U-shaped valve drainage gas recovery design method suitable for shale gas horizontal well
By adopting the U-shaped valve drainage and gas extraction design method in shale gas horizontal wells, the problem of low shale gas extraction efficiency caused by insufficient internal pressure is solved, and the effective mining of shale gas wells of different internal pressures is achieved, which improves the process success rate and the production cycle of shale gas exhaust and mining wells.
Patent Information
- Application Number
- CN202411789906.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2025-02-28
AI Technical Summary
In shale gas horizontal wells, insufficient internal pressure leads to low shale gas extraction efficiency, and the existing technology is difficult to effectively solve this problem.
The U-shaped valve drainage gas extraction design method is adopted to ensure the realization of the gas-liquid mutual push mode by selecting suitable shale gas wells, designing a reasonable pipe column structure and automatic control valves, thereby improving the efficiency of shale gas mining.
The successful mining of shale gas in shale gas wells with different internal pressures has been achieved, the success rate of the U-shaped valve drainage and gas extraction process has been improved, and the self-blasting production cycle of shale gas exhaust and mining wells has been extended.
Smart Images
Figure CN119531775A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of shale gas exploitation, and in particular to a U-valve drainage and gas production design method suitable for shale gas horizontal wells. Background Art
[0002] In the process of shale gas horizontal well drainage and gas production, if the internal pressure of the shale gas well is insufficient, a U-shaped valve needs to be designed on the lowered pipe string to realize shale gas production. The U-shaped valve on the pipe string makes the entire pipe string form a multi-level independent chamber ladder. When the pressurized gas and liquid in the shale gas well enter the U-shaped pipe through the pipe pin, the U-shaped connecting valve on the automatic drainage pipe string will automatically interlock the gas and liquid, and the multi-stage gas and liquid that push each other form a mutual push mode. This mode not only closes the channel for the liquid to go down, but also allows the gas to push the liquid to the upper level when it goes up, repeating this process to achieve the purpose of mutual push and rise of gas and liquid. However, in the actual field application process, not all blindly adopting this process will achieve good results. The selection of gas wells, the design of the number and spacing of U-shaped valves, and the depth of the pipe string directly affect the implementation effect of the process. Therefore, the combined U-shaped valve structure that meets the needs of shale gas drainage and production can be used to produce shale gas in shale gas wells with insufficient internal pressure. Summary of the invention
[0003] The present invention aims to provide a U-valve drainage and gas production design method suitable for shale gas horizontal wells, so as to achieve the purpose of successfully producing shale gas in shale gas wells with different internal pressures.
[0004] To achieve the above object, the present invention adopts the following technical solution: a U-valve drainage and gas production design method suitable for shale gas horizontal wells, comprising the following steps: Step 1: Select a shale gas well with a static pressure exceeding 12 MPa after pressure relief and well shut-in; Step 2: Calculate the minimum production and minimum flow pressure of shale gas wells; Step 3: Measuring the bottom hole static pressure of the shale gas well; Step 4: Measure the downhole liquid level or calculate the oil-casing pressure difference to determine the depth of the downhole liquid; Step 5: Design the pipe string used in the shale gas well, including the outer diameter of the pipe string, the depth of the pipe string lowering and the inner diameter of the pipe string. The outer diameter of the pipe string is designed to ensure that the pipe string can be lowered into the shale gas well. The lowering depth of the pipe string needs to ensure that the pipe string is higher than the liquid accumulation surface. The pipe string lowering depth and bottom hole static pressure data are input into the pipesim software. The drainage flow rate and the friction resistance in the pipe string are within the specified range to obtain the inner diameter value of the pipe string. Step 6: Design the automatic control valve in the string, including the vertical depth difference design between the uppermost automatic control valve and the lowest point of the liquid accumulation, and the vertical depth difference design between the lowermost automatic control valve and the lowest point of the string. The vertical depth difference between the uppermost automatic control valve and the lowest point of the liquid accumulation is calculated by P ≥ ρ gh 最上端 The formula is calculated, where P is the bottom hole static pressure, ρ is the density of the liquid column in the wellbore, g is the gravitational acceleration, and h is the gravitational acceleration. 最上端 It is the vertical depth difference between the uppermost automatic control valve in the pipe string and the lowest point of the liquid accumulation; The vertical depth difference between the lowest automatic control valve and the lowest point of the pipe string is measured by PP wf ≥ ρ gh 最下端 The formula is obtained; where: P is the bottom hole static pressure, P wf is the bottom hole pressure, ρ is the density of the liquid column in the wellbore, g is the gravitational acceleration, h 最下端 It is the vertical depth difference between the automatic control valve at the middle and lower end of the pipe string and the lowest point of the pipe string; For example, the shut-in static pressure of a shale gas well is 15 MPa, and the predicted minimum flow pressure for its self-flowing production is 12 MPa. The difference between the two is 3 MPa. Therefore, the vertical depth of the lowest automatic control valve should not be higher than the vertical depth of 306 m at the lowest point of the string.
