CN102830630A - Coal bed gas multilateral well recovery control stimulation device - Google Patents

Abstract

The invention discloses a coalbed gas branch well drainage control simulation device, which comprises a main pipeline and at least two branch pipelines, the front end of the main pipeline is connected to a gas extraction device for simulating drainage control, and the rear end of the main pipeline is connected to the The front ends of all branch pipelines and the back ends of all branch pipelines are connected to the water pressure input device and/or air pressure input device. The main pipeline and branch pipelines have the same structure and are coal reservoir simulation pipelines. There are flow meters, pulverized coal filter devices and coal sample containers in sequence from front to back on the road. The present invention is aimed at the premise that the pressure transmission changes complicatedly during the multi-branch horizontal well drainage, the water production and gas production are large and small, and the drainage is difficult to control. A coalbed gas branch well drainage control simulation device is developed to simulate different coal Body structure, different hydrogeological conditions, different permeability, and different reservoir pressure conditions, in order to find out the changes in pressure transmission radius, water production, gas production, coal powder, etc. during drainage under different conditions.

Description

Coalbed methane branch well drainage control simulation device

technical field

The invention relates to a coalbed gas branch well drainage control simulation device.

Background technique

my country's coalbed methane resources are very rich. The latest round (2009) of national oil and gas resource evaluation results show that China's current geological resources of shallow coalbed methane buried below 2,000 meters are 36.81 trillion cubic meters, and the recoverable resources of shallow coalbed methane below 1,500 meters are 109,000. One hundred million cubic meters. The amount of coalbed methane resources far exceeds that of the United States, but the actual utilization of coalbed methane production is negligible. There are two main reasons for this: first, most of the coalbeds in my country are low-porosity, low-permeability, low-pressure, and low fluid seepage kinetic energy; It is because the series of experimental researches on different development technologies is not enough, resulting in no breakthrough in development engineering technology.

Vertical wells and horizontal wells are the two main well types for surface coalbed methane development at present. CBM vertical well drilling technology is simple and mature. For most of the low-permeability coal seams in my country, conventional vertical well development technology can never get rid of the limitation of "point". Usually, the drilling and completion plan and storage area are designed with a limited range of wellbore influence. layer transformation measures. In fact, the influence of "surface" should be considered more in the production of coalbed methane, and the interaction effects of micro-fracture distribution law, reservoir stress field and fluid seepage dynamic field in the whole gas reservoir should be considered comprehensively. Multi-branch horizontal wells use rapid water drainage and depressurization to increase production on a large scale. Compared with vertical well fracturing technology, they have certain advantages.

After the horizontal section of the current multi-branch horizontal well is drilled, generally no protective measures (such as lower screens, etc.) are taken. Because the coal seam fractures are relatively developed and the elastic modulus is relatively low, the wellbore in the horizontal section after drilling is very difficult. Unstable and prone to collapse. When the drainage equipment is lowered for drainage, the liquid supply area of the multi-branch horizontal well is relatively large, and the coal seam is a reservoir with strong heterogeneity, and because of the large number of branches, the change law of pressure transmission is relatively complicated, resulting in The outflow of reclaimed water is unpredictable, which increases the difficulty of drainage control. If the drainage work system is not properly controlled during drainage, it is easy to cause more and less outflow of water, resulting in the movement of coal powder in the coal reservoir, resulting in a decrease in permeability and affecting the gas production in the later stage; The inconsistency of the pressure transmission radius and the difference in the desorption radius in each branch lead to the difference in the gas production in the branches. If the drainage system is not proper, the gas production may fluctuate, causing the movement of coal powder and the permeability of coal reservoirs. Some injuries are even fatal, which may lead to no or very little gas production in the later stage. How to formulate a relatively reasonable drainage system according to different hydrogeological conditions, pressure transmission radius, desorption radius, and coal structure is the key to maintain good reservoir permeability and increase gas production of branch wells. The essential.

