Calculation method of maximum depth of casing drilling based on energy method

Abstract

The present invention discloses a method for calculating the maximum depth of casing drilling based on an energy method, which relates to the field of rock and soil drilling engineering. This method can effectively determine the maximum depth of casing drilling with a down-the-hole hammer. This method adopts the material mechanics energy method theory. When the casing is drilled to the maximum depth, all the impact energy is used to overcome the formation friction, and the formation friction is manifested as a change in the strain energy of the casing. Secondly, the energy method theory is used to propose hypothetical conditions for the conversion of impact energy and casing strain energy when the casing is drilled to the maximum depth. Then, the formation friction resistance is determined based on the contact mode and relative motion mode between the formation and the casing. Both strain energy and impact energy are incremental parameters at a certain moment, without considering parameters such as drilling pressure, torque, buoyancy, and casing deadweight. Only inherent parameters such as casing size and material, dynamic friction between the formation and casing, and rated impact energy of the impactor are involved. This method can eliminate interference from other parameters and greatly improve the reliability of the calculation results.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering drilling, and in particular to a method for calculating the maximum depth of pipe drilling based on an energy method. Background Art

[0002] Down-the-hole hammer and casing drilling technology is a construction process widely used in various fields of rock and soil drilling and excavation engineering. It can insert wall casing in real time during the drilling process, maintain the stability of the hole wall, and quickly penetrate complex formations. It has the advantages of high drilling efficiency, safety in the hole, and low construction cost.

[0003] During the process of following the pipe, frictional resistance will be generated between the outer wall of the casing and the formation. As the depth of following the pipe increases, the frictional resistance will continue to increase, and eventually it will be impossible to continue following the pipe. At this time, if the complex formation has been passed through, it can be converted to a conventional drilling process. If the complex formation has not been passed through, it is necessary to optimize the following the pipe process, use double impactors, or segmented construction, or change to a small-diameter following the pipe drill bit to continue following the pipe to overcome the complex formation. However, since the maximum following the pipe depth is difficult to determine, it is not conducive to the overall design of the project.

[0004] Therefore, how to effectively determine the maximum depth of down-the-hole hammer and casing drilling has important guiding significance for the design of drilling projects and the selection of construction equipment, especially in projects such as drilling in deep overburden or ultra-long pipe racks and anchors that need to penetrate thick and complex strata. Summary of the Invention

[0005] The main purpose of the present invention is to provide a method for calculating the maximum depth of casing drilling based on an energy method, aiming to solve the problem of how to effectively determine the maximum depth of casing drilling with a down-the-hole hammer.

[0006] The technical solution proposed by the present invention is:

[0007] A method for calculating the maximum depth of casing drilling based on an energy method is applied to an air hammer casing drilling system; the system includes a casing, a casing shoe, an impactor, and a down-the-hole hammer; the casing shoe is connected to the bottom of the casing, the down-the-hole hammer is disposed in the casing shoe, the hammer head of the down-the-hole hammer extends out of the casing shoe, and the impactor is used to impact the down-the-hole hammer to act on the hammer head to achieve drilling; the method includes:

[0008] Based on the energy method, the calculation formula for the change in strain energy of the casing caused by the work of the impactor is obtained and marked as the first formula. In it, when the down-the-hole hammer drills to the maximum depth with the casing, the impact work of the impactor is completely converted into the strain energy of the elastic deformation of the casing. After the casing is drilled to the maximum depth, when the impactor does not perform impact work, the casing is subjected to the effects of drilling pressure, buoyancy, deadweight, and formation friction, and is in a mechanical equilibrium state. At this time, the formation friction is static friction. When the impactor applies impact work W, the casing is strained by the friction of the formation, and its strain energy increment is ΔV E At this time, the formation friction force is dynamic friction resistance. According to the principle of functional conversion, W and ΔV E equal;

[0009] The side resistance load is obtained according to the lithology of the drilled formation;

[0010] The maximum depth of casing drilling is obtained based on the side drag load and the first formula.

