CN116299716A - Coalbed methane fracturing monitoring method based on microseism well monitoring - Google Patents
Coalbed methane fracturing monitoring method based on microseism well monitoring Download PDFInfo
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 99
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Abstract
The invention discloses a coalbed methane fracturing monitoring method based on microseism well monitoring, which comprises the following steps: s1, preparing a coal bed gas fracturing process; s2, preparing a microseism monitoring process; s3, performing fracturing operation; s4, extracting an effective event and establishing a speed model; s5, detecting the microseism event. The invention adopts the method for monitoring the coal seam gas pressure cracks based on the monitoring in the microseism well, and aims to provide a complete, efficient and high-yield method for monitoring the coal seam gas pressure cracks based on the monitoring in the microseism well.
Description
Technical Field
The invention relates to the technical field of coalbed methane exploration and development, in particular to a coalbed methane fracturing monitoring method based on microseism well monitoring.
Background
Coal bed gas is a gas resource associated with coal, refers to hydrocarbon gas stored in a coal bed, takes methane as a main component, and belongs to unconventional natural gas. The coalbed methane is hydrocarbon gas which is mainly adsorbed on the surface of coal-based particles, partially dissociated in coal pores or dissolved in the coalbed water, is associated mineral resources of coal, and is a clean and high-quality energy and chemical raw material which are newly grown internationally. China has abundant coalbed methane resources, wherein the amount of the resources which are proved to be shallow at 2000m is 30.5 trillion m 3 . However, the geological conditions of China are complex, the exploration and development difficulties are high, only unilateral experience abroad is absorbed, and the method cannot be completely suitable for the coal bed gas monitoring condition of China.
The coal bed gas is developed by fracturing firstly, so that a netlike crack is formed in a low reservoir, and the yield of the coal bed gas is increased. Currently, imaging of fractures formed by fracturing through microseism monitoring technology has a very positive effect on guiding coalbed methane exploitation. The general microseism monitoring methods are divided into two types, namely well monitoring and surface monitoring. The ground monitoring is low in signal-to-noise ratio compared with the underground monitoring, the composition is more complex due to the ground interference, the noise processing difficulty is higher, the reliability is low, and the ground monitoring system is convenient to use only in specific areas. The monitoring in the well is characterized in that a multi-component detector is arranged in a monitoring well adjacent to a fracturing well, earthquake waves of an earthquake event are detected, noise reduction treatment is carried out on the detected signals, the signal to noise ratio is larger, the reliability is higher, the position of a seismic source is determined by utilizing a microseism signal processing technology, so that the data of cracks of an underground reserve layer are determined, the monitoring in the well is more widely used than the monitoring in the ground, and the method is more applicable to the current coalbed methane exploitation environment in China.
In addition, the current detector is arranged in the monitoring well, the phenomenon of lower signal to noise ratio exists, and the accuracy of microseism events can be improved by improving the signal to noise ratio, so that the monitoring effect on the coalbed methane is improved. Thus, there is a need for a complete, efficient, and highly accurate method of monitoring the pressure of a coal seam.
Disclosure of Invention
The invention aims to provide a coalbed methane pressure crack monitoring method based on microseism well monitoring, and provides a complete, efficient and high-precision coalbed methane pressure crack monitoring method based on microseism well monitoring.
In order to achieve the above purpose, the invention provides a coalbed methane fracturing monitoring method based on monitoring in a microseism well, which comprises the following steps:
s1, preparation of coal bed gas fracturing process
Collecting original well data in a project area, and determining a test well selection principle; the preparation of fracturing work comprises fracturing equipment, auxiliary devices, fracturing raw materials and fracturing tubular columns;
s2, microseism monitoring process preparation
The microseism monitoring preparation comprises a three-component detector, a microseism data acquisition instrument, power supply equipment and wireless transmission equipment;
s3, fracturing operation
Carrying out fracturing operation by adopting a quick drilling bridge plug staged fracturing technology, combining a quick drilling bridge plug connected by a cable with a perforating gun by hydraulic pumping to a preset position, lifting a multi-stage perforating device to a perforating position for perforation after setting and releasing the bridge plug, lifting the drilling tool to a wellhead, and injecting a large-displacement optical sleeve into the fracturing operation; repeating the step S3 to finish the operation of a plurality of layer segments;
the three-component detector is arranged on one side of the monitoring well close to the fracturing well and is plugged by cement, so that the three-component detector is ensured to be coupled with the bedrock;
s4, effective event extraction and speed model establishment
After fracturing, setting a long-time window and a short-time window by utilizing the principle that the amplitude of a microseism signal is large and the duration is short, and the amplitude of a noise signal is small and the duration is long, respectively calculating the average energy of the long-time window and the short-time window, and rapidly identifying a microseism event by the ratio of the average energy of the long-time window to the average energy of the short-time window;
establishing an initial velocity model by using the collected P-wave data and S-wave data, correcting the direction of the three-component detector by perforation information, correcting the velocity model, and determining the spatial position of the microseism event;
s5, microseism event detection
And (5) spatial spreading, crack depiction and SRV volume calculation of the microseism event are performed through a software system.
