CN113175316A - New method for plugging underground or underground old crack - Google Patents

New method for plugging underground or underground old crack Download PDF

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CN113175316A
CN113175316A CN202110646904.1A CN202110646904A CN113175316A CN 113175316 A CN113175316 A CN 113175316A CN 202110646904 A CN202110646904 A CN 202110646904A CN 113175316 A CN113175316 A CN 113175316A
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plugging agent
pressure
plugging
fracturing
fracture
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周国君
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BEIJING CSI ENERGY TECHNIQUES CO LTD
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25—Methods for stimulating production
    • E21B43/26—Methods for stimulating production by forming crevices or fractures
    • E21B43/261—Separate steps of (1) cementing, plugging or consolidating and (2) fracturing or attacking the formation
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B33/00—Sealing or packing boreholes or wells
    • E21B33/10—Sealing or packing boreholes or wells in the borehole
    • E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25—Methods for stimulating production
    • E21B43/26—Methods for stimulating production by forming crevices or fractures
    • E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
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Abstract

The invention relates to a new method for plugging underground or underground old cracks, (1) when the cracks are closed or partially closed, plugging agent is added when a fracturing truck starts or is constructed, or after fracturing construction is carried out for a period of time, a pump is stopped and pressure is released simultaneously, and the plugging agent is added after the cracks are slowly closed or partially closed; if the wellbore fluid exceeds 10m3Opening a casing gate in the plugging agent adding process, closing the casing gate after removing a part of wellbore fluid to the ground, and continuously displacing the fluid into the underground crack; (2) when the plugging agent and the displacing liquid enter the crack, the difference value between the construction pressure and the initial pressure before the plugging agent is added is increasedWhen the pressure reaches 5MPa, the injection of the plugging agent is stopped, which indicates that the plugging agent acts and the underground crack is plugged. The method can effectively block the old seam, or block the water outlet in the old seam, and reduce the water content; 100 percent of plugging is achieved, the subsequent fracturing of new cracks is facilitated, the new drainage area can be effectively increased, the yield of the oil-gas well is further improved, and the water content is reduced.

Description

New method for plugging underground or underground old crack
Technical Field
The invention relates to a novel method for plugging underground or underground old cracks, and belongs to the technical field of yield increase of petroleum and natural gas.
Background
In the development process of low-permeability oil and gas reservoirs, fracturing is one of main production increasing measures, and aims to open a seam in the low-permeability reservoir, increase the drainage area and improve the oil and gas yield. The turning fracturing technology is characterized in that a temporary plugging agent or a plugging agent is added in real time in the fracturing process, based on the principle that fluid flows along the direction with the minimum resistance, the plugging agent can enter a blast hole communicated with an original crack or a high permeable layer along with fracturing fluid, high-strength filter cake bridging is generated at the blast hole and in the original crack (or a high permeable zone) in a gathering manner, so that subsequent fracturing fluid cannot enter the original crack and the high permeable zone, the bottom pressure of a well can be increased to a certain degree, secondary fracture is generated under the condition of a certain horizontal two-way stress difference, the original crack initiation direction is changed to generate a new crack, and a new high-flow-conductivity oil-gas flow channel is established.
Temporary plugging of repeated fracturing has begun since the 80 s in the united states, beginning later domestically. In the prior art, the materials of the plugging agent and the plugging removal are always researched, and few people for researching how to add the plugging agent are needed.