[0011] Preferably, the first formula is:

[0012]

[0013] Where W is the single impact energy of the down-the-hole hammer, which is determined by the mechanical rated performance of the down-the-hole hammer and is expressed in J; ΔV E is the change in strain energy of the casing caused by the work done by the impactor, with the unit being J; the external resistance on the casing string varies with the drilling depth, E is the elastic modulus of the casing; A is the cross-sectional area of ​​the casing; Q(x) is the lateral resistance load on the follower pipe at different drilling depths x in the same formation, and l is the drilling depth of the follower pipe.

[0014] Preferably, obtaining the lateral resistance load according to the lithology of the drilled formation includes:

[0015] The lateral resistance load on the heel pipe is obtained based on soil mechanics, pipe jacking and caisson technical specifications. The calculation formula of the lateral resistance load is as follows:

[0016] Q=u∑q si ·l i (2),

[0017] Where: Q is the side resistance load of the casing; u is the outer wall circumference of the casing; q si is the lateral resistance value of the soil layer in the i-th section to the pipe; l i is the length of the layer where the casing enters the i-th soil section.

[0018] Preferably, the step of obtaining the lateral resistance load according to the lithology of the drilled formation further includes:

[0019] The value of the lateral resistance is determined by field tests combined with other in-situ test results or empirical parameter estimation.

[0020] Preferably, when drilling into the same stratum, the calculation formula for the maximum depth of the pipe drilling obtained based on the side resistance load and the first formula is:

[0021]

[0022] Where, l max The maximum depth of drilling with casing.

[0023] Preferably, the method of obtaining the maximum depth of casing drilling based on the side resistance load and the first formula further includes:

[0024] Get the number of layers n drilled with the casing, and the drilling depth x at the nth layer;

[0025] The strain energy change of the casing caused by the side resistance values ​​of the 1st to n-1th layers is directly obtained.

[0026] Preferably, the method of directly obtaining the casing strain energy change value generated by the lateral resistance values ​​of the 1st to n-1th layers further includes:

[0027] Calculate x based on formula (1) and formula (2);

[0028] Compare the x value with the thickness of the nth layer l n size;

[0029] When x≤l n When , the calculation step ends and the maximum drilling depth is obtained;

[0030] When x≥l n When x is less than the corresponding formation thickness, continue to set the maximum drilling depth to the n+1th formation for calculation.

[0031] The above technical solution can achieve the following beneficial effects:

[0032] The energy-based maximum depth calculation method for casing drilling proposed in the present invention can effectively determine the maximum depth of casing drilling by a down-the-hole hammer; the method adopts the material mechanics energy method theory, proposes a more systematic and comprehensive maximum depth calculation method for casing drilling, and provides a calculation formula for the maximum depth of a single formation and calculation steps for multiple formations, which can provide theoretical support for design and construction; and the method is based on the energy method to calculate the maximum drilling depth: mainly considering the strain energy of the casing and the impact energy of the impactor; and the strain energy and impact energy are both incremental parameters at a certain moment, and are not related to parameters such as drilling pressure, torque, buoyancy, and casing deadweight, but only involve inherent parameters such as casing size and material, dynamic friction between the formation and casing, and rated impact energy of the impactor, which can eliminate interference from other parameters and greatly improve the reliability of the calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0034] Figure 1 This is a flow chart of a first embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention;

[0035] Figure 2 This is a schematic diagram of the influence of wall thickness and impact energy on the maximum drilling depth of the root canal in the eighth embodiment of the energy-based maximum drilling depth calculation method proposed by the present invention. DETAILED DESCRIPTION

[0036] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] The present invention proposes a method for calculating the maximum depth of casing drilling based on an energy method.

