CN105092790A - Coal reservoir fracturing physical simulation device and simulation method based on solvent extraction - Google Patents

Abstract

The invention discloses a coal reservoir fracturing physical simulation device and simulation method based on solvent extraction. The device comprises a vacuum sample tank provided with an end cap. A heater is arranged on the outer surface of the vacuum sample tank. An input port of the vacuum sample tank is connected with the output end of an injection system through a pipeline. The pipeline between the injection system and the vacuum sample tank is sequentially provided with a pressure pump and an injection valve. The injection system comprises a gas tank, a solvent tank and a mineral water tank. The input port of the vacuum sample tank is connected with a recycling system through a pipeline provided with a recycling valve and a gas-liquid separator. The recycling system comprises a recycling gas tank and a recycling liquid tank. The vacuum sample tank is further connected with a vacuum pump. By means of the physical simulation device and simulation method, action of organic and/or inorganic solvents on coal and expanding situations of pores and fractures can be simulated after the organic and/or inorganic solvents serve as fracturing liquid to be pressed into the coal under the real reservoir conditions, and bases are provided for subsequent research of coal samples and extraction liquid. Meanwhile, a new thought is provided for the fracturing development technology of coal reservoirs.

Description

Physical simulation device and simulation method of coal reservoir fracturing based on solvent extraction

technical field

The invention relates to the field of improving the physical properties of coal reservoirs, in particular to a physical simulation device and simulation method for coal reservoir fracturing based on solvent extraction.

Background technique

Solvent extraction is one of the earliest and most important research methods of coal structure. Many main understandings and concepts about coal structure are obtained through solvent extraction. It is generally believed that the solvent extraction of coal is carried out through the process of solvent diffusion and penetration-cross-link breakage-coal network structure opening-organic matter dissolution. At present, the research method of obtaining coal structure information by solvent extraction method is still widely valued and applied. In the research of coal chemistry, through solvent extraction, the small molecular phase in coal is released by using the ability of the solvent to accept electrons, so as to achieve the separation of the main body and the object of the coal structure, so as to speculate and verify the structure model of coal and its effect on coal. nature of the impact. The small molecular phase is gradually separated from the macromolecular network structure through step-by-step extraction, and the analysis of soluble and insoluble substances in different solvents can provide a lot of evidence for the establishment and verification of coal structure models on the one hand, and the extraction of The number of small and medium molecules also represents the stability of the physical and chemical properties of coal to a certain extent.

The gas in the coal seam mainly exists in the adsorbed state. Due to the complexity of coal reservoir pores and fractures and the low permeability of the reservoir, in the current ground development practice of coal bed methane, hydraulic fracturing, acid fracturing and other reservoir strengthening measures are often used. , to increase the permeability of the reservoir. Although researchers at home and abroad have done a lot of experiments and research on solvent extraction of coal, mainly for the study of coal chemistry and coal structure, there is no method of organic solvent extraction and proportioning fracturing fluid directly used to improve reservoir conditions The simulated experimental device and research method. In view of the current coalbed methane development process, relying solely on conventional hydraulic fracturing and gas flooding methods, the effect obtained is not significant, it is urgent to explore new reservoir strengthening technology measures to improve the physical properties of the reservoir, thereby increasing the productivity of coalbed methane wells.

Contents of the invention

The purpose of the present invention is to provide a physical simulation device and simulation method for coal reservoir fracturing based on solvent extraction, which can simulate real reservoir conditions. Organic and inorganic solvents can be injected into coal reservoirs as fracturing fluids, and dissolved by organic solvents. The small molecular phase in the macromolecular structure of coal, or the use of inorganic solvents to dissolve minerals in coal, can also inject different proportions of organic mixed solvents or inorganic mixed solvents into the coal body, or combine organic and inorganic solvents, such as The inorganic acid solution is injected into the coal body as the pre-hydraulic pressure, and then the organic solvent is injected as the sand-carrying hydraulic pressure, so as to fully change the pore fissures and air permeability of the coal body, and then use auxiliary equipment to monitor the expansion of the pores and fissures in real time. And through gas injection to detect the gas permeability of coal, to simulate the enhanced permeability process of the reservoir, to provide a new idea for the fracturing development technology of coalbed methane.

