Energy-increasing well repairing method for coal bed gas horizontal well

Abstract

The invention discloses a coal bed gas horizontal well energy increasing and well repairing method. The method comprises the following steps that S1, basic data of a well are collected, and production data of the well are analyzed; s2, configuring an extra-low pressure energizing well repair scheme; s3, a ground process of a continuous pipe nitrogen foam sand washing process; s4, nitrogen foam well washing is carried out; s5, circulating liquid desanding is conducted till the sand content meets the preset condition, and well repairing is ended. The method is suitable for the technical field of unconventional gas field development, nitrogen is injected into a production layer to increase energy, the well bottom pressure is increased, nitrogen foam well flushing fluid with certain viscosity is adopted as well flushing fluid, the density of the nitrogen foam well flushing fluid is designed according to the well bottom pressure, and the well flushing efficiency is improved; a normal circulation channel is established, solid particles in a shaft are discharged out of the shaft, perforation blast holes are dredged at the same time, the effects of purifying the shaft and improving gas production and water production are achieved, a tubular column is fixed, operation under pressure can be achieved, and production halt and operation time can be greatly shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of unconventional gas field development, and in particular is a method for energy enhancement and well repair of a coalbed methane horizontal well. Background Art

[0002] In the field of coalbed methane development, horizontal wells and coal reservoir fracturing transformation have become the most effective methods for coalbed methane development and improving recovery. The characteristics of horizontal wells are: large coal seam drilling surface, large coal reservoir transformation area, low bottom hole pressure, and large gas and water production. During the production process, there is a three-phase flow of gas, liquid, and solid in the wellbore, namely gas, water, proppant return and coal powder, which causes the problem of blasthole blockage, reduces gas production and drainage capacity, and seriously affects normal production. As the coal seam continues to reduce pressure and drain water, the bottom hole pressure continues to decrease. Well repair cannot establish normal circulation, and solid phases such as proppant and coal powder in the wellbore are difficult to carry out of the wellbore, resulting in blockage of the production layer and reduced production capacity.

[0003] At present, the commonly used sand bailing technologies include vacuum sand bailing technology, concentric continuous tube sand bailing technology, etc. The above technologies have the problems of low sand bailing efficiency and frequent sand bailing obstruction. If the sand is flushed to wash the well, there are the following problems: first, normal circulation cannot be established, and solid phase cannot be carried out of the wellbore; second, the well washing fluid easily enters the coal seam, which has great damage to the production layer and affects the production capacity, especially for low-pressure and abnormally low-pressure wells, normal sand flushing and well washing circulation cannot be established, and the well cannot be repaired. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a method for enhancing the energy of a coalbed methane horizontal well and repairing it.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for enhancing the energy of a coalbed methane horizontal well and repairing the well, comprising the following steps:

[0007] Step S1, collecting basic data of the well and analyzing the production data of the well;

[0008] Step S2, configuring an ultra-low pressure energy enhancement workover plan;

[0009] Step S3, surface process of coiled tube nitrogen foam sand washing process;

[0010] Step S4, washing the well with nitrogen foam;

[0011] Step S5, circulating liquid to remove sand until the sand content meets the preset conditions, and the well repair is completed.

[0012] Preferably, in step S1, the basic data of the well includes the well number, well type, fracturing method, pumping start time, production days and bottom hole flowing pressure, and the production data of the well includes horizontal section length, drilling rate, fracturing method, pumping start time and maximum gas production.

[0013] Preferably, the step S2 specifically includes:

[0014] Step S21, check and prepare tools, including: nitrogen generator truck, pump truck, foam generator and vortex flushing tool;

[0015] Step S22, configuring the parameters related to ultra-low pressure energy enhancement workover, including: nitrogen injection energy enhancement data of nitrogen truck, sand flushing fluid dosage, nitrogen foam density, foaming agent dosage, nitrogen dosage and pump truck displacement;

[0016] Step S23, executing step S3 according to the configured parameters, and performing the surface process of the coiled tube nitrogen foam sand washing process.

[0017] Preferably, in step S22, nitrogen generating equipment is used to inject gas into the empty wellbore twice with different displacements to supplement energy before the operation, and nitrogen is injected cumulatively to increase the wellhead pressure, so as to adjust the nitrogen injection energy data of the nitrogen truck. Before the cycle is established, the nitrogen foam gas-liquid ratio is 2:1, and the density is designed to be 0.3-0.4g / cm 3 After the cycle is established, the nitrogen foam density is gradually adjusted to 0.5g / cm 3 The density of nitrogen foam liquid during sand carrying process is maintained at 0.5g / cm 3 The gas-liquid ratio is 1:1 and is adjusted according to the on-site conditions, taking into account the displacement of the nitrogen generator truck, the displacement of the pump truck and the wellhead safety. The displacement control is limited by the wellhead pressure. The wellhead working pressure is required not to exceed 4MPa, and the pump truck displacement is controlled at 220L-430L / min.

