CN113818864B - Simulation device and method for monitoring integrity of hydrate formation cement sheath by DAS (distributed optical System) - Google Patents

Abstract

The invention relates to a simulation device and a simulation method for monitoring integrity of a hydrate formation cement sheath by DAS (data acquisition System), wherein a simulation formation system comprises a kettle cover and a kettle body, wherein the kettle cover and the kettle body are connected through a gland bolt; the kettle cover comprises a top part and a bottom part, an annular hydraulic oil cavity is arranged in the top part of the kettle cover, an annular bulge is convexly extended at the bottom part of the kettle cover, a hydraulic oil pressurizing port is convexly extended at one side of the kettle cover, and the hydraulic oil pressurizing port is communicated with the hydraulic oil cavity; the kettle body is provided with a hydrate generating chamber and a refrigerating cavity, and one side of the kettle body is convexly provided with a refrigerating cavity inlet and a refrigerating cavity outlet; the simulated shaft system is arranged at the bottom of the hydrate generation chamber; the monitoring system is in data connection with the simulation stratum system; the pressure control system comprises a first pressure oil pump and a first pressure gauge, and the first pressure oil pump is connected with the first pressure gauge in series and then is connected with a hydraulic oil pressure port; the low-temperature control system comprises a refrigerating fluid tank, an outlet of the refrigerating fluid tank is connected with an inlet of the refrigerating cavity, and an inlet of the refrigerating fluid tank is connected with an outlet of the refrigerating cavity.

Description

DAS simulation device and method for monitoring cement sheath integrity of hydrate formation

technical field

The invention relates to the technical field of oil and gas exploitation, in particular to a DAS (distributed optical fiber monitoring and sound monitoring technology) simulation device and method for monitoring the integrity of a hydrate formation cement sheath.

Background technique

As a new type of clean energy, natural gas hydrate has become the focus of attention in the oil and gas field due to its wide distribution, large reserves and high energy density. At present, the exploitation of natural gas resources in my country is still in the stage of trial production, and one of the main reasons affecting the commercial exploitation of natural gas hydrate is the integrity of the cement sheath. Good cement sheath integrity can effectively seal formation fluid and prevent formation fluid leakage. However, under the influence of factors such as temperature and pressure changes in the process of natural gas hydrate production, the integrity of the cement sheath is destroyed, resulting in the failure of the cement sheath integrity. The failure of the integrity of the cement sheath may cause damage to the casing, and even cause accidents such as well kicks and blowouts. Therefore, in order to realize the commercial exploitation of natural gas hydrate, a kind of equipment and technology that can monitor the integrity of the cement sheath is needed. To monitor the location and degree of cement sheath integrity failure, and help oilfield workers to do workover and other work.

The current cement sheath integrity monitoring technologies are acoustic logging, acoustic variable density logging, and cement bond logging tools, etc., but these are mostly single-point instantaneous monitoring, and it is difficult to monitor the cement sheath integrity in real time, continuously, and in the entire well section .

Contents of the invention

In view of the above problems, the first object of the present invention is to provide a DAS simulation device for monitoring the integrity of the hydrate formation cement sheath, which can realize real-time, continuous, and full-well section monitoring, is suitable for long-distance detection, and can meet the needs of real-time dynamic monitoring in the well. demand.

The second object of the present invention is to provide a DAS monitoring method for monitoring the integrity of the hydrate formation cement sheath.

To achieve the above object, the present invention takes the following technical solutions:

The DAS simulation device for monitoring the integrity of the hydrate formation cement sheath according to the present invention includes: a simulated formation system, a simulated wellbore system, a monitoring system, a pressure control system and a low temperature control system; the simulated formation system includes a kettle cover and a kettle body , the kettle cover and the kettle body are connected by gland bolts; the kettle cover includes a top and a bottom, the top of the kettle cover is provided with an annular hydraulic oil chamber, and the bottom of the kettle cover protrudes from a ring The annular protrusion extends into the hydraulic oil chamber so that the bottom of the kettle cover fits closely with the top of the kettle cover, and a hydraulic oil pressure port protrudes from one side of the kettle cover. The hydraulic oil pressure port is in communication with the hydraulic oil chamber; the kettle body has a hydrate generation chamber and a refrigeration chamber, the refrigeration chamber is arranged circumferentially around the hydrate generation chamber, and one side of the kettle body is convex Extended with a cooling chamber inlet and a cooling chamber outlet, the cooling chamber inlet communicates with the upper part of the cooling chamber, and the cooling chamber outlet communicates with the lower part of the cooling chamber; the simulated wellbore system is set in the hydrate formation the bottom of the chamber; the monitoring system is connected with the data of the simulated formation system for monitoring the simulated formation system; the pressure control system includes a first pressurized oil pump and a first pressure gauge, and the first pressurized The pressure oil pump is connected in series with the first pressure gauge and then connected to the hydraulic oil pressurization port; the low temperature control system includes a refrigerant liquid tank, the outlet of the refrigerant liquid tank is connected to the inlet of the refrigeration chamber, and the refrigerant The inlet of the liquid tank is connected to the outlet of the refrigeration chamber, so that the refrigeration liquid tank and the refrigeration chamber form a closed circuit.