The present invention adopts following technical scheme:

The physical simulation device of coal reservoir fracturing based on solvent extraction includes a vacuum sample tank with an end cover, a heater is arranged on the outer surface of the vacuum sample tank, and the input port of the vacuum sample tank is connected to the output end of the injection system through a pipeline. The pipeline between the system and the vacuum sample tank is provided with a pressure pump and an injection valve in sequence; the injection system includes a gas tank, a solvent tank and a mineralized water tank, and the output port of the vacuum sample tank is provided with a recovery valve and a gas-liquid separation The pipeline of the device is connected to the recovery system, and the recovery system includes a recovery gas tank and a recovery liquid tank; the vacuum sample tank is also connected with a vacuum pump.

Acoustic emission sensors are installed at both ends of the vacuum sample tank, and an acoustic emission instrument is connected to the outside of the vacuum sample tank.

An overpressure protection device is also provided on the pipeline between the pressure pump and the injection valve.

A pressure gauge is also arranged on the pipeline between the injection valve and the vacuum sample tank.

The pressure pump adopts a pressure pump with adjustable pressure and flow.

The pressure pump has the functions of constant pressure pressurization and constant flow pressurization, and the rated pressure of the pressure pump is greater than 20MPa.

The heater adopts an annular infrared heater, and the annular infrared heater is arranged around the outer surface of the vacuum sample tank.

The end cover is threadedly connected with the vacuum sample tank, and a sealing device is arranged between the end cover and the vacuum sample tank, and the sealing device adopts a rubber sealing ring; the pipeline adopts a high-strength pressure tube.

A simulation method utilizing the physical simulation device for coal reservoir fracturing based on solvent extraction according to any one of claims 1 to 8, comprising the following steps:

A: Design the experimental plan, obtain the temperature, pressure and water content data of the real coal reservoir, and select the type, concentration and pressure required for fracturing according to the experimental results to be obtained;

B: Open the end cover of the vacuum sample tank, put the columnar or granular coal samples in the simulated area into the vacuum sample tank, and then close the end cover of the vacuum sample tank;

C: Start the vacuum pump to draw a vacuum inside the vacuum sample tank;

D: Start the acoustic emission sensor and the acoustic emission instrument to monitor the pore changes caused by the action of the fracturing extract in real time and dynamically;

E: Open the injection valve and start the pressure pump, inject gas and mineralized water according to the measured pressure and water content of the real coal reservoir, and simulate the pressure and water content of the real coal reservoir;

F: Start the annular infrared heater to uniformly heat the vacuum sample tank;

G: When the temperature and pressure in the vacuum sample tank reach the set temperature and pressure, start the pressure pump again and inject the extraction liquid configured according to the experimental plan. When the set pressure of the experimental plan is reached, close the pressure pump and injection valve;

H: Turn off the acoustic emission sensor and the acoustic emission instrument, and extract the acoustic emission data;

I: Stand still until the set time is reached according to the requirements of the experimental plan;

J: open the recovery valve, and start the gas-liquid separator to recover the gas and liquid produced in the vacuum sample tank, and the recovered gas and liquid are stored in the recovery gas tank and the recovery liquid tank respectively; K: open the end cover of the vacuum sample tank and Take out the coal sample, then open the recovery gas tank and the recovery liquid tank to take out the stored gas and liquid.

In the described step A, the extract adopts an organic solvent and/or an inorganic solvent; when in use, select one of the following schemes:

(1) Use organic solvents alone, and use organic solvents as fracturing hydraulic pressure to inject coal samples, weaken the intermolecular bond force in the cross-linked network of coal structure, and dissolve small molecules;

(2) Using inorganic solvent alone, using the acidification of inorganic acid in the inorganic solvent to dissolve the minerals in the coal;

(3) Choose organic mixed solvents or inorganic mixed solvents with different ratios, and press them into the coal sample to enhance the effect of the mixed solvent on the expansion of coal pores and cracks and the effect of anti-permeability;

(4) First use the inorganic acid in the inorganic solvent for acidification treatment, and then use the organic solvent for organic extraction; or press the organic solvent in first, and then use the inorganic acid in the inorganic solvent for acidification treatment, and then use the inorganic acid in the inorganic solvent for acidification treatment, and then use the organic solvent to carry out organic extraction; Perform thorough expansion and enhancement.