Contents of the invention

The purpose of the present invention is to develop a coalbed methane branch well drainage control simulation device for the premise that the pressure transmission changes complicatedly when the multi-branch horizontal well is drained, the water production rate and the gas production rate are large and small, and the drainage is difficult to control. Different coal body structures, different hydrogeological conditions, different permeability, and different reservoir pressure conditions, so as to find out the pressure transmission radius, water production rate, and gas production rate during drainage under different geological conditions of reservoirs and different drainage systems. Based on the changes of , pulverized coal, etc., it is concluded that a relatively reasonable drainage work system under different circumstances can minimize the damage to the reservoir, prolong the gas production peak of CBM branch wells, and provide theoretical guidance for increasing the gas production of multi-branch horizontal wells.

In order to achieve the above object, the present invention adopts the following technical scheme: a coalbed methane branch well drainage control simulation device, including a main pipeline and at least two branch pipelines, the rear end of the main pipeline is connected to the front ends of all branch pipelines, and all branch pipelines The back end of the pipeline is connected to the water pressure input device and/or the air pressure input device. The main pipeline and branch pipelines have the same structure and are coal reservoir simulation pipelines. Flowmeters are arranged on the coal reservoir simulation pipelines from front to back. , Coal filter device and coal sample container.

The coal sample container is connected to a confining pressure pump through a pipe, and the pipe is provided with a pressure gauge. The confining pressure pump is an air pump used to increase the air pressure in the coal sample container to simulate the confining pressure of the coal reservoir.

The pulverized coal filtering device includes a filter container with an inlet and an outlet, and a filter screen is arranged in the filter container, and the filter screen divides the filter container into two chambers, and the inlet and outlet of the filter container are respectively located on both sides of the filter screen.

The water pressure input device is a water pressure input pipeline, and the water pressure input pipeline is provided with a pressure sensor, a PID regulating valve, a switch valve, a water injection pump and a water tank in sequence from front to back.

The front end of the main pipeline is connected to the extraction device for simulated drainage control.

The air pressure input device is an air pressure input pipeline, and the air pressure input pipeline is provided with a pressure sensor, an air compressor, a PID regulating valve, a pressure reducing valve, an on-off valve and a high-pressure gas cylinder in sequence from front to back.

All flow meters, pressure gauges and pressure sensors are connected to the computer data acquisition system.

The front end of the main pipeline is connected to the air extraction cylinder through the back pressure valve, and the air extraction cylinder is connected to the air extraction device. The side walls of the air extraction cylinder are respectively connected to the air bag and the water collection bottle through two connecting pipes, and the connecting pipes are also equipped with flow meters. .

The air extraction device is a plunger type air extraction device, which includes a plunger slidingly connected in the air extraction cylinder and a power device connected to the plunger, and the coal sample container is a rubber sleeve.

The high-pressure gas set in the high-pressure gas cylinder is CO ₂ or N ₂ or He or gas.

The coalbed methane branch well drainage control simulation device of the present invention has the following beneficial effects: all branch pipelines are merged together and connected in series with the main pipeline, and both the main pipeline and the branch pipelines are coal reservoir simulation pipelines, so that Composed of the whole branch well coal reservoir simulation system. Among them, the air pressure input device is mainly used to simulate the air pressure of free gas in the reservoir during drainage and the simulated gas output; the water pressure input device simulates the pressure and flow of water in the reservoir during drainage. The coal reservoir simulation pipeline is mainly used to simulate the stress state of coal and coal with different degrees of fracture development. The air extraction device is mainly for simulated drainage control, so that the pressure change during the simulated drainage is the pressure difference between the main pipeline and the branch pipeline, and the water and gas in the coal sample can be pumped out to control the air pressure and water pressure. pressure, air flow, water flow. The computer data acquisition system is mainly used to display the collected data on the computer.

In summary, the advantages of the present invention are: (1) The present invention can simulate various physical parameters in the drainage process of branch wells under different coal deformation characteristics, different drainage stages, different branch numbers, different confining pressures, and different drainage intensities change rule.

(2) The present invention can provide theoretical guidance for the formulation of reasonable drainage working systems under different coal body deformation characteristics, different drainage stages, different branch numbers, and different confining pressures of coalbed methane branch wells.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a structural schematic diagram of the filter screen.

