CN113818864B - Simulation device and method for monitoring integrity of hydrate formation cement sheath by DAS (distributed optical System) - Google Patents
Simulation device and method for monitoring integrity of hydrate formation cement sheath by DAS (distributed optical System) Download PDFInfo
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- CN113818864B CN113818864B CN202111197134.3A CN202111197134A CN113818864B CN 113818864 B CN113818864 B CN 113818864B CN 202111197134 A CN202111197134 A CN 202111197134A CN 113818864 B CN113818864 B CN 113818864B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/005—Monitoring or checking of cementation quality or level
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
- G09B25/00—Models for purposes not provided for in G09B23/00, e.g. full-sized devices for demonstration purposes
- G09B25/02—Models for purposes not provided for in G09B23/00, e.g. full-sized devices for demonstration purposes of industrial processes; of machinery
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
Technical Field
The invention relates to the technical field of oil and gas exploitation, in particular to a simulation device and a simulation method for monitoring integrity of a hydrate formation cement sheath by DAS (distributed optical fiber monitoring and sound monitoring technology).
Background
As a novel clean energy, natural gas hydrate has become a key focus of the oil and gas field due to the advantages of wide distribution, large reserve and high energy density. At present, the exploitation of natural gas resources in China is still in a pilot mining stage, and one of the main reasons influencing the commercial exploitation of natural gas hydrates is the integrity of cement sheath. The cement sheath has good integrity, can effectively seal formation fluid and prevent the formation fluid from leaking, but the integrity of the cement sheath is damaged under the action of factors such as temperature and pressure change in the natural gas hydrate exploitation process, so that the integrity of the cement sheath fails. The integrity failure of the cement sheath may cause damage to the casing, even cause accidents such as well kick and blowout, and therefore, in order to realize commercial exploitation of the natural gas hydrate, equipment and technology capable of monitoring the integrity of the cement sheath are needed to monitor the position and degree of the integrity failure of the cement sheath and help oil field workers to carry out work such as well repair.
At present, the monitoring technology of the integrity of the cement sheath is acoustic logging, acoustic variable density logging, a cement bond logging instrument and the like, but the technologies are mostly single-point instantaneous monitoring and are difficult to monitor the integrity of the cement sheath in real time, continuously and in a whole well section.
Disclosure of Invention
In view of the above problems, a first object of the present invention is to provide a DAS simulation device for monitoring integrity of a hydrate formation cement sheath, which can realize real-time, continuous and full-interval monitoring, is suitable for long-distance detection, and can meet the requirement of real-time dynamic monitoring in a downhole.
A second object of the present invention is to provide a DAS monitoring method for monitoring integrity of a hydrate formation cement sheath.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention discloses a DAS simulation device for monitoring integrity of a hydrate formation cement sheath, which comprises: 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 extends out 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 extends out 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 convexly extends to form 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 simulation device, preferably, the simulation shaft system includes glass sleeve and simulation sleeve, the glass sleeve with the simulation sleeve respectively vertical set up in the hydrate produces indoor, the glass sleeve cover is established outside the simulation sleeve, just simulation sleeve upper end shutoff.
The simulation device, preferably, the simulation pit shaft system includes first interface fracture simulation wall of a well and simulation sleeve pipe, first interface fracture simulation wall of a well with the simulation sleeve pipe vertically set up respectively in the hydrate generates indoor, first interface fracture simulation wall of a well cover is established outside the simulation sleeve pipe, just simulation sleeve pipe upper end shutoff.
The simulation device, preferably, the simulation pit shaft system includes the second interface fracture simulation wall of a well and simulation sleeve pipe, the second interface fracture simulation wall of a well with the simulation sleeve pipe respectively vertical set up in hydrate generates indoor, the second interface fracture simulation wall of a well cover is established outside the simulation sleeve pipe, just simulation sleeve pipe upper end shutoff.
The simulation device preferably 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.
Preferably, the monitoring system comprises 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 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.
The simulation device, preferably, the bottom of the hydrate generating chamber is provided with a resistance heater.