[0018] Preferably, in step S3, the nitrogen-generating vehicle group injects nitrogen into the wellhead for energy enhancement, monitors the pump pressure, injection displacement and injection volume, waits for the wellhead pressure to stabilize, and starts nitrogen foam well washing after stabilization.

[0019] Preferably, in step S4, a cement truck or a pump truck is used to fully mix the aqueous solution mixed with the foaming agent and nitrogen in a foam generator to form a uniform foam fluid as a sand flushing and well washing fluid; a well entry tool is installed, a coiled tubing is lowered, and the prepared liquid is pumped into the foam generator, and the liquid pumped into the foam generator is mixed with the nitrogen pumped in at the same time to form nitrogen foam, and the nitrogen foam is pumped into the wellbore as a sand flushing medium to perform sand flushing operations to establish a circulation.

[0020] Preferably, in step S4, the well entry tool includes: a connector, a check valve, a release and a vortex flushing tool.

[0021] Preferably, in step S5, after the circulation is established, the density and flow rate of the fluid are controlled, and the oil pipe is lowered to flush the sand column during the circulation. The circulated liquid is passed through a sand settling tank to remove sand particles in the liquid. After sand removal, the foam fluid is directly returned to the water tank for natural degassing and recycled. If the foam is too abundant and the natural degassing is not timely, a defoaming agent is used for defoaming.

[0022] Preferably, in step S5, during the sand cleaning process, the pipe string is pulled back for circulation each time a preset distance is advanced to clean the wellbore sand until it reaches the bottom of the artificial well. When the sand-containing surface of the flushed liquid meets the preset conditions, the well repair is determined to be completed.

[0023] Preferably, in step S5, the preset distance is 100 meters, and when the sand content of the flushed liquid is less than 0.2%, it is determined that the well repair is completed.

[0024] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] The present invention provides an energy-enhancing well repairing process, which increases the bottom hole pressure by injecting nitrogen into the production layer. The well washing fluid uses nitrogen foam well washing fluid with a certain viscosity. The density of the nitrogen foam well washing fluid is designed according to the bottom hole pressure so that it will not leak into the production layer as much as possible, and a normal circulation channel is established to discharge solid particles in the wellbore. At the same time, the perforation holes are unblocked to purify the wellbore and improve the gas and water production effects, so that the pipe string does not move and pressure operation can be achieved, which can greatly reduce the shutdown and operation time; it can control the pressure of the liquid column to prevent the leakage problem encountered by low-pressure sand wells during sand flushing; it can also reduce reservoir pollution, especially the low-density nitrogen foam sand flushing liquid formed has the function of helping to discharge and control filtration loss, and is suitable for low-pressure and low-permeability gas well operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart of a method for enhancing well workover of a coalbed methane horizontal well according to an embodiment of the present invention;

[0027] Figure 2 is a structural diagram of a foam generator according to an embodiment of the present invention;

[0028] Figure 3 is a structural diagram of a vortex flushing tool according to an embodiment of the present invention;

[0029] Figure 4 It is a ground flow chart of a coiled tube nitrogen foam sand washing process according to an embodiment of the present invention;

[0030] Figure 5 A flowchart of on-site construction according to an embodiment of the present invention;

[0031] Figure 6 A production curve diagram of the LX1-Ping 1 well according to an embodiment of the present invention;

[0032] Figure 7 A nitrogen injection energy enhancement pressure curve diagram of a nitrogen vehicle according to an embodiment of the present invention;

[0033] Figure 8 The nitrogen injection energy enhancement pressure curve diagram of two nitrogen vehicles according to an embodiment of the present invention;

[0034] Fig. 9 : is a graph showing the relationship between pressure-load and well depth of LX1-Ping 1 oil-sand flushing cycle according to an embodiment of the present invention;

[0035] Fig.10 1 is a diagram showing the relationship between pressure-load and well depth of the LX1-Ping 1 oil-sand flushing cycle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are described in detail below.

[0037] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10 to 50 is listed for a specific parameter, it is understood that the range of 10 to 40 and 20 to 50 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the range of values ​​"a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the range of values ​​"0 to 5" means that all real numbers between "0 to 5" have been fully listed in this article, and "0 to 5" is only an abbreviation of these numerical combinations.

