Ultralow-temperature temporary plugging agent for shallow oil gas fracturing and application of ultralow-temperature temporary plugging agent

Abstract

The invention discloses an ultralow-temperature temporary plugging agent for shallow oil gas fracturing and application of the ultralow-temperature temporary plugging agent. The ultralow-temperature temporary plugging agent is prepared from the following components in percentage by weight: 60-80% of a polymer base material, 1-5% of a temperature-sensitive regulator, 15-25% of filler and 1-10% of a plasticizer, the total percentage is 100%; wherein the polymer base material is a composition of polycarbonate and polyvinyl alcohol, or a composition of polycarbonate and polyethylene glycol; the temperature-sensitive regulator is selected from poly (N-isopropylacrylamide) or polyvinylpyrrolidone. The filler is at least one of potassium chloride, potassium sulfate and corn starch. The preparation method comprises the following steps: firstly, uniformly blending and stirring the polymer base material, the temperature-sensitive regulator, the filler and the plasticizer in a mixer; and then adding the mixed material into a double-screw extruder for melting, plasticizing and extruding, cooling, granulating or grinding to obtain the ultralow-temperature temporary plugging agent particles or powder for shallow oil gas fracturing. The temporary plugging agent prepared by the invention is used in oil reservoirs of shallow coal bed gas, tight oil gas and shale oil with the oil reservoir temperature range of 10-40 DEG C.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemicals, in particular to an ultra-low temperature temporary plugging agent for shallow oil and gas fracturing and application thereof. Background Art

[0002] Hydraulic fracturing technology greatly improves the permeability of rock formations by creating a complex network of fractures in the formation, thereby increasing the recovery rate of oil and gas. During the hydraulic fracturing process, the use of water-soluble temporary plugging agents can temporarily plug the already formed fractures, allowing subsequent fracturing fluids to enter new fractures or branch fractures. After the transformation is completed, the water-soluble temporary plugging agent gradually dissolves, and the blocked fractures restore their conductivity, thereby increasing the complexity and density of the fracture network and increasing the effective transformation volume, which helps to improve reservoir connectivity and enhance oil and gas flow capacity.

[0003] The dissolution temperature of existing conventional mature temporary plugging products is mostly between 50 and 150°C. For shallow low-temperature wells with a depth of less than 1,000 meters and a reservoir temperature of less than 50°C, existing low-temperature temporary plugging products have the defects of being difficult to dissolve, dissolving too quickly, becoming soft and sticky, and having low pressure strength. Therefore, it is urgent to develop ultra-low temperature water-soluble ultra-low temperature temporary plugging agents for temperatures below 50°C.

[0004] The existing patent CN 201610536454.X discloses an automatic diverting temporary plugging agent suitable for medium and low temperature formations and its preparation method. The prepared automatic diverting temporary plugging agent is environmentally friendly, completely degradable, has no pollution to the reservoir, has good plugging performance, is safe and fast to construct, can effectively realize reservoir staged fracturing, and improve oil and gas recovery, but the temporary plugging agent is only suitable for medium and low temperature formation oil reservoirs, not for ultra-low temperature reservoir fracturing transformation. Patent CN 201810274213.1 provides a low-temperature self-degradable high-strength composite temporary plugging diverting agent and its preparation method, the main components of which are polylactic acid, corn starch, styrene, polycaprolactone, unsaturated polyester, partially hydrolyzed polyacrylamide solution and cross-linking agent, with good plugging performance, high pressure bearing strength, good degradation performance, and no pollution to the reservoir, but the low-temperature self-degradable high-strength composite temporary plugging diverting agent is only suitable for 45-90℃ reservoirs, and the strong degradation time is long; it is also not suitable for reservoir transformation under ultra-low temperature conditions. Patent CN 201911092654.0 discloses a micro-foam temporary plugging agent for shallow low-temperature oil reservoirs and its preparation method, using NaHCO 3 , sodium hexadecylbenzene sulfonate, sodium carboxymethyl cellulose, and soluble starch are used as the main raw materials to prepare a micro-foam temporary plugging agent. The temporary plugging agent is used in shallow low-temperature reservoirs between 30°C and 40°C. It has good injection performance and can preferentially enter low-pressure layers. It has a strong plugging ability for low-pressure layers, but a weak plugging ability for high-pressure layers. Therefore, there is currently a lack of high-strength ultra-low temperature temporary plugging agents that can be used for fracturing and reconstruction of shallow reservoirs. Summary of the invention

[0005] Aiming at the problem that the existing low-temperature temporary plugging agent cannot be applied to shallow oil and gas fracturing under ultra-low temperature conditions of 10-40°C, the present invention provides an ultra-low temperature temporary plugging agent for shallow oil and gas fracturing.