The temporary plugging agent commonly used in the oil field at present is fiber and water-soluble particles with different sizes, and the old joint is plugged and a new joint is opened by utilizing the principle that the temporary plugging agent preferentially enters along the direction with small resistance and the temporary plugging agent is rubbed and accumulated on the inner wall surface of the crack. If the temporary plugging agent cannot be plugged, the fracturing fluid enters along the old joint to extend the old joint, and a new joint cannot be generated, so that the strength and the plugging rate of the temporary plugging agent are the key of the temporary plugging diversion fracturing technology. The invention patent application CN103835691A of China proposes a method for generating multiple cracks in a naturally selected dessert temporary blocking volume fracturing method, and after the cracks are pressed open, a high-strength water-soluble particle temporary blocking agent is added to block the cracks. The Chinese patent application CN103615228A patent application CN temporary plugging fracturing process in degradable fiber seams mentions that a degradable fiber, linear glue and a propping agent are used as temporary plugging fracturing fluid in the seams to form branch seams. The Chinese patent application CN102020984A discloses an overground cross-linked viscoelastic particle temporary plugging agent in the low-permeability oilfield in-seam diversion fracturing temporary plugging agent, a preparation method and application thereof, which forms filter cake bridging in blastholes and a high-permeability zone and finally promotes the generation of new seams. The invention provides an underground cross-linking type powder or particle temporary plugging agent in Chinese patent application CN102344788A 'a temporary plugging agent for horizontal well staged fracturing capable of controlling gel breaking and a preparation method thereof', which realizes effective plugging of a horizontal well section and effective gel breaking through a capsule gel breaker. The Chinese patent application 106350043A 'Compound temporary plugging agent and Compound temporary plugging method for temporary plugging in diverting fracturing' includes temporary plugging agent a (rigid) and temporary plugging agent b (flexible), which are injected into oil well cracks in sequence, and the particles of the temporary plugging agent are all 2-20 meshes. The temporary plugging patent technology basically researches the components of the plugging agent, does not consider the process (time and discharge) of adding the plugging agent, and generally cannot ensure 100 percent plugging from the analysis of construction pressure, namely cannot ensure 100 percent pressure rise. How to effectively ensure 100 percent blocking (pressure rise) is a technical problem to be solved urgently.
Disclosure of Invention
Technical problem to be solved
In order to solve the above problems of the prior art, the present invention provides a new method for plugging old fractures downhole or underground.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
a new method of plugging a downhole or subterranean old fracture comprising the steps of:
(1) when the crack is closed or partially closed, adding the plugging agent when the fracturing truck starts or is constructed at the beginning, or stopping a pump after fracturing construction for a period of time and simultaneously releasing pressure, and adding the plugging agent after the crack is slowly closed or partially closed; if the wellbore fluid exceeds 10m3Opening a casing gate in the plugging agent adding process, closing the casing gate after replacing a part of wellbore fluid to the ground, and continuously adding the replacement fluid into the underground crack;
(2) when the plugging agent and the displacing liquid enter the cracks, stopping injecting the plugging agent or the displacing liquid when the difference value between the pressure after the construction pressure is raised and the initial pressure before the plugging agent is added reaches 5MPa, and indicating that the plugging agent acts and the underground cracks are plugged.
According to the new method, preferably, the fracture closure refers to that in the field construction process, when the net pressure at the bottom of the well is judged to be smaller than the closed fracture according to the pressure curve, the fracture is not opened, namely the fracture is closed; the fracture part is closed, namely after fracturing construction, the pump is stopped to relieve pressure, and the pump-stopping pressure of a wellhead is reduced by more than 50%.
According to the novel method, the discharge amount of the plugging agent and the displacement fluid entering the cracks is preferably controlled to be 0.1-1.5 m3The total dosage of the plugging agent reaches 2-5 m3Then, a displacement fluid, which is a 0.45% xanthan gum solution, was added.
In the novel method, the discharge amount of the plugging agent and the displacement fluid into the fracture is controlled to be 0.5m3Is carried out in/min.
In the novel method, the plugging agent is preferably composed of uncrosslinked fracturing fluid containing sand, high molecular polymer and fiber, wherein the total content of the sand, the high molecular polymer and the fiber is 20-40% in the uncrosslinked fracturing fluid, and the content of the fiber is 0.5-19%.
In the novel method described above, the sand, polymer and fibres are preferably present in a total amount of 20% in the uncrosslinked fracturing fluid.
In the novel process, the sand is preferably sand with a particle size of 1mm to 5mm and 0.125mm to 0.425 mm.
In the novel method, the uncrosslinked fracturing fluid is preferably 0.3-0.5% of xanthan gum or fenugreek gum aqueous solution.
(III) advantageous effects
The invention has the beneficial effects that:
the new method for plugging underground or underground old cracks can be applied to oil field vertical well separate-layer fracturing, horizontal well staged fracturing and old well repeated fracturing, and can be used for plugging old cracks or plugging water in the old cracks to reduce water content; 100 percent of plugging is achieved, the subsequent fracturing of new cracks is facilitated, the new drainage area can be effectively increased, the yield of the oil-gas well is further improved, and the water content is reduced. By applying the method, 100% of plugging, namely pressure rise, can be ensured through testing of a plurality of wells on site, and the oil gas yield is improved.