[0005] Step 7: Design of middle automatic control valve: When the depth of the pipe string is within 1500m, no middle automatic control valve is installed. When the depth of the pipe string is greater than or equal to 1500m, as the depth of the pipe string increases by 500m, an automatic control valve is added at equal intervals between the two automatic control valves at the top and bottom. Step 8: Design the maximum spacing between two adjacent U-shaped valves. Install the U-shaped valve between the uppermost and lowermost automatic control valves. The maximum spacing between two adjacent U-shaped valves meets the following requirements: ρ gh 滞 + wellhead back pressure < bottom hole flow pressure, where h 滞 is the maximum spacing of the U-type valve, ρ gh 滞 It is the gravity of the retained liquid between two adjacent U-valves.
[0006] Preferably, in step 2, the production curve of the gas well is predicted by the RTA method to obtain the minimum production and minimum flow pressure of the shale gas well's self-flowing production.
[0007] Preferably, in step 4, if the shale gas well is in a long-term shutdown state due to fluid accumulation and a tubing string has been installed, a shale gas well with an oil / casing pressure difference greater than 2 MPa is selected.
[0008] Preferably, in step five, the upper portion of the pipe column should be higher than the liquid accumulation surface.
[0009] Preferably, in step five, a bell mouth and a screen tube are provided at the bottom of the pipe column.
[0010] Preferably, in step eight, the distance between two adjacent U-shaped valves is greater than or equal to 10 meters.
[0011] The principles and advantages of this method are: multiple U-valves and automatic gas injection control valves are connected in series on the pipe string to automatically adjust and match the gas pressure and gas volume, obtain a reasonable gas-liquid ratio, maintain the best drainage and gas production efficiency, use the well's own energy to achieve automatic drainage and gas production, and extend the self-flowing production cycle of shale gas drainage wells.
[0012] The U-valve drainage and gas production in the above process requires the static pressure of the shale gas well, so it is necessary to select a shale gas well with a static pressure of more than 12MPa after pressure relief and well shut-in. The number and spacing of the automatic control valve and U-valve are determined by measuring the liquid accumulation depth of the shale gas wellbore, calculating the lifting pressure and the friction resistance of the pipe string.
[0013] This design method helps to significantly improve the success rate of the U-valve drainage and gas production process in field applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 This is the structural diagram of the U-valve for draining water and collecting air.
[0015] Figure 2 This is the height curve of the retained liquid column at different U-valve spacings when the daily output is 3,000 cubic meters; Figure 3 This is the relationship between the U-valve spacing and cost at different well depths. DETAILED DESCRIPTION
[0016] The following is further described in detail through specific implementation methods: like Figure 1 The figure shows the structure of the U-valve drainage and gas production, including going deep into the shale gas well casing 3, placing a pipe string 1 in the casing 3, and setting an automatic control valve 4 on the pipe string 1. When the pipe string depth is greater than or equal to 1500m, as the pipe string depth increases by 500m, an automatic control valve is added to the pipe string 1, and U-valve 2 is continuously set on the pipe string 1. The U-valve 2 can form a multi-level independent chamber ladder for the entire pipe string; a bell mouth and a screen pipe 5 are installed at the lower end of the pipe string 1.
[0017] This embodiment provides a U-valve drainage and gas production design method applicable to shale gas horizontal wells, including the following steps: Step 1: The U-type valve makes full use of the energy of the gas well itself and achieves efficient drainage through structural design. Therefore, the gas well itself must have a certain amount of energy, and the pressure recovery is relatively fast after pressure relief and well closure. Select shale gas wells with a static pressure of more than 12MPa after pressure relief and well closure. It is not advisable to select gas wells with serious formation proppant return or a large amount of insoluble matter in the return to avoid clogging the U-type valve.
