CN110344816B - A monitoring method for oil and gas well sand production based on distributed optical fiber sound monitoring - Google Patents

Abstract

A method for monitoring sand production in oil and gas wells based on distributed optical fiber sound monitoring, comprising: a method for installing a distributed optical fiber sound monitoring device in an oil and gas well to be monitored for sand production, a method for monitoring sand production in the oil and gas well, and a method for monitoring and interpreting sand production in DAS oil and gas wells . The invention adopts distributed optical fiber sound monitoring to realize distributed and real-time monitoring of sand production in all production layers; it can qualitatively judge the degree of sand production in each layer; it can realize temporary monitoring of underground sand production; it can realize sand control in sand production layers Effect evaluation has outstanding significance for practice and research.

Description

A monitoring method for sand production in oil and gas wells based on distributed optical fiber sound monitoring

technical field

The invention relates to a method for monitoring sand production in oil and gas wells based on distributed optical fiber sound monitoring, and belongs to the technical field of oil and gas exploitation.

Background technique

During the exploitation of oil and gas fields, massive or continuous sand production from reservoirs will cause sand burial in oil and gas layers, sand plugging in oil pipes, sand accumulation in surface manifolds, collapse of formation deficits, etc., seriously affecting the normal production of oil and gas wells. Therefore, it is very important to know the sand production layer and sand production volume of oil and gas wells in real time to ensure the safe, efficient and continuous production of oil and gas wells. At present, the sand production monitoring methods used in the field mainly include ultrasonic method, piezoelectric method, acceleration sensor method, etc. These methods are mainly based on wellhead monitoring, and what is obtained is the sand production situation of the whole well, and cannot reveal the production intervals of each production interval in the downhole in real time. sand conditions and the flow of sand particles in the wellbore.

In recent years, with the development of distributed optical fiber acoustic monitoring technology, hereinafter referred to as DAS technology, it provides an important means for distributed and real-time monitoring of reservoir sand production and wellbore sand flow. It is applied to the process of detecting sand production in oil and gas wells.

Contents of the invention

Aiming at the deficiencies of the prior art, the invention discloses a method for monitoring sand production in oil and gas wells based on distributed optical fiber sound monitoring.

SUMMARY OF THE INVENTION

The main principle of DAS technology is to use the principle of coherent optical time-domain reflectometry to inject coherent short-pulse laser into the optical fiber. When external vibration acts on the optical fiber, due to the elastic-optic effect, the internal structure of the fiber core will be slightly changed. As a result, the back Rayleigh scattering signal changes, causing the received reflected light intensity to change. By detecting the intensity change of the Rayleigh scattered light signal before and after the downhole event, the ongoing downhole event can be detected and precisely located. When the reservoir produces sand, the sand particles impact the downhole optical fiber and generate vibration events. According to the vibration events and vibration intensity at different positions of the optical fiber, the sand production layer and the degree of sand production can be determined. At the same time, by monitoring the movement of sand grains entering the wellbore, it can be determined whether sand grain settlement will occur at the current production rate, which in turn can provide guidance for sand-carrying production in oil and gas wells. Because the optical fiber has the characteristics of anti-electromagnetic interference, corrosion resistance, and good real-time performance, it has greater advantages in real-time monitoring of downhole sand production.

Detailed technical scheme of the present invention is as follows:

A method for monitoring sand production in oil and gas wells based on distributed optical fiber sound monitoring, characterized in that it includes: a method for installing a distributed optical fiber sound monitoring device in an oil and gas well to be monitored for sand production;

Wherein, the distributed optical fiber sound monitoring device includes a DAS sand monitor and an armored optical cable, and the DAS sand monitor includes a laser light source, a sound signal receiver, and a computer control and display system;

The DAS sand production monitor is used for real-time monitoring and feedback to monitoring personnel sound data; the armored optical cable is used to be vertically installed in oil and gas wells, and the monitored downhole sand production sound data is transmitted to the DAS sand production monitor;

The method for installing a distributed optical fiber sound monitoring device in an oil and gas well to be monitored for sand production includes:

Installing the armored optical cable in the oil and gas well vertically and along the axial direction of the oil and gas well; the installation depth of the armored optical cable covers all sand producing layers of the oil and gas well to be detected;

The end of the armored optical cable is provided with a part that maintains its natural suspension; the DAS sand production monitor collects the sound signal of the oil and gas well in real time through the armored optical cable, and transmits the sound signal to the computer control and display system.