[0038] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0040] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0041] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0042] Unless otherwise specified, the reaction is carried out at room temperature and pressure.

[0043] Unless otherwise specified, all parts or percentages are by weight.

[0044] In the present invention, all substances used are known substances and can be purchased or synthesized by known methods.

[0045] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and are commercially available.

[0046] The following is a further description of the specific implementation of the method for enhancing the energy of a coalbed methane horizontal well according to the present invention in conjunction with the embodiments. The method for enhancing the energy of a coalbed methane horizontal well according to the present invention is not limited to the description of the following embodiments.

[0047] The invention provides a coalbed methane horizontal well energy enhancement and workover method, which belongs to a new coalbed methane energy enhancement and workover technology and is suitable for workover operations of L-type horizontal wells and straight directional wells in unconventional gas fields.

[0048] The new energy-enhancing well repair technology is the continuous tubing formation energy enhancement + nitrogen foam sand-carrying technology. Its working principle is to inject nitrogen into the formation through a nitrogen-generating truck (nitrogen is an inert gas and does not harm the formation) to enhance the formation energy, increase the bottom hole pressure, thereby preventing the loss of well washing fluid and polluting the formation, and achieving a normal well washing cycle.

[0049] The new method of ultra-low pressure energy-enhanced well repair can make the bottom hole pressure lower than the formation pressure, eliminate the damage of well washing to the formation permeability, and is a new method for repairing ultra-low pressure wells that cannot establish circulation wells. The method provided by the invention is an efficient sand carrying method that can quickly carry out sand and other debris in the wellbore, clean the wellbore and blasthole, and solve the problem of sand production and sand blocking blastholes after large-scale fracturing of coalbed methane in deep and medium layers.

[0050] like Figure 1 As shown, the coalbed methane horizontal well energy enhancement and workover method according to the embodiment of the present invention comprises the following steps:

[0051] Step S1, collecting basic data of the well and analyzing the production data of the well.

[0052] In the embodiment of the present invention, the basic data of the well includes parameters such as well number, well type, fracturing method, pumping start time, drainage days and bottom hole flow pressure. The production data of the well includes: horizontal section length, drilling rate, fracturing method, pumping start time and maximum gas production.

[0053] Step S2, configuring an ultra-low pressure energy enhancement workover plan, including:

[0054] Step S21, checking and preparing tools, including: nitrogen making truck, pump truck, foam generator and vortex flushing tool.

[0055] (1) Foam generator

[0056] Foaming principle of foam generator: The key principle of the foam generator is the combined effect of surface tension and nitrogen pressure. It combines with water molecules to form glue-like properties. When the bubbles are filled to a given shape, the shape of the bubbles is kept stable by surface tension. Based on the principle of mechanical foaming process, nitrogen is pressurized and mixed with foaming agent and foam stabilizer through the ground foam generating device to produce efficient and stable foam liquid, which is transported to the well, thereby achieving the effect of cleaning the wellbore. Figure 2 1 is a structural diagram of a foam generator according to an embodiment of the present invention. The top of the foam generator is provided with a nitrogen inlet, the middle is provided with a liquid inlet, and the bottom is provided with a foam outlet.

[0057] (2) Vortex Flushing Tool

[0058] Vortex flushing is a cleaning technology based on the principle of high-speed rotating water flow. When the water flows into the device, the water molecules entering the jet tube will rotate at high speed to form a vortex, which is driven by centrifugal force to remove dirt on the surface of the casing. The speed and direction of the vortex are controlled by the nozzle and the inlet. The unique water eye design uses hydraulic power to generate radial jets to clean the inner wall of the wellbore and the blasthole, and has a good striking and flushing effect on the sand and sand bridge in the well. Figure 3 4 is a structural diagram of a vortex flushing tool according to an embodiment of the present invention.

[0059] After preparing the tools as mentioned above, perform parameter design.

[0060] Specifically, well pressure before and after energy enhancement: Without affecting the formation space, nitrogen is injected into the bottom of the well before well repair to increase the formation pressure. Since the temperature of the formation downhole is high, increasing the bottom hole pressure will increase the temperature. Injecting room temperature nitrogen makes the temperature change small and negligible. According to Boyle's law and the ideal gas state equation P 1 V 1 =P 2 V 2 , PV=nRT, the volume of nitrogen required to be injected when the bottom hole pressure is greater than the maximum pressure during well washing can be calculated as follows:

[0061] PV = nRT;

[0062] P 1 V 1 =P 2 V 2；

[0063] Ph=10 -3 ρgh;

[0064] Where P is gas pressure, MPa;

[0065] V——gas volume, m 3 ;

[0066] n——gas mole number;

[0067] R——molar gas constant;

[0068] T——gas temperature, K;

[0069] P h ——Hydrostatic pressure, MPa;

[0070] Bottom hole pressure P before nitrogen injection 1 =4.6Mpa; Bottom hole pressure after nitrogen injection P 增 , from the time when the well-washing fluid is injected to the time when the well is repaired to the time when the pressure is stabilized, the maximum pressure in the well is P 洗 , that is, P 增 >P 洗 , a normal well washing cycle can be established.