[0006] The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing provided by the present invention is made of the following components in percentage by weight:

[0007] 60-80% of polymer base material, 1-5% of temperature-sensitive regulator, 15-25% of filler, 1-10% of plasticizer; the total is 100%.

[0008] Wherein, the polymer substrate is a composition of polycarbonate and polyvinyl alcohol or a composition of polycarbonate and polyethylene glycol.

[0009] The temperature-sensitive regulator is selected from poly (N-isopropylacrylamide) or polyvinylpyrrolidone. The working principle of the temperature-sensitive regulator lies in its responsiveness to temperature, that is, when the temperature changes, the molecular structure or aggregation state of the temperature-sensitive regulator will change, thereby affecting its rheological properties. At low temperatures, the intermolecular interactions of poly (N-isopropylacrylamide) or polyvinylpyrrolidone are weak, forming a loose aggregation state; at high temperatures, the intermolecular interactions are enhanced, forming a tight aggregation state, thereby changing the rheological properties of the material. In the present invention, the dissolution temperature of the temporary plugging agent can be regulated by adjusting the content of the temperature-sensitive regulator.

[0010] The filler is at least one of potassium chloride, potassium sulfate and corn starch. Potassium chloride, potassium sulfate and corn starch are used as fillers to achieve that the temporary plugging agent can be dissolved at 10-40°C, and the temporary plugging agent also has high pressure bearing strength during the dissolution process, which is beneficial to the volume transformation of the reservoir under ultra-low temperature conditions.

[0011] The plasticizer is at least one of glycerol, triethylene glycol, and N-methylpyrrolidine. Its function is to improve the compatibility of the inorganic filler and the polymer substrate during the melt plasticization process, so that the toughness of the polymer and the high strength of the inorganic filler are combined, so that the temporary plugging agent has good molding and processing performance, the production process is simple, and it is easy to realize industrial production.

[0012] Preferably, the polymer substrate is a composition of polycarbonate and polyvinyl alcohol in a mass ratio of 1:2. The polyvinyl alcohol is polyvinyl alcohol 0588, with a molecular weight of 20,000 to 100,000.

[0013] Preferably, the polymer substrate is a composition of polycarbonate and polyethylene glycol in a mass ratio of 1:2. The polyethylene glycol is any one of polyethylene glycol 8000, polyethylene glycol 10000, and polyethylene glycol 20000, wherein the numbers represent molecular weight.

[0014] Preferably, the molecular weight of the polycarbonate is 20,000-60,000.

[0015] The preparation method of the above-mentioned ultra-low temperature temporary plugging agent for shallow oil and gas fracturing is as follows:

[0016] First, the polymer substrate, temperature-sensitive regulator, filler, and plasticizer are mixed and stirred evenly in a mixer; then the mixed material is added to a twin-screw extruder for melting, plasticization, extrusion, cooling, and granulation to obtain ultra-low temperature temporary plugging agent particles for shallow oil and gas fracturing. The temporary plugging agent has a density of 1.20 to 1.60 g / cm 3 .

[0017] When the temporary plugging agent is granulated, it can be processed into particles of 1 to 7 mm according to the on-site construction requirements; it can also be further ground into powder with a powder particle size of 10 to 200 meshes.

[0018] Compared with the prior art, the present invention is beneficial in that:

[0019] (1) The temporary plugging agent of the present invention has a dissolution rate of ≥90% within 8 to 72 hours at 10 to 40°C, a simulated fracture bearing strength of ≥20 MPa, and a bearing time of ≥2 hours. It can be used for temporary plugging at or within the fracture of shallow low-temperature reservoirs at 10 to 40°C, has good plugging performance, and is generally applicable to shallow coalbed methane, tight oil and gas, and shale oil reservoirs with a reservoir temperature range of 10 to 40°C. The construction is safe and fast, and can effectively achieve reservoir staged fracturing and improve oil and gas recovery.

[0020] (2) The temporary plugging agent of the present invention is environmentally friendly and non-toxic. It is environmentally friendly and has no residue after dissolution, which reduces damage to the formation or water pollution. The production process of the temporary plugging agent is simple and can be continuously industrialized.

[0021] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the fracturing construction curve of the temporary plugging agent in Example 2. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0024] Example 1

[0025] An ultra-low temperature temporary plugging agent for shallow oil and gas fracturing is made of the following components in weight percentage:

[0026] Polyvinyl alcohol 0588 50.0%, polycarbonate (molecular weight 50000) 25.0%, polyvinyl pyrrolidone 4.0%, potassium chloride 10.0%, potassium sulfate 5.0%, glycerol 2.5%, triethylene glycol 3.0%, N-methylpyrrolidine 0.5%.