Preferably according to the present invention, the armored optical cable is installed on the outer wall of the oil pipe in the oil and gas well, or installed in the annular space between the oil pipe and the casing.

Preferably according to the present invention, the method for monitoring sand production of oil and gas wells based on distributed optical fiber sound monitoring also includes a method for monitoring sand production of oil and gas wells, the steps are as follows:

The laser light source sends pulsed laser light to the single-mode acoustic fiber in the armored optical cable; the sound signal receiver receives the sound signal reflected back from the single-mode acoustic optical fiber in the armored optical cable;

The computer control and display system controls the signal emission and reception of the laser light source and the sound signal receiver.

Preferably according to the present invention, the computer control and display system is used to feed back the sand production conditions of each production interval of the oil and gas well.

Preferably, according to the present invention, the spatial resolution of the DAS sand production monitor is 1 meter, and the highest sampling frequency is 15 kHz.

Preferably according to the present invention, the oil and gas well sand production monitoring method based on distributed optical fiber sound monitoring also includes a DAS oil and gas well sand production monitoring and interpretation method, and the computer control and display system for realizing the interpretation method includes a data preprocessing module and sand production Monitoring data interpretation module:

The data preprocessing module is used to obtain the denoised sound data related to the entry of reservoir sand particles into the wellbore, including steps 1-1)-1-3):

1-1) The frequency-space deconvolution filter is used to process the sound data collected during the sand production monitoring process to obtain sound data with random spike noise removed;

1-2) A band-pass filter is used to limit the frequency range of the sound data to the impact energy range of sand particles entering the wellbore flow, thereby eliminating irrelevant noise signals in the data;

1-3) Obtain the sound data after denoising related to the entry of reservoir sand grains into the wellbore;

The sand production monitoring and interpretation module includes: establishing a sound intensity coordinate system and generating a sound intensity "waterfall diagram", including:

2-1) Establish a sound intensity coordinate system, the depth of the oil and gas well is the abscissa, and the time for sound monitoring of the oil and gas well is the ordinate;

2-2) Use the sound data related to the sand particles entering the wellbore in the reservoir to draw a sound intensity "waterfall diagram" in the above sound intensity coordinate system:

2-3) Define the sand section:

Since the positions of all production intervals in the oil and gas well are known, that is, the depth range covered by the production intervals of the oil and gas well is known, the sound intensity at any time can be extracted from the sound intensity "waterfall diagram" within the depth range covered by the production intervals. The curve of sound intensity changing with oil and gas well depth is shown in Fig. 2; based on the minimum sound intensity value of the sound intensity changing curve with oil and gas well depth extracted at any time within the depth range covered by the production interval, a Horizontal line, as shown by the dotted line in Figure 2;

According to the depth range covered by each production layer, the area method is used to calculate the graph surrounded by the horizontal line based on the minimum sound intensity value and the curve of sound intensity changing with the depth of oil and gas wells within the depth range covered by each production layer area;

Then, the area variance is calculated: the production interval whose area corresponding to the production interval is greater than 1 times the area variance is judged as the sand production interval;

2-4) Define severe sanding, moderate sanding and slight sanding:

Divide the area corresponding to each production interval by the thickness of the production interval to obtain the area per unit thickness of the production interval;

Add the area per unit thickness of each production layer to obtain the total area per unit thickness, and calculate the area percentage per unit thickness corresponding to each production layer;

The area percentage of unit thickness greater than or equal to 50% is defined as severe sanding, the area percentage of unit thickness between 20% and 50% is defined as moderate sanding, and the area percentage of unit thickness less than or equal to 20% is defined as slight sanding.

