CN112487613B - Method and device for determining travel time of stratum wave - Google Patents
Method and device for determining travel time of stratum wave Download PDFInfo
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- CN112487613B CN112487613B CN202011277845.7A CN202011277845A CN112487613B CN 112487613 B CN112487613 B CN 112487613B CN 202011277845 A CN202011277845 A CN 202011277845A CN 112487613 B CN112487613 B CN 112487613B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/12—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
- E21B47/14—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 using acoustic waves
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
Abstract
The patent refers to the field of 'measuring electric variables or magnetic variables'. The method comprises the steps of obtaining a plurality of original acoustic wave single-pole waveforms obtained by measurement while drilling, and determining an array filtering waveform; determining the compressional wave slowness and the shear wave slowness of the formation wave according to the array filtering waveform; according to the longitudinal wave slowness of the stratum wave, the array filtering waveform is subjected to superposition processing to form an actually measured array waveform; calculating a theoretical array waveform according to the array filtering waveform, the longitudinal wave slowness, the transverse wave slowness and set calculation parameters; judging whether a convergence condition is met or not according to the actually measured array waveform and the theoretical array waveform, and if so, extracting the formation longitudinal wave travel time according to the theoretical array waveform; and if not, modifying the stratum density and/or the borehole radius in the calculation parameters, recalculating the theoretical array waveform, and judging whether a convergence condition is met.
Description
Technical Field
The present disclosure relates to, but not limited to, the field of formation evaluation, and in particular, to a method and an apparatus for determining formation wave travel time.
Background
In the field of stratum evaluation, the travel time of the stratum wave extracted from the acoustic logging array acoustic signal has important significance for stratum evaluation, and the stratum wave can be subjected to amplitude or attenuation calculation only when the travel time of the stratum wave is obtained, so that the lithology of the stratum or the properties of pore fluid in rock are evaluated; the travel time of the stratum wave can also be used for radial velocity profile imaging of the stratum, so that the brittleness of the rock is evaluated, and the fracturing operation of the reservoir is guided.
In the cable acoustic logging, the travel time of the stratum wave is easy to calculate, and the travel time is calculated by adopting an energy ratio method or by utilizing the speed of the stratum wave. In the acoustic logging while drilling, the traditional method for calculating the stratum wave travel time by adopting cable acoustic has the problem of low accuracy and is not applicable any more.
Disclosure of Invention
The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.
The embodiment of the disclosure provides a method and a device for determining stratum wave travel time, which are applied to an acoustic logging-while-drilling instrument and remarkably improve the accuracy of calculating the acoustic stratum wave travel time while drilling in the acoustic logging-while-drilling.
The present disclosure provides a method for determining the travel time of a formation wave, which is applied to a logging-while-drilling acoustic logging instrument, comprising,
acquiring a plurality of original while-drilling acoustic monopole waveforms corresponding to a plurality of receivers measured by the acoustic logging-while-drilling instrument at a set measurement depth, and determining an array filtering waveform according to the plurality of original while-drilling acoustic monopole waveforms;
determining the longitudinal wave slowness and the transverse wave slowness of the formation waves according to the array filtering waveform;
according to the longitudinal wave slowness of the formation wave, after the array filtering wave is subjected to superposition processing, an actual measurement array wave is formed;
calculating a theoretical array waveform according to the array filtering waveform, the longitudinal wave slowness, the transverse wave slowness and set calculation parameters; wherein the calculating parameters include: acoustic source distance, fluid sound velocity, formation density, and borehole radius;
judging whether a convergence condition is met or not according to the actually measured array waveform and the theoretical array waveform, and if so, extracting the formation longitudinal wave travel time according to the theoretical array waveform; and if not, modifying the stratum density and/or the borehole radius in the calculation parameters, recalculating the theoretical array waveform, and judging whether a convergence condition is met.
In some exemplary embodiments, the determining an array filtered waveform from the plurality of original acoustic while drilling unipolar waveforms comprises:
setting a drill collar wave band-pass filtering interval according to a drill collar wave sound insulation stop band of the acoustic logging while drilling instrument;
according to the drill collar wave band-pass filtering interval, performing finite impulse response FIR band-pass filtering on the original while-drilling sound wave single-pole waveforms respectively;
and determining the array filtering waveform according to the plurality of filtered waveforms.