[0018] If the gas well has been shut down for a long time due to severe liquid accumulation, and the tubing has been lowered in advance, it is recommended to select a gas well with an oil / casing pressure difference greater than 2MPa.
[0019] Step 2: Calculate the minimum production and minimum flow pressure of shale gas wells; predict the future production curve of the gas well through the RTA method, calculate the minimum production and minimum flow pressure of the gas well's self-flowing production, and provide a basis for subsequent design.
[0020] The full name of the RTA method, modern production decline analysis method, is an effective method for predicting the future production curve of gas wells.
[0021] The RTA method predicts the future production of gas wells by analyzing the production data of gas wells, combining the flow pressure, boundary control equivalent production time function and the change of natural gas physical properties with pressure. This method takes into account more actual production conditions, making the prediction results more reliable.
[0022] Step 3: Measuring the bottom hole static pressure of the shale gas well; Step 4: Before lowering the pipe string into the shale gas well, the depth of the liquid accumulation in the well is determined by measuring the liquid level in the well or calculating the oil-casing pressure difference. The position of the pipe string in the well cannot be lower than the depth of the liquid accumulation. Step 5: Design the tubing used in shale gas wells, including the tubing outer diameter, tubing lowering depth and tubing inner diameter. The tubing outer diameter is designed to ensure that the tubing can be lowered into the shale gas well, and the tubing lowering depth must ensure that the tubing is above the liquid accumulation surface. Input the tubing lowering depth and bottom hole static pressure data into the pipesim software, and set the drainage flow rate and the friction resistance in the tubing within the specified range to obtain the tubing inner diameter value; a bell mouth and a screen tube must be designed at the bottom of the tubing.
[0023] Pipesim software is mainly used for steady-state simulation of multiphase flow and is applicable to the entire life cycle of oil and gas field development. In the early engineering design stage, Pipesim software can be used for wellbore structure design, artificial lift system design, pipelines, surface equipment and overall pipeline network design. In the later daily operation and management stage, it can also be used for wellbore optimization, pipeline and pipeline network optimization research.
[0024] Step 6: Design the automatic control valve in the pipe string, including the vertical depth difference design between the uppermost automatic control valve and the lowest point of the liquid accumulation, and the vertical depth difference design between the lowermost automatic control valve and the lowest point of the pipe string. The vertical depth difference between the uppermost automatic control valve and the lowest point of the liquid accumulation is calculated by P≥ ρ gh 最上端 The formula is calculated, where P is the bottom hole static pressure, ρ is the density of the liquid column in the wellbore, g is the gravitational acceleration, and h is the gravitational acceleration. 最上端 It is the vertical depth difference between the uppermost automatic control valve in the pipe string and the lowest point of the liquid accumulation.
[0025] The vertical depth difference between the lowest automatic control valve and the lowest point of the pipe string is measured by PP wf ≥ ρ gh 最下端 The formula is obtained; where: P is the bottom hole static pressure, P wf is the bottom hole pressure, ρ is the density of the liquid column in the wellbore, g is the gravitational acceleration, h 最下端 It is the vertical depth difference between the automatic control valve at the middle and lower end of the pipe string and the lowest point of the pipe string.
[0026] Step 7: Design of middle automatic control valve: When the pipe string depth is within 1500m, no middle automatic control valve is installed. When the pipe string depth is greater than or equal to 1500m, as the pipe string depth increases by 500m, an automatic control valve is added at equal intervals between the two automatic control valves at the top and bottom. Step 8: Design the maximum spacing between two adjacent U-shaped valves. Install the U-shaped valve between the uppermost and lowermost automatic control valves. The maximum spacing between two adjacent U-shaped valves meets the following requirements: ρ gh 滞 + wellhead back pressure < bottom hole flow pressure, where h 滞 is the maximum spacing of the U-type valve, ρ gh 滞 It is the gravity of the retained liquid between two adjacent U-valves.
[0027] like Figure 2 As shown in the figure, a shale gas well with a minimum daily production of 3,000 cubic meters of self-flowing production is used as an example. 3 / 8 U-shaped pipe string, at this time, the bottom hole pressure is 7MPa, the wellhead back pressure is 1.5MPa, and the downhole liquid level is 2400m. The U-shaped valve design should meet the requirement that the gravity of the retained liquid + the wellhead back pressure < the bottom hole pressure, that is, ρ gh 滞 +1.5MPa<7MPa, can be introduced h 滞 When the gas well is less than 561m, the U-valve string can realize self-flowing production. Figure 2 It can be seen that the distance between U-type valves should not be less than 35m.
