CN107090282B

CN107090282B - Mixed temporary plugging agent, temporary plugging agent mixture, temporary plugging method and application thereof

Info

Publication number: CN107090282B
Application number: CN201710353305.4A
Authority: CN
Inventors: 周国君
Original assignee: BEIJING CSI ENERGY TECHNIQUES Co Ltd
Current assignee: BEIJING CSI ENERGY TECHNIQUES Co Ltd
Priority date: 2017-05-18
Filing date: 2017-05-18
Publication date: 2019-12-13
Anticipated expiration: 2037-05-18
Also published as: CN107090282A

Abstract

the invention relates to a mixed temporary plugging agent, a temporary plugging agent mixture, a temporary plugging method and application, wherein the mixed temporary plugging agent comprises the following components in parts by weight: 1-9 parts of water-soluble high polymer, 3-29 parts of sand and 0-19 parts of soluble or degradable fiber. The mixed temporary plugging agent is prepared into a temporary plugging agent mixture by using 10-100 parts by weight of carrier fluid, and the temporary plugging agent mixture is replaced by displacement fluid to enter a preset position of an underground crack, so that a temporary plugging wall with certain viscosity is formed. The method can be applied to vertical well separate-zone fracturing, horizontal well staged fracturing and old well repeated fracturing, the plugging position can be controlled by controlling the viscosity-raising time (according to the concentration of the temporary plugging agent) and the injection speed (according to the volume of the well shaft and the displacement liquid amount), 100 percent of plugging is raised, the plugging strength is high, the subsequent fracturing new joint (increasing new drainage area) is facilitated, and the yield of the oil-gas well is further improved.

Description

Mixed temporary plugging agent, temporary plugging agent mixture, temporary plugging method and application thereof

Technical Field

The invention belongs to the technical field of production increase of oil and gas wells, and particularly relates to a mixed temporary plugging agent, a construction method and application thereof, which are mainly used for plugging a previously pressed crack in the fracturing process of an oil and gas well so as to open a new crack (in order to increase more new drainage areas).

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 temporary plugging diversion fracturing technology is characterized in that a temporary plugging agent is added in real time in a fracturing process, based on the principle that fluid flows along the direction of the minimum resistance, the temporary plugging agent can enter a blasthole communicated with an original crack or a high permeable layer along with fracturing fluid, high-strength filter cake bridging is generated at the blasthole 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.

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 technology is basically based on friction accumulation (or bridging enrichment) of temporary plugging particles or fibers in a seam or a seam opening (blast hole) to form a bridge plug, the accumulation or enrichment is a fuzzy process, the temporary plugging time and position cannot be determined, the thickness of the temporary plug formed through accumulation cannot be determined due to the problem of temporary plugging agent loss, the strength and the effect of the temporary plug are difficult to guarantee, and meanwhile, the problems of loss and waste of the temporary plugging agent and the problem of residual in subsequent fracturing fluid after temporary plugging exist, so that the subsequent fracturing of a new seam is influenced. In addition, the conventional temporary plugging fracturing technology basically determines the adding amount of the temporary plugging agent according to the change of the construction pressure of the ground, so that the temporary plugging agent needs to be prepared in advance on the ground, and is inevitably added too much, and a part of the temporary plugging agent can be wasted.

Disclosure of Invention

Technical problem to be solved

In order to solve the above problems of the prior art, the present invention provides a mixed temporary plugging agent, which can effectively control the temporary plugging timing, position and strength to form more effective plugging.

The present invention also provides a temporary plugging agent mixture which can control the temporary plugging timing, position and strength, and can form more effective plugging.

The invention also provides a temporary plugging method, which can control the temporary plugging time, position and strength to form more effective plugging in the temporary plugging steering fracturing process.

The invention also provides a mixed temporary plugging agent, a temporary plugging agent mixture and application of the temporary plugging method, which can control the temporary plugging time, position and strength to form more effective plugging in the temporary plugging steering fracturing process.

(II) technical scheme

In order to achieve the purpose, the invention adopts the main technical scheme that:

A mixed temporary plugging agent comprises the following components in parts by weight:

1 to 9 parts of a water-soluble high molecular polymer,

3-29 parts of sand,

0-19 soluble or degradable fibers.

