CN113605881A - Underground fluid pressure measuring system and method based on continuous grating optical fiber - Google Patents
Underground fluid pressure measuring system and method based on continuous grating optical fiber Download PDFInfo
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- CN113605881A CN113605881A CN202110989796.8A CN202110989796A CN113605881A CN 113605881 A CN113605881 A CN 113605881A CN 202110989796 A CN202110989796 A CN 202110989796A CN 113605881 A CN113605881 A CN 113605881A
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 87
- 239000012530 fluid Substances 0.000 title claims abstract description 74
- 238000000034 method Methods 0.000 title claims abstract description 18
- 230000003287 optical effect Effects 0.000 claims abstract description 82
- 239000002184 metal Substances 0.000 claims abstract description 62
- 239000002131 composite material Substances 0.000 claims abstract description 35
- 239000011435 rock Substances 0.000 claims abstract description 24
- 239000011148 porous material Substances 0.000 claims abstract description 20
- 238000005259 measurement Methods 0.000 claims abstract description 13
- 238000012544 monitoring process Methods 0.000 claims abstract description 8
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- 239000007924 injection Substances 0.000 claims description 18
- 229910001220 stainless steel Inorganic materials 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 239000004568 cement Substances 0.000 claims description 13
- 238000009530 blood pressure measurement Methods 0.000 claims description 11
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 10
- 239000002002 slurry Substances 0.000 claims description 9
- 239000010935 stainless steel Substances 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 7
- 229920000642 polymer Polymers 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 6
- 210000005239 tubule Anatomy 0.000 claims description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 5
- 239000001569 carbon dioxide Substances 0.000 claims description 5
- 238000011161 development Methods 0.000 claims description 5
- 239000003921 oil Substances 0.000 claims description 5
- 238000010793 Steam injection (oil industry) Methods 0.000 claims description 4
- 238000010521 absorption reaction Methods 0.000 claims description 4
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/12—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
- E21B47/13—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling by electromagnetic energy, e.g. radio frequency
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/12—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
- E21B47/13—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling by electromagnetic energy, e.g. radio frequency
- E21B47/135—Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling by electromagnetic energy, e.g. radio frequency using light waves, e.g. infrared or ultraviolet waves
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- Fluid Mechanics (AREA)
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- Measuring Fluid Pressure (AREA)
Abstract
The invention provides a system and a method for measuring underground fluid pressure based on continuous grating optical fiber, which comprises a metal sleeve, wherein a pipe column is arranged in the metal sleeve, and the system also comprises an armored optical cable, wherein the armored optical cable comprises an outer armored optical cable and an inner armored optical cable; the outer armored optical cable is fixed on the outer side of the metal sleeve and used for measuring the fluid pressure in the underground rock stratum pore space at each grating position; the inner armored optical cable is fixed on the outer side of the pipe column and used for measuring the fluid pressure in the well at each grating position in the well; the armored optical cables comprise two continuous grating optical fibers, namely a first continuous grating optical fiber and a second continuous grating optical fiber; the composite modulation and demodulation instrument is arranged near a wellhead and is respectively connected with the first continuous grating optical fiber and the second continuous grating optical fiber of the two armored optical cables. The system can realize real-time measurement and monitoring of the fluid pressure inside and outside the whole well section.
Description
Technical Field
The invention belongs to the technical field of measurement of pore fluid pressure of underground or oil-gas underground rock strata or fluid pressure in a shaft, and particularly relates to a system and a method for measuring underground fluid pressure based on a continuous grating optical fiber.
Background
The fiber optic sensing system may be used for surface three-component seismic signals and measurements of downhole pressure, temperature, noise, vibration, sound, seismic waves, flow, compositional analysis, electric and magnetic fields. The system is based on a full armored optical cable structure, and the sensor and the connecting and data transmission cable are all made of optical fibers. At present, there are many underground and underground armored optical cables, such as those buried in shallow trenches below the surface of earth, placed in underground control pipelines, thrown into coiled tubing, directly integrated into the wall of coiled tubing made of composite material, bound and fixed outside coiled tubing, thrown into casing and bound outside casing, and permanently fixed with cementing cement.
