well blockage.

[0064] Well A underwent a production capacity and pressure recovery test in April 2022, and a pressure recovery test in September 2023. The pressure recovery double logarithmic curves are shown below. Figure 4 The interpretation results of the two well tests showed that the effective permeability of well A did not change (the productivity coefficient kh was 2276 mD), but the apparent skin coefficient S of the gas well increased. a There was a significant increase in September 2023, reaching 120 (the production before well shutdown and recovery was 59.89 × 10). 4 m 3 / d). Because the effective permeability near the wellbore of well A did not change, it can be determined that the reservoir was not contaminated during the gas well production process, and the true skin coefficient S remains -2.343. The apparent skin coefficient S will be used to determine the permeability of the reservoir. a =120 and gas well production q g =59.89×10 4 m 3 / d Substitute S a =S+Dq g From this, the non-Darcy flow coefficient D of well A in September 2023 can be calculated to be 2.043 × (10⁻⁶). 4 m 3 / d) -1 That is, in September 2023, the relationship between the skin coefficient and production of well A was S. a = -2.343 + 2.043q g ;

[0065] Compared to April 2022, since the effective permeability of Well A remained unchanged, it can be determined that the reservoir was not contaminated during the gas well production process, and the true skin coefficient S remained at -2.343. However, the non-Darcy flow coefficient D of Well A reached 2.043 × (10⁻⁶) in September 2023. 4 m 3 / d) -1An increase in the non-Darcy flow coefficient D indicates no formation blockage, but wellbore blockage is significantly aggravated.

[0066] Figure 5 The production curve of Well A shows that in the early stage of production (November 2021 to May 2022), there were slight abnormal fluctuations in the oil pressure of the gas well. According to the diagnostic method of this invention, this was caused by the up-and-down movement of blockages in the wellbore. From June 2023 to February 2024, the oil pressure of the gas well dropped abnormally and significantly. According to the diagnostic method of this invention, this was caused by the aggravation of the blockage in the wellbore. It is necessary to implement wellbore unblocking measures to flush out the blockages in the wellbore.

[0067] The present invention also provides a diagnostic device for the type of blockage in deep carbonate gas wells, the diagnostic device comprising:

[0068] The data acquisition unit is used to acquire well production test data of carbonate gas wells in the research area;

[0069] The well test interpretation unit is used to interpret the well test data based on the gas well production capacity well test data to obtain the relationship between the gas well skin coefficient and the production rate.

[0070] The blockage analysis unit is used to determine the type of blockage in deep carbonate gas wells based on the values ​​of the true skin coefficient S and the non-Darcy flow coefficient D.

[0071] Preferably, the diagnostic device further includes:

[0072] The blockage trend unit is used to determine the blockage trend of a gas well based on the changes in the true skin coefficient S and the non-Darcy flow coefficient D at different times.

[0073] Preferably, the diagnostic device further includes:

[0074] The unblocking countermeasures unit proposes targeted unblocking countermeasures after identifying the type of gas well blockage. For wellbore blockage, an effective unblocking method is to flush the blockage in the wellbore during flowback. For formation blockage, an effective unblocking method is to acidize the near-wellbore area.

[0075] In summary, this invention provides a method and device for diagnosing blockage types in deep carbonate gas wells. By interpreting well test data, the following relationship between the well skin coefficient and production rate is obtained: S a =S+Dq gThe type of blockage in deep carbonate gas wells is determined by the values ​​of the true skin coefficient (S) and the non-Darcy flow coefficient (D). Larger values ​​of S and D indicate more severe blockage. This diagnostic method utilizes the relationship between the skin coefficient and production rate obtained from well productivity testing. It can accurately diagnose the type of downhole blockage in deep carbonate gas wells, dynamically evaluate the degree and trend of blockage, and guide the development of appropriate unblocking plans.

[0076] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0077] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0078] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0079] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for diagnosing blockage types in deep carbonate gas wells, characterized in that, The diagnostic method includes the following: Step S1: Use gas well productivity test data to interpret the test results and obtain the following relationship between the gas well skin coefficient and production rate: S a =S+Dq g Among them, S a S is the apparent skin coefficient of the gas well; S is the true skin coefficient of the gas well; D is the non-Darcy flow coefficient, in units of (10). 4 m 3 / d) -1 ;q g For output, in units of 10 4 m 3 / d; Step S2: Determine the type of blockage in deep carbonate gas wells based on the values ​​of the true skin coefficient S and the non-Darcy flow coefficient D; the larger the values ​​of S and D, the more severe the blockage.

2. The diagnostic method according to claim 1, characterized in that, The types of blockage in deep carbonate gas wells in step S2 include the following: Type 1: When S > 0 and D > 0, both the formation and the wellbore are blocked; Type 2: When S > 0 and D = 0, the formation is blocked, but the wellbore is not blocked; Type 3: When S≤0 and D>0, the formation is not blocked, but the wellbore is blocked; Type 4: When S≤0 and D=0, there is no blockage in the formation or wellbore.

3. The diagnostic method according to claim 1 or 2, characterized in that, The diagnostic method also includes the following: Step S3: Obtain the numerical changes of the true skin coefficient S and the non-Darcy flow coefficient D of the gas well at different times before and after, and determine the trend of gas well blockage.

4. The diagnostic method according to claim 3, characterized in that, Step S3 includes: conducting new gas well productivity tests in the later stage, and judging the trend of gas well blockage based on the changes in the true skin coefficient S and non-Darcy flow coefficient D obtained from the gas well productivity test data at different times before and after.

5. The diagnostic method according to claim 3, characterized in that, Step S3 includes: conducting gas well productivity testing in the early stage of the gas well, and only conducting gas well pressure recovery testing in the later stage, based on the effective permeability and apparent skin coefficient S of the gas well at different times. a The changes in the true skin coefficient S and the non-Darcy flow coefficient D of the gas well are obtained to determine the trend of gas well blockage.

6. The diagnostic method according to any one of claims 1-3, characterized in that, Gas well productivity test data is obtained by conducting downhole productivity tests on gas wells. Each test involves 3 to 5 different production points, and multiple tests can be conducted at different times, with an interval of 1 to 2 years.

7. A diagnostic device for blockage types in deep carbonate gas wells, characterized in that, The diagnostic device includes: The data acquisition unit is used to acquire well production test data of carbonate gas wells in the research area; The well test interpretation unit is used to interpret the well test data based on the gas well production capacity well test data to obtain the relationship between the gas well skin coefficient and the production rate. The blockage analysis unit is used to determine the type of blockage in deep carbonate gas wells based on the values ​​of the true skin coefficient S and the non-Darcy flow coefficient D.

8. The diagnostic device according to claim 8, characterized in that, The diagnostic device further includes: The blockage trend unit is used to determine the blockage trend of a gas well based on the changes in the true skin coefficient S and the non-Darcy flow coefficient D at different times.

9. The diagnostic device according to claim 7 or 8, characterized in that, The diagnostic device further includes: The unblocking countermeasures unit proposes targeted unblocking countermeasures after identifying the type of gas well blockage. For wellbore blockage, an effective unblocking method is to flush the blockage in the wellbore during flowback. For formation blockage, an effective unblocking method is to acidize the near-wellbore area.

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