Preferably, the soluble or degradable fibers are 0.5 to 19. The mixed temporary plugging agent can be prepared into a dry solid state (all components can be mixed or subpackaged), when in use, the mixture of all the components can be added into a carrying fluid to be mixed to form gel, the initial viscosity of the gel is low, and the viscosity of the gel is gradually increased along with the increase of the mixing time, so that the temporary plugging time and position can be controlled, the temporary plugging agent does not lose, waste or residual, the thickness and the strength can be ensured, in addition, the sand and the fiber can increase the binding power and the friction resistance of the gel, the strength and the moving difficulty of the gel can be increased, a gel mixture with strong plugging capability is finally formed, and simultaneously, after the temporary plugging is dissolved, the sand in the gel can be kept to support cracks.

In an embodiment of the mixed temporary plugging agent of the present invention, the water-soluble high molecular polymer is one or more of acrylamide copolymers.

For example, the water-soluble high molecular polymer is polyacrylamide, preferably, the molecular weight is 1100 to 2500 ten thousand. The time required for it to reach a certain viscosity can be adjusted by controlling its concentration.

Preferably, the water-soluble high molecular polymer is polyacrylamide and/or 2-acrylamido-2-methylpropanesulfonic acid.

When the polyacrylamide is a mixture of polyacrylamide and 2-acrylamido-2-methylpropanesulfonic acid, the ratio of the polyacrylamide to the 2-acrylamido-2-methylpropanesulfonic acid is 2.5: 1.3-2.8: 1.5.

When the polyacrylamide and the 2-acrylamide-2-methylpropanesulfonic acid are mixed for use, the mixture has the characteristics of good water solubility, good tackifying property and heat tackifying effect, and the 2-acrylamide-2-methylpropanesulfonic acid has the coagulation aiding effect.

In the embodiment of the mixed temporary plugging agent, the sand is quartz sand and/or ceramsite sand, and the particle size is 0.25-8 mm.

Preferably, the sand is quartz sand and/or ceramsite sand, and the particle size is 0.45-3.75 mm.

preferably, the sand is quartz sand and/or ceramsite sand with different particle sizes.

For example, 20 wt% of 6.7 to 8 mm quartz sand, 15 wt% of 4.75 to 6.7 mm ceramsite sand, 12 wt% of 3.35 to 4.75 mm ceramsite sand, 18 wt% of 1.7 to 3.35 mm quartz sand, 20 wt% of 0.71 to 1.7 mm ceramsite sand, and 15 wt% of 0.45 to 0.71 mm quartz sand. Or 22 wt% of quartz sand with the thickness of 3.35-4.75 mm, 28 wt% of ceramsite sand with the thickness of 1.7-3.35 mm, 30 wt% of quartz sand with the thickness of 0.71-1.7 mm and 20 wt% of ceramsite sand with the thickness of 0.45-0.71 mm.

In an embodiment of the hybrid temporary plugging agent of the present invention, the soluble or degradable fiber is preferably 0.8 to 7 parts by weight, wherein the soluble or degradable fiber includes one or more of polyvinyl alcohol fiber, modified polyester fiber, and polyurethane fiber.

Preferably, the polyvinyl alcohol fibers, the modified polyester fibers and the polyurethane fibers are added according to the weight ratio of 1.7:0.5: 3.2. The addition of soluble or degradable fibers can improve the temporary plugging performance of the fiber proppant so as to greatly improve the strength of a temporary plugging layer, and is favorable for preventing backflow and backflow of sand.

preferably, the length of the soluble or degradable fiber is 2-12 mm.

Preferably, the proportion of the fibers with the length of 4 +/-0.5 mm is 55-75 wt%. Preferably, the fiber with the length of 4 +/-0.5 mm accounts for 55-75 wt%, the fiber with the length of less than 3.5 mm accounts for 5-10 wt%, and the fiber with the length of 9-11 mm accounts for 10-15 wt%.

Wherein the soluble or degradable fiber begins to dissolve at more than 60 ℃ and at more than 90 ℃, the dissolution rate is related to underground temperature and time, and the complete dissolution time (the dissolution rate is more than 80%) is generally more than 25 minutes.

the temporary plugging agent mixture comprises any one of the mixed temporary plugging agents and carrier fluid, wherein the weight part of the carrier fluid is 10-100.

Wherein the carrier fluid is a non-crosslinked fracturing fluid having a viscosity of less than 100 mPa sec.

preferably, the carrier fluid is a xanthan gum fracturing fluid and/or a coumarone gum fracturing fluid.