Preferably, in step S1, the test well selection principle is: firstly, selecting a fracturing well, and selecting a test well within a 5m range of the fracturing well; if only one monitoring well is arranged around the fracturing well, adopting a single well monitoring mode; if a plurality of monitoring wells are arranged around the fracturing well and the lithology around the fracturing well is not obviously changed, adopting a multi-well monitoring mode.
Preferably, the microseism monitoring process is performed in synchronization with the coalbed methane fracturing process.
Preferably, the fracturing operation process is performed in construction, so that the same-well cross operation is avoided, and meanwhile, the construction operation is not allowed in the range of 1km of the monitoring well.
Preferably, in step S2, the three-component detector has the characteristics that the sampling rate is more than 1000SPS, the lower limit of the collectable vibration level is more than-3, the frequency bandwidth of the collectable signal is 1-150HZ, and the sensitivity is more than 100V/m/S; the resolution of the microseismic data acquisition instrument is 40A/D; the power supply device is used for supplying power to the microseismic data acquisition instrument and the wireless transmission device.
Preferably, in step S2, the setting depth of the three-component detector is the same as the depth of the fracturing target layer.
Preferably, in step S4, the long-time window energy average energy is calculated as follows:
wherein X (i) (i=1, 2,3 … N) represents the data in the long window, and N represents the number of samples in the long window;
the short time window average energy calculation formula is as follows:
wherein Y (i) (i=1, 2,3 … M) represents the data in the long window, and M represents the number of samples in the long window;
preferably, in step S4, if the accuracy requirement on the microseism event is low, the velocity model may be built only by using the P wave data, and the specific method is as follows:
wherein t is 1 ,t 2 …t n Respectively recording the time from the detector to the microseism, t 0 To give rise to vibration moment, v p At p-wave velocity, (x) 1 ,y 1 )(x 2 ,y 2 )(x n ,y n ) The coordinates of the detectors are respectively, and z is the depth of the seismic source;
if the precision requirement on the microseism event is higher, analyzing the P-wave data and the S-wave data, selecting an event with large energy generated during fracturing, automatically picking up the first arrival of the P-wave and the S-wave through filtering treatment, and determining the position of the microseism event by utilizing the polarization information of the P-wave and the time difference of the P-wave and the S-wave in a combined way; the distance between the microseismic source location and the three component detectors is as follows:
wherein x is mq ,y mq ,z mq Coordinates, x, of the positions of the microseismic sources, respectively pn ,y pn ,z pn Coordinates of the three-component detectors respectively;
p-wave and S-wave time differences DeltaT received at detectors mn The calculation is as follows:
ΔT mn ＝d mn /v s -d mn /v p
wherein, vs, vp are the average speeds of S wave and P wave respectively, and after finishing, the speeds are as follows:
therefore, the invention adopts the method for monitoring the coal seam gas pressure crack based on the monitoring in the microseism well, and has the following technical effects:
(1) The invention provides a complete technology process from preparation of a fracturing process, preparation of a microseism detection process to fracturing operation, establishment of a velocity model, detection and calculation of a microseism event, and provides a new technology for monitoring the pressure of coal bed gas fracturing.
(2) According to the invention, the engineering construction time is selected and the construction environment near the engineering is set, so that the influence of external environment noise on the monitoring of the coal seam gas fracture can be further reduced.
(3) The method utilizes the collected hydraulic fracturing microseism data and the underground collected data to jointly invert the position of the underground microseism, thereby obtaining good effects.
(4) The invention provides two different speed model building methods, which can adapt to different working scenes according to different requirements of microseism event precision.
