A sound velocity testing method based on downhole static detection device

Abstract

The present invention discloses a sound velocity testing method based on a downhole static probe device, comprising the following steps: step 1: assembling a drill bit, a drill rod, a probe rod, a sound wave transmitter, two sound wave receivers and a downhole static probe driving mechanism; step 2: during the drilling process, the downhole static probe driving mechanism synchronously drives the probe to move away from the drill rod and drill downward into the target geological layer; step 3: the probe drills into a specified depth and reaches a certain depth layer of the geological layer, and the average longitudinal wave sound velocity of the current depth layer is calculated; step 4: the drill rod is continued to be driven downward to dig the target geological layer, and after the downhole static probe driving mechanism drives the probe to reach the next depth layer, it jumps to execute step 3 until the average longitudinal wave velocity of each layer on all target geological layers is measured. The present invention can measure the change of the sound velocity of the target geological layer layer by layer as the drilling depth increases, improve the sound velocity measurement accuracy of the target geological layer, and avoid the attenuation of the sound wave caused by long-distance propagation.

Description

Technical Field

[0001] The invention relates to the technical field of static penetration testing, in particular to a sound velocity testing method based on an underground static penetration testing device. Background Art

[0002] In the investigation of marine resources, exploration of submarine geological disasters, and testing of physical parameters of submarine rock and soil sediments, marine static penetration, drilling sampling, and indoor testing complement each other, and marine static penetration is the most direct and effective in-situ testing method, occupying a dominant position in marine engineering survey technology. Many countries have listed it as a must-do item for marine engineering survey. In order to achieve refined surveys in marine engineering, static penetration based on in-situ testing is one of the important technical paths. It will be an important growth point for future marine refined surveys and contains broad market space.

[0003] Downhole static penetration sounding (abbreviated as static penetration sounding) is an important in-situ testing technology in marine surveys. Through downhole static penetration sounding, relevant in-situ test parameters can be obtained, including cone tip penetration resistance, side wall friction resistance, lateral stress, thermal conductivity, ground temperature, inclination, seismic waves, resistivity, sound velocity, etc. Among them, the sound velocity detection of the target geological layer (such as sediment layer) is an important test parameter in downhole static penetration sounding. At present, for geological layers such as sediments, most of the sound velocity testing methods used in actual engineering surveys are to insert a sonic wave transmitting probe into the surface of the seabed sediment, and then use the sonic wave receiver installed on the static penetration sounding probe to receive the transmission signal of the sonic wave transmitting probe, and then calculate the average sound velocity of the sediment longitudinal wave based on the distance and propagation time difference between the sonic wave transmitting probe and the sonic wave receiver. For this type of method, the main problems include: First, most of them can only obtain the sound velocity results within about 50cm (centimeter) below the surface of the fixed station on the seabed sediment, and cannot measure continuously downward. Second, the acoustic wave transmitting probe (also known as the acoustic wave transmitting transducer) is usually fixed in the shallow surface layer of the seabed. As the drilling depth increases, the first distance between the acoustic wave transmitting probe and the acoustic wave receiver gradually increases, while the second distance between the two fixed acoustic wave receivers remains unchanged, so that the ratio of the second distance to the first distance continues to decrease. As a result, due to the influence of propagation attenuation, the measured average sound velocity of the longitudinal wave becomes increasingly inaccurate, and the measurement effect continues to deteriorate. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a sound velocity testing method based on a downhole static probe device, which can solve the technical problems described in the background technology.

[0005] The technical solution to achieve the purpose of the present invention is: a sound velocity testing method based on a downhole static probe device, comprising the following steps:

[0006] Step 1: Assemble the drill bit, drill rod, probe rod, sonic wave transmitter, two sonic wave receivers and downhole static probe driving mechanism, the drill bit is installed at the lower end of the drill rod, the drill rod is a columnar structure with a through hole, an annular cavity is arranged on the columnar structure, that is, a closed columnar structure including an annular cavity is arranged on the periphery of the through hole, the sonic wave transmitter is located at one end of the annular cavity close to the probe rod, two sonic waves are installed on the probe rod at intervals, the downhole static probe driving mechanism passes through the through hole and is connected to the probe rod, and the downhole static probe driving mechanism is used to drive the probe rod forward or backward so that the probe rod can penetrate the target geological layer;

[0007] Step 2: After the assembly is completed, the downhole static probe device is sent into the target geological layer on the seabed, and the drill bit penetrates the target geological layer. During the drilling process, the downhole static probe driving mechanism synchronously drives the probe away from the drill pipe and drills downward into the target geological layer;

[0008] Step 3: The probe drills into the specified depth and reaches a certain depth layer of the geological layer, stops the drilling bit and the probe penetration, records the sending time of the sound wave transmitter sending the sound wave signal, the time when the first sound wave receiver and the second sound wave receiver each receive the sound wave signal, and calculates the average longitudinal wave sound velocity V of the current depth layer according to formula ① p :