The beneficial effects of the present invention are:

1. The present invention adopts distributed optical fiber sound monitoring to realize distributed and real-time monitoring of sand production in all production layers;

2. The distributed optical fiber sound monitoring method of the present invention can qualitatively judge the degree of sand production in each layer;

3. The distributed optical fiber sound monitoring method of the present invention can realize long-term monitoring of underground sand production, and can also realize temporary monitoring of underground sand production.

4. The distributed optical fiber sound monitoring method of the present invention can realize the evaluation of the sand control effect of the sand producing interval, which is of great significance to practice and research.

Description of drawings

Fig. 1 is a schematic diagram of working conditions of a method for monitoring sand production in oil and gas wells based on distributed optical fiber sound monitoring according to the present invention.

Fig. 2 is a schematic diagram of the sand production monitoring results of oil and gas wells monitored at a certain moment by using the method of the present invention.

In Fig. 1-2: 1. Production layer I; 2. Production layer II; 3. Production layer III; 4. Casing; 5. Oil pipe; 6. Wellhead; 7. DAS sand production monitor; 8. Armored optical cable; 9. Keep the heavy part of the armored optical cable hanging naturally; 10. Artificial well bottom.

Detailed ways

The present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings, but is not limited thereto.

As shown in Figures 1 and 2.

Embodiment 1,

A method for monitoring sand production in oil and gas wells based on distributed optical fiber sound monitoring, comprising:

A method for installing a distributed optical fiber sound monitoring device in an oil and gas well to be monitored for sand production;

Wherein, the distributed optical fiber sound monitoring device includes a DAS sand monitor 7 and an armored optical cable 8, and the DAS sand monitor 7 includes a laser light source, a sound signal receiver, and a computer control and display system;

The DAS sand production monitor 7 is used for real-time monitoring and feedback to monitoring personnel for sound data; the armored optical cable 8 is used for vertical installation in oil and gas wells, and transmits the monitored downhole sand production sound data to the DAS sand production monitoring Instrument 7;

The method for installing a distributed optical fiber sound monitoring device in an oil and gas well to be monitored for sand production includes:

Installing the armored optical cable 8 in the oil and gas well vertically and along the axial direction of the oil and gas well; the installation depth of the armored optical cable 8 covers all sand producing layers of the oil and gas well to be detected;

The end of the armored optical cable 8 is provided with a part 9 that maintains its natural suspension; the DAS sand monitor 7 collects the sound signal of the oil and gas well in real time through the armored optical cable 8, and transmits the sound signal to the computer control and display system.

The armored optical cable 8 is installed on the outer wall of the oil pipe in the oil and gas well, or installed in the annular space between the oil pipe 4 and the casing 5 .

Embodiment 2,

The oil and gas well sand production monitoring method based on distributed optical fiber sound monitoring as described in Example 1 also includes a method for monitoring the oil and gas well sand production, the steps are as follows:

Described laser light source sends pulse laser to the single-mode acoustic fiber in the armored optical cable 8; Described sound signal receiver receives the sound signal that is reflected back from the single-mode acoustic optical fiber in the armored optical cable 8;

The computer control and display system controls the signal emission and reception of the laser light source and the sound signal receiver.

The computer control and display system is used to feed back the sand production conditions of each production interval of the oil and gas well.

The spatial resolution of the DAS sand monitor is 1 meter, and the highest sampling frequency is 15 kHz.