Preferably, the mass concentration of the xanthan gum and/or the fenugreek gum in the carrying fluid is 0.1-0.7%.

Further, the carrier fluid contains tween-20, isoamyl alcohol, hydroxyethyl cellulose and sodium borohydride. Preferably, the mass concentrations of the tween-20, the isoamyl alcohol, the hydroxyethyl cellulose and the sodium borohydride in the carrying fluid are 0.03-0.1%, 0.002-0.006%, 0.01-0.09% and 0.001-0.005%, respectively.

According to the invention, researches show that after tween-20, isoamylol, hydroxyethyl cellulose and sodium borohydride are added into the carrying fluid, the utilization rate and the repeated fracturing success rate of the temporary plugging agent mixture can be greatly improved, and the effect of effective plugging is achieved.

Further, the carrying fluid contains potassium chloride and sodium salicylate, and the mass concentration of the potassium chloride and the sodium salicylate in the carrying fluid is preferably 0.01 to 0.1% and 0.005 to 0.01%.

The potassium chloride and the salicylate are added to ensure that the carrier fluid is more stable and is used for preparing the temporary plugging agent to further improve the plugging strength.

A temporary plugging method, comprising the steps of:

S1, preparing a preset amount of any one temporary plugging agent mixture;

s2, mixing the temporary plugging agent mixture prepared in the step S1 and adding the mixture into a shaft;

S3, continuously injecting displacement liquid to displace the temporary plugging agent mixture to the seam opening of the underground reservoir fracture or a preset position in the seam;

S4, controlling the time required for the temporary plugging agent mixture to be coagulated at the preset position in the seam by adjusting the pump injection speed or the discharge capacity according to the liquid amount of the well bore, so that the temporary plugging agent mixture is coagulated at the preset position;

S5, after the temporary plugging agent mixture is coagulated at a preset position, completing temporary plugging;

and S6, after the temporary plugging is finished, the displacement can be lifted and the new fracture can be fractured within half an hour.

The temporary plugging agent mixture is in the process of gradually increasing the viscosity after being prepared, and is suspended along with the slowing of the pumping speed, so that the temporary plugging agent mixture can be further coagulated at a preset time and position to form a final high-strength gel mixture, therefore, the temporary plugging agent mixture has no loss and waste problem, the temporary plugging time, position and thickness are controllable, the construction is simplified, the plugging strength is ensured, meanwhile, the required using amount of the temporary plugging agent mixture can be predicted before the construction is started, and the problem of residual temporary plugging agent mixture is solved.

in step S1, the predetermined amount of the temporary plugging agent mixture is calculated.

Preferably, the predetermined amount of the temporary plugging agent mixture is calculated according to the seam height and the seam width of the position to be plugged and the thickness to be plugged;

In step S3, the predetermined location is a seam or an inside of a fracture of the underground reservoir, and the temporary plugging location can be controlled by adjusting the amount of the displacement fluid. In a specific implementation, the temporary plugging agent mixture in step S1 is obtained by adding any one of the above mixed temporary plugging agents to the carrier fluid in proportion and mixing.

Preferably, the water-soluble high molecular polymer, the sand and the fiber are mixed in proportion and then added into the carrying fluid.

When the preset position is a seam of a underground reservoir fracture, the using amount of the displacement fluid is equal to the amount of the wellbore fluid; and when the preset position is in a seam of the underground reservoir fracture, the using amount of the displacement fluid is larger than the wellbore fluid amount, and the using amount of the displacement fluid is selected according to the position in the seam.

the mixed temporary plugging agent, the temporary plugging agent mixture and the temporary plugging method are applied to the vertical well separate-layer fracturing, the horizontal well separate-section fracturing or the old well repeated fracturing.

(III) advantageous effects

The invention has the beneficial effects that: the mixed temporary plugging agent can be prepared into a dry solid state (the components can be mixed or subpackaged), is convenient to carry and transport, and when the temporary plugging agent is used, the mixture of the components can be added into carrier fluid to form a gel temporary plugging agent mixture. The gel temporary plugging agent mixture has low initial viscosity and gradually increased viscosity along with the increase of preparation time, so that the temporary plugging time and position can be controlled, the temporary plugging agent mixture has no loss, waste and residue of the temporary plugging agent, and the thickness and the strength can be ensured. In addition, the sand and the fibers can increase the adhesive force and the frictional resistance of the gel, are helpful for increasing the strength and the moving difficulty of the gel, finally form a gel mixture with strong plugging capability, and simultaneously, after the temporary plugging is dissolved, the sand can be reserved for supporting cracks.