The simulation device, preferably, the simulated wellbore system includes a glass casing and a simulation casing, the glass casing and the simulation casing are vertically arranged in the hydrate generation chamber respectively, and the glass casing The pipe sleeve is arranged outside the simulated casing, and the upper end of the simulated casing is blocked.

The simulation device, preferably, the simulated wellbore system includes a first interface cracked simulated well wall and a simulated casing, and the first interface cracked simulated well wall and the simulated casing are vertically arranged on the hydration zone respectively. In the material generation chamber, the simulated well wall of the first interface cracking is set outside the simulated casing, and the upper end of the simulated casing is blocked.

The simulated device, preferably, the simulated wellbore system includes a second interface cracked simulated well wall and a simulated casing, and the second interface cracked simulated well wall and the simulated casing are vertically arranged in the hydration zone respectively. In the material generation chamber, the second interface cracking simulated well wall is sleeved outside the simulated casing, and the upper end of the simulated casing is blocked.

In the simulation device, preferably, the pressure control system also includes a second pressurized oil pump and a second pressure gauge; the bottom of the kettle body is provided with a casing internal pressure control pipeline, and the casing internal pressure control pipeline is connected to the Simulate casing communication; the second pressurized oil pump and the second pressure gauge are connected in series to the casing internal pressure control pipeline.

The simulation device, preferably, the monitoring system includes a temperature sensor, a camera, and a computer terminal; the bottom of the kettle body is provided with a USB interface; the temperature sensor is provided on the side wall of the hydrate generation chamber, and It is electrically connected with the USB interface; the camera is arranged on the side wall of the glass sleeve and is electrically connected with the USB interface; the outside of the analog sleeve is wrapped with an optical fiber, and the optical fiber is used to communicate with the external signal conditioner Connect and monitor the vibration degree in the simulation device; the computer terminal is connected with the USB interface through a data line.

In the simulation device, preferably, a resistance heater is arranged at the bottom of the hydrate generation chamber.

In the simulation device, preferably, the pressure control system further includes a first valve and a second valve, the first valve is arranged between the first pressurized oil pump and the first pressure gauge, the The second valve is arranged between the second pressurized oil pump and the second pressure gauge; the low temperature control system also includes a plunger pump, a third valve and a fourth valve, the plunger pump and the first The three valves are sequentially arranged between the refrigerating liquid tank and the inlet of the refrigerating chamber from front to back, and the fourth valve is arranged between the refrigerating liquid tank and the outlet of the refrigerating chamber.

The DAS monitoring method of the present invention monitors the integrity of the cement sheath of the hydrate formation, comprising the following steps:

1) Take the axial length of the simulated casing as the ordinate, and take the monitoring time as the abscissa to establish an interface sound intensity coordinate system;

2) Using the first interface optical fiber vibration related parameters monitored by DAS, the acoustic waterfall diagram is drawn in the axial coordinate system of the simulated casing;

3) Define the axial position and length of cement sheath integrity failure.

Described monitoring method, preferably, the axial position and the length definition of cement sheath integrity failure in described step 3) include the following steps:

3.1) From an interface vibration coordinate system, within the time range of the cement sheath integrity failure simulation, according to the spatial resolution of the DAS monitoring system and the winding angle, select the strength-time curve corresponding to the axial length of the simulated casing;

3.2) Calculate the area and area variance enclosed by the intensity-time curve of each length and the coordinate axis;

3.3) The axial length of the casing corresponding to the area enclosed by the strength-time curve and the coordinate axis is greater than 1 times the area variance is defined as the failure position and degree of the cement sheath.