In some exemplary embodiments, said determining compressional and shear slownesses of formation waves from said array filtered waveforms comprises:
and determining the longitudinal wave slowness of the stratum wave and the transverse wave slowness of the stratum wave by adopting time-slowness correlation analysis according to the array filtering waveform.
In some exemplary embodiments, the forming a measured array waveform after the superimposing processing of the array filtered waveform according to the compressional slowness of the formation wave includes:
and performing forward and backward superposition processing on each filtered waveform in the array filtering waveforms respectively according to the longitudinal wave slowness of the stratum wave in terms of time to form the actually measured array waveform.
In some exemplary embodiments, the plurality of original sonic while drilling unipolar waveforms includes N original sonic while drilling unipolar waveforms, N being an integer greater than 1;
the forming of the actually measured array waveform by performing forward and backward superposition processing on each filtered waveform in the array filtered waveforms according to the longitudinal wave slowness of the formation wave in time respectively comprises:
for the l filtered waveform, the waveform obtained by adopting forward and backward superposition processing according to the longitudinal wave slowness of the stratum wave is as follows:
wherein z is l Indicating the distance of the ith receiver from the sound source. W n (t) represents the filtered waveform of the nth receiver,
representing a waveform after superposition of an ith receiver, representing longitudinal wave slowness of the stratum wave by a DTC, and filtering an original acoustic wave while drilling monopole waveform received by the ith receiver to obtain an ith filtered waveform; l is each integer greater than or equal to 1 and less than or equal to N;
and determining the actually measured array waveform according to the N waveforms obtained after the superposition processing.
In some exemplary embodiments, said calculating a theoretical array waveform from said array filtered waveform, said compressional slowness, said shear slowness, and set calculation parameters comprises:
and intercepting stratum longitudinal wave signals of a preset period from the array filtering waveform, and calculating the theoretical array receiving waveform by adopting a real-axis integration method according to the longitudinal wave slowness, the transverse wave slowness, the set calculation parameters and the intercepted stratum longitudinal wave signals of the preset period.
In some exemplary embodiments, the determining whether a convergence condition is satisfied according to the measured array waveform and the theoretical array waveform includes:
calculating the root mean square error of the actually measured array waveform and the theoretical array waveform;
if the root mean square error is smaller than a preset error threshold, determining that a convergence condition is met; and if the error is larger than or equal to the preset error threshold value, determining that the convergence condition is not met.
In some exemplary embodiments, said extracting the formation longitudinal travel time from said theoretical array waveform comprises:
and extracting the longitudinal wave travel time of the stratum by adopting an energy ratio method or a threshold value method according to the theoretical array waveform.
The present disclosure also provides a method for determining a formation wave travel time, which is applied to a logging-while-drilling acoustic logging tool, including,
selecting a preset number of measuring depths in the depth range of the well to be measured, and respectively executing the method for determining the stratum wave travel time at each measuring depth to determine the stratum longitudinal wave travel time corresponding to the measuring depth;
and determining the stratum wave travel time curve of the well to be measured according to the stratum longitudinal wave travel time corresponding to all the measurement depths in the depth range of the well to be measured.
The present disclosure also provides an electronic device, including a memory and a processor, where the memory stores a computer program for making formation travel time determination, and the processor is configured to read and run the computer program for making formation travel time determination to execute any one of the above methods for determining formation travel time.
Other aspects will be apparent upon reading and understanding the attached figures and detailed description.
