A single-pole acoustic logging tool and method for drilling

Abstract

This invention provides a logging-while-drilling monopole acoustic logging tool and method. A logging acoustic system is installed on the outer wall of the drill collar. Simultaneously, a smooth wall surface exists between the receiving transducer and the transmitting transducer, without sound-insulating grooves or holes, and without requiring inner wall diameter changes. Drill collar waves and formation P-waves will "couple" at specific frequencies and narrow frequency bands. Waveform excitation of the transmitting transducer is performed at these specific frequencies and frequency bands. The full wave train waveform obtained from the receiving transducer array can be used to extract accurate formation P-wave velocity values ​​using the STC method. This structure is simple, reducing the need for processing sound-insulating grooves and holes on the inner and outer walls of the drill collar, while also enabling accurate calculation of formation P-wave velocity values.

Description

Technical Field

[0001] This invention relates to a logging-while-drilling (LWD) acoustic logging instrument, specifically a logging-while-drilling monopole acoustic logging instrument and method. Background Technology

[0002] Logging while drilling (LOD) is an advanced logging technology that has rapidly developed and matured in recent years based on wireline logging technology and drilling engineering. Since the formation parameters obtained by LOD are those of the newly drilled formation, they are closest to the original state of the formation. This makes it more advantageous than conventional wireline logging for evaluating the oil and gas content of complex formations. It plays an increasingly important role in logging of highly deviated and horizontal wells, loose formations, high-pressure formations, and unconventional oil and gas reservoirs.

[0003] The existing cable-based acoustic logging technology faces challenges due to the harsh environment during drilling, characterized by high temperatures, extreme pressures, and intense vibrations. To ensure the rigidity of the drill collar, it cannot be equipped with numerous grooves for sound insulation, unlike cable logging instruments. Even with excellent sound insulation, the receiving transducer still receives a large amount of direct interference waves due to continuous reflections of the sliding P-waves against the outer wall of the drill collar. This results in low accuracy of the measured formation P-waves, which is highly detrimental to actual formation P-wave measurements. Furthermore, drill collars with numerous sound-insulating grooves require additional processing, and during drilling, a large amount of debris enters the sound-insulating grooves, further reducing logging accuracy. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a drilling monopole acoustic logging tool and method; the invention has a simple structure and does not require drilling sound insulation grooves and holes on the inner and outer walls of the drill collar, thus accurately realizing formation longitudinal wave velocity logging.

[0005] This invention is achieved through the following technical solution:

[0006] A logging-while-drilling monopole acoustic logging tool, characterized in that it includes a drill collar and a logging acoustic system;

[0007] The logging acoustic system includes a transmitting transducer and multiple receiving transducers;

[0008] The receiving transducer and the transmitting transducer are arranged sequentially along the height direction on the side wall of the drill collar;

[0009] The inner and outer walls of the drill collar between the receiving transducer and the transmitting transducer are both smooth arc surfaces, and the inner diameter of the drill collar is constant.

[0010] Furthermore, the logging acoustic system is embedded in the outer wall of the drill collar.

[0011] Furthermore, the logging acoustic system is fixedly sleeved onto the side wall of the drill collar by fastening screws.

[0012] Furthermore, the plurality of receiving transducers are at least five and are arranged in an array at equal intervals from bottom to top.

[0013] Furthermore, the drill collar adopts a hollow, thick-walled tubular structure.

[0014] A method for logging while drilling using acoustic logging tools, characterized by comprising the following steps:

[0015] S1: The transmitting transducer emits pulsed sound waves of a specific frequency and frequency band, and the receiving transducer measures the full wave train waveform of the sound field inside the wellbore.

[0016] S2: The STC algorithm is used to calculate the formation longitudinal wave velocity by measuring the full wave train of the well acoustic wave.

[0017] Furthermore, the center frequency of the specific frequency sound wave emitted by the transmitting transducer is 14.5-15.5 kHz.