[0071] Table 1 compares the gas production after conventional workover and after energy-enhanced workover:

[0072] Table 1

[0073]

[0074] Step S22, configuring the parameters related to ultra-low pressure energy enhancement workover, including: nitrogen injection energy enhancement data of nitrogen truck, sand flushing fluid dosage, nitrogen foam density, foaming agent dosage, nitrogen dosage and pump truck displacement.

[0075] (1) Formation energy enhancement design

[0076] Formation energy enhancement design is a key technology for realizing ultra-low pressure well repair. In order to improve the pressure bearing capacity of the formation, nitrogen production equipment is used to inject gas into the empty wellbore twice with different displacements before the operation to supplement energy, observe the changes in wellhead pressure, and establish circulation in the continuous tubing after it stabilizes.

[0077] (2) Design of sand washing fluid dosage

[0078] The wellbore volume is calculated based on the completed well depth and horizontal section length. The sand flushing volume is based on 5 cycles (excluding the volume of well washing fluid). Considering the possible loss during the foam circulation process (calculated as 50 cubic meters), the on-site reserve fluid volume is prepared at 1.2 times the designed volume to ensure operational continuity.

[0079] (3) Nitrogen foam density design

[0080] Before establishing the cycle, the nitrogen foam gas-liquid ratio is 2:1, and the density is designed to be 0.3-0.4g / cm 3 After establishing the cycle, consider

[0081] Taking into account the sandblasting effect, the nitrogen foam density can be gradually adjusted to 0.5g / cm 3 The density of nitrogen foam liquid during sand carrying process is maintained at 0.5g / cm 3 The gas-liquid ratio is 1:1 and adjusted according to the site conditions. During the construction process, if the wellhead pressure rises rapidly, the foam density can be appropriately increased.

[0082] (4) Foaming agent dosage design

[0083] The FP-1 special foaming system is used, and the foaming agent concentration is 0.5-1.0%, and the average is 0.7%.

[0084] Taking into account the influence of multiple on-site cycles (not less than 5 times), defoaming loss (30%), and possible complex situations, a 25% surplus is added, and the design dosage is: design liquid volume × 0.7% × 1.3 × 1.25 = 0.0114 times the design liquid volume.

[0085] (5) Nitrogen dosage design

[0086] The foam mass in the wellbore is 0.3-0.5g / cm 3 , gas-liquid ratio is 2:1 to 1:1 (mass percentage), sand washing process

[0087] The bottom pressure of the well is 15MPa (according to the vertical depth of 1500m), the temperature is 40℃, and it is calculated by the gas state equation that 10000m 3 Corresponding to 110 cubic meters underground, the nitrogen consumption is about

[0088] Designed liquid volume × 2 × 10000 ÷ 110 = 181.8 times the designed liquid volume Nm 3 ;

[0089] Considering the previous formation energy increase of 20000-40000Nm 3 (Determine the injection volume according to the well conditions), nitrogen consumption

[0090] 20000-40000Nm 3 +181.8 times the designed liquid volume.

[0091] (6) Displacement design

[0092] The displacement of nitrogen generator trucks and pump trucks should be designed with wellhead safety in mind. The displacement control is limited by the wellhead pressure.

[0093] The wellhead working pressure is required not to exceed 4MPa (empirical value, confirmed based on the stable wellhead pressure after energy boost), and the pump truck displacement is controlled at 220L-430L / min (corresponding to a gas-liquid ratio of 2:1 to 1:1). The actual displacement is adjusted based on on-site conditions.

[0094] Step S23, according to the configured parameters, execute step S3 to carry out the ground process of the coiled tube nitrogen foam sand washing process, refer to Figure 4 shown.

[0095] Step S3, the nitrogen-generating vehicle group injects nitrogen into the wellhead to increase energy, monitors the pump pressure, injection displacement and injection volume, waits for the wellhead pressure to stabilize, and starts nitrogen foam well washing after stabilization.