Drawings
FIG. 1 is a graph showing the change of fracture width with time when a fracturing fluid is injected at a low speed;
FIG. 2 is a flow back process and a fracture width variation process of a fracturing fluid in a fracture;
FIG. 3 is a monitoring curve of temporary plugging repeated fracturing of a certain oil well in Changqing Ansai;
fig. 4 is a monitoring curve of temporary plugging repeated fracturing of 8 layers of the Changqing house 82-90 well length.
Detailed Description
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
Example 1
The application is in the research and is stopped up the in-process discovery that old fracture in the pit, when the crack does not open or opens very narrowly, is favorable to temporarily stifled fibre and temporarily stifled granule to accumulate in the passageway of crack anterior segment and crack and porthole to the effectual effect that plays temporarily stifled suppress the pressure, steps up.
If the pressure curve has a small peak or does not have a peak in the field construction process, the pressure does not rise and slowly falls, and the crack is opened. The injected temporary plugging agent moves towards the cracks along with the fracturing fluid, and the temporary plugging agent used in the conventional temporary plugging process completely enters the cracks, so that the temporary plugging and pressure building effect cannot be achieved, and the temporary plugging fails.
The old well is repeatedly fractured, why the temporary plugging agent needs to be injected in the fracturing construction at the beginning, because the old well fracture has limited capacity of receiving injected fracturing fluid under the condition that the fracture is not opened, because the old fracture fluid has a certain fluid and has a certain flow conductivity, when the fracturing fluid with a certain viscosity is injected at a low speed, a part of fluid can be received in a filtration mode and the like, and because the fracturing fluid has a certain viscosity, the fracturing fluid cannot be injected continuously like water injection, but the fracture is not opened.
When the amount of the fracturing fluid exceeds the acceptance capacity of the fracture, the net pressure in the fracture begins to increase, the fracture begins to open, and the fracture width increases, so that the temporary plugging operation of the temporary plugging agent is not facilitated.
When the fracturing fluid is injected into the fracture, the width of the fracture changes along with the injection time, as shown in figure 1.
It can be seen from the figure that when the fracturing fluid is injected for too long, the amount of the injected fluid q is greater than qClosure is providedAnd at the moment, the crack starts to be opened, and the temporary plugging agent is added, so that the temporary plugging construction is easy to fail.
If the plugging agent is added in the construction process, the fracturing truck is stopped, the plugging agent is added after the pressure of the wellhead is released, and the wellhead pressure (pump stopping pressure) is released. Fig. 2 is a graph of the change of the width of the fracture along with the increase of the return displacement of the fracturing fluid in the fracture in the pumping-off pressure relief process. After the fracture begins to close, because the liquid in the fracture is subjected to a certain pressure, a part of the liquid can be continuously discharged under the formation pore pressure until the fracture is completely closed. And the flowback liquid is flowback to the wellhead waste liquid pool from the crack. The time judgment is based on the pressure curve in the fracturing being reduced to be close to the closing pressure.
As shown in FIG. 2, the fluid return volume in the new fracture reaches q1At that time, the crack begins to close; the liquid in the crack is continuously and slowly drained to reach q2. The discriminant formula meeting the temporary plugging construction is as follows:
q2-q1≥qtemporary plugging filtration loss
In the formula: q. q.s1-total amount of liquid discharged at the closing of the crack;
q2-total amount of liquid drained for a period of time after fracture closure;
qtemporary plugging filtration lossThe amount of liquid filtered during temporary plugging construction;
therefore, when the fracturing is temporarily blocked after a new fracture is fractured, most of the fracturing fluid in the fracture needs to be drained back or absorbed by the stratum for a long time, and then the temporary blocking agent is added for temporary construction.
Need low discharge volume to pour into fracturing fluid in this application and realize stifled construction temporarily: whether the crack is opened or not is the key for forming temporary plugging because the temporary plugging agent can be successfully accumulated in the front section of the crack and a blast hole. The following theoretical explanation is made for the conditions for opening a fracture in an old fracture (or a new fracture) of an old well. First, the process of changing the width of the fracture during the fracturing process is explained.
