CN117287177A - Coal-bed gas well aerodynamic hole making method based on continuous pressure holding and releasing - Google Patents

Abstract

The embodiment of the invention discloses a coal-bed gas well aerodynamic hole making method based on continuous holding pressure, which comprises the following steps: arranging well positions according to the pre-construction area; drilling a well position to the top of a target coal bed, and setting a sleeve to well cementation; drilling through a target coal seam for a well site; digging holes and reaming holes on the naked eyes of the target coal seam; flushing the well body; placing an oil pipe into the well body after well flushing; injecting gas into the well through the annular gap, closing the valve, and opening the valve after the pressure is suppressed to a preset pressure value to finish one-time pressure suppression and release; repeating the pressure holding and releasing; after the oil pipe is moved to the coal dust sand surface at the bottom of the coal bed, repeatedly suppressing and releasing pressure until the oil pipe moves downwards to a preset height; lifting the oil pipe, repeatedly holding down the pressure, and returning the pulverized coal below a preset value after opening the valve to release the pressure. Based on the concrete setting of the well position, the continuous pressure holding and releasing is adopted, so that pulverized coal and coal dust and the like are synchronously carried out step by step while the pressure holding and releasing are carried out, the hole making efficiency is greatly improved, and the potential safety hazard in the hole making process is reduced.

Description

An aerodynamic caving method for coalbed methane wells based on continuous pressure relief

Technical field

Embodiments of the present invention relate to the field of coal bed methane well cavitation methods, and specifically relate to an aerodynamic cavitation method for coal bed methane wells based on continuous pressure suppression and release.

Background technique

The cave completion process includes drilling, completion, drainage and gas production and other processes. In order to increase the permeability of the coal seam and ensure the desorption and migration of coal seam gas to the maximum extent, cave completion generally requires an effective well diameter of 3 to 4m and a certain range of crushing. bring. Cave completion is actually to repeatedly use special underground tools or means to collapse the underground coal seam, wash the collapsed coal and rock cuttings out of the well, and form a columnar cave in the coal seam section that is several times larger than the well diameter, thereby achieving The coal seam is connected to the wellbore to the maximum extent, forming multi-directional self-supporting induced cracks in the reservoir, which increases the effective radius of the wellbore, improves the permeability of the coal seam, and maximizes the analysis of adsorbed gas in the coal rock reservoir. .

At present, the technological improvement of cave completion mainly focuses on destroying the coal seam through physical or chemical means and then further washing it out. For example, the patent application number 201110340261.4 further introduces water jets to destroy the coal seams; the patent application number 201310003331.6 introduces an alkali solution for soaking. The above method will not only increase the additional cost of well completion, but also uses the method of destroying the coal first and then washing out the coal powder during the operation, which greatly increases the operation time. Although there is currently a method of using gas for fracturing, it often uses one position as the base point and continuously introduces gas to fracturing the coal seam. However, such multiple pressure-holding and releasing operations can easily cause pulverized coal dust in the lower part, etc. It cannot be brought out of the ground smoothly while holding and releasing pressure. Continuous accumulation not only affects the effect of subsequent holding and releasing pressure, but also easily mixes with air, posing a risk of explosion.

Contents of the invention

To this end, embodiments of the present invention provide an aerodynamic caving method for coalbed methane wells based on continuous pressure relief. By setting the well locations arranged in a polygon according to the pre-construction scope, and then based on the specific conditions of the well locations, continuous The operation of permanently holding and releasing the pressure moves the oil pipe for injecting gas step by step, and simultaneously brings out the pulverized coal and shavings step by step while holding and releasing the pressure. This not only greatly improves the efficiency of caving, but also reduces the process of caving. potential safety hazards.