Detailed Description

The mixed temporary plugging agent and the carrier fluid can be separately packaged, are convenient to carry and transport and use, can be prepared into a temporary plugging agent mixture only by adding the mixed temporary plugging agent into the carrier fluid, has low initial viscosity, and gradually increases the viscosity along with the increase of mixing time, so that the temporary plugging time and the temporary plugging position can be effectively controlled, the loss and the waste of the temporary plugging agent are avoided in the using process, the thickness and the strength can be effectively ensured, the construction is simplified, and the cost is saved.

In order that the invention may be better understood, it is described in detail below with reference to specific examples.

Examples 1 to 5 (taking the example that the underground crack is two symmetric cracks at two sides of a shaft, the height of the underground crack to be plugged is 50 meters, the width of the underground crack is 10 millimeters, and the preset plugging thickness is 2 meters).

Example 1

Preparing 100Kg of PAM (polyacrylamide, PAM, molecular weight is 1600 ten thousand), 200Kg of sand and 30Kg of polyvinyl alcohol fiber, mixing the two materials on a sand mixer, then simultaneously and uniformly pouring the two materials into 2 tons of non-crosslinked 0.5% xanthan gum fracturing fluid to form a gel mixture 1 with initial viscosity of 90 mPas, then displacing the gel mixture into a crack opening, and forming a temporary plugging wall with the thickness of 2 m at the crack opening.

Wherein the sand is quartz sand with the particle size of 1-5 mm.

The length of the polyvinyl alcohol fiber is 2-12 mm, wherein 55 wt% of the polyvinyl alcohol fiber with the length of 4 +/-0.5 mm, 10 wt% of the polyvinyl alcohol fiber with the length of less than 3.5 mm, 15 wt% of the polyvinyl alcohol fiber with the length of 9-11 mm, and the balance of 4.5-9 mm and 11-12 mm.

The uncrosslinked 0.5% xanthan gum fracturing fluid is 0.5% by mass of aqueous xanthan gum solution. The viscosity change of the above temporary plugging agent mixture was measured as shown in table 1 below.

TABLE 1

the detection result shows that the viscosity of the temporary plugging agent mixture is gradually increased along with the time extension until the temporary plugging agent mixture is plugged (the viscosity increasing speed is accelerated at a higher temperature), and the temporary plugging agent mixture is plugged according to the preparation time, so the plugging position of the temporary plugging agent mixture can be controlled by controlling the time and the injection speed, the uncontrollable defect of plugging by accumulation or enrichment under the existing temporary plugging technology is avoided, the temporary plugging agent mixture can be prefabricated in a proper amount, the waste caused by loss or residue is avoided, the compressive strength after plugging is measured to be 45MPa/m by a sand filling blasthole model and is enough for opening new seams for subsequent fracturing construction, namely, the temporary plugging agent mixture can be plugged by 100 percent, the plugging agent mixture does not need to be detected by ground construction pressure to determine whether the plugging agent is formed or not, and the construction is convenient and rapid; along with further prolonging of time, the viscosity of the oil-water mixture is gradually reduced until the blockage is removed (the viscosity reduction speed is accelerated under the action of the gel breaker), so that the blockage removal time can be estimated, the oil-water mixture can be naturally and completely removed without damaging the stratum, and the gel breaker can be used for controlling the blockage removal time; in addition, the sand can also be used for supporting cracks, thereby achieving multiple purposes.

example 2

preparing 20Kg of AMPS (2-acrylamide-2-methylpropanesulfonic acid), 60Kg of sand and 328Kg of modified polyester fiber, mixing the three materials on a sand mixing truck, uniformly pouring the mixture into 2 tons of uncrosslinked 0.5% coumaric glue fracturing fluid to form a gel mixture 2 with initial viscosity of 90 mPas, then displacing the gel mixture into the crack for 50m, and suspending the gel mixture in the crack for 50m to form a temporary blocking wall with the thickness of 2 m.