Drawings
FIG. 1 is a schematic diagram of a measurement performed by an acoustic logging while drilling tool in an embodiment of the present disclosure;
FIG. 2 is a flow chart of a method for determining formation travel time in an embodiment of the present disclosure;
FIG. 3 is an example of a forward-backward superposition process for a filtered waveform in an embodiment of the present disclosure;
FIG. 4 is a comparison example of a filtered waveform and a waveform after superposition according to an embodiment of the disclosure;
FIG. 5 is a comparison example of a filtered waveform and a waveform superimposed for the 4 th receiver in the embodiment of the disclosure;
FIG. 6 is a comparison example of a superimposed waveform and a theoretical waveform of a 4 th receiver in an embodiment of the disclosure;
FIG. 7 is a comparison of an original waveform after formation wave enhancement treatment in an embodiment of the disclosure;
FIG. 8 is an example of N receiver waveforms and formation wave travel time curves in an embodiment of the present disclosure;
FIG. 9 is a flow chart of a method for determining formation travel time in another embodiment of the present disclosure;
FIG. 10 is a flow chart of a method for determining formation travel time in another embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.
The following step numbers do not limit a specific execution order, and the execution order of some steps can be adjusted according to specific embodiments.
Example one
The embodiment of the disclosure provides a method for determining stratum wave travel time, which utilizes a while-drilling acoustic logging instrument to measure. The measurement scenario of the acoustic logging-while-drilling tool employed in the embodiments of the present disclosure is shown in fig. 1. The detection part of the acoustic logging-while-drilling instrument goes deep into a well to be measured, and the detection part at least comprises: acoustic transmitters, N receivers (R1-RN).
A method for determining the travel time of a formation wave, the flow of which is shown in fig. 2, comprises,
step 2, determining the compressional wave slowness and the shear wave slowness of the formation wave by adopting a time-slowness correlation analysis method for the array filtering waveform;
step 3, respectively carrying out forward and backward superposition processing on the waveforms of the N receivers according to the longitudinal wave slowness of the stratum wave; the purpose of the superposition processing is to suppress drill collar waves and enhance formation wave signals; respectively superposing the N received waveforms and determining an actually measured array waveform;
step 4, calculating a theoretical array waveform; intercepting a stratum longitudinal wave waveform with a preset period from the filtered waveform in a certain time window; calculating corresponding theoretical waveforms according to the formation compressional wave slowness, the shear wave slowness, the formation density and the borehole radius, and determining a theoretical array waveform according to the N theoretical waveforms; in some exemplary embodiments, the preset period is 2 or 3 periods; in some exemplary embodiments, the formation longitudinal wave waveform of other preset cycles can be intercepted;
step 5, calculating the root mean square error of the theoretical array waveform and the actually measured array waveform in the time window;
step 6, judging whether the root mean square error meets a convergence condition; if yes, executing step 7; if not, modifying the calculation parameters, returning to the step 4, and recalculating the theoretical array waveform; the calculation parameters comprise: formation density or/and wellbore radius. In some exemplary embodiments, the calculation parameters are modified according to a preset modification step or rule.
And 7, extracting the longitudinal wave travel time of the stratum according to the theoretical array waveform.
Step 8, judging whether the acoustic wave single-pole data while drilling at the next depth exist, if so, returning to the step 0, acquiring the acoustic wave single-pole data while drilling at the next depth, and executing the steps 1-7 again; if not, executing step 9;
and 9, acquiring stratum longitudinal wave travel time of all depths of the well to be measured, and determining a stratum wave travel time curve of the well to be measured according to each depth and the corresponding stratum longitudinal wave travel time.
In some exemplary embodiments, step 1 comprises: and performing finite impulse response FIR band-pass filtering on the original while-drilling unipolar waveform to obtain a filtered waveform. The drill collars with different sizes have great difference in sound insulation stop band of drill collar waves. Taking a drill collar with the outer diameter of 6.75 inches as an example, the sound insulation stop band of the drill collar wave is near 8 kHz-15 kHz, so the correspondingly arranged band-pass filtering range is 8 kHz-15 kHz. The corresponding arrangement of the drill collar according to the acoustic logging while drilling tool is not limited to the example.
In some exemplary embodiments, step 2 comprises: and respectively carrying out time-slowness correlation processing on the filtered waveforms to obtain the longitudinal wave slowness DTC and the transverse wave slowness DTS (transverse wave slowness of the hard stratum) of the stratum.