[0018] Furthermore, the frequency band of the sound waves emitted by the transmitting transducer is 1.4-1.6kHz.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] This invention provides a logging-while-drilling monopole acoustic logging tool and method. A logging acoustic system is installed on the outer wall of the drill collar. Simultaneously, a smooth wall surface exists between the receiving transducer and the transmitting transducer, without sound-insulating grooves or holes, and without requiring inner wall diameter changes. Drill collar waves and formation P-waves will "couple" at specific frequencies and narrow frequency bands. Waveform excitation of the transmitting transducer is performed at these specific frequencies and frequency bands. The full wave train waveform obtained from the receiving transducer array can be used to extract accurate formation P-wave velocity values ​​using the STC method. This structure is simple, reducing the need for processing sound-insulating grooves and holes on the inner and outer walls of the drill collar, while also enabling accurate calculation of formation P-wave velocity values. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a drilling monopole acoustic logging tool according to a specific embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the full wave train waveform received by conventional monopole broadband acoustic logging (sound source frequency of 15kHz, bandwidth of 4.5kHz) in the existing technology;

[0023] Figure 3 This is a two-dimensional spectrum of the frequency-wavenumber domain of the acoustic field of the monopole acoustic logging while drilling in a specific embodiment of the present invention;

[0024] Figure 4The excitation intensity curves of drill collar mode waves under different formation P-wave velocities are shown in a specific embodiment of the present invention.

[0025] Figure 5 These are formation P-wave excitation intensity curves under different formation P-wave velocities in a specific embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of the full wave train waveform received by narrow-band monopole acoustic logging (sound source frequency of 15kHz, bandwidth of 1.5kHz) in a specific embodiment of the present invention.

[0027] In the diagram: receiving transducer 1, transmitting transducer 2, drill collar 3. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] This invention provides a logging-while-drilling monopole acoustic logging tool, such as... Figure 1 As shown, it includes drill collar 3 and logging acoustic system;

[0032] The logging acoustic system includes a transmitting transducer 2 and multiple receiving transducers 1; the receiving transducers 1 and the transmitting transducers 2 are arranged sequentially along the height direction on the side wall of the drill collar 3;

[0033] The sidewall of the drill collar 3 between the receiving transducer 1 and the transmitting transducer 2 is a smooth arc surface.

[0034] In a preferred embodiment of the present invention, the logging acoustic system is embedded in the outer wall of the drill collar 3; specifically, the logging acoustic system is fixedly sleeved on the side wall of the drill collar 3 by fastening screws; the plurality of receiving transducers 1 are arranged at preset intervals.

[0035] Furthermore, the plurality of receiving transducers 1 are at least three and arranged in an array from bottom to top with equal spacing. There are no particular limitations, as long as they are suitable for logging while drilling. This is to ensure that the receiving transducers 1 can stably receive pulse acoustic waves of specific frequencies and narrow frequencies emitted by the transmitting transducers 2, thereby improving the fault tolerance and the applicability of the device.

[0036] Another preferred embodiment of the present invention is that the drill collar 3 adopts a hollow thick-walled tubular structure; specifically, there are no special requirements for the shape, material and wall thickness of the drill collar 3, as long as it can be used in logging while drilling.

[0037] This invention provides a method for logging while drilling using acoustic logging tools, comprising the following steps:

[0038] S1: Transmitter 2 emits pulsed sound waves of specific and narrow frequencies, and transmitter 2 measures the full wave train waveform of the sound field inside the borehole.

[0039] S2: Using the STC algorithm, i.e., the slowness-time correlation method, the measured full wave train of well acoustic waves is calculated to obtain the formation P-wave velocity.

[0040] Furthermore, the center frequency of the specific frequency emitted by the transmitting transducer 2 is 14.5-15.5kHz, and the center frequency of the narrow band is 1.4-1.6kHz.

