JPH0522798B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a well drilling monitoring method for monitoring the drilling process of a well and collecting underground information. It was made so that it could be done.

(Conventional technology) Conventionally, in the field of underground engineering such as underground energy development, resource development, and civil engineering, a large number of wells have been drilled for various purposes such as underground investigation, exploration, and resource extraction. ing. When drilling such wells, it is extremely important to collect underground information, but this underground information can be collected by observing cuttings, that is, cuttings and cores produced by conventional well drilling, or by various methods that are carried out after drilling. By analyzing these observations and logging results, we can identify geological strata, water veins, fracture zones,
Confirmation of ore deposits and evaluation of excavation processes were carried out.

(Problem to be solved by the invention) However, in any case, conventionally, it has been difficult to immediately obtain underground information regarding the well to be excavated, and it takes a certain amount of time. There were also restrictions on the types of Therefore, when it comes to drilling wells, new technologies for extracting underground information and technologies for online monitoring of underground information and data showing the state of drilling during well drilling are being emphasized, and their development is being promoted. The problem was that it was necessary.

The purpose of the present invention is to solve the above-mentioned conventional problems and to measure the elastic waves generated by the drilling of a well using the so-called acoustic emission (AE) method. , strength of underground rocks, strength of alteration, strength of welding,
The object of the present invention is to provide a method for monitoring well drilling as a technology that can immediately monitor underground information such as veins, cracks, and fracture zones.

(Means for Solving the Problems) The present invention uses an in-well AE measurement device to measure acoustic emission (AE) signals generated during well drilling, and from the measurement results, the well drilling It is designed to know the progress status and underground information, and is similar to the "direction meter" described in the specification of Japanese Patent Application No. 273348-1983, which was developed by the present inventors as an in-well AE measuring device. The above-mentioned AE can be measured by an in-well three-axis AE measurement system using the "vibrator fixing device installed in the well" described in the specification of No. 236442.
Take measurements.

That is, in the well drilling monitoring method of the present invention, a monitoring well having a desired depth is provided in the vicinity of the land where a desired well is to be drilled, and an acoustic probe having a required sensitivity is installed in the monitoring well. By installing an emission measuring device and measuring the acoustic emission signal generated by the vibration accompanying the drilling of the desired well, the drilling process of the desired well can be monitored and underground. The feature is that information is collected immediately.

(Function) Well drilling is the exploration and extraction of oil and natural gas.
It is being carried out in many fields such as geothermal exploration and extraction, geological surveys, resource exploration, civil engineering surveys, civil engineering works, mining, and many other fields.As it is extremely important, international competition for this type of technology is fierce, and many countries are are competing to develop new technology. The present invention relates to basic well technology, which has the potential to significantly reduce the cost required for well drilling, as well as to instantly obtain underground information that could not be collected using conventional technology. The resulting extremely high practicality can be demonstrated.

(Example) The present invention will be described in detail below with reference to the drawings.

As part of the Ministry of Education, Culture, Sports, Science and Technology's special research project, ``Research on the Design of Artificial Crack Surfaces for Deep Crustal Energy Development (Г Project),'' AE measurements accompanying drilling were performed using the in-well AE measurement system developed by the present inventors.
Promising results were obtained, and the present invention was developed based on these results.

By the way, so-called AE measurement, that is, acoustic emission measurement, uses a piezoelectric type, moving coil, etc. The acoustic emission signal is detected and measured using various types of elastic wave sensors such as molds, and the cause of the acoustic emission signal is identified by analyzing the number of occurrences, total energy, signal waveform, frequency spectrum distribution, etc. In particular, the measurement of acoustic emission signals generated by underground vibrations is becoming popular in the technical fields of civil engineering, architecture, resource development, and especially underground energy development. .

An example of a schematic configuration of a well drilling monitoring system according to the method of the present invention using such acoustic emission measurement is schematically shown in FIG. In the schematic configuration shown in the figure, an observation well 3 is drilled near a desired well 2 to be measured, which is being drilled with a drilling rig 1, and an AE sonde 4 is installed at the bottom of the well 2, and an AE sonde 4 is installed at the bottom of the well. AE signals generated by rubbing of the drill collar or drilling pipe in the desired well 2, or bit abnormalities, geological structures, cracks, fracture zones, etc.
AE that occurs in response to veins, rock strength, slippage, etc.
The signal is detected by the AE end 4 in the observation well 3 and measured by the measurement vehicle 5.