In some exemplary embodiments, step 3 comprises:
in the step 2, although the band-pass filtering processing is adopted, the drill collar wave signals exist in the whole frequency interval, so that the drill collar wave signals still exist in the formation waves. In order to suppress the drill collar waves and enhance the formation wave signals, a forward and backward superposition process is used on the waveforms of the N receivers in time with the formation longitudinal slowness DTC.
And respectively carrying out the following processing on the filtered waveforms of the N receivers:
taking the ith receiver as an example, the method includes: the processing formulas used for the waveforms of the 1 st to l th receivers are:
and the processing formula adopted for the waveforms of the (l + 1) th to the (N) th receivers is as follows:
thus, the waveform after forward and backward superposition for the l-th receiver is:
in the above formula z l Indicating the distance of the ith receiver from the sound source. W n (t) represents the filtered waveform of the nth receiver,
representing the waveform superimposed by the ith receiver.
And determining the actually measured array waveform according to the waveform superposed by the 1-N receivers.
In some exemplary embodiments, step 4 comprises:
intercepting 2 or 3 periods of the stratum longitudinal wave signals as excitation signals of a sound source for the filtered waveforms obtained in the step 2, setting a source distance TR, a well diameter, a fluid sound velocity and a stratum density as well as the stratum longitudinal wave slowness and transverse wave slowness obtained in the step 2, and calculating a theoretical array waveform S (t) by adopting a real-axis integration method; the source distance TR represents the distance of the center of the transmitting transducer (transmitter) from the center of the first receiving transducer (first receiver R1).
In some exemplary embodiments, some numerical methods such as: finite element or finite difference methods compute the theoretical array waveform S (t). The scheme provided by the disclosure is not limited to a specific calculation method, and a person skilled in the art can equivalently substitute and select the calculation method.
In some exemplary embodiments, step 5 comprises:
in the time window, calculating the root mean square error of the theoretical array waveform and the measured array waveform, wherein the calculation formula is as follows:
S l and (t) represents the theoretical waveform corresponding to the calculated I-th receiver.
In some exemplary embodiments, step 6 comprises:
and (5) if the root mean square error in the step (5) is smaller than a preset error threshold value, meeting a convergence condition, performing a step (7), if the root mean square error does not meet the convergence condition, changing the borehole diameter or the formation density, performing a step (4) again until the root mean square error meets the convergence condition, and performing the step (7).
In some exemplary embodiments, step 7 comprises:
and 6, calculating the travel time of the array waveform theoretically calculated in the step 6.
The base line of the waveform in the theoretical array waveform is flat, the starting jump of the arrival point of the longitudinal wave is obvious, and the stratum wave travel time of the current measurement depth can be extracted from the theoretical array waveform by using a conventional energy ratio method or a threshold value method and the like.
In some exemplary embodiments, step 9 comprises:
sequentially executing steps 0-7 aiming at all depth positions of the well to be measured to obtain stratum wave travel time corresponding to all depth positions; namely, the steps 0 to 7 are respectively executed for measuring points with different depths of a preset number in the whole depth range of the well to be measured, and the corresponding stratum wave travel time of each depth is obtained. And drawing a corresponding stratum wave travel time curve according to all the depth positions and the corresponding stratum wave travel times.
Effects of the embodiment
Fig. 3 is a schematic diagram of forward and backward superposition of a filtered waveform (a waveform obtained by filtering an original waveform), in which, taking the l-th receiver as an example, signals received by the 1 st to N-th receivers are respectively superposed with the l-th receiver signal after propagating different distances according to the formation longitudinal wave slowness.
FIG. 4 is a comparison graph of the filtered waveforms and the waveforms after superposition, in which the solid line is the filtered waveform, the dotted line is the waveforms after forward and backward shifting, and in the graph, R1-R8 receiver signals are the results after shifting on the time axis according to different propagation distances with the formation longitudinal wave slowness of 67 μ s/ft, respectively.
Fig. 5 is a comparison between a waveform filtered by the 4 th receiver and a waveform after superposition, wherein a solid line is a filtered waveform signal, and a dotted line is a signal after waveform superposition, it can be seen from the figure that the arrival point of a longitudinal wave is difficult to determine due to the interference of a drill collar wave in the filtered waveform signal, and the arrival point of the longitudinal wave of the formation is easier to determine due to the obvious increase of the amplitude of the longitudinal wave signal of the formation in the signal after waveform superposition. In the figure, longitudinal wave signals of the stratum are in a rectangular window.