The present invention has the following advantages due to the adoption of the above technical scheme:

(1) By simulating the temperature and pressure conditions of the formation, the present invention simulates the preparation of natural gas hydrate and the failure of the cement sheath integrity in the mining process, and uses the distributed optical fiber acoustic monitoring technology to monitor the cracking of the primary and secondary interfaces and the intrusion of cement The decomposition status of natural gas hydrate in the gas ring is monitored, and other methods (such as CT scanning, etc.) are used to verify the monitoring results.

(2) The distributed acoustic optical fiber monitoring of the present invention is monitored by monitoring the phase change of Rayleigh backscattered light without energy loss.

(3) The DAS monitoring of the present invention can perform distributed real-time monitoring, and has strong anti-corrosion and anti-electromagnetic interference capabilities. At the same time, the purpose of monitoring in complex downhole environments can be achieved by optimizing the package.

Description of drawings

Fig. 1 is a schematic structural view of the simulation device of the present invention, wherein the structure of the simulation state of the preparation of natural gas hydrate and the decomposition of the intruded cement sheath hydrate experiment is shown;

Fig. 2 is a simulated borehole wall diagram of cracking at the first interface;

Fig. 3 is a schematic structural view of the simulation device of the present invention, wherein the structure of the simulation state of the first interface cracking experiment is shown;

Fig. 4 is a simulated borehole wall diagram of cracking at the second interface;

Fig. 5 is a schematic structural diagram of the simulation device according to the present invention, which shows the structure of the simulation state of the second interface cracking experiment.

Each reference mark in the figure is:

1-kettle cover; 2-kettle body; 3-glass sleeve; 4-analog sleeve; 5-temperature sensor; 6-resistance heater; 7-gland bolt; 8-hydraulic oil chamber; 9-refrigeration chamber; 10-hydrate generation chamber; 11-casing internal pressure control pipeline; 12-USB interface; 13-data line; 14-computer terminal; 15-camera; Simulated well wall; 18-hydraulic oil pressure port; 19-refrigeration chamber inlet; 20-refrigeration chamber outlet; 21-first pressurized oil pump; 22-first pressure gauge; 23-refrigerant liquid tank; 24-second charging 25-the second pressure gauge; 26-the first valve; 27-the second valve; 28-the plunger pump; 29-the third valve; 30-the fourth valve.

Detailed ways

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so as to better understand the purpose, features and advantages of the present invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but only to illustrate the essence of the technical solutions of the present invention.

The invention provides a DAS simulation device for monitoring the integrity of the hydrate formation cement sheath, including: a simulated formation system, a simulated wellbore system, a monitoring system, a pressure control system and a low temperature control system; the simulated formation system includes a kettle cover and a kettle body , the kettle cover and the kettle body are connected by gland bolts; the kettle cover includes a top and a bottom, the top of the kettle cover is provided with an annular hydraulic oil chamber, and the bottom of the kettle cover protrudes from a ring The annular protrusion extends into the hydraulic oil chamber so that the bottom of the kettle cover fits closely with the top of the kettle cover, and a hydraulic oil pressure port protrudes from one side of the kettle cover. The hydraulic oil pressure port is in communication with the hydraulic oil chamber; the kettle body has a hydrate generation chamber and a refrigeration chamber, the refrigeration chamber is arranged circumferentially around the hydrate generation chamber, and one side of the kettle body is convex Extended with a cooling chamber inlet and a cooling chamber outlet, the cooling chamber inlet communicates with the upper part of the cooling chamber, and the cooling chamber outlet communicates with the lower part of the cooling chamber; the simulated wellbore system is set in the hydrate formation the bottom of the chamber; the monitoring system is connected with the data of the simulated formation system for monitoring the simulated formation system; the pressure control system includes a first pressurized oil pump and a first pressure gauge, and the first pressurized The pressure oil pump is connected in series with the first pressure gauge and then connected to the hydraulic oil pressurization port; the low temperature control system includes a refrigerant liquid tank, the outlet of the refrigerant liquid tank is connected to the inlet of the refrigeration chamber, and the refrigerant The inlet of the liquid tank is connected to the outlet of the refrigeration chamber, so that the refrigeration liquid tank and the refrigeration chamber form a closed circuit. The invention can realize the preparation of the hydrate layer and the formation, and is used for indoor simulation research on the integrity of the wellbore during the hydrate production process, and can meet the requirements of the laboratory test and research for the DAS to monitor the integrity of the wellbore in the hydrate formation.