In order to achieve the above objects, embodiments of the present invention provide the following technical solutions:

In one aspect of the embodiment of the present invention, an aerodynamic cavitation method for coalbed methane wells based on continuous pressure relief is provided, including:

S100. According to the pre-construction area, arrange multiple well locations connected in the center to form a polygon;

S200. After pre-drilling multiple well locations to the top of the target coal seam, lower the casing for cementing so that the bottom of the casing is flush with the top of the coal seam, or the distance between the bottom of the casing and the top of the coal seam is no greater than the casing. 1/5 of the tube length;

S300, uses a coal seam drill bit to penetrate the casing, and drill multiple well locations to penetrate the target coal seam;

S400, use the reaming drill bit to dig out the open hole of the target coal seam and expand it to the preset diameter to achieve pre-completion of the wellbore;

S500. Clean the pre-completed well body, circulate the drilling fluid for multiple cycles, and clean the mud on the hole wall;

S600. Put the oil pipe into the wellbore after cleaning until the bottom of the oil pipe is flush with the top of the coal seam or the top of the casing, or until there is a gap between the bottom of the oil pipe and the top of the coal seam or the bottom of the casing that is no larger than the casing. A distance of 1/10 of the length;

S700: Inject gas and water into the wellbore through the annular gap formed between the casing and the tubing. After injecting the pressure to the preset pressure value, close the air inlet and water inlet valves to hold the pressure, and then open them after holding the pressure to the preset time. The vent valve completes a pressure release;

S800. Repeat step S700 at least once;

S900. After moving the oil pipe to the coal dust surface at the bottom of the coal seam, while moving the oil pipe downward at intervals, repeat steps S700 and S800 until the oil pipe moves downward to the preset height;

S1000. Lift the oil pipe until the bottom of the oil pipe is flush with the top of the coal seam or the top of the casing, or until the distance between the bottom of the oil pipe and the top of the coal seam or the bottom of the casing is no more than 1/10 of the casing length. Repeat the steps. S700-S900, until the venting valve is opened and the returned pulverized coal is lower than the preset value to complete the caving of the coal bed methane well.

As a preferred solution of the present invention, in step S100, the center of the polygon coincides with the center of the pre-construction area, or the distance between the center of the polygon and the center of the pre-construction area is not greater than the center of the pre-construction area. 1/2 the minimum distance from center to edge.

As a preferred solution of the present invention, in step S100, the centers of multiple well locations are connected to form a parallelogram; and,

Set the influence radius of the well position to X, then the distance between the centers of two adjacent well positions is 1.5X-2.1X.

As a preferred solution of the present invention, whenever the oil pipe is at the same height, the number of times of repeating step S700 and step S800 to hold and release the pressure is not less than three times.

As a preferred solution of the present invention, whenever the oil pipe is located at the same height, at least one group of adjacent two pressure-holding processes have different holding pressures.

As a preferred solution of the present invention, whenever the oil pipe is at the same height, during multiple pressure holding and releasing processes, the holding pressure in the two adjacent pressure holding processes increases sequentially;

When the holding pressure increases to the preset peak value, the holding pressure will no longer increase.

As a preferred solution of the present invention, in step S700, while opening the vent valve, it also includes continuously injecting gas into the wellbore through the annular gap, so that gas for returning the pulverized coal to the ground is formed in the wellbore. circulatory pathways.

As a preferred solution of the present invention, in step S900, the distance the oil pipe moves downward each time is no more than 1/3 of the distance between the coal dust surface and the preset height.

As a preferred solution of the present invention, steps S600-S900 are formed as one-time mobile holding and releasing pressure, and there is also a moving flushing process between at least one group of two adjacent moving holding and releasing pressures. The moving flushing process is: moving the oil pipe After being lifted upward to the pulverized coal sand surface, the flushing gas is introduced through the annular gap while continuing to move downward to the preset height.

The embodiments of the present invention have the following advantages:

1. The present invention can effectively reduce the influence radius requirement of a single well position and greatly shorten the processing time by setting multiple well positions arranged in a polygon according to the specific conditions of the pre-construction area;

2. Multiple wells are arranged in polygonal positions. In the actual operation process, the amount of pulverized coal washed out per unit interval is relatively larger, which can better improve the outburst elimination effect;

3. Based on multiple pressure-holding and releasing operations, the gas can be efficiently displaced, thereby reducing the gas content and concentration and reducing safety risks;

4. While holding and releasing the pressure multiple times, the oil pipes are moved at intervals simultaneously, which can effectively discharge the pulverized coal and coal dust at all levels in layers. There is no need to accumulate the pulverized coal and then clear it out at once. , thereby eliminating the need to separate the fracturing and discharge of pulverized coal, greatly improving operating efficiency.

