Geological core drilling method for high ground stress and strong alteration stratum

Abstract

The invention relates to the field of geological drilling, in particular to a geological core drilling method for high ground stress and strong alteration stratum.The geological core drilling method comprises the following steps that (1) coring drilling construction is adopted to penetrate through an alteration stratum; (2) reaming construction is conducted on the alteration stratum; and (3) casing packing is conducted on the alteration stratum. According to the geological core drilling method provided by the invention, a special drilling tool combination is adopted and matched with anti-sloughing flushing fluid with special performance to be used for drilling of high ground stress and strong alteration strata, so that the drilling efficiency is improved, and the construction risk is reduced.

Description

Technical Field

[0001] The invention relates to the field of geological drilling, and in particular to a geological core drilling method for high ground stress and strongly altered strata. Background Art

[0002] With the continuous advancement of the country's new round of strategic actions for mineral exploration breakthroughs, geological prospecting work is gradually expanding to areas with more complex structures, deeper exploration depths, and higher exploration accuracy requirements. In these areas, especially in high-stress and strongly altered strata, prospecting drilling construction faces great challenges. Due to the instability of the hole wall, accidents such as stuck drills, buried drills, and even drill hole scrapping often occur, which seriously hinder the smooth progress of prospecting work.

[0003] Altered strata, as a complex rock mass, are formed by rocks undergoing alteration under the action of hydrothermal fluids. Alteration refers to the process in which the structure, texture and composition of rocks and minerals change under new physical and chemical conditions, generating new mineral combinations. This process is usually accompanied by the removal of certain substances from the original rock and the introduction of new substances, forming a kind of replacement. Alteration not only changes the physical properties of rocks, but also affects their chemical composition. It is a complex geological phenomenon.

[0004] In important mineralization belts, due to strong geological tectonic movements, rock alteration is strong and ground stress is abnormal. It is difficult to carry out geological core drilling in such strata. Taking the Jinchuan copper-nickel polymetallic mining area in Gansu as an example, due to the strong regional tectonic movement, strongly altered strata are commonly encountered in deep prospecting and exploration. These strata are also accompanied by high ground stress, high water sensitivity and high crushability. The use of conventional rope coring and solid-free flushing fluid technology is difficult, drilling construction is difficult, and even scrapping occurs, which seriously restricts the breakthrough of prospecting and exploration.

[0005] There is little research on high geostress and strongly altered strata in the existing technology. Scholars mainly conduct research on single aspects such as highly water-sensitive strata or broken strata. However, strongly altered strata usually have the characteristics of strong water sensitivity, strong fragmentation and high geostress at the same time, which requires higher drilling technology. At present, the technology for drilling in strongly altered strata mainly adjusts the formula of flushing fluid to enhance the anti-collapse inhibition of flushing fluid. For example, the literature (Measures to Improve the Drilling Efficiency of Boreholes in Altered Strata, "Western Exploration Engineering", 2017, 12) conducted research on flushing fluid technology and proposed corresponding formulas to address the problem of low construction efficiency caused by borehole shrinkage and collapse in altered strata. However, this method only considers the aspects of improving the mineralization of flushing fluid and reducing water loss, and does not combine it with drilling technology, so the application effect in actual production is limited. In addition, for strongly altered strata, the process generally adopts multiple up and down sweeping to trim the hole wall, but this method has great construction risks and is prone to drilling accidents such as broken drill rods. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a drilling method suitable for high geostress and strongly altered strata, aiming to improve drilling efficiency, reduce construction risks, and promote breakthroughs in mineral exploration.

[0007] A geological core drilling method for high-stress and strongly altered strata, comprising the following steps:

[0008] (1) Core drilling through altered strata:

[0009] A coring drill assembly without a reamer is used for coring drilling construction, and a first anti-collapse flushing fluid is used during the construction process to complete the coring and drilling work; the coring drill assembly includes a rope coring drill rod, a core tube and a diamond coring drill bit; the performance of the first anti-collapse flushing fluid is as follows:

[0010]

[0011] Since the outer diameter of the reamer is larger than the drill bit, it is easy for the drill to get stuck at the reamer when drilling in altered formations. Removing the reamer can reduce accidents.