The invention is based on the principle of solvent extraction, and injects the solvent with a good proportion to simulate the hydraulic fracturing process of the reservoir and injects the coal columnar sample. The infrared heating device is used to simulate the temperature of the reservoir, the gas tank is used to simulate the gas pressure of the real reservoir, and the mineralized water tank is used to simulate the water content of the real reservoir through a well-proportioned mineralized water to realize the simulation of reservoir fracturing. And the extension of the pore and fracture system of the reservoir is monitored in real time by means of the acoustic emission device, so as to realize the application of the solvent extraction method in the strengthening of the reservoir. The invention can more effectively change the pore and fracture system of the reservoir, and reduce the surface energy, so as to improve the physical properties of the reservoir and reduce the adsorption capacity of coal, thereby greatly improving the desorption, diffusion and seepage capabilities of the coal bed gas. The invention effectively combines solvent extraction and reservoir strengthening, which can realize material exchange with coal after the extraction hydraulic pressure enters the coal seam under real reservoir conditions, and effectively improve the physical properties of the reservoir, which is a physical simulation of subsequent reservoir fracturing technology Provide technical support, and play a pivotal role in the revolution of the scientific research theory of solution extraction to achieve coal permeability enhancement from the laboratory to the engineering application. The invention also has the advantages of simple structure, low manufacturing cost and convenient operation.

Description of drawings

Fig. 1 is the structural representation of the physical simulation device of coal reservoir fracturing based on solvent extraction according to the present invention;

Fig. 2 is a flow chart of the simulation method of the physical simulation device for coal reservoir fracturing based on solvent extraction according to the present invention.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the present invention is described in detail:

As shown in Figure 1, the physical simulation device of coal reservoir fracturing based on solvent extraction according to the present invention comprises a vacuum sample tank 1 provided with an end cover, the end cover is threadedly connected with the vacuum sample tank 1, and the end cover is connected with the vacuum sample tank 1. A sealing device is arranged between the vacuum sample tanks 1 , and the sealing device can be a rubber sealing ring to ensure good airtightness of the vacuum sample tank 1 . The outer surface of the vacuum sample tank 1 is provided with a heater, the heater can be an annular infrared heater 2, and the annular infrared heater 2 is arranged around the outer surface of the vacuum sample tank 1, which can ensure uniform heating of the vacuum sample tank 1. Acoustic emission sensors are installed at both ends of the vacuum sample tank 1, and an acoustic emission instrument is connected to the outside of the vacuum sample tank 1, and the acoustic emission instrument is used to monitor the dynamic change of the pore and fracture system of the coal seam.

The input port of the vacuum sample tank 1 is connected to the output end of the injection system through a pipeline, and the pipeline between the injection system and the vacuum sample tank 1 is provided with a pressure pump 3 , an overpressure protection device 4 , an injection valve 5 and a pressure gauge 6 in sequence. The pressure pump 3 is used to generate pressure to inject the gas and liquid in the injection system into the vacuum sample tank 1. The pressure pump 3 can adopt a pressure pump 3 with adjustable pressure and flow, which has the functions of constant pressure pressurization and constant flow pressurization. The pressure pump 3 The rated pressure is greater than 20Mpa to meet the pressure experiment requirements of simulating deep and ultra-deep reservoirs. The overpressure protection device 4 can improve the safety performance of the present invention and avoid potential safety hazards caused by excessive pressure. The injection valve 5 is used to control the on-off of the pipeline, and the pressure gauge 6 is convenient for experimenters to observe the pressure in the pipeline at any time.

The injection system includes a gas tank 7, a solvent tank 8 and a mineralized water tank 9, and the output port of the vacuum sample tank 1 is connected to the recovery system through a pipeline provided with a recovery valve 10 and a gas-liquid separator 11, and the recovery system includes a recovery gas tank 12 and recovery liquid tank 13. The recovery valve 10 is used to control the on-off of the pipeline, and the gas-liquid separator 11 can separate the gas and liquid generated in the vacuum sample tank 1 and send them to the recovery gas tank 12 and the recovery liquid tank 13 respectively. The middle part of the vacuum sample tank 1 is also connected with a vacuum pump 14, which is used to realize the vacuum state in the vacuum sample tank 1 and avoid the interference of air components on the experiment.

In the present invention, the pipes used are all high-strength pressure pipes, and the pressure is greater than 20Mpa, so as to meet the pressure experiment requirements of simulating deep and ultra-deep reservoirs. The vacuum sample tank 1 is cylindrical, and the diameter of the vacuum sample tank 1 is 150 mm, and the length is 300 mm.