[0041] The six full-wave train waveforms received by the existing single-pole acoustic logging receiver transducer during drilling, such as Figure 2 As shown, the sound source frequency at this time is 15kHz, and the bandwidth is relatively wide at 4.5kHz. Each full wave train contains three "wave packet" envelopes, namely the drill collar wave, the pseudo Rayleigh wave mixed with the formation shear wave, and the Stoneley wave. The formation longitudinal wave is "submerged" by the drill collar wave and cannot be seen, so it is impossible to directly, quickly and accurately obtain the formation longitudinal wave velocity.

[0042] This invention discloses a method for logging while drilling using acoustic instruments. Based on the wave frequencies emitted and received by receiving transducer 1 and transmitting transducer 2, it calculates the two-dimensional spectrum of the acoustic field in the frequency-wavenumber domain of the logging-while-drilling monopole acoustic field, such as... Figure 3 As shown;

[0043] In the 14.5-15.5 kHz range, drill collar waves and formation P-waves were "coupled," which can be seen from the excitation intensity spectra of the two waves, such as... Figure 4 The diagram shows the excitation intensity of the drill collar mode wave, and as shown... Figure 5 The excitation intensity spectrum of the P-wave in the formation shown in these two figures also illustrates the increase in excitation intensity in the 12kHz-15kHz range, proving that the two waves are coupled and mixed here.

[0044] Another preferred embodiment provided by the present invention is shown in Table 1, where the relevant parameters of the device are as follows.

[0045] Longitudinal wave velocity (m / s) Shear wave velocity (m / s) <![CDATA[Density (kg / m 3 )]]> Outer radius (m) Fluid inside the drill collar 1500 —— 1000 0.027 Drill collar 5940 3220 7840 0.090 External fluid of drill collar 1500 —— 1000 0.117 strata 4510 2300 2600 ∞

[0046] Table 1 Model Physical Parameters

[0047] Furthermore, taking the parameters in Table 1 above as an example, such as... Figure 6 The formation model shown depicts the full-wave train waveform of the borehole acoustic field at a source center frequency of 15 kHz and a bandwidth of 1.5 kHz. Each receiving transducer receives waveforms with three wave group envelopes: a wave group resulting from the coupling of drill collar waves and formation P-waves, a wave group resulting from the mixing of pseudo Rayleigh waves and formation S-waves, and a Stoneley wave. The phase velocity of the first wave group, extracted using the STC method, is 4510 m / s, equal to the formation P-wave velocity. This means that the method of this invention can directly obtain an accurate value for the formation P-wave velocity.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of a while-drilling acoustic logging instrument, the method is implemented by a while-drilling monopole acoustic logging instrument device, the while-drilling monopole acoustic logging instrument device comprising a drill collar (3) and a logging acoustic system; the logging acoustic system comprising a transmitting transducer (2) and a plurality of receiving transducers (1); the receiving transducers (1) and the transmitting transducer (2) are sequentially arranged in the height direction on the side wall of the drill collar (3); the inner and outer walls of the drill collar (3) between the receiving transducers (1) and the transmitting transducer (2) are smooth curved surfaces, and the inner diameter of the drill collar (3) is constant; the logging acoustic system is inlaid on the outer wall of the drill collar (3); the logging acoustic system is fixed on the side wall of the drill collar (3) by a fastening screw; the drill collar (3) adopts a hollow thick-walled tubular structure; characterized in that the method comprises the following steps: S1: the transmitting transducer (2) emits a pulse acoustic wave of a specific frequency and frequency band, and the receiving transducer (1) measures the full wave train waveform of the acoustic field in the wellbore; S2: using the STC algorithm to calculate the measured well acoustic full wave train to obtain the formation P-wave velocity; the center frequency of the specific frequency acoustic wave emitted by the transmitting transducer (2) is 14.5-15.5 kHz; the frequency band of the acoustic wave emitted by the transmitting transducer (2) is 1.4-1.6 kHz.

2. The method of claim 1, wherein, The plurality of receiving transducers (1) is at least five, and is arranged in an equal interval from bottom to top.

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