[0012] (2) Hole expansion construction in altered strata:

[0013] After the coring drilling construction is completed, the reaming drilling tool assembly is used to carry out the reaming construction, and the second anti-collapse flushing fluid is used in the reaming process; the reaming drilling tool assembly includes a rope coring drill rod and a diamond drill bit with a guide; the diameter of the drill rod and the drill bit of the reaming drilling tool assembly is larger than the diameter of the drill rod and the drill bit of the coring drilling tool assembly;

[0014] The properties of the second anti-collapse flushing fluid are as follows:

[0015]

[0016] The first anti-collapse flushing liquid and the second anti-collapse flushing liquid both include the following components in mass ratio: 3-5% bentonite, 0.1-0.3% soda ash, 0.5-1.2% fluid loss reducer, 0.3-0.8% metal ion polymer coating agent (MMCA), 1-3% hydrolyzed polyacrylonitrile ammonium salt (NH 4 -HPAN), 2-5% low-fluorescence anti-collapse plugging agent (EP-I), 0.03-0.08% sealing agent, 0-30% ultrafine barite powder, and the balance is water; the sealing agent is prepared by water-soluble epoxy resin and diethylenetriamine in a weight ratio of 2:1;

[0017] Among them, the metal ion polymer coating agent MMCA is prepared by mixing a variety of cationic, anionic and non-ionic monomers with composite metal hydroxides in a certain proportion and adopting a vaporization desolventizing instant polymerization method. It is available at Sichuan Xinchuangneng Petroleum Engineering Technology Co., Ltd. or Shandong Yanggu Jiangbei Chemical Co., Ltd.;

[0018] (3) Casing isolation of altered formations

[0019] After the hole expansion construction is completed, the casing is isolated by using the casing drilling tool assembly; the casing drilling tool assembly includes a rope coring drill rod and a thin-walled diamond drill bit.

[0020] In a preferred specific embodiment, the coring drill assembly includes a wireline coring drill rod with a diameter of 71 mm, a core tube with a diameter of 73 mm, and a diamond drill bit with a diameter of 76 mm; the reaming drill assembly includes a wireline coring drill rod with a diameter of 89 mm and a diamond drill bit with a diameter of 96 mm.

[0021] In a preferred specific embodiment, the funnel viscosity, dynamic shear force and static shear force of the second anti-collapse flushing fluid are higher than those of the first anti-collapse flushing fluid; the water loss of the second anti-collapse flushing fluid is lower than that of the first anti-collapse flushing fluid. The advantages of such a setting are: due to the increase in viscosity and shear force of the second flushing fluid, the flushing fluid can reduce the scouring of the hole wall, and improve the anti-collapse wall protection performance of the flushing fluid; secondly, due to the large amount of rock powder generated by the hole expansion construction, the higher dynamic shear force and static shear force can effectively carry the rock powder, and avoid the rapid precipitation of rock powder in the hole to cause drill jamming; lower water loss can reduce the penetration of free water of the flushing fluid into the hole wall, reduce the hydration expansion strength of the hole wall rock, and at the same time form a denser mud skin to ensure the stability of the hole wall.

[0022] In a preferred specific embodiment, the fluid loss reducer in the first anti-collapse flushing liquid and the second anti-collapse flushing liquid is selected from at least one of low-viscosity sodium carboxymethyl cellulose (LV-CMC) and low-viscosity polyanionic cellulose (LV-PAC).

[0023] In a preferred embodiment, the ultrafine barite powder in the first anti-collapse flushing liquid and the second anti-collapse flushing liquid is 800 mesh or finer; the amount of the ultrafine barite powder added is not more than 0.02 g / cm3 per cycle according to the density of the first anti-collapse flushing liquid or the second anti-collapse flushing liquid during drilling. 3 to add it.

[0024] The circulation cycle refers to the process in which the flushing fluid is output from the mud pump, passes through the drill string and the drill bit to the bottom of the hole, and then flows into the annular space between the drill string and the hole wall, and finally returns to the mud pool on the ground. After purification, it is re-injected into the drill pipe by the mud pump, and this complete cycle repeats itself over and over again.