[0038] As attached Figure 1 As shown, in a first embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention, the method for calculating the maximum depth of casing drilling based on an energy method is applied to an air hammer casing drilling system; the system includes a casing, a casing shoe, an impactor, and a down-the-hole hammer; the casing shoe is connected to the bottom of the casing, the down-the-hole hammer is disposed in the casing shoe, the hammer head of the down-the-hole hammer extends out of the casing shoe, and the impactor is used to impact the down-the-hole hammer to act on the hammer head to achieve drilling; this embodiment includes the following steps:

[0039] Step S110: Based on the energy method, a calculation formula for the strain energy change value caused by the work of the impactor on the casing is obtained and marked as the first formula, wherein when the down-the-hole hammer drills to the maximum depth with the casing, the impact work of the impactor is completely converted into the strain energy of the elastic deformation of the casing, and when the casing is drilled to the maximum depth, when the impactor does not perform impact work, the casing is subjected to the effects of drilling pressure, buoyancy, deadweight, and formation friction, and is in a mechanical equilibrium state. At this time, the formation friction is static friction. When the impactor applies impact work W, the casing is strained by the friction of the formation, and its strain energy increment is ΔV E At this time, the formation friction force is dynamic friction resistance. According to the principle of functional conversion, W and ΔV E equal.

[0040] Specifically, the energy method is a technique in solid mechanics for calculating component deformation and solving statically indeterminate structures. Specifically, an elastic solid deforms under the action of an external force, causing the point of force application to shift along the direction of the force, thereby generating work. Furthermore, this deformation also stores strain energy. Within the elastic deformation range, the strain energy of the solid is reversible; it is fully released when the external force is removed.

[0041] When solving the impact work, the instantaneous stress and deformation are extremely complex. When the energy method is used to utilize the energy conversion relationship during the impact process, the solution process can be greatly simplified and can be used for force analysis of various structures.

[0042] Step S120: Obtaining the lateral resistance load according to the lithology of the drilled stratum.

[0043] Step S130: obtaining a maximum depth of casing drilling based on the side resistance load and the first formula.

[0044] Specifically, from the structure of the air hammer casing drilling system, it can be seen that during normal casing drilling, the work of the impactor transferred to the hammer head needs to be divided into three parts: ① the work of the hammer head in breaking the rock; ② the work of the casing moving along the borehole; ③ the strain energy of the casing's elastic deformation. The stress on the casing's outer wall and the impact work can be divided into three stages:

[0045] (1) When the borehole is shallow, the outer wall of the casing is subject to less frictional resistance. The combined force of the drilling pressure applied by the down-the-hole hammer and the deadweight of the pipe string is greater than the outer frictional resistance of the pipe wall. There is no need for the impactor to work. The casing can move along the hole wall under the action of drilling pressure and deadweight, and the work of the impactor is all used to break the formation.

[0046] (2) As the depth of the casing increases, the contact area between the casing and the formation increases, resulting in an increase in the frictional resistance of the formation on the outer wall of the casing. When the drilling pressure and deadweight are no longer sufficient to overcome the frictional resistance of the formation on the casing, it is necessary to allocate part of the impact energy to be converted into casing movement work and strain energy, and the impact work is performed at the step between the stabilizer and the pipe shoe to achieve casing drilling.

[0047] (3) When the casing is drilled deeper, the casing cannot overcome the formation friction under the action of drilling pressure, deadweight and impact work. The combined work of the three is completely converted into the strain energy of elastic deformation of the casing through the contact between the stabilizer and the pipe shoe step, reaching a state of equilibrium in mechanics. At this time, the casing movement distance is zero, the hammer head of the down-the-hole hammer cannot break the rock, the work of these two parts is zero, and the potential energy change of the pipe string is also zero, and the depth of the casing drilling reaches the maximum.

[0048] From the above analysis, we know that when the casing is drilled at the maximum depth and the hammer is not performing any impact work, the casing is mainly subjected to three forces: drilling pressure P, deadweight G and formation friction Q, which are in a state of equilibrium. When the hammer exerts an impact to generate work W, the strain energy increment ΔV of the casing is E , from the functional principle, we know that the two are equal, and the strain energy is a function of the formation friction resistance exerted on the casing.

[0049] The advantage of functional transformation analysis is that both strain energy and impact energy are incremental parameters at a specific moment in time. They are unrelated to parameters such as weight on bit, torque, buoyancy, and casing deadweight during the construction process. They only involve casing size and material, the friction between the formation and the casing, and the rated impact energy of the impactor. Casing size and material, and the rated impact energy of the impactor are essential data for construction design, with the focus on determining the friction between the formation and the casing.

