阅读说明：本技术 一种适用于延安区域裂缝性漏失地层的三级堵漏剂及其制备方法与堵漏方法 (Three-stage plugging agent suitable for fractured leakage stratum of Yangan area and preparation method and plugging method thereof ) 是由 王波 李伟 侯云翌 张文哲 王涛 薛少飞 杨超 于 2021-01-26 设计创作，主要内容包括：本发明公开一种适用于延安区域裂缝性漏失地层的三级堵漏剂,包括三级堵漏剂,分别为Ⅰ级堵漏剂、Ⅱ级堵漏剂、Ⅲ级堵漏剂；所述Ⅰ级堵漏剂包括如下重量份的原料：水100份、温敏型水凝胶堵漏剂1-3份；所述Ⅱ级堵漏剂包括如下重量份的原料：水100份、温敏型水凝胶堵漏剂0.8-1.5份、单向压力封闭剂DF 2-5份、随钻堵漏剂SD 2-5份、复合堵漏剂4-8份、核桃壳1-3份、橡胶粒1-3份、石棉短绒2-5份；所述Ⅲ级堵漏剂包括如下重量份的原料：水凝胶液31-33份、纤维水泥浆170份；同时,本发明公开所述三级堵漏剂的制备方法。所述三级堵漏剂,能针对性地选择堵漏剂进行堵漏,承压能力高。(The invention discloses a three-stage plugging agent suitable for a fractured leakage stratum of a delayed zone, which comprises three-stage plugging agents, namely a first-stage plugging agent, a second-stage plugging agent and a third-stage plugging agent; the grade I plugging agent comprises the following raw materials in parts by weight: 100 parts of water and 1-3 parts of temperature-sensitive hydrogel plugging agent; the II-grade plugging agent comprises the following raw materials in parts by weight: 100 parts of water, 0.8-1.5 parts of temperature-sensitive hydrogel plugging agent, 2-5 parts of one-way pressure sealing agent DF, 2-5 parts of plugging agent SD while drilling, 4-8 parts of composite plugging agent, 1-3 parts of walnut shell, 1-3 parts of rubber particles and 2-5 parts of asbestos short fibers; the grade III plugging agent comprises the following raw materials in parts by weight: 31-33 parts of hydrogel liquid and 170 parts of fiber cement slurry; meanwhile, the invention discloses a preparation method of the three-level plugging agent. The three-stage plugging agent can be selected for plugging in a targeted manner, and has high pressure bearing capacity.)

1. The utility model provides a tertiary plugging agent suitable for regional fracture nature leakage stratum of ann is prolonged which characterized in that: comprises three-stage plugging agents, namely a first-stage plugging agent, a second-stage plugging agent and a third-stage plugging agent;

the grade I plugging agent comprises the following raw materials in parts by weight: 100 parts of water and 1-3 parts of temperature-sensitive hydrogel plugging agent;

the II-grade plugging agent comprises the following raw materials in parts by weight: 100 parts of water, 0.8-1.5 parts of temperature-sensitive hydrogel plugging agent, 2-5 parts of one-way pressure sealing agent DF, 2-5 parts of plugging agent SD while drilling, 4-8 parts of composite plugging agent, 1-3 parts of walnut shell, 1-3 parts of rubber particles and 2-5 parts of asbestos short fibers;

the grade III plugging agent comprises the following raw materials in parts by weight: 31-33 parts of hydrogel liquid and 170 parts of fiber cement slurry; the hydrogel liquid is prepared from a temperature-sensitive hydrogel plugging agent and water according to the weight ratio (1-3): 30, mixing the components; the fiber cement slurry is formed by mixing fiber cement and water according to the mass ratio of 10: 7;

the composite plugging agent is a composite material prepared by mixing vermiculite, mica sheets and plant fibers according to the ratio of 3:2:5, crushing and distributing the particle size of the composite plugging agent in the range of 1.00-3.00 mm.