(5) According to the invention, the three-component detector is arranged in one side of the monitoring well close to the fracturing well and is plugged by cement, so that the three-component detector is coupled with the bedrock, the signal-to-noise ratio of the microseism event is improved, and the detection effect of S waves is improved.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a schematic flow chart of a method for monitoring the fracture of coal seam gas based on monitoring in a microseismic well;
FIG. 2 is a schematic illustration of single well monitoring of a method for monitoring the fracture of coal seam gas based on microseismic well monitoring according to the present invention;
FIG. 3 is a schematic diagram of multi-well monitoring of a method for monitoring the pressure of a coal seam based on microseismic in-well monitoring according to the present invention.
Detailed Description
The technical scheme of the invention is further described below through the attached drawings and the embodiments.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art. Such other embodiments are also within the scope of the present invention.
It should also be understood that the above-mentioned embodiments are only for explaining the present invention, the protection scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the protection scope of the present invention by equally replacing or changing the technical scheme and the inventive concept thereof within the scope of the present invention.
Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but are intended to be considered part of the specification where appropriate.
The disclosures of the prior art documents cited in the present specification are incorporated by reference in their entirety into the present invention and are therefore part of the present disclosure.
Example 1
A coalbed methane fracturing monitoring method based on microseism well monitoring comprises the following steps:
preparation of a coalbed methane fracturing Process
Collecting original well data in a project area, and determining a test well selection principle; the preparation of fracturing work comprises fracturing equipment, auxiliary devices, fracturing raw materials and fracturing tubular columns;
the test well selection principle is as follows: firstly, selecting a fracturing well, and selecting a test well within a 5m range of the fracturing well; if only one monitoring well is arranged around the fracturing well, adopting a single well monitoring mode; if a plurality of monitoring wells are arranged around the fracturing well and the lithology around the fracturing well is not obviously changed, adopting a multi-well monitoring mode.
Preparation before pressing: the fracturing equipment, the used dosage instrument, the high-pressure manifold, the fracturing wellhead device and the well repairing equipment have good performance, and the construction design is satisfied;
the technical performance and the number of the fracturing agent, the propping agent, the pretreatment liquid and the additive meet the fracturing design requirement;
selecting a fracturing construction pipe and a well tool according to the design requirement of pressing fracture, calculating the depth of a stuck point, and assembling a fracturing pipe column;
and (5) connecting the ground fracturing flow.
After the preparation work is finished, the fracturing construction is carried out, and the working procedures comprise conventional circulation, pressure test, trial extrusion, fracturing, sand adding, replacement extrusion, shut-in diffusion pressure and the like.
Nitrogen-fixing bacteria may be added during fracturing to increase coalbed methane production.
(II) microseism monitoring Process preparation
The microseism monitoring preparation comprises a three-component detector, a microseism data acquisition instrument, power supply equipment and wireless transmission equipment;
the three-component detector has the following characteristics: the sampling rate is more than 1000SPS, the lower limit of the collectable vibration level is more than-3, the frequency bandwidth of the collectable signal is 1-150HZ, and the sensitivity is more than 100V/m/s;
the resolution of the microseismic data acquisition instrument is 32A/D;
the microseismic data acquisition instrument is connected with a wireless terminal through an Ethernet, and the terminal is connected to a wireless center through a wireless signal;
the power supply device is used for supplying power to the microseismic data acquisition instrument and the wireless transmission device.
The setting depth of the three-component detector is the same as the depth of the fracturing target layer.
(III) fracturing operation
And (3) carrying out fracturing operation by adopting a quick drilling bridge plug staged fracturing technology, taking the quick drilling bridge plug connected by a cable and a perforating gun as a drilling tool by hydraulic pumping to a preset position, lifting a multi-stage perforating device to a perforating position for perforation after setting and releasing the bridge plug, then lifting the drilling tool to a wellhead, and adopting a large-displacement optical sleeve to inject the fracturing operation.
Repeating the step (III) to finish the operation of a plurality of intervals.
The three-component detector is arranged on one side of the monitoring well close to the fracturing well and is plugged by cement, so that the coupling of the three-component detector and bedrock is ensured, the signal-to-noise ratio of microseism events is improved, the detection effect on S waves is improved, and the probability is improved for the simultaneous analysis of P wave and S wave data.
(IV) effective time extraction and speed model establishment
After fracturing, setting a long-time window and a short-time window by utilizing the principle that the amplitude of a microseism signal is large and the duration is short, and the amplitude of a noise signal is small and the duration is long, respectively calculating the average energy of the long-time window and the short-time window, and rapidly identifying a microseism event by the ratio of the average energy of the long-time window to the average energy of the short-time window;
the long window energy average energy is calculated as follows:
wherein X (i) (i=1, 2,3 … N) represents the data in the long window, and N represents the number of samples in the long window;
the short time window average energy calculation formula is as follows:
wherein Y (i) (i=1, 2,3 … M) represents the data in the long window, and M represents the number of samples in the long window;
and establishing an initial velocity model by using the collected P-wave data and S-wave data, correcting the direction of the three-component detector by perforation information, correcting the velocity model, and determining the spatial position of the microseism event.