[0050] From the above analysis, we can see that when using the energy method to calculate casing drilling, the following conditions must be met:

[0051] (1) There is no attenuation during the transfer of the impactor's work, and all of it is converted into strain energy;

[0052] (2) The outer wall of the casing is in uniform contact with the formation;

[0053] (3) The casing string is uniform inside and outside;

[0054] (4) The pipe string is within the range of linear elastic deformation.

[0055] The energy-based maximum depth calculation method for casing drilling proposed in the present invention can effectively determine the maximum depth of casing drilling by a down-the-hole hammer; the method adopts the material mechanics energy method theory, proposes a more systematic and comprehensive maximum depth calculation method for casing drilling, and provides a calculation formula for the maximum depth of a single formation and calculation steps for multiple formations, which can provide theoretical support for design and construction; and the method is based on the energy method to calculate the maximum drilling depth: mainly considering the strain energy of the casing and the impact energy of the impactor; and the strain energy and impact energy are both incremental parameters at a certain moment, and are not related to parameters such as drilling pressure, torque, buoyancy, and casing deadweight, but only involve inherent parameters such as casing size and material, dynamic friction between the formation and casing, and rated impact energy of the impactor, which can eliminate interference from other parameters and greatly improve the reliability of the calculation results.

[0056] In addition, the present invention combines the mature empirical parameter method of caisson and jacking pipe construction in foundation engineering, proposes the basis and method for determining the value of the friction resistance between the casing and the formation when drilling with the pipe in the corresponding formation, and puts forward opinions and suggestions on the value of the friction resistance of soft formations and boulder and blocky formations, which can be used as a reference.

[0057] In a second embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention, based on the first embodiment, the first formula is:

[0058]

[0059] Where W is the single impact energy of the down-the-hole hammer, which is determined by the mechanical rated performance of the down-the-hole hammer and is expressed in J; ΔV E is the change in strain energy of the casing caused by the work done by the impactor, with the unit being J; the external resistance on the casing string varies with the drilling depth, E is the elastic modulus of the casing; A is the cross-sectional area of ​​the casing; Q(x) is the side resistance load on the casing at different drilling depths x in the same formation, and l is the drilling depth of the casing.

[0060] In a third embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention, based on the second embodiment, step S120 includes the following steps:

[0061] Step S310: Obtain the lateral resistance load on the pipe based on soil mechanics, pipe jacking, and caisson technical specifications. The calculation formula for the lateral resistance load is as follows:

[0062] Q=u∑q si ·l i (2),

[0063] Where: Q is the side resistance load of the casing; u is the outer wall circumference of the casing; q si is the lateral resistance value of the soil layer in the i-th section to the pipe; l iis the length of the layer where the casing enters the i-th soil section.

[0064] In a fourth embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention, based on the second embodiment, step S120 further includes the following steps:

[0065] Step S410: The lateral resistance value is determined by field testing combined with other in-situ test results or empirical parameter estimation.

[0066] In a fifth embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention, based on the third embodiment, the calculation formula of step S130 is:

[0067]

[0068] Where, l max is the maximum depth of drilling with casing, q s It is the lateral resistance value of the formation to the follower pipe.

[0069] In a sixth embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention, based on the third embodiment, step S130 further includes the following steps:

[0070] Step S610: Obtain the number of strata n drilled with the pipe and the drilling length x in the nth stratum;

[0071] Step S620: directly obtain the casing strain energy change value generated by the lateral resistance values ​​of the 1st to n-1th layers.

[0072] Specifically, when constructing in engineering survey holes and hydrological drilling holes, different strata are generally encountered. At this time, segmented calculations are required to obtain the maximum depth of the pipe drilling.

[0073] In a seventh embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention, based on the sixth embodiment, step S620 further includes the following steps:

[0074] Step S710: Calculate x based on formula (1) and formula (2).

[0075] Step S720: Compare the x value with the thickness of the nth layer l n size.

[0076] Step S730: When x≤l n When , the calculation step ends and the maximum drilling depth is obtained.