Fig. 6 is a comparison between the superposed waveform of the 4 th receiver and the theoretical waveform, in which the solid line is the signal after waveform superposition, and the dotted line is the theoretical calculation signal, it can be seen from the figure that, in the time window of the formation longitudinal wave, the theoretically calculated waveform is well matched with the actually measured waveform, the arrival point of the theoretical waveform is clear, and the waveform baseline is flat.
FIG. 7 is a graph of comparative results of the original waveform calculated by the method of the present disclosure and the formation wave after enhancement treatment. In the figure, the first path is an original unipolar variable density curve while drilling of the first receiver, the second path is a variable density curve after FIR band-pass filtering of the first receiver, the third path is a variable density curve after formation wave enhancement of the first receiver calculated by the method disclosed by the invention, the fourth path is a contrast waveform curve before and after formation wave enhancement of the first receiver, the dotted line is an un-enhanced curve, and the solid line is an enhanced curve. As can be seen from the comparison, by adopting the method provided by the disclosure, the formation wave signal is obviously increased in amplitude, and the signal-to-noise ratio is improved.
FIG. 8 is a filtered variable density curve for N receivers, along with a time-of-flight curve for N receiver formation compressional waves calculated from the theoretical waveforms calculated in this patent. As can be seen from the figure, the travel time curve is well matched with the arrival of the longitudinal wave of the stratum.
It can be seen that the present disclosure provides a method for accurately calculating the travel time of acoustic wave formation while drilling in order to overcome the drawbacks of the prior art. The method utilizes the similarity of array sound waves, and superimposes other receiver signals forwards or backwards by utilizing the slowness of the longitudinal wave of the stratum for different receiver signals, thereby achieving the purpose of suppressing the drill collar waves to enhance the stratum wave signals. Meanwhile, according to the acoustic propagation model of the acoustic wave in the well hole, the array receiving signal is numerically simulated, and compared with the actually measured array signal, relevant parameters are adjusted, so that the root mean square error of the theoretical waveform and the actually measured waveform is minimized, and the travel time information of the stratum wave is accurately acquired. The problem that stratum wave arrival points are difficult to extract due to the interference of environmental noise and drill collar wave noise in the logging-while-drilling environment is solved.
Example two
The embodiment of the present disclosure further provides a method for determining a formation wave travel time, which is applied to a logging while drilling acoustic logging instrument, and a process of the method is shown in fig. 9, and includes:
step 901, acquiring a plurality of original acoustic while drilling unipolar waveforms corresponding to a plurality of receivers measured by the acoustic while drilling logging instrument at a set measurement depth, and determining an array filtering waveform according to the plurality of original acoustic while drilling unipolar waveforms;
step 902, determining the longitudinal wave slowness and the transverse wave slowness of the formation waves according to the array filtering waveform;
903, superposing the array filtering waveform according to the longitudinal wave slowness of the formation wave to form an actually measured array waveform;
step 904, calculating a theoretical array waveform according to the array filtering waveform, the compressional wave slowness, the shear wave slowness and set calculation parameters; wherein the calculating parameters include: acoustic source distance, fluid sound velocity, formation density, and borehole radius;
judging whether a convergence condition is met or not according to the actually measured array waveform and the theoretical array waveform, if so, executing a step 905, and extracting the formation longitudinal wave travel time according to the theoretical array waveform; if not, step 906 is performed to modify the formation density and/or the borehole radius in the calculated parameters, recalculate the theoretical array waveform, and determine whether a convergence condition is satisfied.
In some exemplary embodiments, the determining an array filtered waveform from the plurality of original acoustic while drilling unipolar waveforms in step 901 includes:
setting a drill collar wave band-pass filtering interval according to a drill collar wave sound insulation stop band of the acoustic logging while drilling instrument;
according to the drill collar wave band-pass filtering interval, performing finite impulse response FIR band-pass filtering on the original while-drilling sound wave single-pole waveforms respectively;
and determining the array filtering waveform according to the plurality of filtered waveforms.