The oil and gas well sand production monitoring method based on distributed optical fiber sound monitoring also includes a DAS oil and gas well sand production monitoring and interpretation method, and the computer control and display system for realizing the interpretation method includes a data preprocessing module and a sand production monitoring data interpretation module:

The data preprocessing module is used to obtain the denoised sound data related to the entry of reservoir sand particles into the wellbore, including steps 1-1)-1-3):

1-1) The frequency-space deconvolution filter is used to process the sound data collected during the sand production monitoring process to obtain sound data with random spike noise removed;

1-2) A band-pass filter is used to limit the frequency range of the sound data to the impact energy range of sand particles entering the wellbore flow, thereby eliminating irrelevant noise signals in the data;

1-3) Obtain the sound data after denoising related to the entry of reservoir sand grains into the wellbore;

The sand production monitoring and interpretation module includes: establishing a sound intensity coordinate system and generating a sound intensity "waterfall diagram", including:

2-1) Establish a sound intensity coordinate system, the depth of the oil and gas well is the abscissa, and the time for sound monitoring of the oil and gas well is the ordinate;

2-2) Use the sound data related to the sand particles entering the wellbore in the reservoir to draw a sound intensity "waterfall diagram" in the above sound intensity coordinate system:

2-3) Define the sand section:

Since the positions of all production intervals in the oil and gas well are known, that is, the depth range covered by the production intervals of the oil and gas well is known, the sound intensity at any time can be extracted from the sound intensity "waterfall diagram" within the depth range covered by the production intervals. The curve of sound intensity changing with oil and gas well depth is shown in Fig. 2; based on the minimum sound intensity value of the sound intensity changing curve with oil and gas well depth extracted at any time within the depth range covered by the production interval, a Horizontal line, as shown by the dotted line in Figure 2;

According to the depth range covered by each production layer, the area method is used to calculate the graph surrounded by the horizontal line based on the minimum sound intensity value and the curve of sound intensity changing with the depth of oil and gas wells within the depth range covered by each production layer area;

Then, the area variance is calculated: the production interval whose area corresponding to the production interval is greater than 1 times the area variance is judged as the sand production interval;

2-4) Define severe sanding, moderate sanding and slight sanding:

Divide the area corresponding to each production interval by the thickness of the production interval to obtain the area per unit thickness of the production interval;

Add the area per unit thickness of each production layer to obtain the total area per unit thickness, and calculate the area percentage per unit thickness corresponding to each production layer;

The area percentage of unit thickness greater than or equal to 50% is defined as severe sanding, the area percentage of unit thickness between 20% and 50% is defined as moderate sanding, and the area percentage of unit thickness less than or equal to 20% is defined as slight sanding.

Application example 1,

The specific steps of obtaining the sand production conditions of each production interval of the wellbore under different working systems by using a method for monitoring sand production of oil and gas wells based on distributed optical fiber sound monitoring according to the present invention:

Step 1: Determine the oil and gas well production string according to the oil and gas well production process, determine the length of the armored optical cable 8 armored by the seamless stainless steel tube, and ensure that the length of the armored optical cable 8 exceeds the length of the oil pipe 5 and can be extended to artificial Bottom 10; connect the weight 9 to the lower end of the armored optical cable 8; fix the part of the armored optical cable 8 shorter than the length of the oil pipe 5 in the groove on the outer wall of the oil pipe 5; put the armored optical cable 8 down with the oil and gas well production string into production wells;

Step 2: After passing through the wellhead 6, the armored optical cable 8 is connected to the DAS sand monitor 7 placed on the ground;

Step 3: start the DAS sand production monitor 7, and open the well for production;

Step 4: Observe the sound data displayed on the computer control and display system in the DAS sand monitor 7, after the sound data is stable, record the sound data, and obtain the schematic diagram as shown in Figure 2;

Step 5: Use the built-in DAS oil and gas well sand monitoring and interpretation method in the computer control and display system of the DAS sand production monitor 7 to interpret the sound data collected in step 4 in real time, and obtain the sand production conditions of each production interval of the wellbore;

Step 6: Change the working system of the oil and gas well, repeat steps 4 and 5, and obtain the sand production conditions of each production interval of the wellbore under different working systems.