[0077] Step S740: When x≥l nWhen x is less than the corresponding formation thickness, continue to set the maximum drilling depth to the n+1th formation for calculation.

[0078] Specifically, combined with the analysis of soil mechanics on the type of soil pressure in the formation, according to the characteristics of the hole-forming process of pipe drilling, the loose formation is affected by the vibration of the impactor and the impact of the down-the-hole hammer on the rock. The soil layer near the bottom of the hole should be unstable. After a small deformation under the action of the effective stress of the formation, the hole wall is completely squeezed against the outer wall of the casing. The casing and the hole wall can be regarded as being in a state of complete contact. The pressure value is a parameter related to the effective stress of the formation, the internal friction angle φ and the cohesion c.

[0079] When drilling into formations with a high clay content, the impact rock-breaking method of a down-the-hole hammer is inefficient. Therefore, water and a foaming agent must be added to the hole to create a foam drilling fluid, which disperses the clay into a slurry for discharge. The clay layer is hydrated by the foam, and combined with the surface tension of the foam, a thick mud jacket forms on the outer wall of the casing, providing lubrication and drag reduction.

[0080] The friction resistance value of the follower tube is determined based on analysis:

[0081] In the relevant technical specifications for pipe jacking and caisson [GB50268, CECS246], the side friction resistance is calculated assuming a complete pipe-soil contact model.

[0082] During casing drilling, the frictional resistance of the surrounding soil on the casing's outer wall increases with drilling depth. The frictional resistance exerted on the casing by the formation is a key factor in calculating the casing drilling depth. Depending on the casing drilling operation, its value should be the dynamic frictional resistance. Soil friction can be divided into dynamic friction and static friction.

[0083] During pipe drilling, the casing and soil move directly relative to each other, similar to the relative movement between the caisson and pipe jacking in foundation engineering. In the design of caisson and pipe jacking construction, the values ​​of ground friction resistance are determined through field testing combined with other in-situ testing results or empirical parameter estimation. This method is supported by extensive data and engineering verification, and has a certain degree of reliability.

[0084] In an eighth embodiment of a method for calculating the maximum depth of casing drilling based on an energy method proposed by the present invention, based on the seventh embodiment, step S410 further includes the following steps:

[0085] Step S910: Obtain a unit lateral resistance relationship table between the outer wall of the pipe and the soil.

[0086] Step S920: Obtain the actual lateral resistance value of the drilled formation to the root canal based on the relationship table.

[0087] Specifically, down-the-hole hammers primarily use impact to crush rock, making them less suitable for drilling in formations with high clay content. Therefore, when drilling into formations containing clay, a treatment process involving the addition of water and a foaming agent through the hole is required to hydrate the clay layer, allowing for drilling deslagging and providing lubrication and drag reduction.

[0088] When drilling with casing, steel pipes are used for casing, and foam drilling is used in soft soil layers, clay, silt and some sandy soil layers. The values ​​are shown in Table 1.

[0089] Table 1 shows the unit friction resistance between the outer wall of the pipe and the soil:

[0090]

[0091]

[0092] Table 1

[0093] Based on the analysis in the previous article, the friction resistance of the steel pipe when drilling into the formation (the unit friction resistance in the table is the lateral resistance value of the formation to the root canal) is shown in Table 1. The friction resistance values ​​when adding water and foaming agent lubrication and using drag-reducing mud when drilling in clay and silt are shown.

[0094] Based on this example, a real case analysis is performed:

[0095] Actual drilling conditions in the case: The horizontal construction of a pipe roof in a subway project was carried out in a pebble layer with the largest pebble particle size not less than 200mm, and most of the particles were 20-60mm. Particles with a particle size of more than 20mm accounted for about 70% of the total mass. The filling material was medium-coarse sand with good gradation. The average SPV was 68, indicating a dense state.

[0096] Case 1:

[0097] (1) Single impactor test:

[0098] Through experimental construction, the outer diameter and wall thickness of the casing are φ108mm×5mm and φ133mm×8mm respectively. The φ108 pipe uses an SPM90 impactor and the φ133 pipe uses an SPM110 impactor, and the impact energy is 150J and 180J respectively. In the early stage, a total of 3 φ108 pipes and 2 φ133 pipes were tested, with the pipe depths of 18, 21, 20m and 25, 25.8m respectively.