As shown in Figure 2, the simulation method carried out by the coal reservoir fracturing physical simulation device based on solvent extraction of the present invention comprises the following steps:

A: Design the experimental plan, obtain the temperature, pressure and water content data of the real coal reservoir, and select the type, concentration and pressure required for fracturing according to the experimental results to be obtained;

B: Open the end cover of the vacuum sample tank 1, put the columnar or granular coal sample in the simulated area into the vacuum sample tank 1, and then close the end cover of the vacuum sample tank 1 to ensure the good airtightness of the vacuum sample tank 1;

C: Start the vacuum pump 14 to draw a vacuum inside the vacuum sample tank 1 to avoid the interference of air components on the experiment;

D: Start the acoustic emission sensor and the acoustic emission instrument to monitor the pore changes caused by the action of the fracturing extract in real time and dynamically;

E: Open the injection valve 5 and start the pressure pump 3, inject gas and mineralized water according to the measured pressure and water content and gas content of the real coal reservoir to simulate the pressure and water content of the real coal reservoir;

F: Start the annular infrared heater to uniformly heat the vacuum sample tank 1 to simulate the temperature of the reservoir;

G: When the temperature and pressure in the vacuum sample tank 1 reach the set temperature and pressure, start the pressure pump 3 again and inject the extract prepared according to the experimental plan. The extract can be an inorganic or organic solvent. When the pressure is constant, close the pressure pump 3 and the injection valve 5;

H: Turn off the acoustic emission sensor and acoustic emission instrument, and extract the acoustic emission data for later research;

I: Stand still until the set time is reached according to the requirements of the experimental plan;

J: open the recovery valve 10, and start the gas-liquid separator 11 to reclaim the gas and liquid produced in the vacuum sample tank 1, and the recovered gas and liquid are stored in the recovery gas tank 12 and the recovery liquid tank 13 respectively; K: open the vacuum sample Remove the end cap of the tank 1 and take out the coal sample, then open the recovery gas tank 12 and the recovery liquid tank 13 to take out the stored gas and liquid, providing a basis for subsequent research on coal samples and extracts.

After the above steps are completed, the next step of the experimental test analysis can be carried out according to the coal sample test method, the gas composition analysis method and the extraction liquid related test method.

In the step A, the extract can use an organic solvent and/or an inorganic solvent;

When using the extract in step G, one of the following schemes can be selected:

(1) Use organic solvents alone, and use organic solvents as fracturing hydraulic pressure to inject coal samples, weaken the intermolecular bond force in the cross-linked network of coal structure, and dissolve small molecules;

(2) Using an inorganic solvent alone, using the acidification of the inorganic acid in the inorganic solvent to dissolve the minerals in the coal;

(3) Choose organic mixed solvents or inorganic mixed solvents with different ratios, and press them into the coal sample to enhance the effect of the mixed solvent on the expansion of coal pores and cracks and the effect of anti-permeability;

(4) First use the inorganic acid in the inorganic solvent for acidification treatment, and then use the organic solvent for organic extraction; or press the organic solvent in first, and then use the inorganic acid in the inorganic solvent for acidification treatment, and then use the inorganic acid in the inorganic solvent for acidification treatment, and then use the organic solvent to carry out organic extraction; Perform thorough expansion and enhancement.

It should be noted that the above-mentioned specific embodiments are only exemplary, and under the above-mentioned teaching of the present invention, those skilled in the art can make various improvements and modifications on the basis of the above-mentioned embodiments, and these improvements or modifications all fall within Within the protection scope of the present invention. Those skilled in the art should understand that the above specific description is only for the purpose of explaining the present invention, and is not intended to limit the present invention. The protection scope of the present invention is defined by the claims and their equivalents.

Claims (10)

1. based on the physical simulating device of solvent-extracted coal seam reservoirs pressure break, it is characterized in that: comprise the vacuum sample tank being provided with end cap, vacuum sample tank outside surface is provided with well heater, the input port of vacuum sample tank connects the output terminal of injected system by pipeline, the pipeline between injected system and vacuum sample tank is disposed with forcing pump and fillup valve; Described injected system comprises gas pot, solvent tank and mineralising water pot, and the delivery outlet of vacuum sample tank is connected recovery system by being provided with recovery valve with the pipeline of gas-liquid separator, and described recovery system comprises gas recovery tank and withdrawal liquid tank; Vacuum sample tank is also connected with vacuum pump.