As shown in Figures 1 to 4, a DAS simulation device for monitoring the integrity of the hydrate formation cement sheath provided by the present invention includes: a simulated formation system, a simulated wellbore system, a monitoring system, a pressure control system and a low temperature control system; The system includes a kettle cover 1 and a kettle body 2, the kettle cover 1 and the kettle body 2 are connected by gland bolts 7; the kettle cover 1 includes a top and a bottom, and the top of the kettle cover 1 is provided with an annular hydraulic oil chamber 8, and the kettle The bottom of the cover 1 protrudes with an annular protrusion, and the annular protrusion extends into the hydraulic oil chamber 8, wherein a sealing ring is arranged in the hydraulic oil chamber 8, so that the bottom of the kettle cover 1 is closely matched with the top of the kettle cover 1, A hydraulic oil pressure port 18 protrudes from one side of the kettle cover 1, and the hydraulic oil pressure port 18 communicates with the hydraulic oil chamber 8; the kettle body 2 has a hydrate generating chamber 10 and a cooling chamber 9, and the cooling chamber 9 surrounds the hydrate generating chamber 10 is arranged in the circumferential direction, and one side of the kettle body 2 protrudes from the inlet 19 of the cooling chamber and the outlet 20 of the cooling chamber. It is arranged at the bottom of the hydrate generation chamber 10; the monitoring system is connected with the data of the simulated formation system for monitoring the simulated formation system; the pressure control system includes a first pressurized oil pump 21 and a first pressure gauge 22, the first pressurized The pressure oil pump 21 is connected in series with the first pressure gauge 22 and then connected with the hydraulic oil pressure port 18; the low temperature control system includes a refrigerant liquid tank 23, the outlet of the refrigerant liquid tank 23 is connected with the inlet 19 of the refrigeration chamber, and the inlet of the refrigerant liquid tank 23 is connected with the The cooling cavity outlet 20 is connected so that the cooling liquid tank 23 and the cooling cavity 9 form a closed circuit.

In the above embodiment, preferably, as shown in Figure 1, the simulated wellbore system includes a glass casing 3 and a simulated casing 4, and the glass casing 3 and the simulated casing 4 are vertically arranged in the hydrate generation chamber 10 respectively, The glass casing 3 is set outside the simulation casing 4, and the upper end of the simulation casing 4 is blocked.

In the above embodiment, preferably, as shown in Figures 2 and 3, the simulated wellbore system includes the first interface cracked simulated well wall 16 and the simulated casing 4, and the first interface cracked simulated well wall 16 and the simulated casing 4 are respectively vertical It is directly arranged in the hydrate generation chamber 10, and the first interface cracking simulated well wall 16 is sleeved outside the simulated casing 4, and the upper end of the simulated casing 4 is blocked.

In the above embodiment, preferably, as shown in Figures 4 and 5, the simulated wellbore system includes the second interface cracked simulated well wall 17 and the simulated casing 4, and the second interface cracked simulated well wall 17 and the simulated casing 4 are respectively vertical It is arranged directly in the hydrate generation chamber 10, and the second interface cracking simulated well wall 17 is sleeved outside the simulated casing 4, and the upper end of the simulated casing 4 is blocked.

In the above embodiment, preferably, the pressure control system also includes a second pressurized oil pump 24 and a second pressure gauge 25; the bottom of the kettle body 2 is provided with a casing internal pressure control pipeline 11, and the casing internal pressure control pipeline 11 is connected with the simulated casing 4 connected; the second pressurized oil pump 24 and the second pressure gauge 25 are connected in series to the casing internal pressure control pipeline 11.

In the above embodiment, preferably, the monitoring system includes a temperature sensor 5, a camera 15, an optical fiber and a computer terminal 14, and a USB interface 12 is provided at the bottom of the kettle body 2; the temperature sensor 5 is provided on the side wall of the hydrate generation chamber 10, And be electrically connected with USB interface 12; Camera 15 is arranged on the sidewall of glass casing 3, and is electrically connected with USB interface 12; Analog casing 4 is wrapped with optical fiber outside, and optical fiber is used for connecting with external signal conditioner and analog The vibration degree in the device is monitored; the computer terminal 14 is connected with the USB interface 12 through the data line 13 .

In the above embodiments, preferably, the bottom of the hydrate generation chamber 10 is provided with a resistance heater 6 .