The opening degree of the fracture is related to the size of a net pressure fracture of the bottom-hole fluid, see equations (1) and (2), the size of the net pressure is related to injection displacement and fracture area, see equations (3) and (4), the size of the fracture area (long or high) is related to the fluid loss of the liquid, the considered fracture is the area of an old fracture or a new fracture closed after a propping agent, the fracture is not propped, and the length and the height of the fracture can be seen as constants.
The following are examples of fracture models PKN and KGD:
the width of the PKN model cleft is:
Figure BDA0003110239300000051
in the formula: w is the width of the crack;
Pn-is the net intra-seam pressure;
hf-is the fracture height;
e' -is the in-plane strain modulus.
The net pressure of the PKN model is
Figure BDA0003110239300000061
In the formula:
e-modulus of elasticity of rock;
μa-viscosity of the fluid;
l is the crack length;
q is the pump injection volume.
Similarly, the width of the KGD model crack is:
Figure BDA0003110239300000062
the net pressure of the KGD model is:
Figure BDA0003110239300000063
from the analysis of equations (1), (2), (3) and (4) the following conclusions can be drawn:
fracturing construction with cracks:
W∝P∝Qinjection amount larger than filtration loss (5)
QInjection amount larger than filtration loss＝QInjection displacement-QMaximum fluid loss acceptable for a fracture (6)
In the formula: qInjection displacementInjection displacement at the time of fracturing construction:
Qmaximum fluid loss acceptable for a fracture-maximum injection displacement acceptable when the fracture is not open;
therefore, the condition that the crack is not opened is QInjection displacement≤QMaximum fluid loss acceptable for a fractureAt this time, the injection amount of the fracturing fluid is smaller than the filtration loss, the pressure of the fluid is lower than the closing pressure, and the fracture cannot be opened due to no net pressure.
When Q isInjection displacement＞QMaximum fluid loss acceptable for a fractureAt the moment, the injection amount of the fracturing fluid is larger than the filtration loss, the net pressure begins to increase, so the fracture begins to widen, and the fracture can be opened no matter the stratum has the capacity of receiving the redundant fracturing fluid, so the construction of temporary plugging is not facilitated.
Calculating the discharge capacity to ensure the net pressure P when the old crack is not openedn should beClosure pressure delta less than or equal to old fracturemln(ii) a Namely, it is
Pn≤δmin (7)
And (4) calculating a displacement formula of the crack not to open in the process of injecting the temporary plugging agent by combining the formulas (2) and (4).
The pump injection displacement calculation formula of the PKN model is
Figure BDA0003110239300000071
The net pressure of the KGD model is:
Figure BDA0003110239300000072
the pump injection displacement for ensuring the crack closure when injecting the temporary plugging agent is as follows:
Q≤Qmax (10)
in the formula: qmaxMaximum displacement to ensure that old fractures do not open:
according to the formulas (8), (9) and (10) and the geological conditions of domestic low-permeability reservoir, the displacement during temporary plugging fracturing is calculated to be 0.1-1.5 m3The/min can meet the requirement, and according to the experience, the optimal injection displacement is 0.5m3/min。
It can be seen that the conditions for the success of the temporary plugging fracturing construction are as follows: firstly, the fracture needs to have the capacity of receiving the amount of wellbore fluid and the amount of fluid lost by the plugging agent during accumulation (the adding time of the plugging agent); and secondly, the discharge capacity of the injected fracturing fluid cannot be too large, so that the crack is prevented from being opened (the plugging agent is added at a low discharge capacity). One of the two conditions is not available.