2. The tertiary plugging agent suitable for the fractured leakage stratum of the Yangtze zone as claimed in claim 1, wherein the tertiary plugging agent comprises the following components in percentage by weight: the fiber cement is G-grade oil well cement and chopped glass fiber according to the mass ratio of 100: (3-5) mixing.

3. The tertiary plugging agent suitable for the fractured leakage stratum of the Yangtze zone as claimed in claim 1, wherein the tertiary plugging agent comprises the following components in percentage by weight: the asbestos short fibers are fibers processed by asbestos until the linear length is less than 0.5 mm.

4. The preparation method of the tertiary plugging agent suitable for the fractured leakage stratum of the Yan' an area as claimed in claim 1, which is characterized by comprising the following steps: the method comprises the following steps:

the preparation method of the I-level plugging agent comprises the following steps: adding the temperature-sensitive hydrogel plugging agent into water, and mixing;

the preparation method of the II-grade plugging agent comprises the following steps: firstly, the walnut shells are crushed to the particle size of 3.0-5.0mm, and the rubber particles are crushed to the particle size of 1.0-3.0 mm; then adding the temperature-sensitive hydrogel plugging agent into water, stirring at the rotating speed of 500rpm for 1h, then sequentially adding a unidirectional pressure sealing agent DF and a plugging agent SD while drilling, stirring for 10min, then adding a composite plugging agent, walnut shells, rubber particles and asbestos short fibers, and stirring for 20 min;

the preparation method of the grade III plugging agent comprises the following steps: firstly preparing hydrogel liquid, then preparing fiber cement paste, and respectively storing the hydrogel liquid and the fiber cement paste.

5. A plugging method suitable for a fractured leakage stratum of a delayed zone is characterized by comprising the following steps: the plugging method is characterized in that the I-grade plugging agent, the II-grade plugging agent and the III-grade plugging agent in the three-grade plugging agent of claim 1 are matched according to the severity of leakage occurrence, and the method specifically comprises the following steps:

(1) when the well leakage occurs in the natural crack with the well depth of more than 1500 m and the leakage pressure difference of less than 2MPa, the leakage speed is 30-50m³Selecting a grade I plugging agent for plugging;

(2) when the well leakage occurs in a fractured stratum with the well depth of less than 1500 m and the leakage pressure difference of more than 5MPa, the leakage rate is more than 50m³Selecting a II-grade plugging agent for plugging;

(3) when the well leakage is caused by a fractured and karst cave type stratum and no mud returns from the well mouth, the class III plugging agent is selected for plugging.

6. A plugging method suitable for a fractured leakage stratum of a Yangtze zone according to claim 5, wherein the method comprises the following steps: the method for plugging by selecting the I-grade plugging agent in the step (1) comprises the following specific steps:

taking the grade I plugging agent to be 20m³And (3) completely injecting the I-grade plugging agent into the bottom of the well when the drill bit is lowered to the position of a leaking layer, replacing mud in the drilling tool with the original drilling fluid, closing the well mouth after the I-grade plugging agent is completely pumped into the bottom of the well, suppressing the pressure to 2MPa, stopping suppressing the pressure after 10min, lifting the drilling tool to a position above the liquid level of the I-grade plugging agent, and shutting down the well for waiting for 2 h.

7. A plugging method suitable for a fractured leakage stratum of a Yangtze zone according to claim 5, wherein the method comprises the following steps: the method for plugging by using the II-grade plugging agent in the step (2) comprises the following specific steps:

taking the II-grade plugging agent for 30m³When the drill bit is lowered to the position of a leaking layer, the II-grade plugging agent is completely injected into the bottom of the well, the original drilling fluid is used for replacing mud in the drilling tool, when the II-grade plugging agent is completely pumped into the bottom of the well, the drilling tool is lifted up by 100m, the well mouth is closed, the pressure is suppressed to 2-3MPa, the pressure is stopped after 30min, the drilling tool is lifted up to be above the liquid level of the II-grade plugging agent, the well is shut and waits for 2h, when the drilling tool is lowered to be 100m above the leaking layer, the well mouth is closed, the liquid column pressure is increased to 6MPa, the injection manifold is closed, the pressure is suppressed for 30min, and the pressure change amplitude; if the pressure variation amplitude is larger than 0.5MPa, the II-grade plugging agent is repeatedly selected for plugging.