The fiber grating is an important fiber passive device, has the advantages of small diameter, light weight, good electrical insulation, strong corrosion resistance, strong electromagnetic interference resistance and the like, is easy to realize distributed monitoring, is suitable for working in complicated and severe environments, can realize the measurement of physical quantities such as pressure, temperature, flow, acceleration and the like by selecting the structural design and the packaging process of the sensor, and has been widely applied to the fields of energy chemical industry, aerospace, large civil engineering and the like. The measurement of pressure is one of the hot spots in the development of fiber grating sensing technology in the last decade. Fiber gratings are made using photosensitivity in optical fibers. Photosensitivity in an optical fiber refers to the property that when laser light passes through a doped optical fiber, the refractive index of the optical fiber changes correspondingly with the spatial distribution of light intensity. The spatial phase grating formed in the core is essentially a narrow band (transmissive or reflective) filter or mirror formed in the core. By utilizing the characteristic, a plurality of optical fiber devices with unique performance can be manufactured, and the optical fiber devices have a series of excellent performances of large reflection bandwidth range, small additional loss, small volume, easy coupling with optical fibers, compatibility with other optical devices, no influence of environmental dust and the like.
There are many types of fiber gratings, mainly classified into two main types: one is a Bragg grating (also known as a reflective or short period grating) and the other is a transmission grating (also known as a long period grating). The fiber grating can be structurally divided into a periodic structure and a non-periodic structure, and can also be functionally divided into a filter type grating and a dispersion compensation type grating; among them, the dispersion compensation type grating is a non-periodic grating, which is also called a chirped grating (chirp grating). At present, the application of the fiber grating is mainly focused on the field of fiber communication and the field of fiber sensors.
The fiber Bragg grating longitudinal strain pressure sensor is mainly designed based on the axial strain characteristic of a Fiber Bragg Grating (FBG), and the fiber Bragg grating longitudinal strain pressure sensor is the most reported at present (the most common fiber Bragg grating pressure sensor can be divided into three types of fiber Bragg grating pressure sensors, namely an embedded type, a bonded type and a suspended type according to different installation modes of the fiber Bragg grating.
The embedded fiber grating pressure sensor generally uses a polymer material to encapsulate the fiber grating. The most reported embedded structures at present mainly use a can-type or tubular housing to make the polymer into a cylindrical structure by selecting a polymer material with small elastic modulus and low thermal expansion coefficient, and simultaneously embed the fiber grating in the cylindrical polymer in the transverse or longitudinal direction. The embedded structure can greatly improve the sensitivity of the sensor, reduce the loss of the fiber bragg grating and protect the sensor so as to improve the environmental adaptability and prolong the service life of the sensor.
The sticking type fiber grating pressure sensor is characterized in that a fiber grating is stuck on a mechanical device, and the deformation of the mechanical device is utilized to drive the fiber grating to stretch along the axial direction, so that the reflection wavelength is shifted. Common mechanical devices include diaphragms, thin-walled cylinders), and isostrength beams, among others.
The suspended fiber grating pressure sensor is characterized in that the fiber grating is suspended and fixed on a mechanical device, and the fiber grating is axially stretched by utilizing the deformation of the mechanical device. Relevant mechanical devices include diaphragms, tie rods, bellows, spring tubes, variable-sided triangular and diamond-shaped structures, and the like.
The conventional downhole pressure, temperature, noise and vibration signal measurement generally uses downhole logging instruments or downhole electronic sensors, which need to be resistant to high temperature and high pressure and work for a long time in the downhole, and the working environment and conditions are very difficult to challenge for the conventional electronic sensors, and the electronic sensors are also difficult to be arranged on the outer side of a casing. At present, a grating or an optical fiber pressure sensor is connected at the tail end of an optical fiber to measure the fluid pressure of a single point or a well bottom, and the real-time measurement and monitoring of the underground or underground fluid pressure of the whole well section cannot be realized.
Disclosure of Invention
In order to measure and monitor the fluid pressure in the pore of the underground rock stratum or the fluid pressure of the whole well section in the shaft in real time, realize the comprehensive and accurate evaluation of the hydraulic fracturing transformation effect of the reservoir of the underground shale oil and gas resources, the measurement of the pore fluid pressure of each position in the reservoir, the real-time measurement of the oil, gas and water flow and the change (liquid production profile) of each oil and gas production well section, the injection quantity and the change (water absorption profile) of each water injection or steam injection or carbon dioxide injection or polymer injection well section in the well, and the like, the invention greatly reduces the exploration and development cost of the shale oil and gas resources and improves the final recovery ratio, the invention provides a underground fluid pressure measuring system and a measuring method based on the continuous grating optical fiber, which utilize the fluid pressure measuring armor based on the continuous grating optical fiber fixed outside a metal casing of an underground drilling hole or outside a pipe column in the shaft and a DTS/DPS composite modulation and demodulation instrument near the well mouth, and measuring and monitoring the fluid pressure of each grating position on the continuous grating optical fiber distributed in the whole well section in real time.