[0025] The commonly used barite mesh size is not less than 400 meshes. The inventors have found in practice that adding barite particles with a mesh size of 800 or more to the anti-collapse flushing fluid of the present invention can be well matched with other ingredients. Under the performance requirements of viscosity, dynamic shear force, etc. required for core drilling construction and hole expansion construction, the suspension of barite is better and the stability of the flushing fluid is improved.

[0026] In a preferred embodiment, the preparation method of the first anti-collapse flushing liquid and the second anti-collapse flushing liquid is as follows:

[0027] (1) Add clean water to the blender;

[0028] (2) Add bentonite and soda ash to clean water in sequence to form a base slurry, stir evenly and let stand for 8 hours to hydrate;

[0029] (3) preparing a sealing agent by mixing water-soluble epoxy resin and diethylenetriamine in a weight ratio of 2:1 for later use;

[0030] (4) adding a fluid loss reducer, a metal ion polymer coating agent, polyacrylonitrile ammonium salt, a low-fluorescence anti-collapse plugging agent, a sealing agent and ultrafine barite powder to the hydrated base slurry in sequence; stirring evenly to obtain;

[0031] Wherein, each ingredient in step (4) needs to be stirred evenly before being added.

[0032] In a preferred embodiment, the coring drill assembly, the reaming drill assembly and the casing drill assembly all include an active drill rod with a diameter of 89 mm. Since the active drill rod is a drill rod installed on the drilling rig and only drives the drill rod in the hole to rotate, its diameter is not changed when encountering a strongly altered formation.

[0033] In a preferred embodiment, the inner diameters of the wireline coring drill rod and the thin-walled diamond drill bit are consistent, and the outer diameter of the thin-walled diamond drill bit is 1 to 3 mm larger than the outer diameter of the wireline coring drill rod.

[0034] Beneficial Effects

[0035] The geological core drilling method provided by the present invention adopts special drilling tool combinations for coring drilling construction and hole expansion construction respectively, and cooperates with anti-collapse flushing fluid with special performance, which is used for drilling in high ground stress and strongly altered strata, improves drilling efficiency and reduces construction risks.

[0036] The geological core drilling method provided by the present invention adopts a special flushing fluid, which has the advantages of low linear expansion, high rolling recovery rate, strong stability, etc. It can significantly inhibit the expansion and hydration dispersion of strongly altered strata, thereby reducing drill sticking accidents caused by hydration shrinkage or collapse. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The expansion curve results of the altered rock in Example 2 when immersed in different flushing fluid media;

[0038] Figure 2 The comparison results of rolling recovery rates of altered rocks immersed in different flushing fluid media in Example 2;

[0039] Figure 3 The experimental results of Example 2 before and after adding the curing agent and different coating agents are compared;

[0040] Figure 4 The following are the comparison results of the application effects of different proportions of the curing agent components in Example 2. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are used to illustrate the present invention, rather than to limit the present invention.

[0042] The drilling tools and materials used in the embodiments of the present invention are all commercially available, wherein bentonite is purchased from Weifang Far East Bentonite Co., Ltd.; soda ash is purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; low-viscosity sodium carboxymethyl cellulose (LV-CMC) and low-viscosity polyanionic cellulose (LC-PAC) are purchased from Chongqing Lihong Fine Chemical Co., Ltd.; water-soluble epoxy resin and diethylenetriamine are purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; metal ion polymer coating agent (MMCA) is purchased from Shandong Yanggu Jiangbei Chemical Co., Ltd.; low-fluorescence anti-collapse plugging agent (EP-1) is purchased from Sichuan Southwest Shida Jinniu Petroleum Technology Co., Ltd.; broad-spectrum wall protective agent is purchased from Yanggu County Longquan Chemical Plant; active drill pipe, rope coring drill pipe, core tube and diamond drill bit are purchased from Zhongdizhuang (Wuxi) Drilling Tools Co., Ltd.

[0043] Example 1 Preparation of anti-collapse flushing liquid

[0044] The anti-collapse flushing solution was prepared according to the formula in Table 1.