In the above embodiment, preferably, the pressure control system further includes a first valve 26 and a second valve 27, the first valve 26 is set between the first pressurized oil pump 21 and the first pressure gauge 22, and the second valve 27 is set Between the second pressurized oil pump 24 and the second pressure gauge 25; the low temperature control system also includes a plunger pump 28, a third valve 29 and a fourth valve 30, and the plunger pump 28 and the third valve 29 are arranged in sequence from front to back Between the refrigerant liquid tank 23 and the inlet 19 of the refrigeration chamber, the fourth valve 30 is arranged between the refrigerant liquid tank 23 and the outlet 20 of the refrigeration chamber.

The working process of the simulation device for monitoring the integrity of the hydrate formation cement sheath by DAS according to the present invention is as follows:

1. The preparation of natural gas hydrate comprises the following steps, as shown in Figure 1:

a) Install the glass tube 3 and the simulated casing 4 in the positioning ring at the bottom of the hydrate generation chamber 10;

b) Fill the hydrate generation chamber 10 with silt and fine sand and compact it, then inject 19% tetrahydrofuran aqueous solution several times to build a simulated hydrate reservoir, add an appropriate amount of dyeing agent, cover the upper layer with sand and compact it, and simulate the upper layer Overburden;

c) Cover the kettle cover 1, tighten the gland bolt 7, and check the seal between the kettle cover 1 and the kettle body 2;

d) Inject hydraulic oil to 6MPa into the hydraulic oil chamber 8, inject refrigerant liquid into the refrigeration chamber 9, lower the temperature in the wellbore to -9°C, and meet the temperature and pressure conditions for hydrate preparation;

e) Keep the set temperature and pressure constant for a certain period of time, so that the hydrate is fully formed, and the hydrate sample is composed of sediment skeleton and hydrate;

f) Observe the formation of hydrate through the camera 15 in the glass casing, and wait until the hydrate is completely formed;

g) Adjust the pressure control system to release the pressure to normal atmospheric pressure;

h) Remove the gland bolt 7, open the kettle cover 1, and quickly take out the glass casing 3.

2. Monitoring of the decomposition of intruded cement sheath hydrates, including the following steps:

a) preparing natural gas hydrate reservoir and cement slurry;

b) injecting cement slurry into the reserved annular space of the hydrate synthesis chamber 10;

c) Cover the kettle cover 1, tighten the gland bolt 7, and check the seal between the kettle cover 1 and the kettle body 2;

d) Inject hydraulic oil to 6MPa into the hydraulic oil chamber 8, inject refrigerant liquid into the refrigeration chamber 9, lower the temperature in the wellbore to -9°C, and meet the temperature and pressure conditions for hydrate preparation;

e) Connect the computer terminal 14, the USB interface 12 and the data line 13, turn on the computer terminal 14, and continuously observe and record the DAS signal.

f) Wait for the cement sheath to solidify (about 48 hours), turn on the resistance heater 6, and turn it off after heating for 10 minutes;

g) According to the vibration data recorded in steps e and f, use the monitoring data interpretation module to interpret the monitoring data, and obtain the position and axial length of the cracking of the cement sheath;

h) Adjust the pressure control module to release the pressure to normal atmospheric pressure.

i) Disassemble the gland bolt 7, open the kettle cover 1, take out the cement sheath and confirm the rupture of the cement sheath by CT scan, and compare and verify it with the DAS monitoring results.

3. Crack monitoring of the first interface of natural gas hydrate, including the following steps, as shown in Figure 3:

a) Preparation of gas hydrate reservoir and cement slurry.

b) installing the first interface crack simulation well wall 16 in the positioning ring at the bottom of the hydrate synthesis chamber 10;

c) injecting cement slurry into the reserved annular space of the hydrate synthesis chamber 10;

d) Cover the kettle cover 1, tighten the gland bolt 7, and check the seal between the kettle cover 1 and the kettle body 2;

e) Inject hydraulic oil to 6 MPa into the hydraulic oil chamber 8, inject refrigerant liquid into the refrigeration chamber 9, lower the temperature in the wellbore to -9°C, meet the temperature and pressure conditions for hydrate preparation, and simulate the maintenance of the casing internal pressure of the casing 4 is 3MPa;

f) Connect the computer terminal 14, the USB interface 12 and the data line 13, turn on the computer terminal 14, and continuously observe and record the DAS signal.

g) Wait for the cement sheath to be solidified (about 48 hours), and reduce the casing internal pressure of the simulated casing 4 to 2MPa;

h) Turn on the resistance heater 6 and turn it off after heating for 10 minutes;

i) According to the vibration data recorded in steps f, g and h, use the monitoring data interpretation module to interpret the monitoring data to obtain the position and axial length of the cement sheath-interface debonding;

j) Regulate the pressure control module to release the pressure to normal atmospheric pressure;

k) Remove the gland bolt 7, open the kettle cover 1, take out the cement sheath, observe the stained area of the first interface of the cement sheath, determine the cracking position and degree of the first interface, and compare and verify it with the DAS monitoring results.