[0099] The method proposed in this invention is now used to calculate the maximum pipe support and pipe length. s According to Table 2, take the lower value, i.e. 18kPa, and the elastic modulus E is 202GPa, then Q(x) = u·q s x, first calculate the φ108mm pipe roof + SPM90 impactor, and then substitute it into formula (3) to calculate:

[0100]

[0101] Similarly, the calculation of φ133mm pipe roof + SPM110 impactor is: max =22.97m. This is consistent with the actual test depth.

[0102] (2) Double impactor test

[0103] The improved process adopts front-end impact push + rear-end propulsion, that is, impactors are installed at the bottom of the hole and the hole mouth respectively. The test and construction depths both reach more than 48m, and the maximum depth is 50m.

[0104] From theoretical analysis, it can be seen that after the improved process, tensile strain is generated in the lower section of the tubing string in the hole, and compressive strain is generated in the upper section of the tubing string in the hole. There is a neutral point in the middle of the tubing string that generates neither tensile strain nor compressive strain. Therefore, the maximum length above and below the neutral point is calculated to obtain the maximum tubing depth.

[0105] The maximum depths of the impactors and pipes at the bottom and mouth of the hole were calculated separately: using a φ133×8mm pipe support, a formation friction of 18kPa, and a 270J impactor at the bottom hole, the maximum depth was calculated to be 26.30m; the impactor at the mouth hole, with a 180J impactor, had a maximum depth of 22.97m. The sum of the two is 49.27m, which is consistent with the actual drilling depth.

[0106] Case 2

[0107] The survey holes for the pile foundation of a bridge used in a railway project were drilled in boulder and blocky strata. The DHD350R impactor had a single impact energy of 590J. The outer diameter and wall thickness of the casing were φ146mm×8mm. A total of 21 boreholes were constructed on site, with an average casing depth of 15.7m and a maximum of 18.5m. Most of the boreholes were drilled to a depth of 15-18m.

[0108] Using stress wave theory, the earth pressure coefficient and friction coefficient are taken as 0.1 and 0.35 respectively. Taking into account the drilling pressure and deadweight parameters, the maximum depth calculated is 20.8m.

[0109] Using the energy method theory, the parameters are substituted into equation (3). The friction resistance of the rock and loose rock formations is taken as 40 to 60 kPa according to Table 2. The calculated drilling depth range is 14.85 to 19.46 m. ​​Compared with the stress wave method, the calculation results of the energy method are more consistent with the actual drilling depth.

[0110] Deep optimization suggestions for monitoring:

[0111] The energy method is used to calculate the maximum depth of the casing. According to its relevant parameters, the outer diameter of the casing is generally determined by engineering design, and the friction resistance between the formation and the casing is an objective existence. These two factors are basically determined items. The following is a study and analysis of the changes in the casing wall thickness and impact energy that cause the change in the casing depth.

[0112] The size of the casing is φ146mm, the material is seamless steel pipe, the elastic modulus is 202Gpa, the stratum is gravel layer, the average friction resistance is 18kPa, then the influence of wall thickness and impact energy on depth is shown in the attached Figure 2 .

[0113] Depend on Figure 2 It can be seen that increasing the impact energy and casing wall thickness increases the maximum casing depth to a certain extent, but the increase is small. In actual conditions, due to manufacturing process and size limitations, the rated impact energy of the impactor and the casing wall thickness cannot be increased indefinitely. At the same time, as the impact energy increases, stress fatigue damage at the connection between the pipe shoe and the casing will be exacerbated.

[0114] Therefore, during on-site construction, the technologies for increasing the depth of the pipe are: ① Increasing the impact energy and casing wall thickness under safe and economic conditions; ② Deploying multiple impactors in sections to maximize the impact function effect, such as the dual impactor structure of front-end impact + rear-end propulsion, as well as the upper and lower structures.

