Method for determining water source position of water-bearing gas reservoir formation

Abstract

This invention discloses a method for determining the source location of formation water in a water-bearing gas reservoir. It involves collecting fluid temperatures from different production zones at various times, including temperatures before, after, and before and after well shut-in / shut-out. Simultaneously, it acquires the temperature gradient of the pure water section of the production zone after water production. For wells already in a water-bearing zone, the method calculates the depth of the water source entering the wellbore after well shut-in / shut-out using the temperature difference between the shut-in and shut-out temperatures of the production zone at the same time, based on the temperature gradient and temperature difference of the pure water section of the production zone after water production. For gas wells where the produced water is not from the local formation but has reached water due to increased production pressure differentials and upward flow along fractures or faults, the method accurately determines the specific water-bearing layer and depth of the producing well by using the measured temperature rise of the water-bearing layer before and after water production at downhole measuring points, based on the measured water layer temperature gradient. This method offers high accuracy, aids in production guidance, and ensures long-term stable production of the gas well.

Description

Technical Field

[0001] This invention belongs to the field of determining the source of water production in gas wells after water breakthrough in gas reservoirs, and provides a technical means to formulate reasonable development technology strategies, specifically a method for determining the location of formation water source in water-bearing gas reservoirs. Background Technology

[0002] The sources of water produced by a single well in a gas reservoir can be divided into three categories: water inside the gas reservoir (including condensate water, fracture water, primary movable water within the reservoir and secondary movable water within the reservoir), water outside the gas reservoir (including interlayer water and edge and bottom water), and industrial water used for on-site construction.

[0003] (1) Water inside the gas layer:

[0004] Condensate water: Under formation conditions, some water exists in a gaseous state. During extraction, it liquefies and is produced as the temperature and pressure in the wellbore decrease. Its characteristics include low water production, a constant water-to-gas ratio that varies with gas production, and very low mineralization.

[0005] Fracture water: Water is squeezed out of fractures due to a decrease in gas pressure. It is characterized by a gradual increase in water production over time, but the overall water production is relatively small, and the mineralization is relatively high, but different from that of formation water.

[0006] (2) Water outside the gas layer:

[0007] Interlayer water: Water bodies separated by strata above and below the gas layer, or water contained within mudstone strata, are produced when the water body breaks through the capillary forces within the mudstone strata.

[0008] Its characteristics include: sudden water breakthrough in the gas well, rapid increase and drastic fluctuations in water production; in the later stages of production, due to depletion or insufficient pressure differential, water production usually decreases; water production is localized and has high salinity. Edge and bottom water: When the production zone is close to edge or bottom water layers, edge water intrusion or bottom water surge is likely to occur, resulting in large-scale water production from the gas well. Its characteristics are that it usually occurs in the middle and later stages of gas reservoir development, with continuously increasing and fluctuating water production.

[0009] Due to differences in gas reservoir type, driving mechanism, and reservoir properties, the sources and mechanisms of produced water vary greatly during the natural gas extraction process. Understanding the sources and mechanisms of produced water is one of the important foundations for optimizing gas reservoir development methods and improving development efficiency.

[0010] Currently, scholars both domestically and internationally have conducted extensive research on the identification of water sources in gas reservoirs. Considering the diversity and unique characteristics of water sources in gas wells of edge-bottom water reservoirs, and combining the four main types of water sources commonly found—condensate water, interlayer water channeling, interlayer water, and edge-bottom water—a systematic comprehensive identification method for water sources in single wells is proposed, based on six steps: condensate water analysis, single-well production dynamics analysis, single-well logging interpretation analysis, analysis of dominant seepage channels between wells, identification of water-producing strata, and numerical simulation verification.

[0011] However, the aforementioned research findings did not provide specific detection schemes or conclusions regarding the depth of specific water production sources. The understanding of water production sources was insufficient, and the guidance for production was inadequate. This even greatly affected the long-term stable production of gas wells, restricted the efficient development of gas reservoirs, and did not provide any effective guidance or assistance for natural gas extraction. Summary of the Invention

[0012] The purpose of this invention is to provide a method for determining the location of formation water in a water-bearing gas reservoir, overcoming the shortcomings of existing technologies. This invention can accurately determine the specific water-bearing layer and depth of the producing well based on the measured temperature rise at downhole measuring points and the measured water layer temperature gradient, thereby more accurately predicting the water-bearing layer, depth, and size of the water source.