In order to achieve the purpose, the specific technical scheme of the invention is as follows:
the underground fluid pressure measuring system based on the continuous grating optical fiber comprises a metal sleeve, a tubular column and an armored optical cable, wherein the metal sleeve is internally provided with the tubular column;
the external armored optical cable is fixed on the outer side of the metal sleeve and used for measuring the fluid pressure in the underground rock stratum pore at each grating position;
the inner armored optical cable is fixed on the outer side of the pipe column and used for measuring the fluid pressure in the well at each grating position in the well;
the armored optical cables respectively comprise two grating optical fibers, namely a first continuous grating optical fiber and a second continuous grating optical fiber;
the composite modulation and demodulation instrument is arranged near a wellhead and is respectively connected with the first continuous grating optical fiber and the second continuous grating optical fiber of the two armored optical cables;
the pipe column is an oil pipe or an air pipe in the underground casing pipe;
the first continuous grating fiber is a high-temperature-resistant, high-sensitivity and hydrogen-loss-resistant continuous grating fiber for measuring the temperature of underground fluid;
the second continuous grating fiber is a high-temperature-resistant high-sensitivity hydrogen loss-resistant continuous grating fiber for measuring the pressure of underground fluid;
the armored optical cable at least comprises a continuous stainless steel wire;
the composite modulation and demodulation instrument is a DTS/DPS composite modulation and demodulation instrument.
At least one layer of continuous stainless steel tubule is arranged outside the first continuous grating fiber in the armored optical cable to package the first continuous grating fiber, and high-temperature-resistant fiber paste is filled in the continuous stainless steel tubule; the second continuous grating optical fiber in the armored optical cable is externally extruded with a layer of high-strength high-temperature-resistant composite material, so that the outer diameter of the second continuous grating optical fiber reaches 1-2 mm, gratings in the first continuous grating optical fiber and the second continuous grating optical fiber are distributed at equal intervals, and the interval is 10-50 m.
The first continuous grating optical fiber, the second continuous grating optical fiber and the continuous stainless steel wire are fixed together in parallel, the continuous stainless steel thin tube for packaging the first continuous grating optical fiber and the adjacent continuous stainless steel wire bear the dead weight and the tension of the armored optical cable in a well, and the second continuous grating optical fiber fixed together with the first continuous grating optical fiber in parallel is not bearing and is not stretched.
The outer armored optical cable is fixed on the outer side of the metal sleeve by using annular metal clips at equal intervals, and is sealed and fixed with the metal sleeve and an underground rock stratum by using well cementation cement; the inner armored optical cable is arranged on the outer side of the pipe column and is fixed by annular metal clips at equal intervals.
The annular metal clips are fixedly arranged at the position of each metal sleeve shoe.
The measuring method of the underground fluid pressure measuring system based on the continuous grating optical fiber comprises the following steps:
(a) synchronously and slowly putting the metal sleeve and the external armored optical cable into a drilled well hole;
(b) the annular metal clip is arranged at the junction of the two metal sleeves at the wellhead, so that the outer armored optical cable is fixed and protected from rotating and moving and/or being damaged in the process of casing running;
(c) the inner armored optical cable and the pipe column are fixed together by an annular metal clamp at a well head, so that the inner armored optical cable is protected from rotating and moving and/or being damaged in the process of lowering the pipe column;
(d) pumping cement slurry from the well bottom by using a high-pressure pump truck, returning the cement slurry to the well head from the well bottom along an annular area between the outer wall of the metal casing and the drill hole, and permanently fixing the metal casing, the external armored optical cable and the stratum rock together after the cement slurry is solidified;
(e) connecting the first continuous grating fiber to the DTS signal input end of the composite modulation and demodulation instrument at a wellhead, and connecting the second continuous grating fiber to the DPS signal input end of the composite modulation and demodulation instrument;
(f) the composite modulation and demodulation instrument measures the fluid pressure in the rock stratum pore space of the position or the depth of each grating on the second continuous grating optical fiber in the outer armored optical cable, and synchronously measures the temperature of the position or the depth of each grating on the first continuous grating optical fiber in the outer armored optical cable;