Application example 2,

Using a method for monitoring oil and gas well sand production based on distributed optical fiber sound monitoring described in the present invention to complete the steps of temporary monitoring of oil and gas well downhole sand production:

Step 1: According to the depth of the artificial well bottom 10 of the oil and gas well, determine the length of the armored optical cable 8 armored by a seamless stainless steel tube or armored by a decomposable aluminum alloy to ensure that the length of the armored optical cable 8 exceeds The length of the oil pipe 5 and can extend to the artificial well bottom 10; the weight 9 is connected to the lower end of the armored optical cable 8; the armored optical cable 8 is lowered into the oil and gas well from the annular space between the oil pipe 5 and the casing 4;

Step 2: After passing through the wellhead 6, the armored optical cable 8 is connected to the DAS sand monitor 7 placed on the ground;

Step 3: start the DAS sand production monitor 7, and open the well for production;

Step 4: Observe the sound data displayed on the computer control and display system in the DAS sand monitor 7, after the sound data is stable, record the sound data, and obtain the schematic diagram as shown in Figure 2;

Step 5: Use the built-in DAS oil and gas well sand monitoring and interpretation method in the computer control and display system of the DAS sand production monitor 7 to interpret the sound data collected in step 4 in real time, and obtain the sand production conditions of each production interval of the wellbore;

Step 6: Change the working system of the oil and gas well, repeat steps 4 and 5, and obtain the sand production conditions of each production interval of the wellbore under different working systems;

Step 7: after the test is completed, close the DAS sand monitor 7; if the armored optical cable 8 armored by a seamless stainless steel tube is used, take out the armored optical cable 8 and the The weight 9 completes the temporary monitoring operation of downhole sand production in oil and gas wells; if the armored optical cable 8 made of decomposable aluminum alloy armor is used, the armored optical cable 8 is cut at the wellhead to complete the temporary monitoring operation of downhole sand production in oil and gas wells .

Application example 3,

The steps for evaluating the sand control effect of oil and gas wells by using the sand production conditions of each production interval of the wellbore after sand control obtained by a method for monitoring sand production of oil and gas wells based on distributed optical fiber sound monitoring according to the present invention:

Step 1: According to the depth of the artificial well bottom 10 of the oil and gas well, determine the length of the armored optical cable 8 armored by a seamless stainless steel tube or armored by a decomposable aluminum alloy to ensure that the length of the armored optical cable 8 exceeds The length of the oil pipe 5 and can extend to the artificial well bottom 10; the weight 9 is connected to the lower end of the armored optical cable 8; the armored optical cable 8 is entered into the production well from the annular space between the oil pipe 5 and the casing 4;

Step 2: After passing through the wellhead 6, the armored optical cable 8 is connected to the DAS sand monitor 7 placed on the ground;

Step 3: start the DAS sand production monitor 7, and open the well for production;

Step 4: Observe the sound data displayed on the computer control and display system in the DAS sand monitor 7, after the sound data is stable, record the sound data, and obtain the schematic diagram as shown in Figure 2;

Step 5: Use the built-in DAS oil and gas well sand monitoring and interpretation method in the computer control and display system of the DAS sand production monitor 7 to interpret the sound data collected in step 4 in real time, and obtain the sand production conditions of each production layer in the wellbore before sand control;

Step 6: After the test, close the DAS sand monitor 7; if the armored optical cable 8 armored by a seamless stainless steel tube is used, take out the armored optical cable 8 and the The weight 9 completes the temporary monitoring operation of downhole sand production in oil and gas wells; if the armored optical cable 8 made of decomposable aluminum alloy armor is used, the armored optical cable 8 is cut at the wellhead to complete the temporary monitoring operation of downhole sand production in oil and gas wells ;

Step 7: Implement the sand control process of gravel packing;

Step 8: After the gravel packing sand control process is completed, take out the gravel packing sand control string;

Step 9: Repeat steps 1 to 6 to obtain the sand production conditions of each production interval of the wellbore after sand control;

Step 10: Compare the sand production conditions of each production interval in the wellbore before sand control obtained in step 5 with the sand production conditions of each production interval in the wellbore after sand control obtained in step 9, so as to provide a basis for evaluating the sand control effect of oil and gas wells.