Description of drawings

In order to more clearly explain the embodiments of the present invention or the technical solutions in the prior art, the drawings that need to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only exemplary. For those of ordinary skill in the art, other implementation drawings can be obtained based on the extension of the provided drawings without exerting creative efforts.

The structures, proportions, sizes, etc. shown in this specification are only used to coordinate with the contents disclosed in the specification for the understanding and reading of people familiar with this technology. They are not used to limit the conditions under which the invention can be implemented, and therefore do not have any technical Any structural modification, change in proportion or size adjustment shall still fall within the scope of the technical content disclosed in the present invention without affecting the effectiveness and purpose achieved by the present invention. within the scope that can be covered.

Figure 1 is a layout diagram of well locations in the pre-construction area provided by the embodiment of the present invention;

Figure 2 is a schematic diagram of the layout of well locations in the pre-construction area provided by the embodiment of the present invention;

Figure 3 is a completion structure diagram after drilling provided by the embodiment of the present invention;

Figure 4 is a flow chart of the aerodynamic cavitation method for coal bed methane wells provided by an embodiment of the present invention.

Detailed ways

The following specific embodiments are used to illustrate the implementation of the present invention. Persons familiar with this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention. , not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

The technical solutions of the present invention will be described in detail below through specific examples.

In a specific embodiment, a 222*130m block needs to be caved.

Specifically, according to the above-mentioned pre-construction area, four well locations with centers distributed in a parallelogram shape are further set up in this area. The distances between two adjacent wells are 90m and 70m respectively. The influence radius of each well is 45m, which can basically cover the entire pre-construction area. Its specific deployment location is shown in Figures 1 and 2.

Use a 311.15mm drill bit to drill to the Quaternary strata, lower 244.48mm casing for cementing, then use a 215.9mm drill bit to drill to the top of the coal seam, lower 177.8mm casing for cementing, and then use a 152.4mm drill bit to drill through the coal seam section. The open hole is dug and expanded to 600mm, and a 139.7mm screen tube is lowered (the screen tube is suspended or placed in the well, with the upper part overlapping the steel casing by 10 to 15m), and the drilling fluid is circulated through the well cleaning (of course, it should be noted that, The screen tube here is optional, you can lower it into the screen tube, or you can dig out the holes and expand the holes and clean the well directly). The structure after drilling is shown in Figure 3. Among them, the black part in Figure 3 is the coal seam section.

Use an air booster to inject air into the well. When the gas injection pressure rises significantly, open the well to release the pressure. Operate back and forth for 70 to 80 rounds, and perform continuous pressure-holding and releasing operations to achieve an obvious sudden elimination effect.

Specifically, the aforementioned continuous pressure-holding and releasing operations specifically include:

1) Run the oil pipe down to the top of the coal seam (or the bottom of the cementing casing) to prevent coal seam collapse and bury the pipe string (see Figure 3);

2) Install a well sealing device with a temperature of 10 MPa or above at the wellhead. The well sealing device is closed during the holding operation and opened when the oil pipe is raised;

3) Pressure-holding construction procedure: A. Continuously inject air from the annular gap formed between the casing and the tubing (at the same time, water can also be further introduced for cooling to avoid excessively high temperature inside the wellbore during the pressure-holding process. resulting in an explosion hazard), the casing valve is closed (synchronously, the vent valve on the tubing also needs to be closed to form a closed space inside the well body, thereby facilitating the injection of gas to hold the pressure), hold the pressure to the design pressure value, and quickly open The vent valve relieves pressure and completes one hold. While depressurizing, it is also necessary to further inject air from the annular gap to form a circulation, thereby returning the lower pulverized coal to the ground through the oil pipe. In order to reduce the pollution of pulverized coal to the atmospheric environment, the released air enters the drilling mud pool. B. After holding it in for several times (select the specific number of times according to the actual situation), lower the oil pipe, explore the pulverized coal sand surface at the bottom, inject air to flush the pulverized coal, and lower it while flushing until it reaches the designed position (that is, the bottom of the oil pipe moves downward) to the preset height), and then lift it to the top of the coal seam. C. Repeat steps A and B until the returned pulverized coal chips are lower than the preset value (the preset value of the returned pulverized coal chips should be set accordingly according to the actual situation).