(g) the composite modulation and demodulation instrument measures the fluid pressure in a well at the position or depth of each grating on the second continuous grating optical fiber in the inner armored optical cable, and synchronously measures the temperature at the position or depth of each grating on the first continuous grating optical fiber in the inner armored optical cable;
(h) the method comprises the following steps of utilizing a first continuous grating optical fiber and a composite modulation and demodulation instrument to monitor and measure the change of the temperature of an underground rock stratum outside a metal casing pipe of the whole well section or the change of the temperature of fluid in a shaft in real time, and utilizing a formula according to the monitored and measured actually-measured temperature data in the internal and external measuring well sections of the metal casing pipe:
Δλ/λ＝-Δυ/υ＝KTΔt+Kεε
wherein λ and υ are average light wavelength and frequency respectively; kTAnd KεTemperature and strain standard constants, respectively;
correcting the measured data of the fluid pressure in the pore of the rock stratum or the fluid pressure in the shaft by using the temperature value of the specific measuring position to perform the drift of the scattered light spectrum in the optical fiber caused by the temperature change, and obtaining the real fluid pressure value in the pore of the underground rock stratum of the measuring well section outside the metal casing or the fluid pressure value in the measuring well section in the shaft, wherein the temperature influence is eliminated;
(i) after the oil and gas production well is put into operation, the armored optical cable and the composite modulation and demodulation instrument connected with the armored optical cable are utilized to continuously measure the temperature data of each grating position on the first continuous grating optical fiber in real time, the reservoir pore fluid pressure value of each grating position on the second continuous grating optical fiber or the fluid pressure value of a measurement well section in a shaft is synchronously and continuously measured in real time, the flow rate of oil, gas and water of each oil and gas production well section in the well and the change or the liquid production profile of each oil and gas production well section in the well are calculated by utilizing a multi-parameter comprehensive inversion method, or the injection amount of each water injection well section, steam injection well section, carbon dioxide injection well section or polymer injection well section in the well and the change or the water absorption profile of each water injection well section in the well, so that the long-term real-time dynamic monitoring of the development and production process of the oil and gas well and the change of the well liquid production can be realized.
The invention has the specific technical effects that:
the invention provides a continuous grating fiber-based underground fluid pressure measurement system and a measurement method, wherein a continuous grating fiber-based fluid pressure measurement armored optical cable is arranged on the outer side of an underground metal sleeve or the outer side of an underground pipe column, each grating on the armored optical cable fixed on the outer side of the metal sleeve respectively measures the pressure of fluid in stratum pores at the positions of the gratings, each grating on the armored optical cable arranged on the outer side of the underground pipe column or the outer side of an open hole well respectively measures the fluid pressure in the well hole at the position of each grating, and the real-time measurement and monitoring of the fluid pressure inside and outside the whole well section are realized. The first continuous grating optical fiber in the fluid pressure measurement armored optical cable synchronously measures the temperature change of the whole well section, and the measured well temperature data is used for correcting the temperature drift of the pressure data measured by the second continuous grating optical fiber point by point.
Drawings
Fig. 1 is a schematic view of the arrangement of the external armored cable of the present invention on the outside of the metal sleeve.
FIG. 2 is a schematic view of the deployment of the inner armor cable of the present invention outside of a tubular string.
Fig. 3 is a schematic cross-sectional view of an armored fiber optic cable according to the present invention.
FIG. 4 is a schematic diagram of the structure of a grating fiber of the present invention.
Detailed Description
In order to facilitate an understanding of the invention, the invention is described in more detail below with reference to the accompanying drawings and specific examples. The accompanying drawings illustrate preferred embodiments of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. They are not to be construed as limiting the invention but merely as exemplifications, while the advantages thereof will be more clearly understood and appreciated by way of illustration.