Detailed ways

A coalbed methane branch well drainage control simulation device shown in FIG. 1 and FIG. 2 includes a main pipeline 9 and three branch pipelines 29 .

The front end of the main pipeline 9 is connected to an air extraction device for simulating drainage control, and the front end of the main pipeline 9 is first connected to an air extraction cylinder 21 through a back pressure valve 18, and then the air extraction cylinder 21 is connected to the air extraction device. The side of the air extraction cylinder 21 The wall is also respectively communicated with an air bag 27 and a water collection bottle 28 through two connecting pipes, and a flow meter 16A is arranged on the connecting pipes. Described air extraction device is plunger type air extraction device, and plunger type air extraction device comprises the plunger that is slidably connected in the air extraction cylinder 21 and the power unit that connects plunger, and described power unit is motor 26, and the output of motor 26 The shaft drives a rotating shaft 23 through a belt transmission 24, and the rotating shaft 23 drives the plunger rod 20 to move up and down through a crank slider mechanism 22. The inner wall of the cylinder fits together, so that when the rotating shaft 23 rotates, it can drive the plunger rod 20 to slide up and down in the air extraction cylinder 21 to perform air extraction. The output shaft of the motor 26 is provided with a speed sensor 25 . Of course, the present invention is not limited to the above-mentioned form, and the power device can also be replaced by a pneumatic cylinder or a hydraulic cylinder, or can be directly lifted up and down manually, which can drive the plunger rod 20 to move up and down, and the air extraction device can also be directly connected with The air extraction pump that air extraction cylinder 21 is connected replaces also can.

The gas extraction device constitutes a drainage control simulation system, and the drainage control simulation system discharges the gas and water in the coal sample 10 passing through the main pipeline 9 and the branch pipeline 29 of the coal reservoir simulation system, and provides the main pipeline 9 and the branch pipeline The front part of the road 29 provides a certain pressure value. The rotation speed of the motor 26 can be adjusted according to the experimental requirements. In order to ensure the continuity of the pressure drop of the sample device system during the extraction process, a back pressure valve 18 is specially installed in front of the main pipeline 9 .

The rear end of the main pipeline 9 is connected to the front ends of all the branch pipelines 29 , and the front ends of all the branch pipelines 29 are first communicated and then connected to the rear end of the main pipeline 9 . The rear ends of all the branch pipelines 29 are first connected and then connected to the water pressure input device and the air pressure input device at the same time. The water pressure input device and the air pressure input device are used to input necessary air pressure and water pressure to each branch pipeline 29. The water pressure input device is a water pressure input pipeline 30, and the high pressure pipeline of the water pressure input pipeline 30 is provided with a pressure sensor 8, a PID regulating valve 6, a switch valve 3, a water injection pump 5 and a water tank 1 in sequence from front to back, The water tank 1 is 3m*3m*2m. The air pressure input device is an air pressure input pipeline 31, and the pipeline of the air pressure input pipeline 31 is provided with a pressure sensor 8, an air compressor 7, a PID regulating valve 6, a pressure reducing valve 4, a switch valve 3 and a high pressure pressure sensor from front to back. The gas cylinder 2, the high-pressure gas set in the high-pressure gas cylinder 2 is CO ₂ , or N ₂ or He or gas.

The air pressure input device and the water pressure input device constitute a pressure control system. Through the two devices, the output of different drainage stages and the pressure change during drainage can be simulated, and a single water phase, a single gas phase or a mixture of gas and water can be realized. Phase flow at different pressures. The water tank 1 of the water pressure input device is mainly used to store water, and the water injection pump 5 is used to inject the water in the water tank 1 into the coal reservoir simulation system and provide a certain water pressure value (the maximum water pressure can be set according to the experimental needs ), the PID regulating valve 6 of the water pressure input device mainly realizes the adjustment of the pressure difference, that is, the air extraction device provides a certain pressure value to the front side of the main pipeline 9 and the branch pipeline 29, and the air pressure input device and the water pressure input device provide a certain pressure value to the main pipe. The back side of the pipeline 9 and the branch pipeline 29 provide a certain pressure. When the pressure difference between the two sides reaches a certain value, the PID valve opens to let the water pass through. The PID valve can meet the pressure below 10MPa. The switch valve 3 of the water pressure input device mainly controls the water pressure input pipeline 30 to be in the open or closed state, through the PID regulating valve 6 and the switch valve 3, the flow of single water and the flow of water with different pressure differences are realized. Simultaneously, the flow of water is recorded by the water flow meter 16 and transmitted to the computer in real time.