The sand is quartz sand and ceramsite sand with the particle size of 0.25-8 mm, wherein the quartz sand and the ceramsite sand are 20 wt% of 6.7-8 mm, the ceramsite sand is 15 wt% of 4.75-6.7 mm, the ceramsite sand is 12 wt% of 3.35-4.75 mm, the quartz sand is 18 wt% of 1.7-3.35 mm, the ceramsite sand is 20 wt% of 0.71-1.7 mm, and the quartz sand is 15 wt% of 0.25-0.71 mm.

The length of the modified polyester fiber is 2-12 mm, wherein the length of the modified polyester fiber accounts for 60 wt% of 4 +/-0.5 mm, the weight of the modified polyester fiber accounts for 6.2 wt% below 3.5 mm, the weight of the modified polyester fiber accounts for 10 wt% of 9-11 mm, and the balance is 4.5-9 mm and 11-12 mm.

Wherein the uncrosslinked 0.5% fenugreek gum fracturing fluid is a 0.5% fenugreek gum aqueous solution. The viscosity change of the above temporary plugging agent mixture was measured as shown in Table 2 below.

TABLE 2

The detection result shows that the viscosity change trends of the temporary plugging agent mixture are the same, and the compressive strength of the temporary plugging agent is 40MPa/m, so that the temporary plugging agent is enough for subsequent fracturing construction to open new joints.

Example 3

Preparing 180Kg of PAM + AMPS, 340Kg of sand and 230Kg of polyurethane fiber, mixing the three materials on a sand mixing truck, uniformly pouring the mixture into 2 tons of uncrosslinked 0.45% xanthan gum fracturing fluid to form a gel mixture 3 with initial viscosity of 85 mPas, and then displacing the gel mixture into a crack for 30 m, wherein the gel mixture forms a temporary plugging wall with the thickness of more than 2 m at the crack opening.

Wherein, the weight ratio of the PAM to the AMPS is 2.5:1.3, and the molecular weight of the PAM is 1700 ten thousand.

The sand is quartz sand and ceramsite sand with the particle size of 0.45-4.75 mm, wherein the quartz sand is 22 wt% of 3.35-4.75 mm, the ceramsite sand is 28 wt% of 1.7-3.35 mm, the quartz sand is 30 wt% of 0.71-1.7 mm, and the ceramsite sand is 20 wt% of 0.45-0.71 mm.

The length of the polyurethane fiber is 2-12 mm, wherein the length of the polyurethane fiber accounts for 65 wt% of the fiber with the diameter of 4 +/-0.5 mm, the length of the fiber with the diameter of less than 3.5 mm accounts for 8.6 wt%, and the length of the fiber with the diameter of 9-11 mm accounts for 11.3 wt%.

The uncrosslinked 0.45% xanthan gum fracturing fluid can adopt 0.45% xanthan gum aqueous solution by mass percentage.

The viscosity change of the above temporary plugging agent mixture was measured as shown in Table 3 below.

TABLE 3

The detection result shows that the viscosity change trends of the temporary plugging agent mixture are the same, the compressive strength of the temporary plugging agent is 48MPa/m, and the temporary plugging agent is enough for subsequent fracturing construction to open new seams.

example 4

Preparing 60Kg of PAM (molecular weight is 2500 ten thousand), 460Kg of sand, 380Kg of polyvinyl alcohol and modified polyester fiber, mixing the three materials on a sand mixer, uniformly pouring the mixture into 2 tons of uncrosslinked fracturing fluid at the same time to form a gel mixture 4 with initial viscosity of 95 mPas, then displacing the gel mixture into a crack opening, and pausing the gel mixture at the crack opening to form a temporary plugging wall with thickness of more than 2 m.

Wherein the sand is quartz sand with the particle size of 1-6.5 mm.

the uncrosslinked fracturing fluid can adopt an aqueous solution containing 0.25 percent of fenugreek gum, 0.03 percent of tween-20, 0.005 percent of isoamyl alcohol and 0.05 percent of hydroxyethyl cellulose and 0.003 percent of sodium borohydride by mass percentage. The temporary plugging agent mixture is prepared by mixing Tween-20, isoamylol, hydroxyethyl cellulose and sodium borohydride, and then adding a solvent to the temporary plugging agent mixture.

Wherein the weight ratio of the polyvinyl alcohol to the modified polyester fiber is 2.8:1.5, the length is 2-12 mm, wherein the weight ratio of 4 +/-0.5 mm accounts for 70 wt%, the weight ratio of the 4 +/-0.5 mm to the following 7.5 wt%, and the weight ratio of 9-11 mm to the 12 wt%.