Fig. 1 shows a schematic layout of an outer armored cable 31 of the present invention on the outside of a metal casing 1, and fig. 2 shows a schematic layout of an inner armored cable 32 of the present invention on the outside of a pipe column 2:
the underground fluid pressure measurement system based on the continuous grating optical fiber comprises a metal sleeve 1, wherein a pipe column 2 is arranged in the metal sleeve 1, and the underground fluid pressure measurement system further comprises an armored optical cable, wherein the armored optical cable comprises an outer armored optical cable 31 and an inner armored optical cable 32;
the external armored optical cable 31 is fixed outside the metal casing 1 and used for measuring the fluid pressure in the underground rock stratum pore space at each grating position;
the inner armored optical cable 32 is fixed on the outer side of the pipe column 2 and is used for measuring the fluid pressure in the well at each grating position in the well;
the armored optical cables respectively comprise two grating optical fibers, namely a first continuous grating optical fiber 4 and a second continuous grating optical fiber 5;
the composite modulation and demodulation instrument 6 is placed near a wellhead, and the composite modulation and demodulation instrument 6 is respectively connected with the first continuous grating optical fiber 4 and the second continuous grating optical fiber 5 of the two armored optical cables;
the pipe column 2 is an oil pipe or an air pipe in a cased well;
the first continuous grating optical fiber 4 is a high-temperature-resistant high-sensitivity hydrogen-loss-resistant continuous grating optical fiber for measuring the temperature of underground fluid;
the second continuous grating optical fiber 5 is a high-temperature-resistant high-sensitivity hydrogen-loss-resistant continuous grating optical fiber for measuring the pressure of underground fluid;
the composite modulation and demodulation instrument 6 is a DTS/DPS composite modulation and demodulation instrument.
As shown in fig. 3 and 4, at least one continuous stainless steel wire 8 is arranged in the armored optical cable; the first continuous grating optical fiber 4 in the armored optical cable comprises an inner-layer continuous stainless steel tubule 10, and high-temperature-resistant optical fiber paste 11 is filled in the inner-layer continuous stainless steel tubule 10; a layer of high-strength high-temperature-resistant composite material 9 is extruded outside the second continuous grating optical fiber 5 in the armored optical cable, so that the outer diameter of the second continuous grating optical fiber reaches 1 mm to 2 mm; the gratings in the first continuous grating fiber 4 and the second continuous grating fiber 5 are distributed according to equal spacing, and the spacing is between 10 meters and 50 meters.
The first continuous grating optical fiber, the second continuous grating optical fiber and the continuous stainless steel wire are fixed together in parallel, the continuous stainless steel wire 8 protects the armored optical cable, and when the armored optical cable cloth with the length of thousands of meters is placed underground, the self gravity of the armored optical cable can cause the stretching of the armored optical cable, so that the drift of the scattered light spectrum in the grating optical fiber is caused. In order to eliminate the influence of the stretching of the armored optical cable on the measured pressure data, the continuous stainless steel thin tube 10 and the adjacent continuous stainless steel wire 8 which encapsulate the first continuous grating optical fiber 4 bear the self weight and the stretching of the armored optical cable in a well, and the second continuous grating optical fiber 5 which is fixed with the first continuous grating optical fiber 4 side by side is not bearing and is not stretched.
The external armored optical cable 31 is fixed outside the metal sleeve 1 by annular metal clips 7 at equal intervals, and is sealed and fixed with the metal sleeve 1 and underground rock stratum by well cementing cement; the inner armored optical cable 32 is arranged on the outer side of the pipe column 2 and is fixed by annular metal clips 7 at equal intervals.
The annular metal clip 7 is fixedly arranged at the boot of each metal sleeve 1.
The measuring method of the underground fluid pressure measuring system based on the continuous grating optical fiber comprises the following steps:
(a) synchronously and slowly lowering the metal sleeve 1 and the external armored optical cable 31 into a drilled well hole;
(b) the annular metal clip 7 is arranged at the junction of the two metal sleeves 1 at the wellhead, so that the outer armored optical cable 31 is fixed and protected from rotating and moving and/or being damaged in the process of casing running;
(c) the annular metal clip 7 is used for fixing the inner armored cable 32 and the pipe column 2 together at the well head, so that the armored cable 32 in the fluid can not rotate and move and/or be damaged in the process of lowering the pipe column 2;
(d) pumping cement slurry from the bottom of the well by using a high-pressure pump truck, returning the cement slurry to the wellhead from the bottom of the well along an annular area between the outer wall of the metal casing 1 and the drilled hole, and permanently fixing the metal casing 1, the outer armored optical cable 31 and the stratum rock together after the cement slurry is solidified;
(e) connecting a first continuous grating fiber 4 to a DTS signal input end of the composite modem instrument 6 at a wellhead, and connecting a second continuous grating fiber 5 to a DPS signal input end of the composite modem instrument 6;