[0045] Table 1 Anti-collapse flushing liquid formula

[0046]

[0047]

[0048] Among them, the formula of Experiment 1.2 is the formula recorded in the literature (Measures to Improve the Drilling Efficiency of Boreholes in Altered Zone Formations, "Western Mining Engineering", 2017, 12), and the formula of Experiment 1.3 is a low-solid flushing fluid commonly used in this field.

[0049] The preparation method of experiment 1.1 is as follows:

[0050] 1) Add clean water to the blender;

[0051] 2) Add bentonite and soda ash in the above formula according to the amount of clean water to form a base slurry, stir evenly and let it stand for 8 hours;

[0052] 3) Add fluid loss reducer, metal ion polymer coating agent (MMCA), polyacrylonitrile ammonium salt (NH4-HPAN), low fluorescence anti-collapse plugging agent (EP-I), sealing agent (water-soluble epoxy resin and diethylenetriamine are first prepared in a weight ratio of 2:1) and ultrafine barite powder to the hydrated base slurry in sequence. Stir well to obtain. Each added component should be fully stirred and evenly mixed until there is no "fish eye" or lumps before adding the next component.

[0053] The preparation method of experiment 1.2 is as follows:

[0054] 1) Add clean water to the blender;

[0055] 2) Add bentonite (NV-1) in the above formula according to the amount of clean water to form a base slurry, stir evenly and let it stand for 8 hours;

[0056] 3) Add high temperature resistant modified starch (SHR-1), potassium humate (KHM), hydrolyzed potassium polyacrylonitrile KPAN, sulfonated asphalt (FT), sodium chloride NaCl and modified sulfonated phenolic resin (S-1) to the hydrated base slurry in sequence. Stir evenly to obtain the product. Each added component should be fully stirred evenly, and the next component can be added only after there are no "fish eyes" or lumps.

[0057] The preparation method of experiment 1.3 is as follows:

[0058] 1) Add clean water to the blender;

[0059] 2) Add bentonite (NV-1) in the above formula according to the amount of clean water to form a base slurry, stir evenly and let it stand for 8 hours;

[0060] 3) Add low-viscosity sodium carboxymethyl cellulose (LV-CMC), broad-spectrum wall protector and sulfonated asphalt to the hydrated base slurry in sequence. Stir evenly to obtain the slurry. Each added component should be fully stirred evenly, and the next component can be added only after there are no "fish eyes" or lumps.

[0061] The preparation methods of Experiments 1.4-1.7 are similar to those of Experiment 1.1.

[0062] Example 2 Performance Test of Anti-collapse Flushing Flushing Liquid

[0063] The basic properties of the anti-collapse flushing liquid prepared above were tested using standard funnel viscometer, six-speed rotary viscometer, medium-pressure water loss meter, density meter, pH meter and other methods to test indicators such as funnel viscosity, dynamic shear force, plastic viscosity, static shear force, density, water loss, pH value, etc. The results are shown in Table 2.

[0064] Table 2 Anti-collapse flushing fluid performance

[0065]

[0066] As can be seen from the above table, the flushing fluid formula provided by the present invention has a low water loss, and various rheological parameters can better meet the needs of drilling construction. Furthermore, in order to test the anti-collapse inhibition performance of the flushing fluid formula for strongly altered formations, an NP-01 expansion tester and a GW300-X variable frequency high-temperature roller heating furnace were used to conduct expansion tests and rolling recovery tests on typical strongly altered rocks taken out during drilling construction in the Jinchuan mining area. The specific results are as follows: Figure 1-Figure 4 shown.

[0067] from Figure 1 and Figure 2 It can be seen that the flushing fluid formula provided by the present invention (Experiment 1.1) has a lower linear expansion than the existing flushing fluid formula (Experiment 1.3) and the altered formation flushing fluid formula provided by the existing literature (Experiment 1.2), and at the same time has the highest rolling recovery rate, indicating that the expansion characteristics and hydration dispersibility of the strongly altered formation under the flushing fluid medium conditions of the present invention are weaker, the stability is stronger, and it is less likely to cause hydration shrinkage or collapse to cause drill jamming accidents.