[0013] A method for determining the source location of formation water in a water-bearing gas reservoir includes the following steps:

[0014] S1 collects fluid temperatures at different stages of the production zone, including the temperature T after well opening. 开 and the temperature T after shutting in the well 关 ;

[0015] S2, obtain the temperature gradient G of the pure water section of the production layer after the gas well produces water. T ;

[0016] S3, calculate the post-well opening temperature T of the production section of this gas well during the same period. 开 and the temperature T after shutting in the well 关 Temperature difference ΔT = T 开 -T 关 According to the temperature gradient G of the pure water section of the production layer after the gas well produces water. T The depth H of the water source entering the wellbore after well opening is calculated based on the temperature difference. SY :

[0017]

[0018] Preferably, the fluid temperature of the production zone at different times is obtained by wireline well testing or production logging.

[0019] Preferably, the temperature gradient of the pure water section of the production layer after water production is obtained through wireline well testing.

[0020] Preferably, the temperature gradient of the pure water section of the production layer used to calculate the water source depth and the temperature difference used to calculate the temperature difference are data from the same period.

[0021] Preferably, the size of the bottom water body can be assessed based on the difference in depth between the water source and the production layer.

[0022]

[0023] H represents the depth of the production section.

[0024] Preferably, if the difference between the depth of the water source and the height of the production layer is greater than a set threshold, it is a large-scale water body; if it is less than or equal to the set threshold, it is a small-scale water body.

[0025] A method for determining the source location of formation water in a water-bearing gas reservoir includes the following steps:

[0026] S1 collects fluid temperatures at different stages of the production zone, including the temperature T before the gas well reaches water. g and the temperature T after contact with water w ;

[0027] S2, Obtain the temperature gradient G of the pure water section in the production zone under well-opening conditions. t ;

[0028] S3, based on the temperature T before water breakthrough at the same time in this gas well. g and the temperature T after contact with water w The temperature difference Δt, and the temperature gradient G of the pure water section of the production zone under well-opening conditions. t Calculate the depth H of the water source entering the wellbore after water production. Sy :

[0029] △t=T w -T g

[0030]

[0031] Preferably, the fluid temperature of the production zone at different times is obtained by wireline well testing or production logging.

[0032] Preferably, the temperature gradient of the pure water section of the production layer after water production is obtained through wireline well testing.

[0033] Preferably, the temperature gradient of the pure water section of the production layer used to calculate the water source depth and the temperature difference used to calculate the temperature difference are data from the same period.

[0034] Compared with the prior art, the present invention has the following beneficial technical effects:

[0035] This invention discloses a method for determining the source location of formation water in water-bearing gas reservoirs. This method involves collecting fluid temperatures from production zones at different times, including the temperature T after well opening. 开 and the temperature T after shutting in the well 关 Simultaneously, the temperature gradient G of the pure water section of the production layer after water production is obtained. T The post-well opening temperature T of the production zone during the same period after the gas well produces water was used. 开 and the temperature T after shutting in the well 关 Temperature difference ΔT = T 开 -T 关 According to the temperature gradient G of the pure water section of the production layer after the gas well produces water. T The depth H of the water source entering the wellbore after well opening is calculated based on the temperature difference. SY For gas wells already in water zones, the specific water inflow level and depth after the well is opened can be accurately determined by using the measured temperature rise at the downhole measuring point and the measured water layer temperature gradient. This method is highly accurate, helps guide production, and ensures the long-term stable production of gas wells.

[0036] Furthermore, the fluid temperature of production zones at different times can be obtained by using wireline well testing or production logging methods. This method is simple, does not require the re-establishment of a temperature detection system, and can accurately obtain the fluid temperature of production zones at different times.

[0037] Furthermore, by utilizing wireline well testing operations to simultaneously obtain the temperature gradient of the pure water section of the production layer after water production, the workload of testing is reduced.

[0038] Furthermore, the temperature gradient of the pure water section of the production layer used to calculate the water source depth and the temperature difference used to calculate the temperature difference are data from the same period. Using data from the same period for calculation results in high accuracy and can be reused.

[0039] Furthermore, based on the difference in depth between the water source and the production layer, the scale of the edge and bottom water body can be quickly assessed. This simple method provides effective guidance for the later-stage treatment of gas reservoirs.