[0096] Specifically, two nitrogen-generating trucks inject nitrogen into the wellhead to increase energy. The pump truck must meet the design requirements and focus on monitoring changes in pump pressure, injection displacement, and injection volume, waiting for the wellhead pressure to stabilize. Figure 5 This is a flow chart of the on-site construction, including flowback tank, throttling manifold, nitrogen making truck, pump truck, oil connection equipment, etc. The nitrogen truck increases the energy of the formation, observes the changes in the wellhead pressure, and starts nitrogen foam well washing after it stabilizes.

[0097] Step S4, using a cement truck or a pump truck to fully mix the aqueous solution mixed with the foaming agent and nitrogen in the foam generator to form a uniform foam fluid as the sand flushing and well washing fluid. Install the well entry tool, lower the coiled tubing, pump the prepared liquid into the foam generator, the liquid pumped into the foam generator is mixed with the nitrogen pumped in at the same time to form nitrogen foam, and the nitrogen foam is pumped into the wellbore as the sand flushing medium to perform the sand flushing operation to establish a cycle.

[0098] Among them, the well entry tools include: Φ54mm connector + Φ54mm check valve + Φ54mm drop valve + Φ54mm vortex flushing tool.

[0099] Step S5, after the circulation is established, the density and flow rate of the fluid are controlled, and the oil pipe is lowered to flush the sand column while circulating. The circulated liquid is passed through the sand settling tank to remove the sand particles in the liquid. After the sand is removed, the foam fluid can be directly returned to the water tank for natural degassing and recycled. If the foam is too rich and the natural degassing is not timely, a defoaming agent can be used in an appropriate amount to defoam.

[0100] Step S6, during the sand cleaning process, the pipe string is pulled back for circulation every time the preset distance is advanced to clean the wellbore sand until it reaches the bottom of the artificial well. When the sand content of the flushed liquid meets the preset conditions, it is determined that the well repair is completed.

[0101] In the embodiment of the present invention, the preset distance is 100 meters, and the preset condition is that the sand content of the liquid is less than 0.2%.

[0102] Specifically, during the sand cleaning process, prevent the continuous tubing from getting stuck with sand. After every 100 meters of advance, pull the tubing string back for circulation to clean the wellbore sand until it reaches the bottom of the artificial well. If the sand content of the flushed liquid is less than 0.2%, the well repair is considered complete.

[0103] The following is a description of the method for enhancing well repair of coalbed methane horizontal wells of the present invention by taking the LX1-Ping 1 well in the Yushe-Wuxiang block of the Qinshui coalfield in Shanxi Province as an example.

[0104] Step S1: Collect the basic data of LX1-Ping1 well (including well number, well type, fracturing method, pumping start time, production days, bottom hole flow pressure and other parameters), analyze the well production situation, refer to Table 2 and Figure 6 shown.

[0105] The two L-shaped horizontal wells in Yushe-Wuxiang are located on the same well platform with similar geological conditions and consistent reserve abundance. The effective footage of the horizontal section of the LX1-Ping 1 well is 828m, the effective pure coal seam footage is 759.00m, and the coal seam drilling rate is 91.67%. It is divided into 9 sections for large-scale fracturing, with a large transformation area. It will be put into production on January 5, 2023, with a maximum gas production of 15,000m 3 / d; The horizontal section of the LX1-Ping 2 well on the same platform is 595m long, with a coal seam drilling rate of 69.92%. It is divided into 6 sections for large-scale fracturing and will be put into production on January 5, 2023, with a maximum gas production of 20,000m 3 / d.

[0106] In August 2023, the water production of LX1-Ping 1 well decreased from 14 cubic meters to 11 cubic meters without sand flushing after well repair, a decrease of 3 cubic meters; the flow pressure before well repair was 5.835MPa, and the production began to increase; the flow pressure was 4.413MPa, and the gas production increased to 6291.7 cubic meters. After the well repair, the flow pressure was 3.835MPa, and the gas production was 6261 cubic meters. The power of production increase was smaller than before the well repair, and the water production decreased. Analysis of the sand plugging of the horizontal section of LX1-Ping 1,

[0107] Table 2 LX1-Ping 1 Well Production Data

[0108]

[0109] Step S2: Prepare an ultra-low pressure energy enhancement workover plan.

[0110] 1. Tool preparation

[0111] Prepare one foam generator and one vortex flushing tool, and check whether they are flexible and intact.

[0112] 2. Parameter design

[0113] (1) Formation energy enhancement design

[0114] In order to improve the pressure bearing capacity of the formation, nitrogen production equipment was used to inject gas into the empty wellbore twice with different displacements before the operation to supplement energy. A total of 2.46×104Nm 3 , successfully increased the wellhead pressure by nearly 4 times. The wellhead pressure of 1 nitrogen injection vehicle is 3.0MPa, and the wellhead pressure of 2 nitrogen injection vehicles is 3.6MPa. Figure 7 and Figure 8 shown.