[0068] The flushing liquid formula provided by the present invention contains a special sealing agent, which has the advantage that when added to the flushing liquid, it can utilize the material itself and other polymer treatment agents such as metal ion polymer coating agent (MMCA) in the system to produce catalytic and cross-linking effects, forming a relatively dense polymer film on the rock surface, which can greatly improve the inhibitory property of the flushing liquid. Figure 3 By comparing Experiment 1.1 and Experiment 1.4, it can be seen that the expansion of the same altered rock formation is significantly reduced after adding the curing agent.

[0069] In addition, in order to evaluate the effects of different coating agents, the metal ion polymer coating agent (MMCA) was replaced by other commonly used coating agents such as zwitterionic coating agent FA367 and potassium polyacrylate K-PAM for comparison (the coating agent added in Experiment 1.5 was FA367). Figure 3 From the comparison between Experiment 1.1 and Experiment 1.5, it can be seen that, when other components are the same, the metal ion polymer coating agent (MMCA) provided by the present invention has a lower expansion amount and a better effect.

[0070] The curing agent in the flushing fluid formula provided by the present invention is prepared by first preparing a water-soluble epoxy resin and diethylenetriamine in a weight ratio of 2:1. This component and ratio have a great influence on the wall protection effect of the altered formation. Figure 4 It can be seen that when the curing agent only uses water-soluble epoxy resin (Experiment 1.6) or diethylenetriamine (Experiment 1.7), the inhibition of altered rock formation is poor and the expansion amount is high.

[0071] Example 3 Field Test

[0072] In the underground ZK12-2 drilling construction in the Jinchuan copper-nickel polymetallic mining area in Gansu Province, conventional rope coring drilling technology was used (the drilling tool combination is: Active drill pipe Rope coring drill rod + upper reamer Core tube + lower reamer Diamond drill bit), the flushing fluid used was conventional solid-free flushing fluid (clean water + 0.03-0.05% (mass concentration) polyacrylamide + 0.05-0.1% (mass concentration) plant gum). When drilling to 653 meters, the drilling encountered a strong altered formation, which made drilling difficult. The main manifestations were reduced diameter and stuck drill, pump suffocation, difficulty in lifting and lowering drill tools, large rotation torque, and difficulty in drilling. In the early stage, the flushing fluid formula was optimized for the altered formation, and low-solid mud was used (the formula was: clean water + 5% bentonite + 0.5% low-viscosity sodium carboxymethyl cellulose (LV-CMC) + 2% broad-spectrum wall protective agent + 1.5% sulfonated asphalt), but it still failed to effectively solve the problem.

[0073] For this purpose, the patented technology is used. First, the core drilling construction is carried out: the drill tool in the hole is pulled out, the upper reamer and the lower reamer are removed, and the core drilling tool combination with a smaller diameter is replaced for drilling, forming a " Active drill pipe Rope Coring Drill Pipe Core tube The active drill pipe is a drill pipe installed on the drilling rig, which only drives the drill pipe in the hole to rotate. Therefore, its diameter is not changed when encountering strongly altered formations. Since the outer diameter of the reamer is larger than the drill bit, it is easy to get stuck at the reamer position when drilling in altered formations. Therefore, removing the reamer can avoid accidents to a certain extent.

[0074] Replacing the coring drill bit assembly with a smaller diameter has many advantages: first, it can increase the annular gap in the upper hole section (the gap between the drill string and the hole wall), so that the performance adjustment range of the flushing fluid is larger (it can be adjusted to higher viscosity and higher density of the flushing fluid), and it can be applied to more complex altered formations; second, when using a smaller diameter for construction, even if a drill is stuck or other accidents occur, the original diameter hole expansion and milling accident drill bit can be used to deal with it, reducing the construction risk; third, the weight of the drill string is reduced, which can effectively reduce the load on the drilling rig and avoid insufficient torque or lifting force of the drilling rig when complex accidents occur; in addition, when drilling with a smaller diameter, because the diameter is relatively smaller, the coring effect for strongly altered and broken formations is better, and the core recovery rate is higher.

[0075] While replacing the coring drill, the performance of the anti-collapse flushing fluid of the present invention is adjusted and replaced. The specific performance is shown in Table 3.