[0040] This invention discloses a method for determining the source location of formation water in water-bearing gas reservoirs after well opening. This method enables the determination of the source location of formation water in water-bearing gas reservoirs where water has emerged due to increased production pressure differential and upwelling along fractures or faults. It also involves collecting fluid temperatures from different production zones, including the temperature T after well opening. 开 and the temperature T after shutting in the well 关 ;Utilizing the temperature gradient G in the pure water section of the production layer after water production t ; and the temperature T before water breakthrough at the same time as the gas well. g and the temperature T after contact with water w The temperature difference Δt can be used to determine the depth H of the water source entering the wellbore after water production. SyThis invention addresses situations where produced water is not from the local formation but has surged along fractures or faults due to increased production pressure differentials, leading to water breakthrough. It utilizes the measured temperature gradient of the producing formation before water breakthrough to determine the temperature difference between the pure gas layer and the pure water layer after breakthrough. By using this measured water layer temperature gradient, the specific water-bearing layer and depth of the producing well can be accurately determined. This allows for more accurate prediction of the water-bearing layer and depth, as well as assessment of the water source size. It provides rational and efficient development suggestions for water control and gas production with water present after breakthrough, ensuring long-term stable production of the gas reservoir and well. Attached Figure Description

[0041] Figure 1 This is a plan view of a water-gas reservoir in an embodiment of the present invention.

[0042] Figure 2 This is a schematic diagram of an east-west cross-section of a water-gas reservoir in an embodiment of the present invention.

[0043] Figure 3 This is a schematic diagram of a north-south cross-section of a water-gas reservoir in an embodiment of the present invention. Detailed Implementation

[0044] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0045] The present invention provides a method for determining the source location of formation water in a water-bearing gas reservoir, which is used to confirm the water-bearing layer and depth of a gas reservoir well that is already in a water-bearing area, or to confirm that the produced water is not from the current formation, but has flowed up along fractures or faults due to increased production pressure differential, thus determining the source location of formation water.

[0046] Specifically, the following steps are included:

[0047] For the detection of fluid temperature and temperature gradient in the downhole production section:

[0048] S1, firstly, collect the fluid temperature of the production zone at different times, including the temperature T before the gas well reaches water. g Temperature T after contact with water w and the temperature T after well opening 开 Temperature T after well shut-in 关 ;

[0049] Different periods refer to the time periods involved in normal production, and temperature parameters within the same time period are compared;

[0050] The temperature T before the gas well reaches waterg and the temperature T after contact with water w This is used to calculate the location of formation water sources in water-bearing gas reservoirs where the produced water is not from the local formation, but rather rises along fractures or faults due to increased production pressure differentials.

[0051] Temperature T after well opening 开 and the temperature T after shutting in the well 关 This method is used to calculate the location of formation water sources in gas reservoirs that are already in water zones. If the temperature of the water zone in a gas reservoir that is in a water zone has stabilized in the same period, the depth of the water source can be calculated based on the temperature difference between the well shut-in and the well opening in that area.

[0052] This invention uses wireline well testing or production logging methods to obtain the fluid temperature of production zones at different times.

[0053] S2, obtain the temperature gradient G of the pure water section of the production layer after the gas well produces water. T Or, under well-opening conditions, the temperature gradient G in the pure water section of the production zone. t ;

[0054] Specifically, the temperature gradient of the pure water section of the production layer after water production is obtained through wireline well testing to obtain accurate temperature gradient data of the pure water section of the production layer.

[0055] For wells already located in water-bearing areas, determine the location of the formation water source:

[0056] S3, If the gas well is already in a water zone, then the temperature T after well opening should be used as the reference for the production zone of the gas well at the same time. 开 Temperature T after well shut-in 关 Calculate the temperature difference ΔT:

[0057] △T=T 开 -T 关 ;

[0058] Then, based on the temperature gradient G of the pure water section of the production layer after the gas well produces water... T The depth H of the water source entering the wellbore after well opening is calculated. SY :

[0059]

[0060] The temperature gradient of the pure water section of the production layer after water production in this gas well is used at this time, along with the temperature T of the production layer after well opening. 开 Temperature T after well shut-in 关 Data from the same period, i.e., data under the same temperature environment, is used to avoid inaccurate calculations due to environmental factors.

[0061] Then, based on the difference in depth between the water source and the production layer, the size of the bottom water body can be assessed; H is the depth of the production layer.