The simulation device preferably further comprises a first valve and a second valve, the first valve is arranged between the first pressurized oil pump and the first pressure gauge, and the second valve is arranged 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.
The DAS monitoring method for integrity of the hydrate formation cement sheath comprises the following steps:
1) Establishing an 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;
2) 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;
3) The axial position and length of the cement sheath integrity failure are defined.
The monitoring method preferably includes the following steps of, in step 3), defining the axial position and length of the integrity failure of the cement ring:
3.1 From an interface vibration coordinate system, in the time range of cement sheath integrity failure simulation, selecting a strength-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;
3.2 Calculating the area and the 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 formed by the intensity-time curve and the coordinate axis is more than 1 time of area variance is defined as the failure position and degree of the cement sheath.
Due to the adoption of the technical scheme, the invention has the following advantages:
(1) The invention simulates the integrity failure of the cement sheath in the preparation and exploitation processes of the natural gas hydrate by simulating the formation temperature and pressure conditions, monitors the cracking condition of the first interface and the second interface and the decomposition condition of the natural gas hydrate invading the cement sheath by a distributed optical fiber acoustic monitoring technology, and verifies the monitoring result by other modes (such as CT scanning and the like).
(2) The distributed acoustic optical fiber monitoring of the invention monitors by monitoring the phase change of the back rayleigh scattered light without energy loss.
(3) The DAS monitoring of the invention can carry out distributed real-time monitoring, has strong corrosion resistance and electromagnetic interference resistance, and can achieve the purpose of monitoring in a complex underground environment by optimizing the packaging material.
Drawings
FIG. 1 is a schematic structural diagram of a simulation apparatus according to the present invention, wherein the structure of the simulation state of natural gas hydrate preparation and intrusive cement sheath hydrate decomposition experiment is shown;
FIG. 2 is a view of a simulated borehole wall for cracking at a first interface;
FIG. 3 is a schematic structural diagram of a simulation apparatus according to the present invention, wherein a first interface cracking experiment simulation state structure is shown;
FIG. 4 is a diagram of a second interface fracture simulation borehole wall;
fig. 5 is a schematic structural diagram of a simulation apparatus according to the present invention, in which a simulated state structure of a second interfacial cracking experiment is shown.
The various reference numbers in the figures are:
1-a kettle cover; 2-kettle body; 3-a glass sleeve; 4-simulating a casing; 5-a temperature sensor; 6-a resistance heater; 7-a gland bolt; 8-a hydraulic oil chamber; 9-a refrigeration cavity; a 10-hydrate formation chamber; 11-a line for controlling the internal pressure of the casing; 12-a USB interface; 13-a data line; 14-a computer terminal; 15-a camera; 16-the first interface cracks the simulated borehole wall; 17-the second interface cracks the simulation well wall; 18-hydraulic oil pressure port; 19-refrigeration cavity inlet; 20-outlet of the refrigeration cavity; 21-a first pressurized oil pump; 22-a first pressure gauge; 23-a refrigerant tank; 24-a second pressurized oil pump; 25-a second pressure gauge; 26-a first valve; 27-a second valve; 28-plunger pump; 29-a third valve; 30-fourth valve.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the objects, features and advantages of the invention can be more clearly understood. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but are merely intended to illustrate the spirit of the technical solution of the present invention.
The invention provides a simulation device for DAS monitoring integrity of a hydrate formation cement sheath, which comprises: 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 extends out 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 extends out 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 convexly extends to form 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 well bore system is arranged at the bottom of the hydrate generating 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 method can realize the preparation of the hydrate layer and the stratum, is used for indoor simulation research on the integrity of the shaft in the hydrate exploitation process, and can meet the indoor test research requirement of DAS monitoring on the integrity of the shaft of the hydrate stratum.