[0027] The preparation method of the temporary plugging agent comprises the following steps:

[0028] (1) Pour the weighed materials into a mixer and mix for 20 minutes until they are evenly mixed;

[0029] (2) Melt extrusion: Add the mixed materials to a twin-screw extruder for melt plasticization and extrusion. The feeding section temperature of the twin-screw extruder is 40°C, the melting section temperature is 140°C, the compression section temperature is 150°C, and the metering section temperature is 165°C. The melt plasticization time is 3 min. The die diameter of the extruder is 2.0 mm.

[0030] (3) Cooling: air cooling, temperature is 30-40℃;

[0031] (4) Pelletizing: the particle size is 1 to 3 mm, and the granular temporary plugging agent A1 is obtained;

[0032] (5) Grinding: The particle size after grinding is 10-200 mesh, and the powder temporary plugging agent is A2.

[0033] The granular temporary plugging agent A1 and the powder temporary plugging agent A2 were mixed in a weight ratio of 1:1 and added to tap water, with the amount accounting for 3% of the mass of tap water; the dissolution rate of the temporary plugging agent under different temperatures and different dissolution time conditions was tested, and the test results are shown in Table 1. At the same time, the pressure bearing strength of the temporary plugging agent was measured to be ≥20MPa, and the pressure bearing time was 2h.

[0034] Table 1 Dissolution rate of ultra-low temperature temporary plugging agent at different temperatures in Example 1

[0035]

[0036] Example 2

[0037] An ultra-low temperature temporary plugging agent for shallow oil and gas fracturing is made of the following components in weight percentage:

[0038] Polycarbonate (molecular weight 20000) 25.0%, polyethylene glycol 10000 50.0%, polyvinyl pyrrolidone 1.0%, potassium chloride 10.0%, potassium sulfate 10.0%, glycerol 1.5%, triethylene glycol 2.0%, N-methylpyrrolidine 0.5%.

[0039] The preparation method of the temporary plugging agent comprises the following steps:

[0040] (1) Pour the weighed materials into a mixer and mix for 20 minutes until they are evenly mixed;

[0041] (2) Melt extrusion: Add the mixed materials to a twin-screw extruder for melt plasticization and extrusion. The feeding section temperature of the twin-screw extruder is 40°C, the melting section temperature is 140°C, the compression section temperature is 150°C, and the metering section temperature is 165°C. The melt plasticization time is 3 min. The die diameter of the extruder is 2.0 mm or 5.0 mm.

[0042] (3) Cooling: air cooling, temperature is 30-40℃;

[0043] (4) Pelletizing: temporary plugging agent particles with a particle size of 1-3 mm and 3-7 mm are obtained, which are named temporary plugging agent particles B1 and B2, respectively.

[0044] The granular temporary plugging agents B1 and B2 were mixed in a weight ratio of 3:1 and added to tap water, with the added amount accounting for 3% of the mass of tap water; the dissolution rate of the temporary plugging agent under different temperatures and different dissolution times was tested, and the test results are shown in Table 2. At the same time, the test showed that the bearing strength of the temporary plugging agent was ≥20MPa and the bearing time was 2h.

[0045] Table 2 Dissolution rate of ultra-low temperature temporary plugging agent at different temperatures in Example 2

[0046]

[0047] Example 3

[0048] An ultra-low temperature temporary plugging agent for shallow oil and gas fracturing, composed of the following components by weight percentage:

[0049] Polycarbonate 20.0%, polyethylene glycol 10000 40.0%, poly N-isopropylacrylamide 5.0%, potassium chloride 10.0%, potassium sulfate 10.0%, starch 5.0%, glycerol 5.0%, triethylene glycol 2.0%, N-methylpyrrolidine 3.0%.

[0050] The preparation method of the temporary plugging agent comprises the following steps:

[0051] (1) Pour the weighed materials into a mixer and mix for 20 minutes until they are evenly mixed;

[0052] (2) Melt extrusion: Add the uniformly mixed materials into a twin-screw extruder for melt plasticization and extrusion. The feeding section temperature of the twin-screw extruder is 40°C, the melting section temperature is 140°C, the compression section temperature is 145°C and the metering section temperature is 155°C. The melt plasticization time is 3 min. The extruder die diameter is 2.0 mm.

[0053] (3) Cooling: air cooling, temperature is 30-40℃;

[0054] (4) Pelletizing: The particle size is 1 to 3 mm, and a temporary plugging agent C suitable for a low-temperature reservoir at 20°C is obtained.

[0055] 3.0% of temporary plugging agent C was added to tap water, and the dissolution rate of the temporary plugging agent at different temperatures and different dissolution times was tested. The results are shown in Table 3. Moreover, the pressure bearing strength of the ultra-low temperature temporary plugging agent is ≥20MPa, and the pressure bearing time is 2h.