[0115] (2) Design of sand washing fluid dosage

[0116] The completed well depth is 2550m, the horizontal section is 1722-2550m, the section length is 828m; the wellbore volume is 30m 3 calculate.

[0117] rush

[0118] The amount of sand used is based on 150m3 for 5 cycles. 3 Design (excluding the amount of fluid used for well washing), taking into account the possible loss during the foam circulation process (loss is calculated as 50m 3 Budget), the initial design of foam sand washing liquid consumption is 200m 3 , the on-site spare liquid volume is prepared at 1.2 times the design volume to ensure operation continuity.

[0119] (3) Nitrogen foam density design

[0120] Before establishing the cycle, the nitrogen foam gas-liquid ratio is 2:1, and the density is designed to be 0.3-0.4g / cm 3After establishing the cycle, consider

[0121] Taking into account the sandblasting effect, the nitrogen foam density can be gradually adjusted to 0.5g / cm 3 The density of nitrogen foam liquid during sand carrying process is maintained at 0.5g / cm 3 The gas-liquid ratio is 1:1 and adjusted according to the site conditions. During the construction process, if the wellhead pressure rises rapidly, the foam density can be appropriately increased.

[0122] (4) Foaming agent dosage design

[0123] Using FP-1 special foaming system, the concentration of foaming agent is 0.5-1.0%, and the average is 0.7%.

[0124] In view of the influence of multiple cycles on site (not less than 5 times), defoaming loss (30%), and possible complex situations, a 25% surplus is added, and the design dosage is:

[0125] 200×0.0114 times=2.28 tons;

[0126] (5) Nitrogen dosage design

[0127] The foam mass in the wellbore is 0.3-0.5g / cm 3 , gas-liquid ratio is 2:1 to 1:1 (mass percentage), sand washing process

[0128] The pressure at the bottom of the well is 15MPa (according to the vertical depth of 1500m), the temperature is 40℃, and the gas state equation is used to calculate that 10000Nm 3 Corresponding to 110 cubic meters underground, the nitrogen consumption is approximately:

[0129] 181.8 times the designed liquid volume Nm 3 =181.8×200=36360Nm 3

[0130] Considering the previous formation energy increase of 20000-40000Nm 3 (Injection volume is determined according to well conditions), nitrogen consumption needs 20000-40000Nm 3 +36360Nm 3 =56360-76360Nm 3 .

[0131] (6) Displacement design

[0132] Considering the displacement of nitrogen generator truck, pump truck and wellhead safety, the displacement control is limited by the wellhead pressure.

[0133] The working pressure does not exceed 4MPa (empirical value, based on the stable pressure of 3.6MPa after energy increase), the displacement of the pump truck is controlled at 220L-430L / min (corresponding to the gas-liquid ratio of 2:1 to 1:1), and the actual displacement is adjusted according to the on-site conditions.

[0134] (7) Ground equipment and materials

[0135] Table 3 Ground equipment and material preparation

[0136]

[0137]

[0138] Step S3: Two nitrogen trucks inject nitrogen into the wellhead to increase energy. The pump trucks must meet the design requirements, and the pump pressure, injection displacement, and injection volume changes are monitored in particular.

[0139] Step S4: Use a cement truck or pump truck to fully mix the aqueous solution mixed with the foaming agent with the high-pressure gas in the foam generator to form a uniform foam fluid as the sand flushing and well washing fluid. Install the well entry tool (Φ54mm connector + Φ54mm check valve + Φ54mm hand release + Φ54mm vortex flushing tool), lower the coiled tubing, pump the prepared liquid into the foam generator, and the liquid pumped into the foam generator is mixed with the nitrogen pumped in at the same time to form nitrogen foam, which is pumped into the wellbore as the sand flushing medium to perform sand flushing operations and establish a cycle.

[0140] Step S5: After the circulation is established, the density and flow rate of the fluid are controlled, and the oil pipe is lowered to flush the sand column while circulating. The circulated liquid is passed through the sand settling tank to remove the sand particles in the liquid. After the sand is removed, the foam fluid can be directly returned to the water tank for natural degassing and recycled. If the foam is too rich and the natural degassing is not timely, a defoaming agent can be used appropriately for defoaming.

[0141] Step S6: During the sand cleaning process, prevent the coiled tubing from getting stuck. Pull the tubing string back and forth every 100 meters to clean the wellbore sand until it reaches the bottom of the artificial well. If the sand content of the flushed liquid is less than 0.2%, the well repair is considered complete. See the on-site construction drawing. Fig. 9 Among them, the blue line represents the depth of the coiled tubing; the green line represents the circulation pressure (pump pressure); and the red line represents the load change.