In order to better understand the specific solution of the present invention, a pressure-holding and releasing operation is further described in detail here: that is, gas and water for pressure-holding are injected into the wellbore through the annular gap between the casing and the tubing ( The gas is used to increase the pressurized gas, and the water is used for cooling to avoid explosions inside the well body). When the pressure inside the well body is suppressed to the preset pressure value, the air inlet and outlet connected to the annular gap are closed. water valve (during this process, the vent valve on the oil pipe is closed); then open the vent valve to provide a discharging channel for the pulverized coal, that is, the pulverized coal is released through the oil pipe. At the same time, when the pulverized coal is released, During the process, the air inlet valve can be further opened, and gas can be introduced from the air inlet valve to further form a gas path from the annular gap to the bottom coal powder, and then discharged through the oil pipe, so as to better effectively release the coal powder.

It should be noted that in step B, holding and releasing the pressure multiple times is not limited to the oil pipe being at the same height. During the operation, each time the oil pipe moves downward to a height, the pressure needs to be held and released several times. That is, when the oil pipe is in the initial position (the bottom of the oil pipe is flush with the top of the coal seam or the bottom of the casing, or until there is a gap of no more than 1/10 of the casing length between the bottom of the oil pipe and the top of the coal seam or the bottom of the casing) distance), follow step A above to hold and release the pressure several times; then move the oil pipe down to another height, and then hold and release the pressure several times until the oil pipe finally moves to the preset height. The number of movements of the oil pipe between the initial position and the preset position can be set according to the actual situation. The number of movements can be set based on the height or the amount of pulverized coal returned after each pressure release. Those skilled in the art can use this as a reference to make targeted settings based on the actual situation, which will not be described in detail here.

When the above-mentioned intermittent holding and releasing operation reaches the final movement of the oil pipe to the preset height, the oil pipe can be directly lifted to the initial position, and then the aforementioned intermittent holding and releasing operation is repeated. Of course, you can also perform the intermittent holding and releasing operation until the oil pipe finally moves to the preset height, and then add a moving flushing process. After the moving and flushing process, directly lift the oil pipe to the initial position, and then repeat the aforementioned intermittent holding and releasing operation. operate. Specifically, the mobile flushing process here is to move the bottom of the oil pipe to the coal pulverized sand surface, and inject gas and water into the annular gap (as mentioned before, the water here is used for cooling), thereby pulverizing the coal. Flushing, during this flushing process, the oil pipe continues to move downward until it moves to the preset height.

Whether it is the pressure-holding and releasing process or the moving flushing process, the pulverized coal will be returned through the oil pipe. In step C, the pulverized coal and coal dust returned from the pressure-holding and releasing process or the moving flushing process can be used as a reference. When it is lower than the preset value When, the well completion is achieved.

At the same time, in the aforementioned step B, during the holding and releasing process of the oil pipe at the same height, the holding pressure increases sequentially each time. The last holding pressure during the holding and releasing process at the same height is not greater than the preset peak value.

It should be further explained that if the oil pipe is at the preset height and the holding pressure has increased to the preset peak value, the holding pressure can be repeated to the preset peak value multiple times, or the oil pipe can be lifted to the height of step A to continue. Repeat steps A and B until the returned pulverized coal chips are lower than the preset value.

The technical solution of the present invention adopts conventional ground vertical well drilling + cave building technology, and the construction technology is simple, the construction accident rate is relatively low, and the risk is relatively small. By arranging multiple well locations, the construction period is effectively shortened, the relative amount of coal extracted is increased, and the outburst elimination effect is greatly improved. Further, through continuous pressure-holding and releasing operations, the gas content and concentration are greatly reduced while achieving efficient gas displacement. In addition, multiple continuous pressure holding and releasing at different levels can effectively destroy the coal seam structure, return part of the pulverized coal dust, and release the stress, further improving the anti-reflection and sudden-relief effect.

Furthermore, such continuous pressure holding and releasing, through further regulation of pressure parameters, etc., not only reduces the risk of explosion, but also establishes a gas circulation channel, which can bring pulverized coal to the surface during the holding and releasing operation, thereby improving the well's stability. The bottom plays a flushing role and further frees up space for subsequent coal release. The simultaneous release and removal of pulverized coal is achieved.