8. A plugging method suitable for a fractured leakage stratum of a Yangtze zone according to claim 5, wherein the method comprises the following steps: the method for plugging by using the grade III plugging agent in the step (3) specifically comprises the following steps:

taking a grade-III plugging agent 20t, firstly injecting the hydrogel liquid into a bottom hole leaking layer position, then continuously pumping fiber cement paste to the bottom hole position, after finishing, replacing the fiber cement paste in the drilling tool with the original drilling fluid, lifting the drilling tool to a position above the liquid level of the fiber cement paste, and performing pressure holding and setting for 12 hours; drilling down to remove the cement plug after the upper cement is solidified, and if no leakage occurs, successfully stopping the leakage; and if the leakage occurs, the third-level plugging agent is matched again according to the severity of the leakage.

Technical Field

The invention belongs to the technical field of petroleum drilling, and particularly relates to a three-level plugging agent suitable for a fractured leakage stratum of an extended safety area, a preparation method thereof and a plugging method.

Background

The lost circulation is one of the common underground complex conditions in the drilling process, not only can the drilling time be consumed and mud is lost, but also a series of complex conditions such as drilling sticking, blowout, well collapse and the like can be caused, and even the well is scrapped, so that the great economic loss is caused. The Yanan regional exploration and development area is located on the Yishan slope of the Oridosi basin, a low-pressure layer prone to leakage exists in a part of the oil field in the drilling process, according to the regional drilling condition, the well leakage frequently occurs in the drilling of western oil production plants such as Jingbian, Wuqi, Fangbian, West district and the like, and the leakage rate is 5-60 m³The drilling time is different from the drilling time, and mud returns to cause well collapse even the drilling tool is buried to cause well filling sidetrack when the leakage is serious, so that the drilling period is seriously influenced, and the drilling cost is increased. As can be seen from statistical data, the most common loss in well drilling in the western region is permeability loss and microcrack loss of sandstone formation, and the leakage rate is generally 12m³Within the hour, frequent leakage occurs and is repeated, and the leakage stoppage measures are adopted when being improper, so that the fractured well leakage is easy to cause.

At present, related researches and inventions aiming at the plugging agent have a plurality of achievements, but the function and the efficiency of various products are different. For example, von jew, huangwei and the like disclose an underground cross-linked gel plugging agent in patent CN105778874A "drilling underground cross-linked gel plugging agent and plugging method thereof", the plugging agent is made of materials such as high molecular polymer polyacrylamide, cross-linking agent, bagasse, sawdust, polymer elastomer and the like, but the plugging agent mainly comprises polymer materials, the pressure-bearing strength in the stratum is not as good as that of a rigid plugging agent, and the plugging agent has more components and is more complex to prepare; the patent CN102127403A published by Zhang Jun et al, "efficient leak stopping agent for drilling well", uses walnut shell, sawmilling surface, cotton seed, husk and other materials to mix to form an efficient leak stopping agent. However, the current plugging agent has single effect and limited application range, and the application of the plugging agent is limited.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a three-level plugging agent suitable for a fractured leakage stratum of a delayed zone, a preparation method thereof and a plugging method thereof.