[0009]

[0010] Wherein, R0 represents the vertical distance from the sound wave transmitter to the probe rod, that is, the straight-line distance between the sound wave transmitter and the projection point of the sound wave transmitter projected onto the axis of the probe rod, d represents the distance from the projection point to the first sound wave receiver, the first sound wave receiver is a sound wave receiver close to the drill bit and the sound wave transmitter, D0 represents the distance between the first sound wave receiver and the second sound wave receiver, dt represents the time difference between the sound wave signal reaching the first sound wave receiver and the second sound wave receiver respectively, the first sound wave receiver and the second sound wave receiver are the two sound wave receivers;

[0011] Step 4: Continue to drive the drill pipe downward to the target geological layer. After the downhole static exploration drive mechanism drives the probe to the next depth layer, jump to execute step 3 until the average longitudinal wave velocity of each layer on all target geological layers is measured.

[0012] Furthermore, the acoustic wave transmitter is fixedly or detachably installed in the annular cavity of the drill rod.

[0013] Further, the interval distance between the first sound wave receiver and the second sound wave receiver is kept fixed.

[0014] Furthermore, the two sound wave receivers are fixed on the probe rod or the two sound wave receivers can move synchronously along the probe rod, and the interval distance between the two sound wave receivers always remains unchanged.

[0015] Further, the drill bit is connected to the drill rod through threads.

[0016] Furthermore, the drill rod is provided with a plurality of acoustic wave transmitters, and the acoustic wave transmitter is installed in the annular cavity of the drill rod closest to the probe rod.

[0017] Furthermore, the probe rod is a cylindrical rod, the drill rod is a cylindrical structure, and the axis of the static probe driving mechanism, the axis of the probe rod and the axis of the drill rod coincide and are located on the same straight line.

[0018] Furthermore, in step 4, when the drill pipe reaches a certain depth, the probe rod is synchronously lowered to the depth along the borehole through which the drill pipe penetrates, and then the pressure in the borehole is increased, and the probe rod is penetrated downward again at a constant speed for a certain distance through the downhole static probe drive mechanism.

[0019] The beneficial effects of the present invention are as follows: the present invention can measure the change in the sound velocity of the target geological layer (sediment layer) layer by layer as the drilling depth increases. When the drill rod reaches a certain depth, the probe rod is synchronously lowered to the depth along the borehole through which the drill rod penetrates, and then the pressure in the borehole is increased, and the probe rod is again penetrated downward at a constant speed for a certain distance through the downhole static probe drive mechanism. Since the sound wave transmitter is located near the drill bit, the sound velocity of the sediment layer between the drill bit and the two sound wave receivers on the probe rod can be measured. And by repeatedly increasing the drilling depth downward, the change in the sound velocity of the sediment can be continuously measured layer by layer. In addition, since the sound wave transmitter is installed at one end of the drill bit close to the probe rod, the distance between the sound wave transmitter and the sound wave receiver is shorter, which can improve the accuracy of the sound velocity measurement of the target geological layer, and avoid the attenuation of the sound wave caused by long-distance propagation, and avoid the problem of poor or even failure of the sound wave measurement effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention;

[0021] Figure 2 It is a schematic diagram of the assembly of the drill rod and the drill bit;

[0022] Figure 3 It is a cross-sectional schematic diagram of the drill pipe;

[0023] Figure 4 It is a schematic diagram of the process of the present invention;

[0024] In the figure, 1-downhole static exploration driving mechanism, 2-drill rod, 3-sonic wave transmitter, 4-drill bit, 5-first acoustic wave receiver, 6-second acoustic wave receiver, 7-probe rod. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0026] like Figure 1-Figure 4 As shown, a sound velocity testing method based on a downhole static sounding device is shown, wherein the downhole static sounding device includes a drill bit 4, a drill rod 2, a sounding rod 7, and a downhole static sounding driving mechanism 1. The drill rod 2 is a columnar structure with a through hole, and the through hole is extended along the axial direction of the drill rod 2. An annular cavity is also provided in the drill rod 2, that is, a closed columnar structure including an annular cavity is provided on the periphery of the through hole, and the lower end of the drill rod 2 is fixedly connected to the drill bit 4, that is, the drill bit 4 is fixedly connected to the lower end of the closed columnar structure, and the drill bit 4 is provided around the through hole. The downhole static exploration driving mechanism 1 passes through the through hole and is fixedly connected to the exploration rod 7, and the downhole static exploration driving mechanism 1 is arranged along the axial direction of the through hole, one end of the exploration rod 7 is located outside or inside the through hole and is fixedly connected to the downhole static exploration driving mechanism 1, and a probe is arranged on the other end of the exploration rod 7 located outside the through hole, and the probe is used to drive the exploration rod 7 into the target geological layer. The downhole static exploration driving mechanism 1 is used to drive the exploration rod 7 forward or backward, that is, to drive the exploration rod 7 to follow the drill bit 4 to move forward in the direction of the target geological layer (such as sediment) or move backward away from the target geological layer, so that the probe on the exploration rod 7 penetrates into the target geological layer.