4. Crack monitoring of the second interface of natural gas hydrate, including the following steps, as shown in Figure 5:

a) preparing natural gas hydrate reservoir and cement slurry;

b) installing the second interface crack simulation well wall 17 in the positioning ring at the bottom of the hydrate synthesis chamber 10;

c) injecting cement slurry into the reserved annular space of the hydrate synthesis chamber 10;

d) Cover the kettle cover 1, tighten the gland bolt 7, and check the seal between the kettle cover 1 and the kettle body 2;

e) Inject hydraulic oil to 6 MPa into the hydraulic oil chamber 8, inject refrigerant liquid into the refrigeration chamber 9, lower the temperature in the wellbore to -9°C, meet the temperature and pressure conditions for hydrate preparation, and simulate the maintenance of the casing internal pressure of the casing 4 is 3MPa;

f) Connect the computer terminal 14, the USB interface 12 and the data line 13, open the computer terminal 14, and continuously observe and record the DAS signal;

g) Wait for the cement sheath to solidify (about 48 hours), and reduce the internal pressure of the inner casing of the simulated casing 4 to 2MPa;

h) Turn on the resistance heater 6 and turn it off after heating for 10 minutes;

i) According to the vibration data recorded in steps f, g and h, use the monitoring data interpretation module to interpret the monitoring data to obtain the position and axial length of the cement sheath two interface debonding;

j) Regulate the pressure control module to release the pressure to normal atmospheric pressure;

k) Disassemble the gland bolt 7, open the kettle cover 1, take out the cement sheath, observe the stained area of the second interface of the cement sheath, determine the cracking position and degree of the second interface, and compare and verify it with the DAS monitoring results.

The present invention also provides a DAS monitoring method for monitoring the integrity of the hydrate formation cement sheath, comprising the following steps:

1) Taking the axial length of the simulated casing 4 as the ordinate and the monitoring time as the abscissa, establish an interface sound intensity coordinate system;

2) Using the first interface optical fiber vibration related parameters monitored by DAS, the acoustic waterfall diagram is drawn in the axial coordinate system of the simulated casing 4;

3) Define the axial position and length of cement sheath integrity failure.

In the foregoing embodiment, preferably, the axial position and length definition of cement sheath integrity failure in said step 3) includes the following steps:

3.1) From an interface vibration coordinate system, within the time range of the cement sheath integrity failure simulation, according to the spatial resolution of the DAS monitoring system and the winding angle, select the strength-time curve corresponding to the 4 axial length of the simulated casing;

3.2) Calculate the area and area variance enclosed by the intensity-time curve of each length and the coordinate axis;

3.3) The axial length of the casing corresponding to the area enclosed by the strength-time curve and the coordinate axis is greater than 1 times the area variance is defined as the failure position and degree of the cement sheath.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (6)

1. A DAS simulation device for monitoring integrity of a hydrate formation cement sheath, comprising: the system comprises a simulated formation system, a simulated shaft system, a monitoring system, a pressure control system and a low-temperature control system;

the simulated stratum system comprises a kettle cover and a kettle body, wherein the kettle cover and the kettle body are connected through a gland bolt;

the kettle cover comprises a top and a bottom, an annular hydraulic oil cavity is arranged in the top of the kettle cover, an annular bulge protrudes from the bottom of the kettle cover, the annular bulge extends into the hydraulic oil cavity so that the bottom of the kettle cover is tightly matched with the top of the kettle cover, a hydraulic oil pressurizing port protrudes from one side of the kettle cover, and the hydraulic oil pressurizing port is communicated with the hydraulic oil cavity; the kettle body is provided with a hydrate generation chamber and a refrigeration chamber, the refrigeration chamber is circumferentially arranged around the hydrate generation chamber, one side of the kettle body is convexly provided with a refrigeration chamber inlet and a refrigeration chamber outlet, the refrigeration chamber inlet is communicated with the upper part of the refrigeration chamber, and the refrigeration chamber outlet is communicated with the lower part of the refrigeration chamber;