A three-stage plugging agent suitable for fractured leakage stratum of a delayed zone comprises three-stage plugging agents, namely a first-stage plugging agent, a second-stage plugging agent and a third-stage plugging agent;

the grade I plugging agent comprises the following raw materials in parts by weight: 100 parts of water and 1-3 parts of temperature-sensitive hydrogel plugging agent;

the II-grade plugging agent comprises the following raw materials in parts by weight: 100 parts of water, 0.8-1.5 parts of temperature-sensitive hydrogel plugging agent, 2-5 parts of one-way pressure sealing agent DF, 2-5 parts of plugging agent SD while drilling, 4-8 parts of composite plugging agent, 1-3 parts of walnut shell, 1-3 parts of rubber particles and 2-5 parts of asbestos short fibers;

the grade III plugging agent comprises the following raw materials in parts by weight: 31-33 parts of hydrogel liquid and 170 parts of fiber cement slurry; the hydrogel liquid is prepared from a temperature-sensitive hydrogel plugging agent and water according to the weight ratio (1-3): 30, mixing the components; the fiber cement slurry is formed by mixing fiber cement and water according to the mass ratio of 10: 7;

the composite plugging agent is a composite material prepared by mixing and crushing vermiculite, mica sheets and plant fibers, and the particle size of the composite plugging agent is distributed between 1.00 and 3.00 mm.

Preferably, the fiber cement is G-grade oil well cement and chopped glass fiber according to a mass ratio of 100: (3-5) mixing.

Preferably, the asbestos fluff is a fiber of asbestos processed to a linear length of less than 0.5 mm.

The preparation method of the three-level plugging agent suitable for the fractured leakage stratum of the Yangan area comprises the following steps:

the preparation method of the I-level plugging agent comprises the following steps: adding the temperature-sensitive hydrogel plugging agent into water, and mixing;

the preparation method of the II-grade plugging agent comprises the following steps: firstly, the walnut shells are crushed to the particle size of 3.0-5.0mm, and the rubber particles are crushed to the particle size of 1.0-3.0 mm; then adding the temperature-sensitive hydrogel plugging agent into water, stirring at the rotating speed of 500rpm for 1h, then sequentially adding a unidirectional pressure sealing agent DF and a plugging agent SD while drilling, stirring for 10min, then adding a composite plugging agent, walnut shells, rubber particles and asbestos short fibers, and stirring for 20 min;

the preparation method of the grade III plugging agent comprises the following steps: firstly preparing hydrogel liquid, then preparing fiber cement paste, and respectively storing the hydrogel liquid and the fiber cement paste.

A plugging method suitable for fractured leakage stratum of a delayed zone, which is to match and use the I-grade plugging agent, the II-grade plugging agent and the III-grade plugging agent in the three-grade plugging agent of claim 1 according to the severity of leakage occurrence, and specifically comprises the following steps:

(1) when the well leakage occurs in the natural crack with the well depth of more than 1500 m and the leakage pressure difference of less than 2MPa, the leakage speed is 30-50m³Selecting a grade I plugging agent for plugging;

(2) when the well leakage occurs in a fractured stratum with the well depth of less than 1500 m and the leakage pressure difference of more than 5MPa, the leakage rate is more than 50m³Selecting a II-grade plugging agent for plugging;

(3) when the well leakage is caused by a fractured and karst cave type stratum and no mud returns from the well mouth, the class III plugging agent is selected for plugging.

Preferably, the method for plugging by using the I-grade plugging agent in the step (1) comprises the following steps:

taking the grade I plugging agent to be 20m³Injecting the grade I plugging agent into the bottom of a well when a drill bit is lowered to a leaking layer position, replacing mud in a drilling tool with the original drilling fluid, stopping pressure building after the grade I plugging agent is pumped into the bottom of the well, closing the well mouth, building the pressure to 2MPa, stopping the pressure building after 10min, lifting the drilling tool to a position above the liquid level of the grade I plugging agent, and shutting the wellWait for 2 h.