[0028] Step 9: If Figure 3 As shown, the smaller the spacing between U-shaped valves is, the better. A smaller spacing means that under a fixed pipe string length, setting more U-shaped valves will incur higher costs. Therefore, the spacing between two adjacent U-shaped valves is greater than or equal to 10 meters.
[0029] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.
Claims
1. A U-valve drainage and gas production design method suitable for shale gas horizontal wells, characterized by: The steps include: Step 1: Select a shale gas well with a static pressure exceeding 12 MPa after pressure relief and well shut-in; Step 2: Calculate the minimum production and minimum flow pressure of shale gas wells; Step 3: Measuring the bottom hole static pressure of the shale gas well; Step 4: Measure the downhole liquid level or calculate the oil-casing pressure difference to determine the depth of the downhole liquid; Step 5: Design the pipe string used in the shale gas well, including the outer diameter of the pipe string, the depth of the pipe string lowering and the inner diameter of the pipe string. The outer diameter of the pipe string is designed to ensure that the pipe string can be lowered into the shale gas well. The lowering depth of the pipe string needs to ensure that the pipe string is higher than the liquid accumulation surface. The pipe string lowering depth and bottom hole static pressure data are input into the pipesim software. The drainage flow rate and the friction resistance in the pipe string are within the specified range to obtain the inner diameter value of the pipe string. Step 6: Design the automatic control valve in the string, including the vertical depth difference design between the uppermost automatic control valve and the lowest point of the liquid accumulation, and the vertical depth difference design between the lowermost automatic control valve and the lowest point of the string. The vertical depth difference between the uppermost automatic control valve and the lowest point of the liquid accumulation is calculated by P ≥ ρ gh 最上端 The formula is calculated, where P is the bottom hole static pressure, ρ is the density of the liquid column in the wellbore, g is the gravitational acceleration, and h is the gravitational acceleration. 最上端 It is the vertical depth difference between the uppermost automatic control valve in the pipe string and the lowest point of the liquid accumulation; The vertical depth difference between the lowest automatic control valve and the lowest point of the pipe string is measured by PP wf ≥ ρ gh 最下端 The formula is obtained; where: P is the bottom hole static pressure, P wf is the bottom hole pressure, ρ is the density of the liquid column in the wellbore, g is the gravitational acceleration, h 最下端 It is the vertical depth difference between the automatic control valve at the middle and lower end of the pipe string and the lowest point of the pipe string; Step 7: Design of middle automatic control valve: When the depth of the pipe string is within 1500m, no middle automatic control valve is installed. When the depth of the pipe string is greater than or equal to 1500m, as the depth of the pipe string increases by 500m, an automatic control valve is added at equal intervals between the two automatic control valves at the top and bottom. Step 8: Design the maximum spacing between two adjacent U-shaped valves. Install the U-shaped valve between the uppermost and lowermost automatic control valves. The maximum spacing between two adjacent U-shaped valves meets the following requirements: ρ gh 滞 + wellhead back pressure < bottom hole flow pressure, where h 滞 is the maximum spacing of the U-type valve, ρ gh 滞 It is the gravity of the retained liquid between two adjacent U-valves.
2. A U-valve drainage and gas production design method suitable for shale gas horizontal wells according to claim 1, characterized in that: In step 2, the production curve of the gas well is predicted by the RTA method to obtain the minimum production and minimum flow pressure of the shale gas well's self-flowing production.
3. A U-valve drainage and gas production design method suitable for shale gas horizontal wells according to claim 2, characterized in that: In step 4, if the shale gas well is in a long-term shutdown state due to liquid accumulation and a tubing string has been installed, a shale gas well with an oil / casing pressure difference greater than 2 MPa is selected.
4. A U-valve drainage and gas production design method suitable for shale gas horizontal wells according to claim 3, characterized in that: In step five, the upper portion of the pipe string should be higher than the liquid accumulation surface.
5. A U-valve drainage and gas production design method suitable for shale gas horizontal wells according to claim 4, characterized in that: In step five, a bell mouth and a screen tube are provided at the bottom of the pipe string.
6. A U-valve drainage and gas production design method suitable for shale gas horizontal wells according to claim 5, characterized in that: In step eight, the distance between two adjacent U-shaped valves is not less than 10 meters.