the simulated wellbore system is arranged at the bottom of the hydrate generation chamber;

the monitoring system is in data connection with the simulated formation system and is used for monitoring the simulated formation system;

the pressure control system comprises a first pressure oil pump and a first pressure gauge, and the first pressure oil pump is connected with the first pressure gauge in series and then is connected with the hydraulic oil pressure port;

the low-temperature control system comprises a refrigerating fluid tank, an outlet of the refrigerating fluid tank is connected with an inlet of the refrigerating cavity, and an inlet of the refrigerating fluid tank is connected with an outlet of the refrigerating cavity, so that the refrigerating fluid tank and the refrigerating cavity form a closed loop;

the simulated shaft system comprises a glass sleeve and a simulated sleeve, the glass sleeve and the simulated sleeve are respectively vertically arranged in the hydrate generation chamber, the glass sleeve is sleeved outside the simulated sleeve, and the upper end of the simulated sleeve is blocked;

the simulated shaft system comprises a first interface cracking simulated well wall and a simulated casing pipe, wherein the first interface cracking simulated well wall and the simulated casing pipe are respectively vertically arranged in the hydrate generation chamber, the first interface cracking simulated well wall is sleeved outside the simulated casing pipe, and the upper end of the simulated casing pipe is blocked;

the simulation pit shaft system comprises a second interface cracking simulation well wall and a simulation sleeve, the second interface cracking simulation well wall and the simulation sleeve are respectively vertically arranged in the hydrate generation chamber, the second interface cracking simulation well wall is sleeved outside the simulation sleeve, and the upper end of the simulation sleeve is blocked.

2. The simulation apparatus of claim 1, wherein the pressure control system further comprises a second pressurized oil pump and a second pressure gauge;

a sleeve internal pressure control pipeline is arranged at the bottom of the kettle body and is communicated with the simulation sleeve;

and the second pressure oil pump and the second pressure gauge are connected in series and then are connected with the casing internal pressure control pipeline.

3. The simulation apparatus of claim 2, wherein the monitoring system comprises a temperature sensor, a camera, an optical fiber and a computer terminal;

the bottom of the kettle body is provided with a USB interface;

the temperature sensor is arranged on the side wall of the hydrate generation chamber and is electrically connected with the USB interface;

the camera is arranged on the side wall of the glass sleeve and is electrically connected with the USB interface;

the optical fiber is wound outside the simulation sleeve and is used for being connected with an external signal demodulator and monitoring the vibration degree in the simulation device;

and the computer terminal is connected with the USB interface through a data line.

4. The simulation apparatus of claim 3, wherein the bottom of the hydrate formation chamber is provided with a resistive heater.

5. The simulation device of claim 4, wherein the pressure control system further comprises a first valve disposed between the first pressurized oil pump and the first pressure gauge and a second valve disposed between the second pressurized oil pump and the second pressure gauge;

the low-temperature control system further comprises a plunger pump, a third valve and a fourth valve, wherein the plunger pump and the third valve are sequentially arranged between the refrigerating liquid tank and the refrigerating cavity inlet from front to back, and the fourth valve is arranged between the refrigerating liquid tank and the refrigerating cavity outlet.

6. A method for monitoring the integrity of a hydrate formation cement sheath based on the DAS of claim 5, comprising the steps of:

establishing a first interface sound intensity coordinate system by taking the axial length of the simulation casing as a vertical coordinate and the monitoring time as a horizontal coordinate;

drawing an acoustic waterfall graph in a simulated sleeve axial coordinate system by using the relevant parameters of the first interface optical fiber vibration monitored by the DAS;

defining the axial position and the length of the integrity failure of the cement sheath;

wherein the defining of the axial position and length of the cement sheath integrity failure comprises the steps of:

selecting an intensity-time curve corresponding to the axial length of the simulated casing according to the spatial resolution and the winding angle of the DAS monitoring system in the time range of the integrity failure simulation of the cement sheath from the first interface sound intensity coordinate system;

calculating the area and the area variance enclosed by the strength-time curve and the coordinate axis of each length;

and defining the axial length of the casing corresponding to the area formed by the strength-time curve and the coordinate axis and larger than 1 time of area variance as the failure position and degree of the cement sheath.

Images