[0062]

[0063] For produced water that is not from this formation, but rather due to increased production pressure differential causing water to seep up along fractures or faults, the location of the formation water source must be determined as follows:

[0064] S4. If the water produced by the gas well is not from this formation, but rather due to increased production pressure differential causing water to seep up along fractures or faults, then the water level should be determined based on the temperature T before water breakthrough at the same time. g and the temperature T after contact with water w Temperature difference;

[0065] Combining the temperature difference and the temperature gradient G of the pure water section in the production zone under well-opening conditions t Calculate the depth H of the water source entering the wellbore after water production. sy :

[0066] △t=T w -T g

[0067]

[0068] T 关 Temperature at point H in the production zone after the well is shut in, in °C;

[0069] T 开 Temperature at point H in the production zone after the well is opened, in °C;

[0070] T g Temperature at point H in the production zone before water breakthrough at the gas well, in °C;

[0071] T w Temperature at point H in the production zone after water breakthrough at the gas well, in °C;

[0072] G T Temperature gradient of the pure water section of the production layer after gas well water production, ℃ / / ;

[0073] H SY Location of water source, / ;

[0074] G t Temperature gradient of the pure water section in the production zone under well-opening conditions, ℃ / / .

[0075] This invention utilizes the temperature variations in the production zones within a gas reservoir at different times to determine the depth of the water source.

[0076]

[0077]

[0078] This provides reasonable and efficient development suggestions for water control after water breakthrough and gas extraction with water, and provides a basis for ensuring the long-term stable production of gas wells.

[0079] Example:

[0080] like Figure 1 As shown, for the ultra-deep and ultra-high pressure edge water gas reservoir S, its structure is an east-west trending short-axis anticline. Four wells A, B, C, and D were drilled along the long axis of the structure. The four wells A, B, C, and D were tested and put into production.

[0081] Well A encountered water during the oil testing phase and was already in a water-affected area, so it was designed as a drainage well.

[0082] Well C is located in a high structural position with a large water-avoidance height. It suddenly produces water, with rapid water inflow, large water volume, and strong energy, exhibiting characteristics of a violent flooding.

[0083] The two gas production wells B and D on the east and west wings of well C are producing normally, with no signs of water production.

[0084] Well A is known to be a water-bearing well during oil testing, located in the water zone on the western wing of the S gas reservoir structure.

[0085] Before the official start of drainage in Well A, a pressure gauge was lowered to a depth of 5307.45 m / s in the well. During the lowering process, the static temperature gradient of the production zone was measured to be 2.26℃ / 100℃ / s.

[0086] The static temperature at the measuring point before the well is opened and after the well is closed is 107.39℃, which is the temperature after the well is opened; after well A is opened and drained, the flow temperature at the measuring point rises rapidly and eventually stabilizes at 110.83℃, which is the temperature after the well is opened.

[0087] After the downhole temperature and pressure test is completed, a flow temperature gradient test is conducted while the pressure gauge is being pulled up. The flow temperature gradient of the production section is 1.00℃ / 100℃ / .

[0088] Calculate the depth of the measuring point:

[0089] The temperature difference between the static and flowing temperatures at point 5307.45 is approximately 3.44℃. Based on the temperature gradient of the pure water section (1.00℃ / 100℃), the water source location is calculated to be at point 5651.45.

[0090]

[0091]

[0092] The value of △H is 344 / , indicating that the water-producing section of well A moved rapidly downward to supply fluid after well opening. Based on the value of △H, it can be determined that the water body in the western wing of the S gas reservoir is relatively small.

[0093] like Figure 2 As shown

[0094] Well C is a gas production well located in the high part of the S gas reservoir structure, with a water avoidance height of 473 m. After 621 days of trial production, it suddenly produced a large amount of water, and the oil pressure and gas production dropped rapidly. Its daily water production was 120 t and the oil pressure dropped at a rate of 4 MPa / month.

[0095] Well B is a gas production well located in the middle-high part of the western side of Well C in the S gas reservoir structure. The water avoidance height is 203 / . So far, no signs of water have been observed, ruling out the possibility that the water source of Well C comes from the western wing side water intrusion.

[0096] Before water production from Well C, the measured temperature at a depth of 4900 m was 105℃. After water production, the measured temperature gradient in the production zone was 1.00℃ / 100 m, and the temperature at a depth of 4900 m was 108.5℃.