(f) the composite modulation and demodulation instrument 6 measures the fluid pressure in the rock stratum pore space of the position or the depth of each grating on the second continuous grating fiber 5 in the outer armored optical cable 31, and synchronously measures the temperature of the position or the depth of each grating on the first continuous grating fiber 4 in the outer armored optical cable 31;
(g) the composite modem instrument 6 measures the fluid pressure in the well at the position or depth of each grating on the second continuous grating fiber 5 in the inner armored fiber cable 32, and synchronously measures the temperature at the position or depth of each grating on the first continuous grating fiber 4 in the inner armored fiber cable 32;
(h) the change of the underground rock stratum temperature outside the metal casing 1 of the whole well section or the change of the fluid temperature in the shaft is monitored and measured in real time by utilizing the first continuous grating optical fiber 4 and the composite modulation and demodulation instrument 6, and according to the monitored and measured temperature data in the internal and external measuring well sections of the metal casing 1, the formula is utilized:
Δλ/λ＝-Δυ/υ＝KTΔt+Kεε
wherein λ and υ are average light wavelength and frequency respectively; kTAnd KεTemperature and strain standard constants, respectively;
correcting the measured data of the fluid pressure in the pore of the rock stratum or the fluid pressure in the shaft by using the temperature value of the specific measuring position to perform the drift of the scattered light spectrum in the optical fiber caused by the temperature change, and obtaining the real fluid pressure value in the pore of the underground rock stratum of the measuring well section outside the metal casing 1 or the fluid pressure value of the measuring well section in the shaft, wherein the temperature influence is eliminated;
(i) after the oil and gas production well is put into operation, the armored optical cable and the composite modulation and demodulation instrument 6 connected with the armored optical cable are used for continuously measuring the temperature data of each grating position on the first continuous grating optical fiber 4 in real time, the reservoir pore fluid pressure value of each grating position on the second continuous grating optical fiber 5 or the fluid pressure value of a measurement well section in a shaft in real time and continuously, the flow rate and the change of oil, gas and water or a liquid production profile of each oil and gas production well section in the well or the injection amount and the change of carbon dioxide or polymer injection well section in the well or a water absorption profile of each water injection or steam injection or carbon dioxide injection or polymer injection well section in the well are calculated by a multi-parameter comprehensive inversion method, and therefore the long-term real-time dynamic monitoring of the development and production process of the oil and gas well and the change of the well liquid production is achieved.
Claims (5)
1. The underground fluid pressure measurement system based on the continuous grating optical fiber is characterized by comprising a metal sleeve (1), wherein a pipe column (2) is arranged in the metal sleeve (1), and the underground fluid pressure measurement system further comprises an armored optical cable, wherein the armored optical cable comprises an outer armored optical cable (31) and an inner armored optical cable (32);
the external armored optical cable (31) is fixed on the outer side of the metal casing (1) and is used for measuring the fluid pressure in the underground rock stratum pore space at each grating position;
the inner armored optical cable (32) is fixed on the outer side of the pipe column (2) and is used for measuring the fluid pressure in the well at each grating position in the well;
the armored optical cables respectively comprise two continuous grating optical fibers, namely a first grating optical fiber (4) and a second grating optical fiber (5);
the composite modulation and demodulation instrument (6) is placed near a wellhead, and the composite modulation and demodulation instrument (6) is respectively connected with the first continuous grating optical fiber (4) and the second continuous grating optical fiber (5) of the two armored optical cables;
the pipe column (2) is an oil pipe or an air pipe in an underground casing;
the first grating optical fiber (4) is a continuous grating optical fiber which is high-temperature resistant, high-sensitivity and hydrogen loss resistant and is used for measuring the temperature of underground fluid;
the second grating fiber (5) is a continuous grating fiber which is high-temperature resistant, high-sensitivity and hydrogen loss resistant and is used for measuring the pressure of underground fluid;
the composite modulation and demodulation instrument (6) is a DTS/DPS composite modulation and demodulation instrument.
2. The continuous grating fiber optic based subterranean fluid pressure measurement system of claim 1, wherein said armored fiber optic cable comprises at least one continuous stainless steel wire (8);
at least one layer of continuous stainless steel tubule (10) is arranged outside the first continuous grating fiber (4) for packaging, and high temperature resistant fiber paste (11) is filled in the continuous stainless steel tubule (10); the second continuous grating fiber (5) is externally extruded with a layer of high-strength high-temperature-resistant composite material (9) to enable the outer diameter of the second continuous grating fiber to reach 1-2 mm, gratings in the first continuous grating fiber (4) and the second continuous grating fiber (5) are distributed at equal intervals, and the intervals are 10-50 m.