[0027] An acoustic wave transmitter 3 is installed in the annular cavity of the drill rod 2. The acoustic wave transmitter 3 is fixedly or detachably installed in the annular cavity of the drill rod 2. For example, the acoustic wave transmitter 3 is transversely installed on the side wall of the annular cavity.

[0028] The first sound wave receiver 5 and the second sound wave receiver 6 are arranged on one end of the probe rod 7 away from the through hole, that is, two sound wave receivers are arranged on the other end outside the through hole, and the first sound wave receiver 5 and the second sound wave receiver 6 are arranged at intervals and the interval between them is kept fixed. For example, the two sound wave receivers are fixed on the probe rod 7 or the two sound wave receivers can be moved synchronously along the probe rod 7, but the interval between the two sound wave receivers always remains unchanged.

[0029] The drill bit 4 can be connected to the drill rod 2 by threading. When multiple drill rods 2 are provided and the drill rods 2 are arranged at different heights, only the annular cavity needs to be provided on the lowest drill rod 2, and the other drill rods 2 can maintain a solid structure, and the acoustic wave transmitter 3 is installed in the annular cavity of the lowest drill rod 2. Installing the acoustic wave transmitter 3 in the annular cavity of the lowest drill rod 2 can make it possible to measure the sound velocity change of the target geological layer (such as the sedimentary layer) layer by layer as the drilling depth gradually increases, that is, the penetration depth continues to increase.

[0030] In an optional embodiment, the probe rod 7 is a cylindrical rod, and the line connecting the centers of the circles is the center line (also the axis) of the probe rod 7. The drill rod 2 is also a cylindrical structure, and the downhole static probe driving mechanism 1 passes through the through hole of the drill rod 2, and the axis of the static probe driving mechanism, the axis of the probe rod 7 and the axis of the drill rod 2 coincide and are located on the same straight line.

[0031] The method comprises the following steps:

[0032] Step 1: Assemble the drill bit 4, the drill rod 2, the probe rod 7, the sonic wave transmitter 3, the sonic wave receiver and the downhole static probe driving mechanism 1.

[0033] Step 2: After the assembly is completed, under the action of an external device, the downhole static exploration device is sent into the target geological layer on the seabed, so that the drill bit 4 can drill into the target geological layer, and during the drilling process, the downhole static exploration drive mechanism 1 synchronously drives the probe away from the drill pipe 2 and drills downward into the target geological layer.

[0034] Step 3: The probe drills into the specified depth and reaches a certain depth layer of the geological layer, stops the drill bit 4 and the probe penetration, records the sending time of the sound wave signal sent by the sound wave transmitter 3, the time when the first sound wave receiver 5 and the second sound wave receiver 6 respectively receive the sound wave signal, and calculates the average longitudinal wave sound velocity V of the current depth layer according to formula ① p :

[0035]

[0036] In the formula, reference Figure 1 , R0 represents the vertical distance from the sound wave transmitter 3 to the probe rod 7, that is, the straight-line distance between the sound wave transmitter 3 and the projection point of the sound wave transmitter 3 projected onto the axis of the probe rod 7, d represents the distance from the projection point to the first sound wave receiver 5, the first sound wave receiver 5 is a sound wave receiver close to the drill bit 4 and the sound wave transmitter 3, D0 represents the distance between the first sound wave receiver 5 and the second sound wave receiver 6, and dt represents the time difference between the sound wave signal arriving at the first sound wave receiver 5 and the second sound wave receiver 6 respectively.

[0037] Step 4: Continue to drive the drill rod 2 downward to the target geological layer. After the downhole static exploration drive mechanism 1 drives the probe to the next depth layer, jump to execute step 3 until the average longitudinal wave velocity of each layer on all target geological layers is measured.

[0038] By repeatedly executing step 3 and step 4, the probe can follow the drill bit 4 during excavation to measure the average P-wave velocity of the target geological layer layer by layer under drilling conditions, thereby measuring the average P-wave velocity of each layer.