Preferably, the method for plugging by using the II-grade plugging agent in the step (2) is as follows:

taking the II-grade plugging agent for 30m³When the drill bit is lowered to the position of a leaking layer, the II-grade plugging agent is completely injected into the bottom of the well, the original drilling fluid is used for replacing mud in the drilling tool, when the II-grade plugging agent is completely pumped into the bottom of the well, the drilling tool is lifted up by 100m, the well mouth is closed, the pressure is suppressed to 2-3MPa, the pressure is stopped after 30min, the drilling tool is lifted up to be above the liquid level of the II-grade plugging agent, the well is shut and waits for 2h, when the drilling tool is lowered to be 100m above the leaking layer, the well mouth is closed, the liquid column pressure is increased to 6MPa, the injection manifold is closed, the pressure is suppressed for 30min, and the pressure change amplitude; if the pressure variation amplitude is larger than 0.5MPa, the II-grade plugging agent is repeatedly selected for plugging.

Preferably, the method for plugging by using the class III plugging agent in the step (3) comprises the following steps:

taking a grade-III plugging agent 20t, firstly injecting the hydrogel liquid into a bottom hole leaking layer position, then continuously pumping fiber cement paste to the bottom hole position, after finishing, replacing the fiber cement paste in the drilling tool with the original drilling fluid, lifting the drilling tool to a position above the liquid level of the fiber cement paste, and performing pressure holding and setting for 12 hours; drilling down to remove the cement plug after the upper cement is solidified, and if no leakage occurs, successfully stopping the leakage; and if the leakage occurs, the third-level plugging agent is matched again according to the severity of the leakage.

The temperature-sensitive hydrogel plugging agent provided by the invention is prepared by adopting the prior art; preferably, the temperature-sensitive hydrogel plugging agent disclosed in patent CN 110183579A is adopted as the temperature-sensitive hydrogel plugging agent.

The invention has the advantages that:

(1) the plugging agent provided by the invention judges the severity of leakage according to the characteristics of a leakage stratum, the leakage speed and other conditions, and specifically selects the plugging agent for plugging according to the severity of leakage; the plugging slurry can be injected into the well bottom for one time and is subjected to continuous pressure building, the plugging range of the plugging slurry in a near-well-barrel crack stratum is effectively enlarged, the bearing capacity is improved, the bearing capacity can reach 6MPa, a leakage layer is plugged in a short time, and a good leakage-proof and plugging effect is achieved;

(2) the problems that the leakage passage is difficult to effectively cut off by using the traditional bridging plugging slurry singly and the leakage rate and the leakage amount are reduced are solved, the selectivity and the dependency of a single plugging material on the size of the crack and the leakage passage are avoided, and the plugging success rate of the crack leakage in the drilling process of the delay area is improved.

Detailed Description

The temperature-sensitive hydrogel plugging agent adopted in the embodiment of the invention is the temperature-sensitive hydrogel plugging agent disclosed in embodiment 1 of patent CN 110183579A.

Example 1

The I-grade plugging agent comprises 100 parts of water and 3 parts of temperature-sensitive hydrogel plugging agent;

the preparation method of the I-level plugging agent comprises the following steps: and adding the temperature-sensitive hydrogel plugging agent into water, and mixing.

Example 2

The first-stage plugging agent comprises 100 parts of water and 1 part of temperature-sensitive hydrogel plugging agent;

the preparation method of the grade I plugging agent is the same as that of the example 1.

Example 3

The II-grade plugging agent comprises the following raw materials in parts by weight: 100 parts of water, 0.8 part of temperature-sensitive hydrogel plugging agent, 2 parts of one-way pressure sealing agent DF, 2 parts of while-drilling plugging agent SD, 4 parts of composite plugging agent, 2 parts of walnut shell, 2 parts of rubber particles and 2 parts of asbestos short fibers;

the asbestos short fibers are fibers processed by asbestos until the linear length is less than 0.5 mm;

the composite plugging agent is a composite material prepared by mixing vermiculite, mica sheets and plant fibers according to the mass ratio of 3:2:5, crushing and distributing the particle size of the composite plugging agent in the range of 1.00-3.00 mm;

the preparation method of the II-grade plugging agent comprises the following steps: firstly, the walnut shells are crushed to the particle size of 3.0-5.0mm, and the rubber particles are crushed to the particle size of 1.0-3.0 mm; and then adding the temperature-sensitive hydrogel plugging agent into water, stirring at the rotating speed of 500rpm for 1h, then sequentially adding a unidirectional pressure sealing agent DF and a plugging agent SD while drilling, stirring for 10min, then adding a composite plugging agent, walnut shells, rubber particles and asbestos short fibers, and stirring for 20 min.