The high-pressure cylinder 2 of the air pressure control device is connected with the air compressor to provide the air pressure required for the experiment. When the pressure in the high-pressure gas cylinder 2 can meet the experiment, the air compressor is not needed to run, and when the pressure cannot meet the experiment, the air compressor is used to provide the pressure required for the experiment to achieve the purpose of simulating the air pressure in the reservoir . The PID regulating valve 6, on-off valve 3 and air flow meter 16 of the air pressure control device have similar functions to the water pressure control system and will not be repeated here.

The main pipeline 9 and the branch pipeline 29 have the same structure and are coal reservoir simulation pipelines. The coal reservoir simulation pipeline is provided with flowmeter 16, switch valve 3A, coal powder filter device 14, switch valve 3B, coal Sample container 11 and switch valve 3C. The coal sample container 11 is a rubber casing, and the coal sample 10 is loaded in the rubber casing. The two ports of the rubber casing are respectively connected to the coal reservoir simulation pipeline, and the side wall of the coal sample container 11 is connected to the confining pressure pump 13 through a pipe. A pressure gauge 12 is provided on the pipe, and a confining pressure pump 13 is an air pump used to increase air pressure into the coal sample container 11 to simulate the confining pressure suffered by the coal reservoir. Described pulverized coal filtering device 14 comprises the filter container that has the airtight setting of inlet and outlet, and filter container is made of transparent toughened glass, and filter container is also connected on the coal reservoir simulation pipeline by its inlet and outlet, and inside the filter container Set filter screen 15, filter screen 15 divides filter container into two chambers, the inlet and outlet of filter container are positioned at the both sides of filter screen 15 respectively, namely the inlet and outlet of filter container are positioned at the filter container wall of two chambers respectively .

The main pipeline 9 and the branch pipelines 29 constitute a coal reservoir simulation system, which is mainly used to simulate the coal with different degrees of fracture development, the wellbore structure of the horizontal section of the multi-branched horizontal well and the stress state of the coal, so that The results of the drainage work system that are closer to the actual situation are obtained. The three-way coal reservoir simulation pipeline constitutes three branch pipelines to simulate each branch of the branch well, and the number of branches can be added or deleted according to the actual situation. The three-way coal reservoir simulation pipeline is connected in parallel, through their respective The control valve can not only realize one-way gas and water flow, but also realize multi-way gas and water flow, which is used to simulate the influence of gas and water changes on permeability under different drainage stages and different pressure transmissions. The pulverized coal produced in the coal reservoir simulation device is collected through the pulverized coal filter device 14. The transparent tempered glass used in the pulverized coal filter device 14 can observe the change of the amount of pulverized coal in real time; the three-way coal reservoir simulation pipeline Then they are merged together and connected in series with another coal reservoir simulation pipeline, the main pipeline 9, to form the entire coal reservoir simulation system. In the three-way coal reservoir simulation device, the same coal body structure, degree of deformation, and fracture development degree are roughly similar to the coal, and coal with different coal body structure and fracture development degree is relatively large. Coal sample 10 uses glue The casing is tightly wrapped, and the confining pressure pump 13 mainly provides different air pressures to the coal sample 10 in the rubber casing to simulate the confining pressure on the coal sample 10 and simulate the stress on the coal reservoir.