[0115] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0116] Through the description of the above embodiments, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better embodiment. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for enabling a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present invention.

[0117] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A method for calculating the maximum depth of casing drilling based on an energy method, characterized in that: Applicable to an air hammer and pipe drilling system; the system includes a casing, a pipe shoe, a hammer, and a down-the-hole hammer; the pipe shoe is connected to the bottom of the casing, the down-the-hole hammer is arranged on the pipe shoe, the hammer head of the down-the-hole hammer extends out of the pipe shoe, and the hammer is used to impact the down-the-hole hammer to act on the hammer head to achieve drilling; the method includes: Based on the energy method, the calculation formula for the change in strain energy of the casing caused by the work of the impactor is obtained and marked as the first formula. In it, when the down-the-hole hammer drills to the maximum depth with the casing, the impact work of the impactor is completely converted into the strain energy of the elastic deformation of the casing. After the casing is drilled to the maximum depth, when the impactor does not perform impact work, the casing is subjected to the effects of drilling pressure, buoyancy, deadweight, and formation friction, and is in a mechanical equilibrium state. At this time, the formation friction is static friction. When the impactor applies impact work W, the casing is strained by the friction of the formation, and its strain energy increment is ΔV E At this time, the formation friction force is dynamic friction resistance. According to the principle of functional conversion, W and ΔV E equal; The side resistance load is obtained according to the lithology of the drilled formation; The maximum depth of casing drilling is obtained based on the side drag load and the first formula.

2. The method for calculating the maximum depth of casing drilling based on the energy method according to claim 1, characterized in that: The first formula is: Where W is the single impact energy of the down-the-hole hammer, which is determined by the mechanical rated performance of the down-the-hole hammer and is expressed in J; ΔV E is the change in strain energy of the casing caused by the work done by the impactor, with the unit being J; the external resistance on the casing string varies with the drilling depth, E is the elastic modulus of the casing; A is the cross-sectional area of ​​the casing; Q(x) is the lateral resistance load on the follower pipe at different drilling depths x in the same formation, and l is the drilling depth of the follower pipe.

3. The method for calculating the maximum depth of casing drilling based on the energy method according to claim 2, characterized in that: The lateral resistance load is obtained according to the lithology of the drilled stratum, including: The lateral resistance load on the heel pipe is obtained based on soil mechanics, pipe jacking and caisson technical specifications. The calculation formula of the lateral resistance load is as follows: Q=u∑q si ·l i (2), Where: Q is the side resistance load of the casing; u is the outer wall circumference of the casing; q si is the lateral resistance value of the soil layer in the i-th section to the pipe; l i is the length of the layer where the casing enters the i-th soil section.

4. The method for calculating the maximum depth of casing drilling based on the energy method according to claim 2, characterized in that: The method of obtaining the lateral resistance load according to the lithology of the drilled stratum further includes: The value of the lateral resistance is determined by field tests combined with other in-situ test results or empirical parameter estimation.

5. The method for calculating the maximum depth of casing drilling based on the energy method according to claim 3, characterized in that: When drilling into the same stratum, the maximum depth of the following pipe drilling is calculated based on the side resistance load and the first formula: Where, l max The maximum depth of drilling with pipe.

6. The method for calculating the maximum depth of casing drilling based on the energy method according to claim 3, characterized in that: The method of obtaining the maximum depth of casing drilling based on the side resistance load and the first formula further includes: Get the number of layers n drilled with the casing, and the drilling depth x at the nth layer; The strain energy change of the casing caused by the side resistance values ​​of the 1st to n-1th layers is directly obtained.

7. The method for calculating the maximum depth of casing drilling based on the energy method according to claim 6, characterized in that: The method further includes: directly obtaining the casing strain energy change value generated by the lateral resistance values ​​of the 1st to n-1th layers; and then: Calculate x based on formula (1) and formula (2); Compare the x value with the thickness of the nth layer l n size; When x≤l n When , the calculation step ends and the maximum drilling depth is obtained; When x≥l n When x is less than the corresponding formation thickness, continue to set the maximum drilling depth to the n+1th formation for calculation.

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