[0076] Table 3 Basic properties of core drilling flushing fluid

[0077]

[0078]

[0079] The anti-collapse flushing liquid formula of the present invention achieves the basic performance shown in Table 3. Specifically, the formula is (mass concentration): clean water + 3-5% bentonite + 0.1-0.3% soda ash + 0.5-1.2% fluid loss reducer (low-viscosity sodium carboxymethyl cellulose (LV-CMC) or low-viscosity polyanionic cellulose (LV-PAC)) + 0.3-0.8% metal ion polymer coating agent (MMCA) + 1-3% polyacrylonitrile ammonium salt (NH 4 -HPAN) + 2-5% low-fluorescence anti-collapse plugging agent (EP-I) + 0.05-0.10% sealing agent (prepared by water-soluble epoxy resin and diethylenetriamine in a weight ratio of 2:1) + 0-30% ultra-fine barite powder (800 mesh or finer).

[0080] The preparation method of the anti-collapse flushing liquid includes: 1) adding clean water to a mixer; 2) adding bentonite and soda ash in turn according to the above formula ratio according to the amount of clean water to form a base slurry, stirring evenly and then standing for hydration for 8 hours; 3) adding fluid loss reducer, metal ion polymer coating agent (MMCA), polyacrylonitrile ammonium salt (NH4-HPAN), low fluorescence anti-collapse plugging agent (EP-I), sealing agent and ultrafine barite powder to the hydrated base slurry in turn. Each added component should be fully stirred evenly, and the next component should be added after there is no "fish eye" or block.

[0081] During the construction, the performance of the flushing fluid is monitored at any time, and the amount of components added is adjusted according to the situation in the hole. Among them, the amount of barite added is adjusted according to the degree of diameter reduction caused by the high ground stress formation, and the amount is gradually increased to achieve the effect of gradually increasing the density of the flushing fluid (according to the increase of no more than 0.02g / cm per cycle). 3 to make adjustments).

[0082] By replacing the drilling tool assembly and adopting a new flushing fluid formula, the altered stratum was crossed. However, due to the limited flushing fluid wall protection period and the large amount of drilling work in the lower part, in order to ensure the safety of the later construction, the method of the present invention was used to expand the altered stratum. Specifically, the expansion construction includes the following contents:

[0083] The coring drill with a smaller diameter used in coring drilling construction is replaced with an expansion drill assembly to expand the altered layer. The expansion drill assembly is: Active drill pipe Rope Coring Drill Pipe Diamond drill bit with guide.

[0084] While replacing the reaming drill, the performance of the anti-collapse flushing fluid of the present invention is adjusted and replaced, as shown in Table 4.

[0085] Table 4 Basic properties of flushing fluid for hole expansion drilling

[0086]

[0087] The anti-collapse flushing fluid formula of the present invention is used to achieve the basic performance shown in Table 4. Its specific formula is the same as that of the "coring drilling construction in altered strata", except that the specific addition amount is adaptively changed according to its performance requirements.

[0088] After the hole expansion construction reaches the bottom, the altered formation is sealed with casing. Specifically, the drill is started again, and the casing is replaced with a casing drilling tool assembly to lower the casing for isolation (using the drill pipe as the casing), that is, the active drill pipe + rope coring drill pipe (that is, casing) + thin-walled diamond drill bit (casing shoe). The inner diameter of the casing shoe is consistent with the inner diameter of the drill pipe, and the outer diameter is 1 to 3 mm larger than the outer diameter of the casing. The purpose is to rotate the entire drill string if there is any resistance during the casing installation process, so as to achieve the bottom sweep of the hole and lower the casing to the predetermined position. Finally, the casing is sealed for the altered rock formation.

[0089] After the casing is used to isolate the altered layer, normal drilling is resumed according to the conventional rope coring drilling process.