The pulverized coal filtering device 14, the air bag 27 and the water collecting bottle 28 constitute a data acquisition and output collection system, which mainly collects the coal dust discharge of the main branch and each branch coal sample 10 caused by the flow of gas and water during the experiment, And the water and methane gas produced during the experiment were collected. Wherein, pulverized coal can be collected by pulverized coal filtering device 14, and pulverized coal filtering device 14 is designed as a transparent tempered glass bottle of high pressure resistance, and there is fixed groove in the bottle, can filter screen 15 be fixed in the bottle, can be used at any time simultaneously. Observe the amount of pulverized coal in the pulverized coal filter 14, when the amount of pulverized coal is more, the test should be suspended and the switch valves 3A, 3B before and after the pulverized coal filter 14 are closed tightly, then the pulverized coal filter 14 is unscrewed, Transfer the pulverized coal out, dry the pulverized coal with a desiccant, and then weigh it with a balance to obtain the pulverized coal output of the main branch and each branch during the experiment. Wherein, the filter screen 15 that is fixed in the pulverized coal filter device 14 can use the screen cloth of different specifications, can be 60 meshes, also can be 40 meshes, 20 meshes and 80 meshes, according to experiment needs, can choose different screen cloths. The methane gas produced during the experiment can be collected by the air bag 27, and the water can be collected by the water collection bottle 28.

All flow meters 16, 16A, pressure gauge 12, pressure sensor 8, and speed sensor 25 are all connected to computer data acquisition system 17, and flow meter 16, pressure gauge 12, pressure sensor 8, speed sensor 25 and computer data acquisition system 17 constitute data acquisition The display system mainly monitors the water pressure and air pressure provided in the pressure system, the gas-water flow through each branch sample device and the main branch sample device, the total water production and gas production during the drainage process, and the 26 speeds of the motor through the computer. Automatically read and record. Wherein the automatic reading of water pressure and air pressure provided in the pressure system is connected with the computer through the pressure sensor 8, and the automatic reading of the engine speed is then realized by being connected with the computer through the speed sensor 25 on the output shaft.

Of course, the present invention is not limited to the above-mentioned form, and any of the water pressure input device and the air pressure input device can be provided according to needs, and the number of branch pipelines 29 can also be provided with two or more according to actual conditions. And the high-pressure gas that is provided with in the high-pressure gas cylinder 2 also can be N Or He or gas, when using high-pressure gas, should pay attention to safety.

The coalbed methane branch well drainage control simulation device described in the present invention has specific operation steps as follows:

(1) Preparation of coal sample 10

The coal sample 10 is collected according to the requirements of the experiment. The coal sample 10 can be made into a cylindrical coal sample 10 of Φ50cm×50 cm, or the coal sample 10 can not be prepared, and the coal block can be directly put into the rubber casing.

(2) Air tightness inspection

Connect the pipeline according to the schematic diagram of the system connection device, and inject a small amount of gas into the system to check the airtightness of the device.

(3) Selection of the number of branch sample devices

According to experimental requirements, multiple branch pipelines 29 such as two branch pipelines 29 connected in parallel, three branch pipelines 29 connected in parallel, and four branch pipelines 29 connected in parallel can be selected for simulation experiments.

(4) Set the threshold of PID control valve 6

According to the requirements of the experiment, set the threshold value of the PID regulating valve 6, that is, when the pressure difference exceeds this value, the PID valve will automatically open.

(5) Set the confining pressure

According to the requirements of the experiment, the confining pressure of the confining pressure pump 13 is set to a predetermined pressure.

(6) Pressure test

The multi-branch pipeline 29 simulates the change characteristics of the physical parameters of the multi-branch well at different drainage stages. The experiment can be realized by controlling the valves of the water tank 1 and the high-pressure gas cylinder 2 . In the stage of saturated water single-phase flow, only the valve of water tank 1 can be opened, and the water injection pump 5 can be used to provide a certain water pressure; in the stage of unsaturated water single-phase flow, the valve of high-pressure gas cylinder 2 can be slightly opened on the basis of providing a certain water pressure; In the air-water two-phase flow stage, water pressure and air pressure are provided at the same time, and the water pressure provided can be appropriately reduced as the experiment progresses.

(7) Selection of drainage speed

Start the motor 26, set the speed of the motor 26 according to the experimental needs, and carry out the drainage experiment simulation.

