Modification method and device for increasing yield of low-yield coal-bed gas well

Abstract

The invention belongs to the technical field of coal bed gas development, and discloses a transformation method for increasing the yield of a low-yield coal bed gas well, which comprises the following steps of: firstly, removing blockage through oscillation, discharging blockage removal sewage, then injecting a nano desorption accelerant into a coal bed, closing the well to infiltrate the coal bed, and recovering the production. According to the method disclosed by the invention, negative-pressure oscillation blockage removal and wide infiltration of the nano desorption agent are adopted, so that the flowability of a large-range coal seam crack system is greatly improved, and the desorption speed, the desorption degree, the coal seam gas yield and the coal seam gas recovery rate of the coal seam gas are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of coalbed methane development, and in particular relates to a method and a device for improving the production of a low-yield coalbed methane well. Background Art

[0002] In the field of coalbed methane exploration and development, cluster wells and "L"-type horizontal underwater casing cementing are usually used to desorb and produce methane molecules (coalbed methane) adsorbed on the surface of coal particles by draining water and reducing pressure, so as to realize coalbed methane extraction. Among them, cluster wells usually drill a vertical well and multiple directional inclined wells in a well site through a coal seam or multiple coal seams, and then perform layered perforation and fracturing to drain water and gas production; "L"-type horizontal wells are horizontal wells of 800-1200m or even longer drilled in the middle of the coal seam through fixed directional technology, and then perforated and fractured to drain water and gas production after casing and cementing.

[0003] At present, the above two mining methods have the following problems. On the one hand, since coal seams are relatively fragile compared with other strata, fracturing transformation will produce a large amount of coal powder, especially tectonic coal will produce more coal powder, which will be carried into the deep coal seams by the fracturing fluid and block the original microcracks of the coal seams and the ends of the fracturing water cracks under the action of high pressure; these blocked coal powders are difficult to loosen and unblock without the action of external force, especially the shallow coalbed methane with ground pore pressure is even more difficult to unblock, which causes permanent blockage of the coal seam seepage channel. On the other hand, during the drainage and gas production process, the looser coal powder will move toward the wellbore with the water flow, and a part of the coal powder will be transported to the ground by the drainage pump along with the produced water, while most of the coal seams or other solid phase particles will be retained and accumulated in the pores between the proppant (fracture sand or expanded clay) particles in the fracturing support seams. As the drainage time increases, the coal powder or other solid phase particles accumulate more and more, and the conductivity of the fracturing support seams decreases until they are completely blocked; at the same time, the chemical additives of the traditional coalbed methane fracturing fluid will also pollute the coal seams, resulting in a low fracturing fluid return rate; therefore, the blockage of the coal seam microcracks and fracturing support seams and the pollution of the coal seams by the traditional fracturing fluid lead to a decrease in the seepage capacity of the coal seams, slowing down the drainage and depressurization speed of the coal seams, resulting in a low fracturing fluid return rate, a small coal seam depressurization desorption range (depressurization desorption funnel radius), and a low degree of coalbed methane desorption in medium and high-rank coal seams, resulting in a low gas production of coalbed methane wells, a small coalbed methane recovery rate, and low economic benefits of coalbed methane wells.

[0004] Furthermore, the current coalbed methane well unblocking operations are all carried out under positive pressure (the pressure of the liquid column in the wellbore unblocking operation is much greater than the current pore pressure of the coal seam). Since the coal seam has been drained and produced gas for a long time, the coal seam pressure is deficient. The positive pressure unblocking operation can easily cause the coal powder deposited on the fracturing support to flow back into the coal seam, causing secondary blockage of the coal seam microcracks, and the unblocking operation effect is very poor.

[0005] Therefore, being able to provide a method for increasing the production of low-yield coalbed methane wells is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method and device for increasing the production of a low-yield coalbed methane well, which solves the problems in the prior art such as a large amount of coal powder generated by fracturing transformation permanently blocking the original micro-cracks of the coal seam, the accumulation of mobile coal powder blocking the fracturing support seams, and fracturing fluid contaminating the coal seam, which cause the coal seam to have a reduced seepage capacity, reduced conductivity of the fracturing support seams, poor drainage and pressure reduction effect of the coal seam, low fracturing fluid return rate, small coal seam pressure reduction and desorption range, low gas production, low coalbed methane recovery rate, and poor economic benefits. It also overcomes the disadvantage of secondary blockage of the coal seam caused by unblocking under positive pressure.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for increasing the production of a low-yield coalbed methane well comprises the following steps: firstly, unblocking is performed by shaking, then the unblocking wastewater is discharged, and then a nano-desorption promoter is injected into the coal seam, and the well is shut down to infiltrate the coal seam before resuming production.