Claims (3)

1. A method for monitoring sand production in oil and gas wells based on distributed optical fiber sound monitoring, characterized in that it comprises: a method for installing a distributed optical fiber sound monitoring device in an oil and gas well to be monitored for sand production; The method for installing a distributed optical fiber sound monitoring device in an oil and gas well to be monitored for sand production includes: Installing the armored optical cable in the oil and gas well vertically and along the axial direction of the oil and gas well; the installation depth of the armored optical cable covers all sand producing layers of the oil and gas well to be detected; The end of the armored optical cable is provided with a part that maintains its natural suspension; the DAS sand monitoring instrument collects the sound signal of the oil and gas well in real time through the armored optical cable, and transmits the sound signal to the computer control and display system; The computer control and display system is used to feed back the sand production situation of each production interval of the oil and gas well; the spatial resolution of the DAS sand production monitor is 1 meter, and the highest sampling frequency is 15 kHz; The oil and gas well sand production monitoring method based on distributed optical fiber sound monitoring also includes a DAS oil and gas well sand production monitoring and interpretation method, and the computer control and display system for realizing the interpretation method includes a data preprocessing module and a sand production monitoring data interpretation module: The data preprocessing module is used to obtain denoised sound data related to reservoir sand entering the wellbore, including steps 1-1)-1-3): 1-1) The frequency-space deconvolution filter is used to process the sound data collected during the sand production monitoring process to obtain the sound data with random spike noise removed; 1-2) Band-pass filters are used to limit the frequency range of sound data to the impact energy range of sand particles entering the wellbore flow, thereby eliminating irrelevant noise signals in the data; 1-3) Obtain the denoised sound data related to the entry of reservoir sand into the wellbore; The sand monitoring data interpretation module includes: establishing a sound intensity coordinate system and generating a sound intensity "waterfall diagram", including: 2-1) Establish a sound intensity coordinate system, the depth of the oil and gas well is the abscissa, and the time for sound monitoring of the oil and gas well is the ordinate; 2-2) The sound intensity "waterfall diagram" is drawn in the above-mentioned sound intensity coordinate system by using the sound data related to the reservoir sand entering the wellbore: 2-3) Define the sand section: Extract the curve of sound intensity changing with the depth of oil and gas wells at any time within the depth range covered by the production interval from the "waterfall diagram" of sound intensity, and extract the sound intensity at any time within the depth range covered by the production interval. Make a horizontal line based on the minimum sound intensity value of the curve of intensity versus oil and gas well depth; According to the depth range covered by each production layer, the area method is used to calculate the graph surrounded by the horizontal line based on the minimum sound intensity value and the curve of sound intensity changing with the depth of oil and gas wells within the depth range covered by each production layer area; Then, the area variance is calculated: the production interval whose area corresponding to the production interval is greater than 1 times the area variance is judged as the sand production interval; 2-4) Define severe sanding, moderate sanding and slight sanding: Divide the area corresponding to each production interval by the thickness of the production interval to obtain the area per unit thickness of the production interval; Add the area per unit thickness of each production layer to obtain the total area per unit thickness, and calculate the area percentage per unit thickness corresponding to each production layer; The area percentage per unit thickness greater than or equal to 50% is defined as severe sanding, the area percentage of unit thickness between 20% and 50% is defined as moderate sanding, and the area percentage of unit thickness less than or equal to 20% is defined as slight sanding. 2. A method for monitoring sand production in oil and gas wells based on distributed optical fiber sound monitoring according to claim 1, wherein the armored optical cable is installed on the outer wall of the tubing in the oil and gas well, or between the tubing and the casing in the annular space between. 3. A kind of oil and gas well sand production monitoring method based on distributed optical fiber sound monitoring according to claim 1, is characterized in that, this monitoring also comprises the method for monitoring described oil and gas well sand production, and the steps are as follows: The laser light source sends pulsed laser light to the single-mode acoustic fiber in the armored optical cable; the sound signal receiver receives the sound signal reflected from the single-mode acoustic optical fiber in the armored optical cable; The computer control and display system controls the signal emission and reception of the laser light source and the sound signal receiver.

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