(8) Collection of pulverized coal during drainage

When selecting different drainage stages, different branch numbers, different confining pressures, and different drainage speeds to carry out the experiment, the motor 26 should be closed earlier, the experiment should be suspended, and the coal dust filter 14 of the main pipeline 9 and each branch pipeline 29 should be opened. The pulverized coal is collected, dried and weighed separately, and the weighing results are recorded. When opening the pulverized coal filtering device 14, the front and rear two switch valves 3A, 3B must be closed tightly to ensure the airtightness of the whole system.

(9) Data processing

According to the various data collected by the computer data acquisition system 17, the permeability of the coal sample 10 of the main pipeline 9 and each branch pipeline 29 under different conditions is calculated, and on this basis, different drainage stages and different branch numbers are calculated. , Relational diagram of parameters such as gas production, water production, pulverized coal volume, permeability and drainage speed under different confining pressures.

(10) Coupling Analysis

Coupling analysis of the relationship between different drainage stages, different numbers of branches, and drainage speed under different confining pressures, gas production, water production, coal powder production, coal sample 10 permeability and other parameters, it is concluded that branch wells at different drainage stages, different The number of branches and the most reasonable drainage speed under different confining pressures.

Claims (10)

1. a coal-seam gas branch well array is adopted the control analogue means; It is characterized in that: comprise main line and at least two branch lines; The rear end of main line connects the front end of all branch lines; The rear end of all branch lines is communicated with the back and connects hydraulic pressure input media and/or air pressure input media, and the identical coal seam reservoirs simulation pipeline that is with the branch line structure of main line is provided with flowmeter, coal powder filter and coal sample container on the coal seam reservoirs simulation pipeline from front to back successively.

2. coal-seam gas as claimed in claim 1 branch well array is adopted the control analogue means; It is characterized in that: said coal sample container connects the confined pressure pump through pipe; Pipe is provided with tensimeter, and the confined pressure pump is to be used in the coal sample container, increasing the air pump of air pressure with the suffered confined pressure of simulation coal seam reservoirs.

3. coal-seam gas as claimed in claim 2 branch well array is adopted the control analogue means; It is characterized in that: coal powder filter comprises the filtering container that has import and export; Establish filter screen in the filtering container; Filter screen is divided into two chambers with filtering container, and the import and export of filtering container lays respectively at the both sides of filter screen.

4. coal-seam gas as claimed in claim 3 branch well array is adopted the control analogue means; It is characterized in that: said hydraulic pressure input media is the hydraulic pressure intake line, is provided with pressure transducer, PID variable valve, switch valve, waterflood pump and water tank on the hydraulic pressure intake line from front to back successively.

5. coal-seam gas as claimed in claim 4 branch well array is adopted the control analogue means; It is characterized in that: said air pressure input media is the air pressure intake line, is provided with pressure transducer, air compressor, PID variable valve, reduction valve, switch valve and gas cylinder on the air pressure intake line from front to back successively.

6. adopt the control analogue means like each described coal-seam gas branch well array of claim 1-5, it is characterized in that: the front end of main line connects and is used to the air extractor that control is adopted by the row of simulation.

7. coal-seam gas as claimed in claim 6 branch well array is adopted the control analogue means, and it is characterized in that: all flowmeters, tensimeter and pressure transducer all connect computer data acquisition system.

8. coal-seam gas as claimed in claim 7 branch well array is adopted the control analogue means; It is characterized in that: the front end of said main line connects the cylinder of bleeding through check valve; The cylinder of bleeding connects air extractor again; The sidewall of cylinder of bleeding also is communicated with air bag and collection bottle respectively through two connecting pipes respectively, also is equipped with flowmeter on the connecting pipe.

9. coal-seam gas as claimed in claim 8 branch well array is adopted the control analogue means; It is characterized in that: said air extractor is the plunger type air extractor; It comprises the plunger and the propulsion system that are connected plunger that is slidingly connected in the cylinder of bleeding, and said coal sample container is the gum cover pipe.

10. coal-seam gas as claimed in claim 9 branch well array is adopted the control analogue means, and it is characterized in that: it is CO that gases at high pressure are set in the said gas cylinder ₂Perhaps N ₂Perhaps He or methane gas.

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