[0142] The oil pipeline depth is 1300m, the nitrogen truck starts pumping, and the displacement is 2400Nm 3 / h, the circulation is established normally and the liquid outlet is normal;

[0143] The oil pipe was lowered 1650m, the pump skid displacement was increased to 250L / min, the circulation was normal, and the liquid outlet was normal;

[0144] The oil pipe was lowered for 1800m circulation and pulled back for 50m. The circulation was normal and the liquid outlet was normal.

[0145] The oil pipe was lowered for 1900m circulation and pulled back for 50m. The circulation was normal and the liquid outlet was normal.

[0146] The tubing was lowered for 2000m circulation and pulled back for 1300m. The circulation was normal, the fluid outlet was normal, and the wellbore sand was brought out.

[0147] The oil pipe was lowered for 2100m circulation and pulled back for 50m. The circulation was normal and the liquid outlet was normal.

[0148] The oil pipe was lowered for 2200m circulation and pulled back for 50m. The circulation was normal and the liquid outlet was normal.

[0149] The tubing was lowered for 2300m circulation and pulled back for 300m. The circulation was normal, the fluid outlet was normal, and the wellbore sand was brought out.

[0150] The oil pipe was lowered for 2400m of circulation and pulled back for 50m. The circulation was normal and the liquid outlet was normal.

[0151] The oil pipe is lowered 2513m for circulation to the bottom of the artificial well. The water quality of the inlet and outlet is consistent. The well washing is completed. Fig. 9 shown.

[0152] After the well was repaired by the new ultra-low pressure energy-enhanced well repair process, the gas production of the well recovered quickly. Fig.10 shown.

[0153] Table 4 Construction status of LX1-Ping 1 well

[0154] hashtag Construction reasons Construction Date Resumption date Remark LX1-Ping 1 Well Sand buried pay zone, blasthole 2024.4.9 2024.4.15 Fast production recovery

[0155] In summary, the new energy-enhancing well repair process provided by the present application is a continuous tubing formation energy enhancement + nitrogen foam sand-carrying process. Its working principle is to inject nitrogen into the formation through a nitrogen-generating vehicle to enhance the formation energy, increase the bottom hole pressure, and prevent the well-washing fluid from leaking and contaminating the formation, so as to achieve a normal well-washing cycle. The use of continuous tubing nitrogen foam well washing is to utilize the characteristics of foam fluid with high viscosity, low density, and good carrying performance. The foam fluid is used as a carrying fluid to circulate in the tubing and annulus, so that a negative pressure relative to the coal seam is established at the bottom of the well. Under the action of this negative pressure difference, the foam fluid is relied on to disperse the sand accumulated in the well and clean the blasthole to achieve the purpose of well washing and sand flushing, solve the problem of sand production after large-scale fracturing, and restore production capacity. The present invention uses ultra-low pressure well repair technology at the bottom of the well to carry out the sediment in the wellbore, while reducing damage to the formation and restoring production capacity as soon as possible.

[0156] The present application proposes an energy-enhanced well repairing process, which increases the bottom hole pressure by injecting nitrogen into the production layer. The well washing fluid uses nitrogen foam well washing fluid with a certain viscosity. The density of the nitrogen foam well washing fluid is designed according to the bottom hole pressure to prevent it from leaking into the production layer as much as possible, and a normal circulation channel is established to discharge solid particles in the wellbore. At the same time, the perforation holes are unblocked to purify the wellbore and improve the gas and water production.

[0157] The energy-enhanced well repair process is a new process for high-efficiency sand flushing and plugging removal in low-pressure horizontal wells, which is formed by matching foam generating devices and downhole eddy current flushing tools, combining wellbore multiphase flow state analysis, foam stability control, and foam sand carrying performance, and adjusting the foam liquid density in real time. The present invention is a high-efficiency sand-carrying method that can quickly carry out sand and other debris in the wellbore, clean the wellbore and blastholes, and solve the problems of sand production and sand plugging of blastholes after large-scale fracturing of coalbed methane in deep and medium layers.

[0158] The advantages of this application are: the pipe string can be kept stationary and pressure-operated, which can greatly reduce shutdown and operation time; it can control the liquid column pressure and prevent leakage problems encountered in low-pressure sand wells during sand flushing; it can also reduce reservoir pollution, especially the low-density nitrogen foam sand flushing liquid formed can help drain and control filtration loss, and is suitable for low-pressure and low-permeability gas well operations.