In some exemplary embodiments, the drill collar-wave isolation stopbands vary greatly for drill collar-wave sizes. Taking the drill collar with the outer diameter of 6.75in as an example, the sound insulation stop band of the drill collar wave is around 8 kHz-15 kHz, so the correspondingly arranged band-pass filtering range is 8 kHz-15 kHz. The corresponding arrangement of the drill collar of the acoustic logging while drilling tool is not limited to the example.
In some exemplary embodiments, determining compressional and shear slownesses of formation waves from the array filtered waveforms as described in step 902 includes:
and determining the compressional wave slowness of the formation wave and the shear wave slowness of the formation wave by adopting time-slowness correlation analysis according to the array filtering waveform.
In some exemplary embodiments, the forming a measured array waveform by performing the superposition processing on the array filtered waveform according to the compressional slowness of the formation wave in step 903 includes:
and performing forward and backward superposition processing on each filtered waveform in the array filtering waveforms respectively in time according to the longitudinal wave slowness of the formation wave to form the actual measurement array waveform.
In some exemplary embodiments, the plurality of original while-drilling acoustic monopole waveforms comprises N original while-drilling acoustic monopole waveforms, N being an integer greater than 1;
the step of forming the actually measured array waveform by performing forward and backward superposition processing on each filtered waveform in the array filtered waveforms according to the longitudinal wave slowness of the formation wave in terms of time respectively comprises the following steps:
for the l filtered waveform, the waveform obtained by adopting forward and backward superposition processing according to the longitudinal wave slowness of the formation wave is as follows:
wherein z is l Indicating the distance of the ith receiver from the sound source. W n (t) represents the filtered waveform of the nth receiver,
representing a waveform after superposition of an ith receiver, representing longitudinal wave slowness of the stratum wave by a DTC, and filtering an original acoustic wave while drilling monopole waveform received by the ith receiver to obtain an ith filtered waveform; is divided intoEach integer greater than or equal to 1, less than or equal to N, respectively;
and determining the actually measured array waveform according to the N waveforms obtained after the superposition processing.
In some exemplary embodiments, the filtered waveforms of the N receivers are respectively processed as follows:
taking the ith receiver as an example, the method includes: the processing formula adopted for the waveforms of the 1 st to l th receivers is:
and the processing formula adopted for the waveforms of the (l + 1) th to the (N) th receivers is as follows:
thus, the waveform after forward and backward superposition for the l-th receiver is:
in the above formula z l Indicating the distance of the ith receiver from the sound source. W n (t) represents the filtered waveform of the nth receiver,
representing the waveform after the i-th receiver is superimposed.
And determining the actually measured array waveform according to the waveform superposed by the 1-N receivers.
In some exemplary embodiments, the calculating a theoretical array waveform according to the array filtered waveform, the compressional slowness, the shear slowness and the set calculation parameters in step 904 includes:
and intercepting stratum longitudinal wave signals of a preset period from the array filtering waveform, and calculating the theoretical array receiving waveform by adopting a real-axis integration method according to the longitudinal wave slowness, the transverse wave slowness, the set calculation parameters and the intercepted stratum longitudinal wave signals of the preset period.
In some exemplary embodiments, the determining whether a convergence condition is satisfied according to the measured array waveform and the theoretical array waveform includes:
calculating the root mean square error of the actually measured array waveform and the theoretical array waveform;
if the root mean square error is smaller than a preset error threshold, determining that a convergence condition is met; and if the error is larger than or equal to the preset error threshold value, determining that the convergence condition is not met.
In some exemplary embodiments, the root mean square error of the measured array waveform and the theoretical array waveform is calculated according to the following equation:
S l and (t) represents the theoretical waveform corresponding to the calculated I-th receiver.
In some exemplary embodiments, said extracting the formation compressional travel time from said theoretical array waveform in step 905 comprises:
and extracting the longitudinal wave travel time of the stratum by adopting an energy ratio method or a threshold value method according to the theoretical array waveform.