If the precision requirement on the microseism event is lower, the speed model A can be built only through P wave data, and the specific method is as follows:
wherein t is 1 ,t 2 …t n Respectively recording the time from the detector to the microseism, t 0 To give rise to vibration moment, v p At p-wave velocity, (x) 1 ,y 1 )(x 2 ,y 2 )(x n ,y n ) The coordinates of the detectors are respectively, and z is the depth of the seismic source;
projecting the monitoring result onto the x-y plane, drawing the length and azimuth of crack, and projecting the monitoring result onto r θ On the plane, the length and the height of the crack can be drawn; projecting the monitoring result to z θ On the plane, the propensity for cracking can be mapped.
If the precision requirement on the microseism event is higher, analyzing the P wave data and the S wave data, selecting events with large energy generated during fracturing, automatically picking up first arrivals of the P wave and the S wave through filtering treatment, and establishing a velocity model B by utilizing the polarization information of the P wave, wherein the time difference of the P wave and the S wave is combined to determine the position of the microseism event; the distance between the microseismic source location and the three component detectors is as follows:
wherein x is mq ,y mq ,z mq Coordinates, x, of the positions of the microseismic sources, respectively pn ,y pn ,z pn Coordinates of the three-component detectors respectively;
p-wave and S-wave time differences DeltaT received at detectors mn The calculation is as follows:
ΔT mn ＝d mn /v s -d mn /v p
wherein, vs, vp are the average speeds of S wave and P wave respectively, and after finishing, the speeds are as follows:
only the coordinate positions of the microseism focus are provided, when the number of detectors is more than 3, the positions of the focus can be solved, and the precision is higher through comprehensive solving of P waves and S waves. Meanwhile, the detector is arranged on one side close to the fracturing well and is coupled with the bedrock, so that the signal-to-noise ratio of an actual microseism event is improved, and the detection effect of S waves is improved.
(V) microseismic event detection
And (5) spatial spreading, crack depiction and SRV volume calculation of the microseism event are performed through a software system.
The microseism monitoring process and the coalbed methane fracturing process are synchronously carried out. When the fracturing operation process is under construction, the same-well cross operation is avoided, and meanwhile, the construction operation is not allowed within the 1km range of the monitoring well, so that the background environment noise can be reduced.
Therefore, the method for monitoring the coal seam gas fracture based on the monitoring in the microseism well is adopted, the engineering construction time is selected, and the construction environment nearby the engineering is set, so that the influence of external environment noise on the monitoring of the coal seam gas fracture can be further reduced; the positions of underground micro earthquakes are jointly inverted by utilizing the collected hydraulic fracturing micro earthquake data and underground collected data, so that a good effect is obtained; two different speed model building methods are provided, and different working scenes can be adapted according to different requirements of microseism event precision; according to the invention, the three-component detector is arranged in one side of the monitoring well close to the fracturing well and is plugged by cement, so that the three-component detector is coupled with the bedrock, the signal-to-noise ratio of the microseism event is improved, and the detection effect of S waves is improved.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting it, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that: the technical scheme of the invention can be modified or replaced by the same, and the modified technical scheme cannot deviate from the spirit and scope of the technical scheme of the invention.
Claims (8)
1. A coalbed methane fracturing monitoring method based on microseism well monitoring is characterized in that: the method comprises the following steps:
s1, preparation of coal bed gas fracturing process
Collecting original well data in a project area, and determining a test well selection principle; the preparation of fracturing work comprises fracturing equipment, auxiliary devices, fracturing raw materials and fracturing tubular columns;
s2, microseism monitoring process preparation
The microseism monitoring preparation comprises a three-component detector, a microseism data acquisition instrument, power supply equipment and wireless transmission equipment;
s3, fracturing operation
Carrying out fracturing operation by adopting a quick drilling bridge plug staged fracturing technology, combining a quick drilling bridge plug connected by a cable with a perforating gun by hydraulic pumping to a preset position, lifting a multi-stage perforating device to a perforating position for perforation after setting and releasing the bridge plug, lifting the drilling tool to a wellhead, and injecting a large-displacement optical sleeve into the fracturing operation; repeating the step S3 to finish the operation of a plurality of layer segments;
the three-component detector is arranged on one side of the monitoring well close to the fracturing well and is plugged by cement, so that the three-component detector is ensured to be coupled with the bedrock;
s4, effective event extraction and speed model establishment
After fracturing, setting a long-time window and a short-time window by utilizing the principle that the amplitude of a microseism signal is large and the duration is short, and the amplitude of a noise signal is small and the duration is long, respectively calculating the average energy of the long-time window and the short-time window, and rapidly identifying a microseism event by the ratio of the average energy of the long-time window to the average energy of the short-time window;
establishing an initial velocity model by using the collected P-wave data and S-wave data, correcting the direction of the three-component detector by perforation information, correcting the velocity model, and determining the spatial position of the microseism event;
s5, microseism event detection
And (5) spatial spreading, crack depiction and SRV volume calculation of the microseism event are performed through a software system.