2. the physical simulating device based on solvent-extracted coal seam reservoirs pressure break according to claim 1, is characterized in that: described vacuum sample tank two ends are provided with acoustic emission inductor, and vacuum sample tank is externally connected to Acoustic radiating instrument.

3. the physical simulating device based on solvent-extracted coal seam reservoirs pressure break according to claim 1, is characterized in that: the pipeline between described forcing pump and fillup valve is also provided with over-pressure safety device.

4. the physical simulating device based on solvent-extracted coal seam reservoirs pressure break according to claim 1, is characterized in that: the pipeline between described fillup valve and vacuum sample tank is also provided with tensimeter.

5. the physical simulating device based on solvent-extracted coal seam reservoirs pressure break according to claim 1, is characterized in that: described forcing pump adopts pressure flow adjustable pressure pump.

6. the physical simulating device based on solvent-extracted coal seam reservoirs pressure break according to claim 1, is characterized in that: described forcing pump has constant voltage pressurization and constant current pressurization function, and the rated pressure of forcing pump is greater than 20MPa.

7. the physical simulating device based on solvent-extracted coal seam reservoirs pressure break according to claim 1, is characterized in that: described well heater adopts annular infrared heater, and annular infrared heater is around being arranged on vacuum sample tank outside surface.

8. the physical simulating device based on solvent-extracted coal seam reservoirs pressure break according to claim 1, it is characterized in that: described end cap is threaded with vacuum sample tank, be provided with packoff between end cap and vacuum sample tank, packoff adopts rubber seal; Described pipeline adopts high-strength press solenoid.

9. utilize the analogy method of carrying out based on the physical simulating device of solvent-extracted coal seam reservoirs pressure break in claim 1 to 8 described in any one, it is characterized in that, comprise the following steps:

A: contrived experiment scheme, obtains the temperature of true coal seam reservoirs, pressure and property of water-bearing data, and according to the experiment effect intending obtaining, pressure needed for slective extraction liquid kind, concentration and pressure break;

B: the end cap opening vacuum sample tank, puts into vacuum sample tank by the column in simulation area or granular coal sample, then closes the end cap of vacuum sample tank;

C: start vacuum pump by inner for vacuum sample tank extracting vacuum;

D: start acoustic emission inductor and Acoustic radiating instrument, monitors the hole change caused because of the effect of pressure break extract real-time dynamicly;

E: open fillup valve and starting pressure pump, injects gas and mineralized water according to the pressure of the true coal seam reservoirs recorded and the property of water-bearing, the pressure of coal seam reservoirs and the property of water-bearing under Reality simulation state;

F: start annular infrared heater, carries out homogeneous heating to vacuum sample tank;

G: when the temperature and pressure in vacuum sample pot reaches after design temperature and pressure, starting pressure pump also injects the extract configured according to experimental program again, when reaching experimental program set pressure, closing presure pump and fillup valve;

H: close acoustic emission inductor and Acoustic radiating instrument, extracts acoustic emission data;

I: require to leave standstill according to experimental program until arrive setting-up time;

J: open recovery valve, and the gas and the liquid that start that gas-liquid separator reclaims generation in vacuum sample tank, the gas of recovery and liquid are stored in gas recovery tank and withdrawal liquid tank respectively; K: open the end cap of vacuum sample tank and take out coal sample, then opens gas recovery tank and withdrawal liquid tank takes out the gas and liquid that store.

10. analogy method of carrying out based on the physical simulating device of solvent-extracted coal seam reservoirs pressure break according to claim 9, is characterized in that: in described steps A, and extract adopts organic solvent and/or inorganic solvent; When injecting extract in step G, select the one in following several scheme:

(1) adopt organic solvent separately, utilize organic solvent to be pressed into coal sample as fracturing liquid, weaken the intermolecular association bonding force in texture of coal cross-linked network, by small molecular phase stripping;

(2) adopt inorganic solvent separately, utilize the acidization of the mineral acid in inorganic solvent to be dissolved by the mineral matter in coal;

(3) organic mixed solvent of different ratio or inorganic mixed solvent is selected, to strengthen mixed solvent to the expansion in coal mesopore crack and anti-reflection action effect in press-in coal sample;

(4), after first utilizing the mineral acid in inorganic solvent to carry out acidification, recycling organic solvent carries out organic extraction; Or first organic solvent is pressed into, and then utilizes the mineral acid in inorganic solvent to carry out acidification, coal mesopore crack is expanded and anti-reflection effect up hill and dale.