EXAMPLE III
The embodiment of the present disclosure further provides a method for determining a formation wave travel time, which is applied to a logging while drilling acoustic logging instrument, and a flow of the method is shown in fig. 10, where the method includes:
step 101, selecting a preset number of measurement depths within the depth range of a well to be measured, and respectively executing the method for determining the stratum wave travel time at each measurement depth to determine the stratum longitudinal wave travel time corresponding to the measurement depth;
and 102, determining a stratum wave travel time curve of the well to be measured according to stratum longitudinal wave travel times corresponding to all measurement depths in the depth range of the well to be measured.
In some exemplary embodiments, a preset number of measurement depths (depth positions, depth points) are evenly distributed over the depth range of the well to be measured; or distributed according to preset variable depth intervals.
Example four
The embodiment of the present disclosure further provides a device 110 for determining a formation wave travel time, which is applied to an acoustic logging while drilling tool, and includes:
the filtering module 1101 is configured to acquire a plurality of original while-drilling acoustic monopole waveforms corresponding to a plurality of receivers measured by the acoustic logging-while-drilling tool at a set measurement depth, and determine an array filtering waveform according to the plurality of original while-drilling acoustic monopole waveforms;
a slowness determination module 1102 configured to determine compressional slowness and shear slowness of the formation waves according to the array filtered waveforms;
a superposition module 1103 configured to form an actually measured array waveform after performing superposition processing on the array filtering waveform according to the longitudinal wave slowness of the formation wave;
a theoretical waveform determining module 1104 configured to calculate a theoretical array waveform based on the array filtering waveform, the compressional wave slowness, the shear wave slowness, and a set calculation parameter; wherein the calculating parameters include: acoustic source distance, fluid sound velocity, formation density, and borehole radius;
a formation wave travel time determining module 1105 configured to determine whether a convergence condition is satisfied according to the measured array waveform and the theoretical array waveform, and if so, extract a formation longitudinal wave travel time according to the theoretical array waveform; and if not, modifying the formation density and/or the borehole radius in the calculation parameters, returning to the theoretical waveform determining module 1104 to recalculate the theoretical array waveform, and then judging whether a convergence condition is met.
In some exemplary embodiments, the determining means further comprises a curve plotting module 1106;
the curve drawing module 1106 is configured to determine a formation wave travel time curve of the well to be measured according to the formation longitudinal wave travel times of all the preset number of measurement depths within the depth range of the well to be measured.
The disclosed embodiment also provides an electronic device, which includes a memory and a processor, and is characterized in that the memory stores a computer program for determining formation wave travel time, and the processor is configured to read and run the computer program for determining formation wave travel time to execute any one of the above methods for determining formation wave travel time.
The embodiment of the disclosure also provides a storage medium, in which a computer program is stored, where the computer program is configured to execute any one of the above methods for determining formation wave travel time when running.
It will be understood by those of ordinary skill in the art that all or some of the steps of the methods, systems, functional modules/units in the devices disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be performed by several physical components in cooperation. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as is well known to those of ordinary skill in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by a computer. In addition, communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media as known to those skilled in the art.
Claims (10)
1. A method for determining the travel time of stratum waves is applied to a logging-while-drilling acoustic logging instrument and is characterized by comprising the following steps of,
acquiring a plurality of original acoustic monopole waveforms while drilling corresponding to a plurality of receivers measured by the acoustic logging-while-drilling instrument at a set measurement depth, and determining an array filtering waveform according to the plurality of original acoustic monopole waveforms while drilling;
determining the compressional wave slowness and the shear wave slowness of the formation wave according to the array filtering waveform;
according to the longitudinal wave slowness of the formation wave, after the array filtering wave is subjected to superposition processing, an actual measurement array wave is formed;
calculating a theoretical array waveform according to the array filtering waveform, the longitudinal wave slowness, the transverse wave slowness and set calculation parameters; wherein the calculating parameters include: acoustic source distance, fluid sound velocity, formation density, and borehole radius;
judging whether a convergence condition is met or not according to the actually measured array waveform and the theoretical array waveform, and if so, extracting the formation longitudinal wave travel time according to the theoretical array waveform; and if not, modifying the stratum density and/or the borehole radius in the calculation parameters, recalculating the theoretical array waveform, and judging whether a convergence condition is met.