As shown in fig. 1 to 4, the present invention provides a simulation apparatus for DAS monitoring integrity of a hydrate formation cement sheath, including: 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 1 and a kettle body 2, wherein the kettle cover 1 and the kettle body 2 are connected through a gland bolt 7; the kettle cover 1 comprises a top part and a bottom part, wherein an annular hydraulic oil cavity 8 is arranged in the top part of the kettle cover 1, an annular bulge protrudes from the bottom part of the kettle cover 1 and extends into the hydraulic oil cavity 8, a sealing ring is arranged in the hydraulic oil cavity 8 so that the bottom part of the kettle cover 1 is tightly matched with the top part of the kettle cover 1, a hydraulic oil pressurizing port 18 protrudes from one side of the kettle cover 1, and the hydraulic oil pressurizing port 18 is communicated with the hydraulic oil cavity 8; the kettle body 2 is provided with a hydrate generation chamber 10 and a refrigeration chamber 9, the refrigeration chamber 9 is circumferentially arranged around the hydrate generation chamber 10, one side of the kettle body 2 is convexly provided with a refrigeration chamber inlet 19 and a refrigeration chamber outlet 20, the refrigeration chamber inlet 19 is communicated with the upper part of the refrigeration chamber 9, and the refrigeration chamber outlet 20 is communicated with the lower part of the refrigeration chamber 9; the simulated well bore system is arranged at the bottom of the hydrate generating chamber 10; 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 21 and a first pressure gauge 22, wherein the first pressure oil pump 21 is connected with the first pressure gauge 22 in series and then is connected with the hydraulic oil pressure port 18; the low temperature control system comprises a refrigerating fluid tank 23, an outlet of the refrigerating fluid tank 23 is connected with a refrigerating cavity inlet 19, and an inlet of the refrigerating fluid tank 23 is connected with a refrigerating cavity outlet 20, so that the refrigerating fluid tank 23 and the refrigerating cavity 9 form a closed loop.
In the above embodiment, preferably, as shown in fig. 1, the simulated wellbore system includes a glass casing 3 and a simulated casing 4, the glass casing 3 and the simulated casing 4 are respectively vertically disposed in the hydrate generation chamber 10, the glass casing 3 is sleeved outside the simulated casing 4, and the upper end of the simulated casing 4 is sealed.
In the above embodiment, preferably, as shown in fig. 2 and 3, the simulated wellbore system includes a first interface cracking simulated wellbore wall 16 and a simulated casing 4, the first interface cracking simulated wellbore wall 16 and the simulated casing 4 are respectively vertically disposed in the hydrate generation chamber 10, the first interface cracking simulated wellbore wall 16 is sleeved outside the simulated casing 4, and the upper end of the simulated casing 4 is plugged.
In the above embodiment, preferably, as shown in fig. 4 and 5, the simulated wellbore system includes a second interface cracking simulated wellbore wall 17 and a simulated casing 4, the second interface cracking simulated wellbore wall 17 and the simulated casing 4 are respectively vertically disposed in the hydrate generation chamber 10, the second interface cracking simulated wellbore wall 17 is sleeved outside the simulated casing 4, and the upper end of the simulated casing 4 is plugged.
In the above embodiment, preferably, the pressure control system further includes a second pressurized oil pump 24 and a second pressure gauge 25; a sleeve internal pressure control pipeline 11 is arranged at the bottom of the kettle body 2, and the sleeve internal pressure control pipeline 11 is communicated with the simulation sleeve 4; the second pressurizing oil pump 24 and the second pressure gauge 25 are connected in series and then connected to the casing internal pressure control line 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 the bottom of the kettle body 2 is provided with a USB interface 12; the temperature sensor 5 is arranged on the side wall of the hydrate generating chamber 10 and is electrically connected with the USB interface 12; the camera 15 is arranged on the side wall of the glass sleeve 3 and is electrically connected with the USB interface 12; the optical fiber is wound outside the simulation sleeve 4 and is used for being connected with an external signal demodulator and monitoring the vibration degree in the simulation device; the computer terminal 14 is connected with the USB interface 12 through a data line 13.