[0056] Table 3 Dissolution rate of ultra-low temperature temporary plugging agent at different temperatures in Example 3

[0057]

[0058] Comparative Example 1

[0059] On the basis of Example 3, the dosage ratio of each original component and the preparation method were kept unchanged, and only the dosage of poly (N-isopropylacrylamide) was adjusted to 3%, thereby obtaining temporary plugging agent particles C1.

[0060] Comparative Example 2

[0061] On the basis of Example 3, the dosage ratio of each original component and the preparation method were kept unchanged, and only the dosage of poly (N-isopropylacrylamide) was adjusted to 1%, thereby obtaining temporary plugging agent particles C2.

[0062] Table 4 Experimental data on the effect of temperature-sensitive regulator on the dissolution rate of ultra-low temperature temporary plugging agent (30°C)

[0063]

[0064] From the dissolution rate data corresponding to 1%, 3% and 5% of the temperature-sensitive regulator in Table 4, it can be concluded that by adjusting the content of the temperature-sensitive regulator, the dissolution time and the final dissolution rate of the temporary plugging agent under low temperature conditions can be effectively controlled, thereby adjusting the applicable temperature of the temporary plugging agent.

[0065] The low-temperature temporary plugging agent prepared according to Example 2 has a dissolution rate of 6.28 in 0.5h at 30°C and a dissolution rate of up to 96.55% in 20h. The low-temperature granular temporary plugging agents B1 and B2 of Example 2 are preferably used in the shale oil reservoir of the LC4-S1 well, with a vertical depth of about 600m, a formation temperature of about 30°C, and a formation pressure of about 30MPa; the perforation well section is 2510m-2525m, and the construction displacement is 8.2-12.3m 3 / min, construction pressure 35~55MPa, construction liquid volume 1500m 3 , construction sand volume 60m 3. 1-3mm and 3-7mm ultra-low temperature particle temporary plugging agents B1 and B2 of 30℃ low temperature reservoir were used for temporary plugging and diversion construction of seam mouth. 150kg of 1-3mm ultra-low temperature particle temporary plugging agent B1 and 50kg of 3-7mm ultra-low temperature particle temporary plugging agent B2 were added. The construction pressure before temporary plugging was 41.8MPa, and the construction pressure after temporary plugging was 48.6MPa. The pressure increase before and after temporary plugging was about 6.8MPa. The temporary plugging effect was obvious. The construction curve is as follows Figure 1 shown.

[0066] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. An ultra-low temperature temporary plugging agent for shallow oil and gas fracturing, characterized in that: Made of the following components in weight percentage: 60-80% polymer substrate, 1-5% temperature-sensitive regulator, 15-25% filler, 1-10% plasticizer; total 100%; Wherein, the polymer substrate is a composition of polycarbonate and polyvinyl alcohol, or a composition of polycarbonate and polyethylene glycol; The temperature-sensitive regulator is selected from poly (N-isopropylacrylamide) or polyvinylpyrrolidone.

2. The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to claim 1, characterized in that: The filler is at least one of potassium chloride, potassium sulfate and corn starch.

3. The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to claim 1, characterized in that: The plasticizer is at least one of glycerol, triethylene glycol and N-methylpyrrolidine.

4. The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to claim 1, characterized in that: The polymer substrate is a composition of polycarbonate and polyvinyl alcohol in a mass ratio of 1:

2.

5. The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to claim 4, characterized in that: The polyvinyl alcohol is polyvinyl alcohol 0588, and the molecular weight is 20000-100000.

6. The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to claim 1, characterized in that: The polymer substrate is a composition of polycarbonate and polyethylene glycol in a mass ratio of 1:

2.

7. The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to claim 6, characterized in that: The polyethylene glycol is any one of polyethylene glycol 8000, polyethylene glycol 10000 and polyethylene glycol 20000.

8. The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to claim 1, characterized in that: The molecular weight of the polycarbonate is 20,000-60,000.

9. The ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to any one of claims 1 to 8, characterized in that: The preparation method is as follows: First, the polymer substrate, the temperature-sensitive regulator, the filler and the plasticizer are mixed and stirred evenly in a mixer; then the mixture is added into a twin-screw extruder for melting, plasticizing and extrusion, cooled and granulated to obtain ultra-low temperature temporary plugging agent particles for shallow oil and gas fracturing; or further ground into a powder temporary plugging agent.

10. The use of the ultra-low temperature temporary plugging agent for shallow oil and gas fracturing according to any one of claims 1 to 8, characterized in that: Used for shallow oil and gas fracturing at ultra-low temperature conditions of 10-40℃.

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