The invention provides a reliable method for plugging underground old cracks, which comprises the steps of injecting plugging agent after closing or partially closing the old cracks (the pressure is reduced or the pump-stopping pressure of a well head is reduced by more than 50 percent after a construction pressure curve does not have a peak), namely when the old cracks are closed on the propping agent in the old cracks, adding the plugging agent when a fracturing truck is started (construction is started), or releasing the pressure after a packer is set, starting the fracturing truck to add the plugging agent when the pressure is released, stopping the fracturing truck and releasing the pressure at the well head if the plugging agent is added in the construction process, then starting the fracturing truck to add the plugging agent, and releasing the pressure of the well head (pump-stopping pressure) by more than 50 percent. And use less than 1.5m3Permin (0.5 m)3Min is optimal), and 100 percent of plugging or blocking can be guaranteed only when the plugging agent and the displacing fluid enter the old underground cracks. In the fracturing construction process, underground cracks are sealed and plugged, and the underground cracks are opened at equal pressure after pumps are stopped (construction is stopped) and blowout and pressure relief are carried out (more than 50% of wellhead pressure is relieved by pressure relief)After partial closure, the plugging agent and displacement fluid are added with a displacement volume below one side and enter the downhole fracture. In the process that the underground old cracks are blocked, the pressure is raised when the pressure is reflected on a construction pressure curve, and then the displacement is quickly raised, so that new cracks can be opened. The component of the plugging agent is formed by sand grains with different sizes and high molecular polymer and soluble (or insoluble) fiber in the uncrosslinked fracturing fluid, and the content of the sand grains, the high molecular polymer and the fiber is as high as 20 percent to 40 percent (20 percent is optimal). The uncrosslinked fracturing fluid is 0.3-0.5% of xanthan gum or fenugreek gum aqueous solution.
Example 2
The old well in the Ansai area of the Changqing oil field is repeatedly fractured, the plugging agent is added when the old well is pumped (constructed), and the thickness of the plugging agent is 0.5m3The plugging agent and the displacing fluid (xanthan gum solution with the mass percent of 0.45%) are added into the underground old cracks at the/min discharge amount, the differential pressure of the construction pressure (compared with the pressure before the plugging agent is injected, namely the differential value of the pressure after the construction pressure is raised and the initial pressure before the plugging agent is added) reaches more than 5MPa, the plugging agent is shown to be in effect, the underground cracks are plugged, the plugging agent is stopped to be injected, and the fracturing monitoring curve is shown in figure 3. Wherein the plugging agent comprises 140Kg of sand with the particle size of 1-5 mm and the particle size of 40-120 meshes, 30Kg of polyacrylamide with the molecular weight of 1500-2000 ten thousand and 60Kg of polyvinyl alcohol fiber with the length of 4mm, the liquid in the plugging agent is 0.4% of xanthan gum aqueous solution, and the total content of the sand, the high molecular polymer and the fiber is 20% by mass in the 0.4% of xanthan gum aqueous solution.
And (3) comparing the repeated fracturing effects of 10 old wells in the Changqing oilfield Ansai area, wherein 5 wells adopt the method to temporarily block the constructed oil well, the added temporary plugging agent is the plugging agent formula described in the example 2, and the difference between the construction fracturing pressure after the plugging agent is added and the pressure when the plugging agent is injected is more than 5MPa, so that the temporary plugging of old joints is considered to be successful. In addition, in the process of repeatedly plugging the fracturing exploration by temporary plugging in the early stage of 5 wells, a larger displacement (A) is used>1.5m3Min), oil wells with no significant increase in pressure after temporary plugging with addition of polyvinyl alcohol were considered to have not plugged old joints. The 10 test wells in the block of the Changqing oil field are marked with the number of 1-10, wherein the last 5 test wells are filled with plugging agentThe rear 5 wells were pressurized and the front 5 wells were not pressurized. The method is adopted, when the crack is closed or partially closed and is not greatly opened, the plugging agent is added when the fracturing truck starts (is constructed), the underground crack is closed (is closed on the propping agent in the old crack) or is slightly opened, or the pump is stopped and the pressure is released simultaneously after the fracturing construction is carried out for a period of time, so that the crack is slowly closed or partially closed, and then the plugging agent is added (when the construction pressure is observed and is close to the closing pressure); if the wellbore fluid exceeds 10m3Opening a casing gate in the plugging agent adding process, closing the casing gate after replacing a part of wellbore fluid to the ground, and continuously adding the replacement fluid into the underground crack; the discharge amount of the plugging agent and the displacing liquid (namely 0.4 percent xanthan gum or fenugreek gum solution) entering the crack must be controlled to be 1m3Within the discharge capacity of/min, the total dosage of the plugging agent and the plugging agent carrier fluid is 2-5 m3And then adding displacement liquid, otherwise, the underground crack is too large to be opened and blocked. The same plugging agent added into 10 wells is prepared by mixing 80Kg of sand with the particle size of 1-5 mm, 140Kg of sand with the particle size of 40-120 meshes, 30Kg of high molecular polymer (2000 ten thousand polyacrylamide) and 60Kg of fiber, wherein the mass of the plugging agent is 20-40%. The discharge capacity of the front 5 wells during filling is 2m3And/min. The filling discharge of the rear 5 wells is 0.5m3Min; the liquid carrying the plugging agent in 10 wells is aqueous solution containing 0.4% xanthan gum or fenugreek gum.