In the above embodiment, preferably, the bottom of the hydrate generating chamber 10 is provided with the electric 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 disposed between the first pressurizing oil pump 21 and the first pressure gauge 22, and the second valve 27 is disposed between the second pressurizing oil pump 24 and the second pressure gauge 25; the low-temperature control system further comprises a plunger pump 28, a third valve 29 and a fourth valve 30, the plunger pump 28 and the third valve 29 are sequentially arranged between the refrigerant liquid tank 23 and the refrigerating chamber inlet 19 from front to back, and the fourth valve 30 is arranged between the refrigerant liquid tank 23 and the refrigerating chamber outlet 20.
The working process of the DAS simulation device for monitoring the integrity of the hydrate formation cement sheath provided by the invention is as follows:
1. natural gas hydrate preparation comprising the steps of, as shown in figure 1:
a) Installing a glass tube 3 and a simulation sleeve 4 in a positioning ring at the bottom of a hydrate generation chamber 10;
b) Filling fine sand into a hydrate generation 10 chamber and compacting, then injecting 19% tetrahydrofuran aqueous solution for multiple times to construct a simulated hydrate reservoir, adding a proper amount of coloring agent, covering and compacting the upper layer with sandy soil, and simulating an overburden layer;
c) Covering the kettle cover 1, screwing down the gland bolt 7, and checking the sealing of the kettle cover 1 and the kettle body 2;
d) Hydraulic oil is injected into the hydraulic oil cavity 8 to 6MPa, refrigerating fluid is injected into the refrigerating cavity 9, the temperature in the shaft is reduced to-9 ℃, and the temperature and pressure condition for preparing the hydrate is met;
e) Keeping the set temperature and pressure unchanged for a certain time to fully generate a hydrate, wherein a hydrate sample consists of a sediment skeleton and the hydrate;
f) Observing the generation condition of the hydrate through a camera 15 in the glass sleeve until the hydrate is completely generated;
g) Adjusting a pressure control system, and releasing pressure to normal atmospheric pressure;
h) The gland bolt 7 is disassembled, the kettle cover 1 is opened, and the glass sleeve 3 is taken out quickly.
2. The method for monitoring the hydrate decomposition of the invaded cement sheath comprises the following steps:
a) Preparing a natural gas hydrate reservoir layer and cement paste;
b) Injecting cement slurry into a reserved annulus of the hydrate synthesis chamber 10;
c) Covering the kettle cover 1, screwing down the gland bolt 7, and checking the sealing of the kettle cover 1 and the kettle body 2;
d) Hydraulic oil is injected into the hydraulic oil cavity 8 to 6MPa, refrigerating fluid is injected into the refrigerating cavity 9, the temperature in the shaft is reduced to-9 ℃, and the temperature and pressure condition for preparing the hydrate is met;
e) And connecting the computer terminal 14, the USB interface 12 and the data line 13, opening the computer terminal 14, and continuously observing and recording the DAS signals.
f) After the cement sheath is cured (about 48 hours), turning on the resistance heater 6, heating for 10min, and then turning off;
g) According to the vibration data recorded in the steps e and f, the monitoring data are explained by using a monitoring data explanation module, and the position and the axial length of the cement sheath cracking are obtained;
h) And adjusting the pressure control module, and releasing the pressure to normal atmospheric pressure.
i) The gland bolt 7 is disassembled, the kettle cover 1 is opened, the cement sheath is taken out, the fracture condition of the cement sheath is determined through CT scanning, and the fracture condition is compared with DAS monitoring results for verification.
3. Monitoring the natural gas hydrate first interface cracking comprises the following steps, as shown in figure 3:
a) Preparing a natural gas hydrate reservoir and cement paste.
b) Installing a first interface cracking simulation well wall 16 in a positioning ring at the bottom of the hydrate synthesis chamber 10;
c) Injecting cement slurry into a reserved annulus of the hydrate synthesis chamber 10;
d) Covering the kettle cover 1, screwing down the gland bolt 7, and checking the sealing of the kettle cover 1 and the kettle body 2;
e) Hydraulic oil is injected into the hydraulic oil cavity 8 to 6MPa, refrigerating fluid is injected into the refrigerating cavity 9, the temperature in the shaft is reduced to-9 ℃, the temperature and pressure condition for preparing hydrate is met, and the internal pressure of the simulated casing 4 is kept at 3MPa;
f) And connecting the computer terminal 14, the USB interface 12 and the data line 13, opening the computer terminal 14, and continuously observing and recording the DAS signals.