Well 2, which is subject to drilling monitoring by measuring such AE signals, is Higashi-Hachimantai field hydraulic fracturing well F.
-1, the depth of the well to be measured at the start of measurement was 312 m, and the depth of the well at the end of drilling, that is, when it was stopped, was 379.25 m. The depth of the kick-off point (KOP), that is, the bending point between the vertical well and the inclined well, is 60 m, and the well is an inclined well drilled by rotary drilling with a maximum offset of 46 m.A casing of 10' was inserted to a depth of 40.34 m. be. This well was excavated by drilling an 8'5/8 tricone bit from 45m to 359m, and from 359m to 359m.
Coring up to 379.25m was done using 101mm HQ bits. The geological strata in the well drilling area are Quaternary strata, and up to a depth of 117m is descitic tuff called the Kanto Mori First Layer, with a depth of 116.7 to 257.5m.
This is the Kanto Mori 2nd layer, which is composed of tuff breccia and andesitic lapilli tuff, and below 257.5 m in depth is descitic welded tuff called Owasegawa tuff. AE measurements using the monitoring method of the present invention were carried out during excavation of the Owasegawa tuff at its deepest point, but the strength of welding in the Owasegawa tuff varies with depth.

The AE measurement in the drilling monitoring of the well mentioned above is
This was carried out using an in-well AE measurement system developed by Tohoku University. This in-well AE measurement system is
The direction and distance of the AE signal source can be determined from the amplitude and phase of the arriving wave by analyzing the X, Y, and Z triaxial data of the arrival direction of the P wave and the arrival time difference between the P wave and the S wave at a single measurement point. A three-axis AE measurement method is used to determine the location of the source and identify the location of the source. The configuration of the AE measurement system is shown in Figure 2.

In the illustrated wellbore AE measurement system, a rig is installed, and the wellbore AE sonde 4 suspended by a multicore armored cable 6 is immersed in the water gushing out in the observation well 3 and lowered to the bottom of the wellbore, as shown in Figure 1. In this way, the AE signal generated from the desired well 2 is detected,
It is led to the measuring vehicle 5 via a multi-core armored cable 6. This in-well AE sonde 4 includes a piezoelectric accelerometer housed in a cylindrical case for detecting acceleration in the three-axis directions of XYZ, and a preamplifier for amplifying the three-axis measurement data. −273348
As described in the specification of the present patent application, an electronic compass in which the direction of a sonde is measured by rotating a Hall effect element driven by a motor; As described in , it consists of a fixed arm that is driven by a DC motor and fixes both the upper and lower ends of the cylindrical case to the inner wall of the well at 120° intervals, and the XYZ three-axis direction detection output signal is transmitted to the multicore. Processing is performed by a ground analysis device inside the measurement vehicle 5 guided through the cable 6.
The piezoelectric accelerometer used as a transducer consists of 12 transducers connected in parallel, divided into three groups, and set in three axes at right angles to each other to capture AE signals. The overall sensitivity of the sonde is
It is 0.316-3.16V/Gal in the frequency range of 7Hz-7KHz.

For ground analysis equipment, in-well AE sonde 4
The AE sonde 4 is fixed to the inner wall of the well by operating the fixed motor drive device 7 that controls the drive motor of the fixed arm provided for
The acceleration detection output signal in the three axes of XYZ obtained by operating the electronic compass within the
The data is led to an automatic data processing device 11 via a main amplifier 10 having an amplification gain of
Ring down counter 20, pen writing recorder 2
It also leads to 1. The results of data processing by the automatic data processing device 11 are sent to the personal computer 12.
via the printer 13 and floppy data diskette 14 for recording and storage,
While observing using the first and second display devices 15 and 16, color-coded recording is performed using the color printer 17.

The measurable frequency band of the AE signal in the in-well AE measurement system with the above-mentioned configuration is the aforementioned 7Hz to 7KHz.
Measurement well 3 located approximately 150m horizontal distance from well -1
AE sonde 4 was fixed near the bottom of the AE-1 well at a depth of 210 m and the necessary measurements were taken.
The observed AE signal was recorded on a video cathedral data recorder 18, and data analysis was performed after the measurement was completed.

As described above, a continuous AE signal was observed as the well was drilled, and an example of the AE signal waveform is shown in FIG. In the figure, waveform Y is the well 2 to be drilled.
The waveform Z is a horizontal component directed in the direction of , and the waveform Z is a vertical component. The amplitude of the AE signal is 0.01~0.4Gal,
Background noise was approximately 0.001 Gal.

Next, the depth of the tricone bit excavation section
Figure 4 shows how the RMS level of the AE signal from 320 to 347 m changes with excavation depth and the state of cutting corresponding to the AE signal.
Furthermore, the manner in which the RMS level of the AE signal changes over time at each depth is sequentially shown in FIG.