Example 4

The II-grade plugging agent comprises the following raw materials in parts by weight: 100 parts of water, 1 part of temperature-sensitive hydrogel plugging agent, 3 parts of one-way pressure sealing agent DF, 3 parts of while-drilling plugging agent SD, 5 parts of composite plugging agent, 1 part of walnut shell, 1 part of rubber particles and 3 parts of asbestos short fibers;

the asbestos short fibers and the composite plugging agent are the same as in the embodiment 3;

the preparation method is the same as example 3.

Example 5

The II-grade plugging agent comprises the following raw materials in parts by weight: 100 parts of water, 1.5 parts of temperature-sensitive hydrogel plugging agent, 5 parts of one-way pressure sealing agent DF, 5 parts of while-drilling plugging agent SD, 8 parts of composite plugging agent, 3 parts of walnut shell, 3 parts of rubber particles and 5 parts of asbestos short fiber;

the asbestos short fibers and the composite plugging agent are the same as in the embodiment 3;

the preparation method is the same as example 3.

Example 6

The grade III plugging agent comprises the following raw materials in parts by weight: 31 parts of hydrogel liquid and 170 parts of fiber cement slurry; the hydrogel liquid is prepared from a temperature-sensitive hydrogel plugging agent and water according to a weight ratio of 1: 30, mixing the components; the fiber cement slurry is formed by mixing fiber cement and water according to the mass ratio of 10: 7; the fiber cement is G-grade oil well cement and chopped glass fiber according to the mass ratio of 100: 5, mixing the components;

the III-grade plugging agent is prepared in time when used on site, and the preparation method comprises the following steps: preparing hydrogel liquid, preparing fiber cement paste, and storing the hydrogel liquid and the fiber cement paste respectively; when the fiber cement paste is used, the hydrogel liquid is injected first, and then the fiber cement paste is injected.

Example 7

The grade III plugging agent comprises the following raw materials in parts by weight: 33 parts of hydrogel liquid and 170 parts of fiber cement slurry; the hydrogel liquid is prepared from a temperature-sensitive hydrogel plugging agent and water according to a weight ratio of 3: 30, mixing the components; the fiber cement slurry is formed by mixing fiber cement and water according to the mass ratio of 10: 7; the fiber cement is G-grade oil well cement and chopped glass fiber according to the mass ratio of 100: 3, mixing;

the grade III plugging agent is prepared in time when used on site, and the preparation method is the same as that of example 6.

The third-level plugging agent can be formed by combining the first-level plugging agent, the second-level plugging agent and the third-level plugging agent provided by the embodiment.

Example 8

In this embodiment, the T36 well in the western region of the extended oilfield is located in a certain oil production plant in the western region of extended oil field, and the drilling process shows that the well leaks when the well is drilled to 960m, and the leakage rate is 38m³H is used as the reference value. According to the condition leakage situation, judging that the first-grade plugging agent is used for plugging, and by adopting the first-grade plugging agent provided by the embodiment 1 of the invention, the method for plugging by using the first-grade plugging agent specifically comprises the following steps:

taking the grade I plugging agent to be 20m³And (3) pumping the prepared I-grade plugging agent into the bottom of the well along a water hose, a water tap, a kelly bar and a drill rod by using a slurry pump, replacing mud in the drilling tool with original drilling fluid, calculating the required time after the I-grade plugging agent is completely injected according to the well depth and the discharge capacity of the slurry pump during injection, closing the well mouth when the I-grade plugging agent is completely pumped into the bottom of the well, suppressing the pressure to 2MPa, stopping the pressure after 10min, lifting the drilling tool to be above the liquid level of the I-grade plugging agent, closing the well for 2h, completing the plugging operation, and waiting for successful plugging.