The viscosity change of the above temporary plugging agent mixture was measured as shown in Table 4 below.

TABLE 4

The detection result shows that the viscosity change trends of the temporary plugging agent mixture are the same, the compressive strength of the temporary plugging agent is 49MPa/m, and the temporary plugging agent is enough for subsequent fracturing construction to open new seams.

Example 5

preparing 140Kg of AMPS, 580Kg of sand, 110Kg of polyvinyl alcohol fiber, modified polyester fiber and polyurethane fiber, uniformly pouring the materials into 2 tons of uncrosslinked 0.45 percent xanthan gum mixed 0.3 percent of coumarins gum fracturing fluid after mixing the materials on a sand mixing truck to form a gel mixture 5 with initial viscosity of 95 mPas, and then displacing the gel mixture into cracks to form temporary plugging walls with thickness of more than 2 meters at the seams.

Wherein the sand is half of ceramsite sand and quartz sand with the particle size of 0.5-5 mm respectively.

Wherein the weight ratio of the polyvinyl alcohol fibers to the modified polyester fibers to the polyurethane fibers is 1.7:0.5:3.2, the length of the polyvinyl alcohol fibers is 2-12 mm, wherein the weight ratio of the polyvinyl alcohol fibers to the modified polyester fibers to the polyurethane fibers is 75 wt%, the weight ratio of the polyvinyl alcohol fibers to the modified polyester fibers to the polyurethane fibers is less than 3.5 wt%, and the weight ratio of the polyvinyl alcohol fibers to the polyurethane fibers is 13.4 wt%.

the uncrosslinked xanthan gum 0.45% and fenugreek gum fracturing fluid 0.3% can be aqueous solution of xanthan gum 0.45% and fenugreek gum 0.3%.

The viscosity change of the above temporary plugging agent mixture was measured as shown in Table 5 below.

TABLE 5

The detection result shows that the viscosity change trends of the temporary plugging agent mixture are the same, the compressive strength of the temporary plugging agent is 43MPa/m, and the temporary plugging agent is enough for subsequent fracturing construction to open new seams.

Example 6

This example is based on example 4, and the components of the carrying fluid are further improved, and potassium chloride with the mass concentration of 0.05% and salicylate with the mass concentration of 0.005% in the carrying fluid are added to obtain a gel mixture 6. The potassium chloride and the salicylate are added to ensure that the carrier fluid is more stable and is used for preparing the temporary plugging agent to further improve the plugging strength. The viscosity change of the gel mixture 6 was measured as shown in the following Table 6.

TABLE 6

The detection result shows that the viscosity change trends of the temporary plugging agent mixture are the same, the compressive strength of the temporary plugging agent is 50MPa/m, and the temporary plugging agent is enough for subsequent fracturing construction to open new seams.

Because the viscosity of the temporary plugging agent mixture is gradually increased in the injection process, the temporary plugging agent mixture is generally controlled to reach the preset plugging position before the viscosity reaches 300 mPa seconds, so that the temporary plugging agent mixture can not only avoid the difficulty in injection due to excessive viscosity, but also avoid the loss at the preset plugging position due to excessive viscosity.

In conclusion, the mixed temporary plugging agent consists of water-soluble high-molecular polymers (polyacrylamides), quartz sand (or ceramsite sand) with different sizes and soluble or degradable fibers (polyvinyl alcohol and the like), and after being mixed on a wellhead sand mixing truck, non-crosslinked fracturing fluid (such as xanthan gum fracturing fluid) is carried into a crack opening or a crack of a underground stratum, and then a gel mixture with strong plugging capability (the compressive strength is more than 40 MPa/m) is formed, so that the plugging success rate is 100%, and the plugging strength is enough for the subsequent fracturing construction to open a new crack. That is, the invention forms gel by using water-soluble polymer, the viscosity of the gel is low at first (usually less than 100 mPas), about 300 mPas can be reached in about 10 minutes, sand and fiber with different particle sizes in the gel can effectively increase the strength and moving difficulty (cohesive force and frictional resistance) of the gel, and finally the temporary plugging wall with enough strength can be obtained in a preset time.