2. The method for monitoring the gas fracture of the coal bed based on the monitoring in the microseism well according to claim 1, wherein the method comprises the following steps of: in step S1, the test well selection principle is as follows: firstly, selecting a fracturing well, and selecting a test well within a 5m range of the fracturing well; if only one monitoring well is arranged around the fracturing well, adopting a single well monitoring mode; if a plurality of monitoring wells are arranged around the fracturing well and the lithology around the fracturing well is not obviously changed, adopting a multi-well monitoring mode.
3. The method for monitoring the gas fracture of the coal bed based on the monitoring in the microseism well according to claim 1, wherein the method comprises the following steps of: the microseism monitoring process and the coalbed methane fracturing process are synchronously carried out.
4. The method for monitoring the gas fracture of the coal bed based on the monitoring in the microseism well according to claim 1, wherein the method comprises the following steps of: when the fracturing operation process is under construction, the cross operation of the same well is avoided, and meanwhile, the construction operation is not allowed within the 1km range of the monitoring well.
5. The method for monitoring the gas fracture of the coal bed based on the monitoring in the microseism well according to claim 1, wherein the method comprises the following steps of: in the step S2, the three-component detector has the characteristics that the sampling rate is more than 1000SPS, the lower limit of the collectable vibration level is more than-3, the frequency bandwidth of the collectable signal is 1-150HZ, and the sensitivity is more than 100V/m/S; the resolution of the microseismic data acquisition instrument is 40A/D; the power supply device is used for supplying power to the microseismic data acquisition instrument and the wireless transmission device.
6. The method for monitoring the gas fracture of the coal bed based on the monitoring in the microseism well according to claim 1, wherein the method comprises the following steps of: in step S2, the setting depth of the three-component detector is the same as the depth of the fracturing target layer.
7. The method for monitoring the gas fracture of the coal bed based on the monitoring in the microseism well according to claim 1, wherein the method comprises the following steps of: in step S4, the long window energy average energy is calculated as follows:
wherein X (i) (i=1, 2,3 … N) represents the data in the long window, and N represents the number of samples in the long window;
the short time window average energy calculation formula is as follows:
wherein Y (i) (i=1, 2,3 … M) represents the data in the long window, and M represents the number of samples in the long window;
8. the method for monitoring the gas fracture of the coal bed based on the monitoring in the microseism well according to claim 1, wherein the method comprises the following steps of: in step S4, if the accuracy requirement on the microseism event is low, the velocity model may be built only by the P-wave data, and the specific method is as follows:
wherein t is 1 ,t 2 …t n Respectively recording the time from the detector to the microseism, t 0 To give rise to vibration moment, v p At p-wave velocity, (x) 1 ,y 1 )(x 2 ,y 2 )(x n ,y n ) The coordinates of the detectors are respectively, and z is the depth of the seismic source;
if the precision requirement on the microseism event is higher, analyzing the P-wave data and the S-wave data, selecting an event with large energy generated during fracturing, automatically picking up the first arrival of the P-wave and the S-wave through filtering treatment, and determining the position of the microseism event by utilizing the polarization information of the P-wave and the time difference of the P-wave and the S-wave in a combined way; the distance between the microseismic source location and the three component detectors is as follows:
wherein x is mq ,y mq ,z mq Coordinates, x, of the positions of the microseismic sources, respectively pn ,y pn ,z pn Coordinates of the three-component detectors respectively;
p-wave and S-wave time differences DeltaT received at detectors mn The calculation is as follows:
ΔT mn ＝d mn /v s -d mn /v p
wherein, vs, vp are the average speeds of S wave and P wave respectively, and after finishing, the speeds are as follows:
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