3. The continuous grating fiber-based underground fluid pressure measurement system of claim 1, wherein the external armored optical cable (31) is fixed outside the metal casing (1) by using annular metal clips (7) with equal intervals and is sealed and fixed with the metal casing (1) and underground rock strata by using cementing cement; the inner armored optical cable (32) is arranged on the outer side of the pipe column (2) and is fixed by annular metal clips (7) at equal intervals.
4. A continuous grating fiber based subterranean fluid pressure measurement system according to claim 1, wherein said annular metal clip (7) is fixedly mounted at each metal sleeve (1) shoe.
5. The method of measuring a continuous grating fiber based subterranean fluid pressure measurement system according to any one of claims 1 to 4, comprising the steps of:
(a) synchronously and slowly putting the metal sleeve (1) and the external armored optical cable (31) into a drilled well hole;
(b) the annular metal clip (7) is arranged at the junction of two metal sleeves (1) at the wellhead, so that the outer armored optical cable (31) is fixed and protected from rotating and moving and/or being damaged in the sleeve descending process;
(c) the inner armored cable (32) and the pipe column (2) are fixed together by an annular metal clamp (7) at a well head, so that the inner armored cable (32) is protected from rotating and moving and/or being damaged in the process of lowering the pipe column (2);
(d) pumping cement slurry from the well bottom by using a high-pressure pump truck, returning the cement slurry to the well head from the well bottom along an annular area between the outer wall of the metal casing (1) and the drilled hole, and permanently fixing the metal casing (1), the external armored optical cable (31) and formation rock together after the cement slurry is solidified;
(e) connecting a first continuous grating fiber (4) to the DTS signal input of the composite modem instrument (6) at the wellhead and a second continuous grating fiber (5) to the DPS signal input of the composite modem instrument (6);
(f) the composite modulation and demodulation instrument (6) measures the fluid pressure in the rock stratum pore space of the position or the depth of each grating on the second continuous grating optical fiber (5) in the outer armored optical cable (31), and synchronously measures the temperature of the position or the depth of each grating on the first continuous grating optical fiber (4) in the outer armored optical cable (31);
(g) the composite modulation and demodulation instrument (6) measures the fluid pressure in the well at the position or depth of each grating on the second continuous grating fiber (5) in the inner armored optical cable (32), and synchronously measures the temperature at the position or depth of each grating on the first continuous grating fiber (4) in the inner armored optical cable (32);
(h) the change of the underground rock stratum temperature outside the metal casing pipe (1) of the whole well section or the change of the fluid temperature in the shaft is monitored and measured in real time by utilizing the first continuous grating optical fiber (4) and the composite modulation and demodulation instrument (6), and according to the monitored and measured temperature data in the internal and external measuring well sections of the metal casing pipe (1), the formula is utilized:
Δλ/λ＝-Δυ/υ＝KTΔt+Kεε
wherein λ and υ are average light wavelength and frequency respectively; kTAnd KεRespectively temperature and strain gaugesQuasi-constant;
correcting the measured data of the fluid pressure in the pore of the rock stratum or the fluid pressure in the shaft by using the temperature value of the specific measuring position to perform the drift of the scattered light spectrum in the optical fiber caused by the temperature change, and obtaining the real fluid pressure value in the pore of the underground rock stratum of the measuring well section at the outer side of the metal casing (1) or the fluid pressure value of the measuring well section in the shaft, wherein the temperature influence is eliminated;
(i) after the oil and gas production well is put into operation, the armored optical cable and the composite modulation and demodulation instrument (6) connected with the armored optical cable are utilized to continuously measure the temperature data of each grating position on the first continuous grating optical fiber (4) in real time, the reservoir pore fluid pressure value of each grating position on the second continuous grating optical fiber (5) or the fluid pressure value of a measurement well section in a shaft is synchronously and continuously measured in real time, and the flow of oil, gas and water of each oil and gas production well section in the well and the change or the liquid production profile of the oil, gas and water, or the injection quantity of each water injection or steam injection or carbon dioxide injection or polymer injection well section in the well and the change or the water absorption profile of the oil and gas production well are calculated by a multi-parameter comprehensive inversion method, so that the long-term real-time dynamic monitoring of the development and production process of the oil and gas well and the well liquid production change of the oil and gas production well is realized.
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