g) Waiting for the cement sheath to be cured (about 48 hours), and reducing the internal pressure of the simulation casing 4 to 2MPa;
h) Turning on the resistance heater 6, heating for 10min, and then turning off;
i) According to the vibration data recorded in the steps f, g and h, the monitoring data are interpreted by a monitoring data interpretation module to obtain the debonding position and the axial length of the interface of the cement sheath;
j) Adjusting a pressure control module, and releasing the pressure to normal atmospheric pressure;
k) The gland bolt 7 is disassembled, the kettle cover 1 is opened, the cement sheath is taken out, the first interface dyeing area of the cement sheath is observed, the first interface cracking position and degree are determined, and the first interface cracking position and degree are compared with DAS monitoring results for verification.
4. Monitoring the natural gas hydrate second interface cracking, which comprises the following steps, as shown in figure 5:
a) Preparing a natural gas hydrate reservoir layer and cement paste;
b) Installing a second interface cracking simulation well wall 17 in a positioning ring at the bottom of the hydrate synthesis chamber 10;
c) Injecting cement slurry into a reserved annulus of the hydrate synthesis chamber 10;
d) Covering the kettle cover 1, screwing down the gland bolt 7, and checking the sealing of the kettle cover 1 and the kettle body 2;
e) Hydraulic oil is injected into the hydraulic oil cavity 8 to 6MPa, refrigerating fluid is injected into the refrigerating cavity 9, the temperature in the shaft is reduced to-9 ℃, the temperature and pressure condition for preparing hydrate is met, and the internal pressure of the simulated casing 4 is kept at 3MPa;
f) Connecting a computer terminal 14, a USB interface 12 and a data line 13, opening the computer terminal 14, and continuously observing and recording DAS signals;
g) Waiting for the cement sheath to be cured (about 48 hours), and reducing the internal pressure of the inner sleeve of the simulation sleeve 4 to 2MPa;
h) Turning on the resistance heater 6, heating for 10min, and then turning off;
i) According to the vibration data recorded in the steps f, g and h, the monitoring data are interpreted by a monitoring data interpretation module to obtain the debonding position and the axial length of the interface of the cement sheath II;
j) Adjusting a pressure control module, and releasing the pressure to normal atmospheric pressure;
k) And disassembling the gland bolt 7, opening the kettle cover 1, taking out the cement sheath, observing a second interface dyeing area of the cement sheath, determining the second interface cracking position and degree, and comparing and verifying with DAS monitoring results.
The invention also provides a DAS monitoring method for monitoring integrity of a hydrate formation cement sheath, which comprises the following steps:
1) Establishing an interface sound intensity coordinate system by taking the axial length of the simulation sleeve 4 as a vertical coordinate and the monitoring time as a horizontal coordinate;
2) Drawing an acoustic waterfall graph in an axial coordinate system of the simulation sleeve 4 by using the relevant parameters of the first interface optical fiber vibration monitored by the DAS;
3) The axial position and length of the cement sheath integrity failure are defined.
In the above embodiment, preferably, the axial position and length definition of the failure of the integrity of the cement ring in the step 3) includes the following steps:
3.1 From an interface vibration coordinate system, in the time range of cement sheath integrity failure simulation, selecting a strength-time curve corresponding to the axial length of the simulation sleeve 4 according to the spatial resolution and the winding angle of the DAS monitoring system;
3.2 Calculating the area and the 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 formed by the intensity-time curve and the coordinate axis is more than 1 time of area variance is defined as the failure position and degree of the cement sheath.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the 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.
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| CN105259337B (en) * | 2015-11-20 | 2017-03-22 | 中国地质大学（武汉） | Hydrate/ice-containing low-temperature stratum well cementation simulation experiment reaction kettle |
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