As seen in these figures, the signal level of the AE signal changes depending on the depth, and the signal level is particularly high in the section between 332 m and 340 m in depth. Also, the darkened part of the cutting shown in Figure 4 is the part where the degree of welding is strong.
This portion corresponds well to the portion where the AE signal level is high in FIG. 5. On the other hand, it is known that the crushing strength of welded tuff corresponds to the strength of welding. Therefore, it is reasonable that the AE signal level from the strongly welded portion is higher. In addition, near a depth of 328 m, the cutting becomes darker in response to a local increase in the AE signal level, indicating that the tip of the bit has reached the local strongly welded layer. As for the cuttings, the presence of local strongly welded layers is not very evident because cuttings are taken at every 1 m depth. On the other hand, for the AE signal,
The existence and depth of a local strongly welded layer can be known quite clearly.

Now, the vicinity of the 313m depth where the AE signal waveform is shown in the top row of Figure 5 is a weakly welded tuff layer containing andesite gravel, as can be seen from the cutting shown in Figure 4. It can be seen that high-level AE signals corresponding to gravel are observed intermittently. Also, the depth is shown in the second stage of Figure 5.
The AE signal waveform shown in the vicinity of 324 m is a typical example of the AE signal waveform obtained when excavating a tricone bit, and it clearly shows how the underground rock body is gradually broken down by the bit. Furthermore, the AE signal waveform shown near the depth of 346 m in the bottom row of Fig. 5 is an example of the AE signal waveform obtained when excavating a nearly homogeneous layer, and the AE signal waveform shown in the top row near the depth of 313 m. In contrast, the impulsive AE signal waveform does not appear much.

Next, Fig. 6 shows a comparison of the AE signal level from the well being drilled and the drilling rate. The excavation rate has a negative correlation with the strength of the rock body, and is a measure of the strength of the rock body, but as shown in Figure 6,
There is a tendency for the excavation rate to be low in sections with high AE signal levels. However, in wells deeper than 337 m, the bit load is increased to 4t to 5t, which increases both the drilling rate and the AE signal level. Since the excavation rate is measured at every certain excavation length, changes in local rock strength are not reflected in the excavation rate data.

Next, Fig. 7 shows a comparison between the results of conventional electrical logging and sonic logging and the results of AE measurement.
The results of electrical logging and sonic logging have conventionally been used as a guideline for determining the density and presence of cracks in underground rock bodies, but the results shown in the figure indicate that the results of electrical logging at depths of 331 to 345 m. This only suggests that the section is strongly welded and the area shallower than 320m is weakly welded, and it is impossible to obtain data that shows detailed changes in local rock strength as shown by the changes in the AE signal level shown in the figure. It has not been done.

Figure 8 shows the results of AE measurements showing various drilling conditions of the well. The upper part of Figure 8 shows the AE signal waveform representing the state in which the drill collar is rubbing against the pit wall.As can be seen from the figure, the rotation speed of the drilling pipe
A clear repetitive waveform corresponding to 60 rpm is observed. In addition, the middle part of Figure 8 shows the AE signal waveform obtained when jarring, which is a resonance phenomenon of the dug pipe, occurs, and shows that the AE signal level increases abnormally as the jarring occurs. There is. Furthermore, the lower part of FIG. 8 shows an example of the AE signal waveform obtained during re-excavation after the completion of excavation. In general, when drilling a well, after drilling a certain length, the excavated area is re-drilled several times in order to correct minute hole bends that occur during drilling and to dredge the cutting. shows the AE signal waveform that occurs during re-excavation. As shown in the figure, when the excavation ends, the AE
When the signal level drops and each subsequent re-excavation,
The occurrence of an AE signal can be seen, and in the example shown,
Through two re-drillings, the well was corrected and the cutting dredged, etc., and the AE signal level no longer increased. If extreme hole bending, roughening of the pit wall, collapse, etc. occur, clear differences will appear in the AE signal waveform during re-excavation, corresponding to these conditions.

As shown in the above AE measurement results, continuous AE signals can be observed as the well is drilled, and the signal waveform and signal level reflect the underground structure and well drilling conditions. Therefore, it is thought that this can be used to monitor well drilling as described below.

First, changes in the geological formations can be monitored. In the above AE measurement results, the AE signal level changes depending on the strength of rock welding within the same stratum, that is, the strength of the rock, but the AE signal level also changes considerably due to changes in the stratum. You can expect that. Conventionally, changes in the strata have been confirmed by geological engineers visually observing cuttings taken out from inside the well during drilling, but by combining the above-mentioned AE measurement, changes in the strata can be detected immediately and to some extent. Since quantitative data can be obtained, it is expected that confirmation of geological changes will become easier and more reliable. In addition, if a certain amount of data has been accumulated, such as changes in the AE signal level that have occurred at the geological boundary in other wells, such as changes in the AE signal level that have occurred at the geological boundary in other wells, it may be necessary to use only the drilling engineer rather than the well geotechnical engineer. Therefore, it is thought that it will be possible to immediately judge changes in the strata, and its realization is considered to be extremely effective.