TABLE 1 10 test wells in a block of the Changqing oilfield
Figure BDA0003110239300000091
Figure BDA0003110239300000101
As can be seen from Table 1, the method for temporarily plugging old cracks can effectively plug old cracks, so that the differential pressure of construction pressure (compared with the pressure when fracturing fluid is injected at the beginning) is increased to more than 5 MPa. With filling displacement of 2m3At the time of min, the construction pressure of the rear 5 wells,slightly elevated compared to the pressure at the start of injection of the fracturing fluid. From the oil production condition of the later oil well, the oil yield of the oil well with obvious pressurization (the differential pressure is more than or equal to 5MPa) in the temporary plugging process is over 1 ton, and the oil well with unobvious pressurization (the differential pressure is far less than 5MPa) in the temporary plugging process basically has no yield increasing effect.
Comparative example
The well length of 8 layers of the old well in the Changqing oil field is 2770-2776 m, and the discharge capacity is 2.6m when the plugging agent is added3The plugging agent in example 2 is used in an amount of 3.5m3The discharge capacity is stable, the construction pressure is not increased, the blocking agent is also shown not to block underground cracks, and the fracturing monitoring curve is shown in figure 4.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in other forms, and any person skilled in the art can change or modify the technical content disclosed above into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.

Claims (8)

1. A new method for plugging old underground or underground fractures is characterized by comprising the following steps:
(1) when the crack is closed or partially closed, adding the plugging agent when the fracturing truck starts or is constructed at the beginning, or stopping a pump after fracturing construction for a period of time and simultaneously releasing pressure, and adding the plugging agent after the crack is slowly closed or partially closed; if the wellbore fluid exceeds 10m3Opening a casing gate in the plugging agent adding process, closing the casing gate after replacing a part of wellbore fluid to the ground, and continuously adding the replacement fluid into the underground crack;
(2) when the plugging agent and the displacing liquid enter the cracks, stopping injecting the plugging agent or the displacing liquid when the difference value between the pressure after the construction pressure is raised and the initial pressure before the plugging agent is added reaches 5MPa, and indicating that the plugging agent acts and the underground cracks are plugged.
2. The new method as claimed in claim 1, wherein the fracture closure means that in the field construction process, when the net pressure at the bottom of the well is judged to be less than the closed fracture according to the pressure curve, the fracture is not opened, namely the fracture is closed; the fracture part is closed, namely after fracturing construction, the pump is stopped to relieve pressure, and the pump-stopping pressure of a wellhead is reduced by more than 50%.
3. The method of claim 1, wherein the amount of the plugging agent and the displacement fluid that enter the fracture is controlled to be 0.1-1.5 m3The plugging agent and the carrier fluid of the plugging agent are used for a time of 2-5 m3Then, a displacement fluid, which is a 0.45% xanthan gum solution, was added.
4. The method of claim 1, wherein the amount of the plugging agent and displacement fluid displaced into the fracture is controlled to be 0.5m3Is carried out in/min.
5. The novel method of claim 1, wherein the plugging agent is comprised of a non-crosslinked fracturing fluid containing sand, a high molecular polymer, and fibers, wherein the total content of sand, high molecular polymer, and fibers is 20-40% of the non-crosslinked fracturing fluid, and wherein the content of fibers is 0.5-19%.
6. The method of claim 5, wherein the sand, polymer and fiber are present in a total amount of 20% in the uncrosslinked fracturing fluid.
7. The method of claim 5, wherein the sand is sand having a particle size of 1mm to 5mm and 0.125mm to 0.425 mm.
8. The novel method of claim 5, wherein the uncrosslinked fracturing fluid is a 0.3 to 0.5% aqueous solution of xanthan or fenugreek gum.
CN202110646904.1A 2021-06-10 2021-06-10 New method for plugging underground or underground old crack Pending CN113175316A (en)

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