Example 9

In this embodiment, an X241 well group in the west region of the Yanan area is taken as an example, and the well group is located in a certain oil production plant in the Yanan plug area and comprises two directional wells X241-3 and 241-4. X241-3 designed well depth 1860 m. According to the geological and drilling data of the adjacent well, the well leaks when the well is drilled to 1560m, and the leakage rate is 56m³H is used as the reference value. Judging that the second-level plugging agent should be used for plugging according to the condition leakage condition, wherein the second-level plugging agent provided by the embodiment 4 of the invention is adopted, and the method for plugging by the second-level plugging agent specifically comprises the following steps:

taking the II-grade plugging agent for 30m³The drill bit is lowered to the position of the leaking layer, and the II-level plugging agent is put along the water hose, the water tap, the kelly bar,Pumping a drill rod into a well bottom, replacing mud in a drilling tool with original drilling fluid, calculating the time required for the whole injection of the II-grade plugging agent to be 35min according to the well depth and the discharge capacity of a mud pump during the injection, lifting the drilling tool by 100m after the II-grade plugging agent is completely pumped into a shaft, closing the well mouth to be 2-3MPa, stopping the pressure holding after 30min, lifting the drilling tool to be above the liquid level of the II-grade plugging agent, closing the well for waiting for 2h, stopping the well mouth when the drilling tool is lowered to be above 100m of a leaking layer, lifting the pressure of a liquid column to be 6MPa, closing an injection manifold, holding the pressure for 30min, wherein the pressure change amplitude is less than 0.5MPa, and the plugging is.

Example 10

This example is illustrated for gas well C22-1 in the east of the Yanan gas field, which is located in the east region of Yanan Changan. According to the working condition and the loss condition of the well in the drilling process, when the well is drilled to 1772m, the drilling tool is emptied, the drilling fluid is lost and no mud returns from a well head, and the well loss is caused by a fractured and karst cave type stratum. According to the condition leakage situation, judging that the grade-III plugging agent is used for plugging, and by adopting the grade-III plugging agent provided by the embodiment 6 of the invention, the method for plugging by using the grade-III plugging agent specifically comprises the following steps:

taking 20t of a III-grade plugging agent, firstly pumping all the hydrogel liquid into a leaking layer position at the bottom of a well, then continuously pumping fiber cement paste to the bottom of the well, after the completion, replacing the fiber cement paste in a drilling tool with the original drilling fluid, lifting the drilling tool to a position above the liquid level of the fiber cement paste, and performing pressure-holding and setting-waiting for 12 hours; and the cement plug after the upper cement is solidified is removed by the drill, so that no leakage occurs, and the plugging is successful.

Performance detection

1. Evaluation of pressure-bearing Capacity

A pressure-bearing capacity evaluation experiment is carried out on the plugging agent provided by the embodiment of the invention by using a DL-III type fracture plugging instrument, a fracture module with the fracture width of 3mm is adopted in the experiment, and the pressure-bearing and plugging capacity of the fracture is shown in Table 1.

Table 1 evaluation of crack plugging ability test results

The experimental results in the table 1 show that the plugging agent provided by the embodiment of the invention has a good plugging effect on a 3mm fracture model, the pressure bearing capacity is higher than 6MPa, and the grade I plugging agent provided by the embodiment 1 can realize continuous and complete filling when entering a fracture, but the leakage amount is relatively large; the II-grade plugging agent provided by the embodiments 4 and 5 mainly uses particle plugging materials, can be filled in a bridge in a crack, has the pressure bearing of 7MPa, and has relatively less leakage.