Although the present invention has been described in detail with general descriptions and specific examples above, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims (9)

1. An aerodynamic caving method for coalbed methane wells based on continuous pressure relief, which is characterized by including: S100. According to the pre-construction area, arrange multiple well locations connected in the center to form a polygon; S200. After pre-drilling multiple well locations to the top of the target coal seam, lower the casing for cementing so that the bottom of the casing is flush with the top of the coal seam, or the distance between the bottom of the casing and the top of the coal seam is no greater than the casing. 1/5 of the tube length; S300, uses a coal seam drill bit to penetrate the casing, and drill multiple well locations to penetrate the target coal seam; S400, use the reaming drill bit to dig out the open hole of the target coal seam and expand it to the preset diameter to achieve pre-completion of the wellbore; S500. Clean the pre-completed well body, circulate the drilling fluid for multiple cycles, and clean the mud on the hole wall; S600. Put the oil pipe into the wellbore after cleaning until the bottom of the oil pipe is flush with the top of the coal seam or the bottom of the casing, or until there is a gap between the bottom of the oil pipe and the top of the coal seam or the bottom of the casing that is no larger than the casing. A distance of 1/10 of the length; S700: Inject gas and water into the wellbore through the annular gap formed between the casing and the tubing. After injecting the pressure to the preset pressure value, close the air inlet and water inlet valves to hold the pressure, and then open them after holding the pressure to the preset time. The vent valve completes a pressure release; S800. Repeat step S700 at least once; S900. After moving the oil pipe to the coal dust surface at the bottom of the coal seam, while moving the oil pipe downward at intervals, repeat steps S700 and S800 until the oil pipe moves downward to the preset height; S1000. Lift the oil pipe until the bottom of the oil pipe is flush with the top of the coal seam or the top of the casing, or until the distance between the bottom of the oil pipe and the top of the coal seam or the bottom of the casing is no more than 1/10 of the casing length. Repeat the steps. S700-S900, until the venting valve is opened and the returned pulverized coal is lower than the preset value to complete the caving of the coal bed methane well. 2. A method for aerodynamic caving of coalbed methane wells according to claim 1, characterized in that, in step S100, the center of the polygon coincides with the center of the pre-construction area, or the center of the polygon coincides with the center of the pre-construction area. The distance between the centers shall not be greater than 1/2 of the minimum distance from the center to the edge of the pre-construction area. 3. A coal bed methane well aerodynamic caving method according to claim 1 or 2, characterized in that, in step S100, the centers of multiple well locations are connected to form a parallelogram; and, Set the influence radius of the well position to X, then the distance between the centers of two adjacent well positions is 1.5X-2.1X. 4. An aerodynamic cavitation method for a coalbed methane well according to claim 1 or 2, characterized in that, whenever the oil pipe is at the same height, the number of times of repeating steps S700 and S800 to hold and release pressure is no less than three times. 5. An aerodynamic cavitation method for coalbed methane wells according to claim 4, characterized in that whenever the oil pipe is located at the same height, at least one group of adjacent two pressure-holding processes have different holding pressures. 6. An aerodynamic caving method for coalbed methane wells according to claim 5, characterized in that whenever the oil pipe is located at the same height, during the multiple pressure-holding and releasing processes, the pressure-holding pressure in the two adjacent pressure-holding processes will increase. The pressure increases sequentially; When the holding pressure increases to the preset peak value, the holding pressure will no longer increase. 7. A coal bed methane well aerodynamic cavitation method according to claim 1 or 2, characterized in that, in step S700, while opening the venting valve, it also includes continuously injecting gas into the well body through the annular gap to A gas circulation path for returning the pulverized coal to the ground is formed in the well body. 8. An aerodynamic caving method for coal bed methane wells according to claim 1 or 2, characterized in that, in step S900, the distance the oil pipe moves downward each time is no greater than the distance between the coal pulverized sand surface and the preset height. 1/3 of the distance. 9. An aerodynamic cavitation method for coalbed methane wells according to claim 1 or 2, characterized in that steps S600-S900 are formed as one movement and pressure release, and at least one group of two adjacent movements and pressure releases. There is also a moving flushing process between the oil pipes. The moving flushing process is as follows: after the oil pipe is lifted upward to the coal dust surface, the flushing gas is introduced through the annular gap while it continues to move downward to the preset height.