Claims

1. A geological core drilling method for high-stress and strongly altered strata, characterized in that: The following steps are involved: (1) Core drilling through altered strata: A coring drill assembly without a reamer is used for coring drilling construction, and a first anti-collapse flushing fluid is used during the construction process; the coring drill assembly includes a rope coring drill rod, a core tube and a diamond coring drill bit; the properties of the first anti-collapse flushing fluid are as follows: (2) Hole expansion construction in altered strata: After the coring drilling construction is completed, the hole enlarging construction is carried out by using the hole enlarging drill tool assembly, and the second anti-collapse flushing fluid is used during the hole enlarging process; the hole enlarging drill tool assembly includes a rope coring drill rod and a diamond drill bit with a guide; the diameter of the drill rod and the drill bit of the hole enlarging drill tool assembly is larger than the diameter of the drill rod and the drill bit of the coring drill tool assembly; The performance of the second anti-collapse flushing liquid is as follows: The first anti-collapse flushing liquid and the second anti-collapse flushing liquid both comprise the following components in a mass ratio: 3-5% bentonite, 0.1-0.3% soda ash, 0.5-1.2% fluid loss reducer, 0.3-0.8% metal ion polymer coating agent (MMCA), 1-3% hydrolyzed polyacrylonitrile ammonium salt (NH4-HPAN), 2-5% low-fluorescence anti-collapse plugging agent (EP-I), 0.05-0.10% sealing agent, 0-30% ultrafine barite powder, and the balance is water; the sealing agent is prepared by water-soluble epoxy resin and diethylenetriamine in a weight ratio of 2:1; (3) Casing isolation of altered formations After the hole expansion construction is completed, the casing is isolated by using a casing drilling tool assembly; the casing drilling tool assembly includes a rope coring drill rod and a thin-walled diamond drill bit.

2. The geological core drilling method according to claim 1, characterized in that: The coring drill tool combination includes a rope coring drill rod with a diameter of 71 mm, a core tube with a diameter of 73 mm, and a diamond drill bit with a diameter of 76 mm; the reaming drill tool combination includes a rope coring drill rod with a diameter of 89 mm and a diamond drill bit with a diameter of 96 mm.

3. The geological core drilling method according to claim 1, characterized in that: The funnel viscosity, dynamic shear force and static shear force of the second anti-collapse flushing liquid are all higher than those of the first anti-collapse flushing liquid; and the water loss of the second anti-collapse flushing liquid is lower than that of the first anti-collapse flushing liquid.

4. The geological core drilling method according to claim 3, characterized in that: The fluid loss reducer in the first anti-collapse flushing liquid and the second anti-collapse flushing liquid is selected from at least one of low-viscosity sodium carboxymethyl cellulose (LV-CMC) and low-viscosity polyanionic cellulose (LV-PAC).

5. The geological core drilling method according to claim 3, characterized in that: The ultrafine barite powder in the first anti-collapse flushing liquid and the second anti-collapse flushing liquid is 800 mesh or finer; the amount of the ultrafine barite powder added is not more than 0.02 g / cm per cycle according to the density of the first anti-collapse flushing liquid or the second anti-collapse flushing liquid during the drilling process. 3 to add it.

6. The geological core drilling method according to claim 1, characterized in that: The preparation methods of the first anti-collapse flushing liquid and the second anti-collapse flushing liquid are as follows: (1) Add clean water to the blender; (2) Add bentonite and soda ash to clean water in sequence to form a base slurry, stir evenly and let stand for 8 hours to hydrate; (3) preparing a sealing agent by mixing water-soluble epoxy resin and diethylenetriamine in a weight ratio of 2:1 for later use; (4) adding a fluid loss reducer, a metal ion polymer coating agent, polyacrylonitrile ammonium salt, a low-fluorescence anti-collapse plugging agent, a sealing agent and ultrafine barite powder to the hydrated base slurry in sequence; stirring evenly to obtain; Wherein, each ingredient in step (4) needs to be stirred evenly before being added.

7. The geological core drilling method according to claim 1, characterized in that: The coring drill assembly, the hole reaming drill assembly and the casing drill assembly all include an active drill rod with a diameter of 89 mm.

8. The geological core drilling method according to claim 1, characterized in that: In step (3), the inner diameters of the rope coring drill rod and the thin-walled diamond drill bit are consistent, and the outer diameter of the thin-walled diamond drill bit is 1 to 3 mm larger than the outer diameter of the rope coring drill rod.

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