[0159] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for enhancing the energy of a coalbed methane horizontal well, characterized in that: The following steps are involved: Step S1, collecting basic data of the well and analyzing the production data of the well; Step S2, configuring an ultra-low pressure energy enhancement workover plan; Step S3, surface process of coiled tube nitrogen foam sand washing process; Step S4, washing the well with nitrogen foam; Step S5, circulating liquid to remove sand until the sand content meets the preset conditions, and the well repair is completed.

2. A method for enhancing the energy of a coalbed methane horizontal well according to claim 1, characterized in that: In step S1, the basic data of the well includes the well number, well type, fracturing method, pumping start time, production days and bottom hole flow pressure, and the production data of the well includes horizontal section length, drilling rate, fracturing method, pumping start time and maximum gas production.

3. A method for enhancing the energy of a coalbed methane horizontal well according to claim 1, characterized in that: The step S2 specifically includes: Step S21, check and prepare tools, including: nitrogen generator truck, pump truck, foam generator and vortex flushing tool; Step S22, configuring the parameters related to ultra-low pressure energy enhancement workover, including: nitrogen injection energy enhancement data of nitrogen truck, sand flushing fluid dosage, nitrogen foam density, foaming agent dosage, nitrogen dosage and pump truck displacement; Step S23, executing step S3 according to the configured parameters, and performing the surface process of the coiled tube nitrogen foam sand washing process.

4. A method for enhancing the energy of a coalbed methane horizontal well according to claim 1, characterized in that: In step S22, nitrogen generating equipment is used to inject gas into the empty wellbore twice with different displacements to supplement energy before the operation, and nitrogen is injected cumulatively to increase the wellhead pressure, so as to adjust the nitrogen injection energy data of the nitrogen truck. Before the cycle is established, the nitrogen foam gas-liquid ratio is 2:1, and the density is designed to be 0.3-0.4g / cm 3 After the cycle is established, the nitrogen foam density is gradually adjusted to 0.5g / cm 3 The density of nitrogen foam liquid during sand carrying process is maintained at 0.5g / cm 3 The gas-liquid ratio is 1:1 and is adjusted according to the on-site conditions, taking into account the displacement of the nitrogen generator truck, the displacement of the pump truck and the wellhead safety. The displacement control is limited by the wellhead pressure. The wellhead working pressure is required not to exceed 4MPa, and the pump truck displacement is controlled at 220L-430L / min.

5. A method for enhancing the energy of a coalbed methane horizontal well according to claim 1, characterized in that: In step S3, the nitrogen-generating vehicle group injects nitrogen into the wellhead to increase energy, monitors the pump pressure, injection displacement and injection volume, waits for the wellhead pressure to stabilize, and starts nitrogen foam well washing after stabilization.

6. A method for enhancing the energy of a coalbed methane horizontal well according to claim 1, characterized in that: In step S4, a cement truck or a pump truck is used to fully mix the aqueous solution mixed with a foaming agent and nitrogen in a foam generator to form a uniform foam fluid as a sand flushing and well washing fluid; a well entry tool is installed, a coiled tubing is lowered, and the prepared liquid is pumped into the foam generator. The liquid pumped into the foam generator is mixed with the nitrogen pumped in at the same time to form nitrogen foam, and the nitrogen foam is pumped into the wellbore as a sand flushing medium to perform sand flushing operations and establish a circulation.

7. A method for enhancing the energy of a coalbed methane horizontal well according to claim 6, characterized in that: In step S4, the well entry tool includes: a connector, a check valve, a release tool and a vortex flushing tool.

8. A method for enhancing the energy of a coalbed methane horizontal well according to claim 1, characterized in that: In step S5, after the circulation is established, the density and flow rate of the fluid are controlled, and the oil pipe is lowered to flush the sand column during the circulation. The circulated liquid is passed through a sand settling tank to remove sand particles in the liquid. After sand removal, the foam fluid is directly returned to the water tank for natural degassing and recycled. If the foam is too abundant and the natural degassing is not timely, a defoaming agent is used for defoaming.

9. A method for enhancing the energy of a coalbed methane horizontal well according to claim 1, characterized in that: In step S5, during the sand cleaning process, the pipe string is pulled back for circulation each time a preset distance is advanced to clean the wellbore sand until it reaches the bottom of the artificial well. When the sand-containing surface of the flushed liquid meets the preset conditions, it is determined that the well repair is completed.

10. A method for enhancing the energy of a coalbed methane horizontal well according to claim 9, characterized in that: In step S5, the preset distance is 100 meters, and when the sand content of the flushed liquid is less than 0.2%, it is determined that the well repair is completed.

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