Because the temporary plugging agent mixture is a gel mixture with gradually increased viscosity from the beginning of injection to the crack, compared with the prior temporary plugging technology, the temporary plugging agent mixture has no problems of loss and waste and residue of the temporary plugging agent, can ensure that the temporary plugging agent stays in the crack or at the preset position of the crack opening and the like, and can meet the plugging requirement on strength when reaching enough thickness.

the invention creatively adds sand and fiber in the gel, obtains unexpected technical effect, obviously improves the plugging performance, in particular, the invention is different from the principle that the prior art forms bridge plugging by friction accumulation and enrichment, the invention mixes the temporary plugging agent and the fracturing fluid to form a gel mixture which enters a certain part of the crack without loss and residue, overcomes the defects of loss and residue waste and no guarantee of thickness in the prior art, and can control the time required by the mixture of the temporary plugging agent to be coagulated at a preset position in the crack by adjusting the pumping speed (discharge capacity), further increases the viscosity of the mixture of the temporary plugging agent, further bonds, finally increases the strength of the obtained mixture, increases the plugging capability, and because the adding amount of the temporary plugging agent is determined according to the height of the crack to be plugged without observing the pressure of a well head, the method can quantify before construction, overcomes the defect that in the prior art, whether the temporary plugging agent is blocked or not is judged according to the pressure of a well head (namely under the condition that the discharge capacity is unchanged, if the pressure of the well head rises, the temporary plugging agent is judged to be accumulated in a seam or the seam is blocked, the temporary plugging agent is stopped to be added), and the temporary plugging agent has to be prepared more to cause waste.

Claims

1. A temporary plugging agent mixture is characterized by comprising a mixed temporary plugging agent and carrier fluid, wherein the weight part of the carrier fluid is 10-100,

The mixed temporary plugging agent comprises the following components in parts by weight:

1 to 9 parts of a water-soluble high molecular polymer,

3-29 parts of sand,

0-19 of soluble or degradable fibers;

The water-soluble high polymer is polyacrylamide and/or 2-acrylamide-2-methylpropanesulfonic acid with the molecular weight of 1100-2500 ten thousand;

The sand is quartz sand and/or ceramsite sand, and the particle size of the sand is 0.25-8 mm;

The soluble or degradable fibers comprise one or more of polyvinyl alcohol fibers, modified polyester fibers and polyurethane fibers;

The length of the soluble or degradable fiber is 2-12 mm, wherein the fiber with the length of 4 +/-0.5 mm accounts for 55-75 wt%;

the carrying fluid is a non-crosslinked fracturing fluid with the viscosity of less than 100 mPas; the carrying fluid is a xanthan gum fracturing fluid and/or a fenugreek gum aqueous solution with the mass concentration of 0.1-0.7%.

2. The temporary plugging agent mixture of claim 1 wherein: the carrying fluid contains Tween-20, isoamylol, hydroxyethyl cellulose and sodium borohydride, and the mass concentrations of the Tween-20, the isoamylol, the hydroxyethyl cellulose and the sodium borohydride in the carrying fluid are 0.03-0.1%, 0.002-0.006%, 0.01-0.09% and 0.001-0.005% respectively.

3. The temporary plugging agent mixture according to claim 2, wherein the carrier fluid further comprises potassium chloride and sodium salicylate, and the mass concentration of the potassium chloride and the sodium salicylate in the carrier fluid is 0.01-0.1% and 0.005-0.01%.

4. A temporary plugging method is characterized by comprising the following steps:

S1, preparing a predetermined amount of the temporary plugging agent mixture according to any one of claims 1-3;

S3, injecting a displacement fluid to displace the temporary plugging agent mixture to a seam opening of the underground reservoir fracture or a preset position in the seam;

S4, controlling the time required for the temporary plugging agent mixture to be coagulated at a preset position in the seam by adjusting the pump injection speed or the discharge capacity according to the liquid amount of the well bore, so that the temporary plugging agent mixture is coagulated at the preset position in the seam opening or the seam;

5. The temporary plugging method according to claim 4, wherein:

in the step S1, calculating the predetermined amount of the temporary plugging agent mixture according to the seam height and the seam width of the position to be plugged and the thickness to be plugged;

in the step S3, the predetermined position is a seam or a seam inside a fracture of the underground reservoir, and the temporary blocking position is controlled by adjusting the amount of the displacement fluid.

6. Use of a temporary plugging agent mixture according to any one of claims 1 to 3 or a temporary plugging method according to claim 4 or 5 in vertical well zonal fracturing, horizontal well staged fracturing or old well re-fracturing.