2. The method of claim 1,
determining an array filtering waveform according to the plurality of original acoustic monopole waveforms while drilling, including:
setting a drill collar wave band-pass filtering interval according to a drill collar wave sound insulation stop band of the acoustic logging-while-drilling instrument;
according to the drill collar wave band-pass filtering interval, performing finite impulse response FIR band-pass filtering on the original while-drilling sound wave single-pole waveforms respectively;
and determining the array filtering waveform according to the plurality of filtered waveforms.
3. The method according to claim 1 or 2,
determining compressional wave slowness and shear wave slowness of the formation waves according to the array filtering waveforms, comprising:
and determining the longitudinal wave slowness of the stratum wave and the transverse wave slowness of the stratum wave by adopting time-slowness correlation analysis according to the array filtering waveform.
4. The method according to claim 1 or 2,
and forming an actually measured array waveform after superposing the array filtering waveform according to the longitudinal wave slowness of the stratum wave, wherein the actually measured array waveform comprises the following steps:
and performing forward and backward superposition processing on each filtered waveform in the array filtering waveforms respectively in time according to the longitudinal wave slowness of the formation wave to form the actual measurement array waveform.
5. The method of claim 4,
the original while-drilling acoustic monopole waveforms comprise N original while-drilling acoustic monopole waveforms, wherein N is an integer greater than 1;
the forming of the actually measured array waveform by performing forward and backward superposition processing on each filtered waveform in the array filtered waveforms according to the longitudinal wave slowness of the formation wave in time respectively comprises:
for the l filtered waveform, the waveform obtained by adopting forward and backward superposition processing according to the longitudinal wave slowness of the stratum wave is as follows:
wherein z is l Denotes the distance, W, of the l-th receiver from the sound source n (t) represents the filtered waveform of the nth receiver,
representing a waveform after superposition of an ith receiver, representing longitudinal wave slowness of the stratum wave by a DTC, and filtering an original acoustic wave while drilling monopole waveform received by the ith receiver to obtain an ith filtered waveform; l is each integer greater than or equal to 1 and less than or equal to N;
and determining the actually measured array waveform according to the N waveforms obtained after superposition processing.
6. The method according to claim 1 or 2,
the method for calculating the theoretical array waveform according to the array filtering waveform, the compressional wave slowness, the shear wave slowness and the set calculation parameters comprises the following steps:
and intercepting stratum longitudinal wave signals of a preset period from the array filtering waveform, and calculating the theoretical array receiving waveform by adopting a real-axis integration method according to the longitudinal wave slowness, the transverse wave slowness, the set calculation parameters and the intercepted stratum longitudinal wave signals of the preset period.
7. The method of claim 1,
the judging whether a convergence condition is met according to the actually measured array waveform and the theoretical array waveform comprises the following steps:
calculating the root mean square error of the actually measured array waveform and the theoretical array waveform;
if the root mean square error is smaller than a preset error threshold, determining that a convergence condition is met; and if the error is larger than or equal to the preset error threshold value, determining that the convergence condition is not met.
8. The method of claim 1,
the method for extracting the travel time of the longitudinal wave of the stratum according to the theoretical array waveform comprises the following steps:
and extracting the longitudinal wave travel time of the stratum by adopting an energy ratio method or a threshold value method according to the theoretical array waveform.
9. A method for determining the travel time of stratum waves is applied to a logging-while-drilling acoustic logging instrument and is characterized by comprising the following steps,
selecting a preset number of measurement depths in the depth range of a well to be measured, respectively executing the method in any one of claims 1 to 8 at each measurement depth, and determining the longitudinal wave travel time of the stratum corresponding to the measurement depths;
and determining a stratum wave travel time curve of the well to be measured according to stratum longitudinal wave travel time corresponding to all the measurement depths in the depth range of the well to be measured.
10. An electronic device comprising a memory and a processor, wherein the memory has stored therein a computer program for making formation wave travel time determinations, and the processor is arranged to read and run the computer program for making formation wave travel time determinations to perform the method of any of claims 1 to 9.
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