[0039] The present invention can measure the change of the sound velocity of the target geological layer (sediment layer) layer by layer as the drilling depth increases. When the drill rod 2 reaches a certain depth, the probe rod 7 is synchronously lowered to the depth along the borehole penetrated by the drill rod 2, and then the pressure in the borehole is increased, and the probe rod 7 is again penetrated downward at a certain distance at a uniform speed through the downhole static exploration drive mechanism 1. Because the sound wave transmitter 3 is located near the drill bit 4, the sound velocity of the sediment layer between the drill bit 4 and the two sound wave receivers on the probe rod 7 can be measured. And by repeatedly increasing the drilling depth downward, the change of the sound velocity of the sediment can be continuously measured layer by layer. In addition, since the sound wave transmitter 3 is installed at one end of the drill bit 4 near the probe rod 7, the distance between the sound wave transmitter 3 and the sound wave receiver is shorter, which can improve the accuracy of the sound velocity measurement of the target geological layer, and avoid the attenuation of the sound wave caused by long-distance propagation, and avoid the problem of poor or even failure of the sound wave measurement effect.

[0040] The embodiment disclosed in this specification is only an example of a unilateral feature of the present invention, and the protection scope of the present invention is not limited to this embodiment, and any other functionally equivalent embodiments fall within the protection scope of the present invention. For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A sound velocity testing method based on a downhole static probe device, characterized in that: The steps include: Step 1: Assemble a drill bit, a drill rod, a probe rod, an acoustic wave transmitter, two acoustic wave receivers and a downhole static probe driving mechanism, wherein the drill bit is installed at the lower end of the drill rod, the drill rod is a columnar structure with a through hole, an annular cavity is arranged on the columnar structure, that is, a closed columnar structure including an annular cavity is arranged on the periphery of the through hole, the acoustic wave transmitter is located at one end of the annular cavity close to the probe rod, a first acoustic wave receiver and a second acoustic wave receiver are arranged on one end of the probe rod away from the through hole, the first acoustic wave receiver and the second acoustic wave receiver are arranged at intervals and the interval distance between the two is kept fixed, the downhole static probe driving mechanism passes through the through hole and is connected to the probe rod, and the downhole static probe driving mechanism is used to drive the probe rod forward or backward so that the probe rod can penetrate the target geological layer; Step 2: After the assembly is completed, the downhole static probe device is sent into the target geological layer on the seabed, and the drill bit penetrates the target geological layer. During the drilling process, the downhole static probe driving mechanism synchronously drives the probe away from the drill pipe and drills downward into the target geological layer; Step 3: The probe drills into the specified depth and reaches a certain depth layer of the geological layer, stops the drilling bit and the probe penetration, records the sending time of the sound wave transmitter sending the sound wave signal, the time when the first sound wave receiver and the second sound wave receiver each receive the sound wave signal, and calculates the average longitudinal wave sound velocity Vp of the current depth layer according to formula ①: Wherein, R0 represents the vertical distance from the sound wave transmitter to the probe rod, that is, the straight-line distance between the sound wave transmitter and the projection point of the sound wave transmitter projected onto the axis of the probe rod, d represents the distance from the projection point to the first sound wave receiver, the first sound wave receiver is a sound wave receiver close to the drill bit and the sound wave transmitter, D0 represents the distance between the first sound wave receiver and the second sound wave receiver, dt represents the time difference between the sound wave signal reaching the first sound wave receiver and the second sound wave receiver respectively, the first sound wave receiver and the second sound wave receiver are the two sound wave receivers; Step 4: Continue to drive the drill pipe downward to the target geological layer. After the downhole static exploration drive mechanism drives the probe to the next depth layer, jump to execute step 3 until the average longitudinal wave velocity of each layer on all target geological layers is measured.

2. The sound velocity testing method based on the downhole static detection device according to claim 1 is characterized in that: The sound velocity testing method based on the downhole static detection device is characterized in that the sound wave transmitter is fixedly or detachably installed in the annular cavity of the drill pipe.

3. The sound velocity testing method based on the downhole static detection device according to claim 1 is characterized in that: The two sound wave receivers are fixed on the probe rod or the two sound wave receivers can move synchronously along the probe rod, and the interval distance between the two sound wave receivers always remains unchanged.

4. The sound velocity testing method based on the downhole static detection device according to claim 3 is characterized in that: The drill bit is connected to the drill rod by threads.

5. The sound velocity testing method based on the downhole static detection device according to claim 4 is characterized in that: The drill rods are provided with a plurality of them, and the sound wave transmitter is installed in the annular cavity of the drill rod closest to the probe rod.

6. The method for testing the velocity of sound based on a downhole static probe device according to claim 5, characterized in that: The probe rod is a cylindrical rod, the drill rod is a cylindrical structure, and the axis of the static probe driving mechanism, the axis of the probe rod and the axis of the drill rod coincide and are located on the same straight line.

7. The method for testing the velocity of sound based on a downhole static probe device according to claim 6, characterized in that: In step 4, when the drill pipe reaches a certain depth, the probe rod is synchronously lowered to the depth along the borehole through which the drill pipe penetrates, and then the pressure in the borehole is increased, and the probe rod is penetrated downward again at a constant speed for a certain distance through the downhole static probe drive mechanism.

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