[0009] At present, conventional coalbed methane well unblocking operations are carried out under positive pressure (the pressure of the liquid column in the wellbore unblocking operation is much greater than the current pore pressure of the coal seam). Since the coal seam has been drained and produced gas for a long time and the coal seam pressure is depleted, the positive pressure unblocking operation can easily cause the coal powder deposited on the fracturing support to flow back into the coal seam, causing secondary blockage in the coal seam microcracks, and the unblocking operation has almost no effect. Therefore, in order to eliminate the secondary blockage caused by sewage backflow during the unblocking operation, the present invention realizes negative pressure unblocking by pumping out the unblocking sewage to the ground while unblocking, and improves the fluidity of the coal seam fracture system in a large range by adopting the extensive infiltration of nano-desorbents, and the desorption rate, desorption degree, coalbed methane production and recovery rate of coalbed methane are greatly improved.

[0010] Preferably, the oscillation adopts an electric pulse oscillator or a coal seam resonator.

[0011] The present invention adopts a pulse oscillator or coal seam resonator that generates strong electric pulse vibrations after being powered on. The liquid in the wellbore and the cracks transmits the oscillation energy to the blocked parts of the cracks. Under continuous oscillation or multiple rounds of oscillation operations, the blocked coal powder will loosen and fall off, and be carried to the ground by the drainage pump along with the water flow, thereby achieving the effect of unblocking.

[0012] Preferably, the deblocking is performed by analyzing the rise and fall of the liquid level to determine the deblocking effect.

[0013] Preferably, the nano-desorption promoter is a silicon-based nano-material, which is ground into 5-50 nm particles by physical and chemical grinding, and then chemically compounded twice to make one end of the silicon-based nano-particle lipophilic and the other end hydrophilic.

[0014] The nano desorption promoter used in the present invention has ultra-low surface tension and ultra-low interfacial tension, can effectively reduce capillary resistance, can turn large groups of water molecules into very small water molecule groups, so that water can more easily pass through the nano-scale channels of the coal seam, can improve the return rate of the fracturing fluid, can efficiently change the wetting phase of the coal seam, promote the rapid desorption of a large number of methane molecules from the surface of coal particles, accelerate the desorption speed and desorption degree of coalbed methane, and improve the coalbed methane production and coalbed methane recovery rate.

[0015] Preferably, the injection is facilitated by pressurization and / or shaking.

[0016] Preferably, the specific method of injection is: normal pressure injection in the first stage, pressurized injection in the second stage, and oscillating pressurized injection in the third stage.

[0017] Preferably, the shut-in time is 24 hours.

[0018] The device according to the above-mentioned method for increasing the production of a low-yield coalbed methane well comprises a shock unblocking system, an unblocking sewage pumping system and a nano-desorption promoter injection system;

[0019] Wherein, the unblocking sewage pumping system comprises a drainage pipe column, a drainage pump is provided at the bottom of the drainage pipe column, and the drainage pump is electrically connected to the drainage pump control cabinet;

[0020] The oscillating unblocking system includes an oscillator and an oscillator control cabinet, wherein the oscillator is arranged at the bottom of the drainage pump and is electrically connected to the oscillator control cabinet;

[0021] The nano desorption accelerator injection system comprises an injection casing sleeved outside the drainage and production pipe column, and the top of the casing is connected to a pump truck and a liquid storage tank in sequence.

[0022] Preferably, the liquid level in the drainage pipe string is 30-50m higher than the coal seam.

[0023] Preferably, a pressure sensor is provided at the bottom of the injection sleeve.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention provides a method and device for increasing the production of a low-yield coalbed methane well. The present invention adopts negative pressure oscillation to remove blockage and extensive infiltration of nano-desorbents, so that the fluidity of a coalbed fracture system in a larger range is greatly improved, and the desorption rate, desorption degree, coalbed methane production and recovery rate are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 The present invention is a device structure diagram of a method for increasing the production of a low-yield coalbed methane well. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] like Figure 1 A device for increasing the production of a low-yield coalbed methane well, comprising a vibration unblocking system, an unblocking sewage pumping system and a nano-desorption accelerator injection system;

[0031] The unblocking sewage pumping system includes a drainage pipe column 2, a drainage pump 3 is provided at the bottom of the drainage pipe column 2, and the drainage pump 3 is electrically connected to the drainage pump control cabinet 6;

[0032] The oscillating unblocking system includes an oscillator 5 and an oscillator control cabinet 9. The oscillator 5 is arranged at the bottom of the drainage pump, and is electrically connected to the oscillator control cabinet 9 through the screen pipe 4 and the drainage pump 3;

[0033] The nano desorption accelerator injection system includes an injection casing 1 which is sleeved on the outside of the production and drainage pipe column. The top of the casing 1 is connected to a pump truck 7 and a liquid storage tank 8 in sequence. A pressure sensor is provided at the bottom of the injection casing 1.