Next, AE measurements are expected to be used to detect differences in rock mechanical properties and fracture systems within the same stratum. In other words, in the AE measurement explained above, the strength and weakness of rock welding was detected, but in the same way, alteration and strength of strata can also be determined from the results of AE measurement, and furthermore, the strength and weakness of rock welding can be determined by the strength of rock welding. Since this is directly related to fracture toughness, conventional methods have been used to monitor drilling using mechanical data such as the number of revolutions of the drilling pipe, bit load, and amount of muddy water. It is thought that it may be possible to estimate the fracture toughness of underground rock bodies online. In addition, AE measurement
As can be seen from the data near 328m, it is possible to detect local changes in mechanical properties with high sensitivity, so it is possible to detect veins in the strata, slickensides, minute slips in the strata that do not lead to faults, or fracture zones. It is suitable for use in detecting ruptures in Detection of such fracture systems is extremely important for oil and geothermal development, rock survey, etc. However, in the case of tricone excavation or percution excavation, it is difficult to detect the presence of a fracture system by observing the cuttings obtained during excavation, and in the case of core excavation, the cost is also high. In addition, cracks tend to occur in the core during excavation and core collection, making it difficult to make judgments based on core observation. Therefore, AE measurement can be considered to be extremely effective in detecting fracture systems. Furthermore, the immediacy of AE measurement is particularly effective in cases such as when drilling a heated well, where immediate and appropriate responses are required depending on underground conditions.

Furthermore, as mentioned above with reference to Fig. 8, AE measurement can be used to monitor the drilling process, and one of the targets for monitoring is drilling problems such as rubbing of the trench pipe or drill collar against the pit wall, or defective bits. This is to detect accidents and failures that occur from time to time, and another monitoring target is to judge whether the well completion is good or bad, such as hole bending or collapse, and the extraction of this information is based on the AE obtained by measurement.
Analysis of the RMS signal waveform of the signal is extremely effective.

(Effects of the Invention) As is clear from the above explanation, according to the well drilling monitoring method of the present invention using measurement of AE, that is, acoustic emission, the wells being drilled can be Taking full advantage of the advantages of AE measurement, the
By observing AE signal waveforms and analyzing data, it is possible to immediately monitor the process of well drilling and collect underground information, which has the extraordinary effect of immediately performing appropriate response processing necessary for well drilling. can.

[Brief explanation of drawings]

FIG. 1 is a configuration layout diagram schematically showing an example of the general configuration of a well drilling monitoring system according to the method of the present invention, FIG. 2 is a block diagram showing the configuration of an AE measurement system used in the monitoring method of the present invention, and FIG. The figure is a signal waveform diagram showing an example of the AE signal waveform, Figure 4 is a signal waveform diagram showing an example of how the AE signal level depends on well depth in comparison with the cutting behavior, and Figure 5 is a signal waveform diagram showing the AE signal level at various depths. Figure 6 is a signal waveform diagram showing an example of how the signal level changes over time. Figure 6 is a signal waveform diagram showing an example of the correspondence between AE signal level and well drilling rate. Figure 7 is a diagram showing AE measurement results and conventional electricity.・A line diagram showing examples of correspondence with sonic logging results, and FIG. 8 is a signal waveform diagram showing examples of correspondence between various well drilling conditions and AE signal waveforms. 1...Drilling rig, 2...Monitored well, 3...
Observation well, 4...AE sonde, 5...measurement vehicle, 6...
...Multicore armored cable, 7...Fixed motor drive device, 8...Electronic compass drive device, 9...XY recorder, 10...3 channel main amplifier, 11...Automatic data processing device, 12...Personal computer , 13...Printer, 14...Floppy diskette, 15...Display device, 16...Display device, 17...Color printer, 18...Data recorder, 19...Digital storage oscilloscope, 20...Ring Down counter, 21...pen writing recorder.

Claims (1)

[Claims] 1. A monitoring well with a desired depth is installed near the land where the desired well is to be drilled, and an acoustic emission measuring device with the required sensitivity is placed inside the monitoring well. The method is characterized in that by measuring an acoustic emission signal generated by vibrations caused by the drilling of the desired well using a measuring device, the drilling process of the desired well is immediately monitored and underground information is collected. Well drilling monitoring method.