[0097] The temperature difference before and after water is encountered at a depth of 4900 m is calculated to be approximately 3.5℃. Based on the temperature gradient of the pure water section (1.00℃ / 100 m), the water source is calculated to be located below 5250 m.

[0098]

[0099] Based on the structural features of the S gas reservoir, it is determined that the water source of well C originates from the formation water on the southern wing of the structure and is connected along the fault.

[0100] This invention provides a method for determining the source location of formation water in a water-bearing gas reservoir, which utilizes the fluid temperature of the production zone at different times, including the temperature T before water breakthrough at the gas well. g Temperature T after contact with water w and the temperature T after well opening 开 Temperature T after well shut-in 关 Furthermore, the temperature gradient of the pure water section in the production layer after water production is used. By measuring the temperature difference under different conditions, two methods can be employed: First, for wells already in a water-bearing zone, the specific water-bearing layer and depth can be accurately determined after well opening based on the measured temperature rise at downhole measuring points and the measured water layer temperature gradient. Second, for water produced from sources other than the local layer, where increased production pressure differentials lead to water breakthrough along fractures or faults, the temperature difference between the pure gas layer temperature before water production and the pure water layer temperature after water production can be measured using the measured temperature gradient of the production layer. This allows for more accurate prediction of the water-bearing layer and depth, as well as assessment of the water source size. This provides rational and efficient development suggestions for water control and gas production with water after water breakthrough, ensuring the long-term stable production of gas reservoirs and wells.

[0101] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for determining the source location of formation water in a water-bearing gas reservoir, characterized in that, Includes the following steps: S1 collects fluid temperatures at different stages of the production zone, including the temperature T after well opening. 开 and the temperature T after shutting in the well 关 ; S2, obtain the temperature gradient G of the pure water section of the production layer after the gas well produces water. T ; S3, calculate the post-well opening temperature T of the production section of this gas well during the same period. 开 and the temperature T after shutting in the well 关 Temperature difference ΔT = T 开 -T 关 According to the temperature gradient G of the pure water section of the production layer after the gas well produces water. T The depth H of the water source entering the wellbore after well opening is calculated based on the temperature difference. SY :

2. The method for determining the source location of formation water in a water-bearing gas reservoir according to claim 1, characterized in that, The fluid temperature of the production zone at different times can be obtained by using wireline well testing or production logging methods.

3. The method for determining the source location of formation water in a water-bearing gas reservoir according to claim 1, characterized in that, The temperature gradient of the pure water section of the production layer after water production is obtained through wireline well testing.

4. The method for determining the location of formation water in a water-bearing gas reservoir according to claim 1, characterized in that, The temperature gradient of the pure water section of the production layer used to calculate the water source depth and the temperature difference used to calculate the temperature difference are data from the same period.

5. The method for determining the source location of formation water in a water-bearing gas reservoir according to claim 1, characterized in that, The size of the bottom water body can be assessed based on the difference between the depth of the water source and the height of the production layer. H represents the depth of the production section.

6. The method for determining the source location of formation water in a water-bearing gas reservoir according to claim 5, characterized in that, If the difference between the depth of the water source and the height of the production layer is greater than a set threshold, it is considered a large-scale water body; if it is less than or equal to the set threshold, it is considered a small-scale water body.

7. A method for determining the location of formation water source in a water-bearing gas reservoir, characterized in that, Includes the following steps: S1 collects fluid temperatures at different stages of the production zone, including the temperature T before the gas well reaches water. g and the temperature T after contact with water w ; S2, Obtain the temperature gradient G of the pure water section in the production zone under well-opening conditions. t ; S3, based on the temperature T before water breakthrough at the same time in this gas well. g and the temperature T after contact with water w The temperature difference Δt, and the temperature gradient G of the pure water section of the production zone under well-opening conditions. t Calculate the depth H of the water source entering the wellbore after water production. sy : △t=T w -T g 8. The method for determining the location of formation water source in a water-bearing gas reservoir according to claim 7, characterized in that, The fluid temperature of the production zone at different times can be obtained by using wireline well testing or production logging methods.

9. The method for determining the source location of formation water in a water-bearing gas reservoir according to claim 7, characterized in that, The temperature gradient of the pure water section of the production layer after water production is obtained through wireline well testing.

10. The method for determining the source location of formation water in a water-bearing gas reservoir according to claim 7, characterized in that, The temperature gradient of the pure water section of the production layer used to calculate the water source depth and the temperature difference used to calculate the temperature difference are data from the same period.

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