[0034] The installation method is as follows: first, the wellbore (i.e., injection casing 139.7 mm) 1 of the coalbed methane well is pulled out, a drainage pipe string 2 (73 mm) is installed in the wellbore 1, a high-power electric pulse oscillator 5 is installed at the lower part of the drainage pump 3 of the drainage pipe string, the oscillator 5 is lowered to the coal seam and aligned with the perforation and fracturing position (the power supply cable is attached to the outside of the drainage pipe string and connected to the ground on the oscillator control cabinet), so that the liquid level 11 in the wellbore is higher than the coal seam 1030-50 m (slightly positive pressure), the ground wellhead device is installed, the injection pump truck 7 is connected to one side of the casing 1 (the other side of the casing has been connected to the coalbed methane production metering manifold of the well site), and a set of liquid storage tanks 8 filled with coalbed methane nano-desorption promoter solution are connected to the injection pump truck;

[0035] The specific unblocking process is:

[0036] Start the pulse oscillator to start the unblocking and oscillating work. Due to the blockage, the fluid in the blocked area cannot be effectively removed during the drainage process, forming a local relatively high pressure. After the blockage is unblocked by oscillation, the fluid in the blocked area will flow out to the wellbore, causing the wellbore liquid level to rise. Therefore, the unblocking effect is judged by monitoring the wellbore liquid level change through the bottom hole pressure sensor installed on the drainage pipe column. If the liquid level rises, it means that the unblocking effect is more obvious. After 3-6 rounds of unblocking by oscillation, quickly start the drainage pump to pump the bottom hole unblocking sewage (containing a large amount of coal powder and other solid particles) to the ground in time to avoid the sewage from flowing back to the micro-cracks of the blocked coal seam when the nano desorption promoter solution is injected. Repeat the operation of unblocking by oscillation and pumping sewage until the blockage is completely eliminated;

[0037] After confirming that the bottom well sewage has been pumped out, start the surface injection pump truck and inject the coalbed methane nano-desorption promoter solution into the coal seam through the oil casing annulus at a certain displacement. During the injection process, the relationship between the detected liquid level drop speed and the injection volume is used to calculate the speed of liquid absorption at different pressures. Based on these data, reasonable injection parameters are further determined to achieve the designed injection volume. During the injection period, the first injection stage is to slowly increase the injection displacement. Through the bottom hole pressure sensor of the production and drainage string, the height of the oil casing annulus liquid level is observed to find a more suitable stable displacement under a certain liquid level height and maintain it for a certain time. Make the under-pressure coal seam absorb a larger amount of coalbed methane desorbent solution more fully at an appropriate flow rate; the second injection stage (pressurized injection): increase the injection volume and injection pressure (after filling the wellbore annulus), and continue to inject the remaining designed injection desorption liquid volume; the third injection stage (oscillation pressurized injection) is: if the pressurized injection volume is small, start the oscillation unblocking device at this time, oscillate and unblock while oscillating and pressurizing until the remaining liquid volume is fully injected. After the designed liquid volume is injected, shut down the well for 24 hours to allow the coalbed methane desorption promoter solution to fully infiltrate the coal seam, remove the oscillation unblocking pipe string, and re-insert the drainage and gas production pipe string to resume production.

[0038] The various embodiments are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to in detail.

[0039] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for increasing the production of a low-yield coalbed methane well, characterized in that: First, after unblocking by shaking, the unblocking wastewater is discharged, and then the nano-desorption promoter is injected into the coal seam. After the well is closed and the coal seam is infiltrated, production can be resumed.

2. The method for increasing the production of a low-yield coalbed methane well according to claim 1, characterized in that: The oscillation adopts an electric pulse oscillator or a coal seam resonator.

3. The method for increasing the production of a low-yield coalbed methane well according to claim 1, characterized in that: The blocking removal is performed by analyzing the rise and fall of the liquid level to determine the blocking removal effect.

4. The method for increasing the production of a low-yield coalbed methane well according to claim 1, characterized in that: The nano desorption promoter is a silicon-based nano material, which is ground into 5-50 nm particles through physical and chemical grinding and then chemically compounded twice to make one end of the silicon-based nano particle lipophilic and the other end hydrophilic.

5. The method for increasing the production of a low-yield coalbed methane well according to claim 1, characterized in that: The infusion is facilitated by pressurization and / or shock.

6. A method for increasing the production of a low-yield coalbed methane well according to claim 5, characterized in that: The specific method of injection is: normal pressure injection in the first stage, pressurized injection in the second stage, and oscillating pressurized injection in the third stage.

7. The method for increasing the production of a low-yield coalbed methane well according to claim 1, characterized in that: The well shut-in time is 24h.

8. A device for increasing the production of a low-yield coalbed methane well according to any one of claims 1 to 7, characterized in that: It includes a shaking unblocking system, an unblocking sewage pumping system and a nano-desorption accelerator injection system; Wherein, the unblocking sewage pumping system comprises a drainage pipe column, a drainage pump is provided at the bottom of the drainage pipe column, and the drainage pump is electrically connected to the drainage pump control cabinet; The oscillating unblocking system includes an oscillator and an oscillator control cabinet, wherein the oscillator is arranged at the bottom of the drainage pump and is electrically connected to the oscillator control cabinet; The nano desorption accelerator injection system comprises an injection casing sleeved outside the drainage and production pipe column, and the top of the casing is connected to a pump truck and a liquid storage tank in sequence.

9. The device according to claim 8, characterized in that The liquid level in the drainage pipe string is 30-50m higher than the coal seam.

10. The device according to claim 8, characterized in that A pressure sensor is provided at the bottom of the injection sleeve.

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