Chemical temporary plugging agent for oil testing operation of leakage reservoir as well as preparation method and application of chemical temporary plugging agent

Abstract

The invention discloses a chemical temporary plugging agent for oil testing operation of a water leakage reservoir, and belongs to the field of well completion processes of oil and gas wells. The acid-soluble gel material comprises the following raw materials in percentage by weight: 80%-90% of an acid-soluble gel material and 10%-20% of an acid-soluble granular material. The invention also discloses a preparation method of the chemical temporary plugging agent for the oil testing operation of the water leakage reservoir. The leakage reservoir formation testing operation chemical temporary plugging agent provided by the invention can remarkably improve the pressure bearing capacity of a crack plugging layer, the pressure bearing capacity of the crack plugging layer can be improved by 164% at most compared with that of a crack plugging layer formed by purely using a gel chemical temporary plugging agent, the plugging layer can be completely removed through an acidification method after the operation is finished, the purpose of reservoir protection is achieved, and the leakage reservoir formation testing operation chemical temporary plugging agent has the advantages of simple preparation process and low cost. The chemical temporary plugging agent provided by the invention has wide application prospect and market scale in the development aspect of gas fields such as Sichuan, Tarim and the like.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well completion technology, specifically to a chemical temporary plugging agent for oil testing operations in leaking reservoirs, its preparation method, and its application. Background Technology

[0002] After years of exploitation, the pressure coefficient of fractured oil and gas reservoirs decreases. During well testing operations, well control fluid loss often occurs. The loss of well control fluid into the reservoir can easily induce damage such as solid phase blockage, fluid sensitivity, and liquid phase trapping, leading to well control risks. As the amount of well control fluid loss increases, the range of loss damage can reach several meters to tens of meters, and even hundreds of meters in fractured reservoirs, causing a significant decrease in oil and gas production and increasing the difficulty of unblocking and stimulation.

[0003] Compared to plugging techniques during drilling, temporary plugging techniques during well testing require careful consideration of numerous factors, including plugging efficiency, reservoir damage, pressure bearing capacity, and acid solubility. Currently, temporary plugging techniques during well testing are mainly divided into mechanical temporary plugging, physical bridge plug temporary plugging, and chemical plugging agent temporary plugging. Mechanical temporary plugging involves running a plugging string into the lost reservoir to isolate the fractures from the wellbore, preventing kill fluid from leaking into the reservoir and causing damage. However, mechanical temporary plugging is extremely expensive. Physical bridge plugging utilizes acid-soluble particulate and fiber materials to deposit and accumulate in the fractures, forming a dense, high-pressure bridge plug that isolates the fractures from the wellbore, preventing kill fluid from leaking into the reservoir. Physical bridge plugging is low-cost, simple to implement, and uses readily available materials, but its effectiveness largely depends on the matching relationship between the particle size and the fracture width. Chemical plugging utilizes polymer gels to crosslink or solidify in the reservoir fractures, forming slugs with a certain strength to isolate the fractures from the wellbore. The gel materials used in chemical plugging are highly adaptable, with no requirements on fracture width or shape, and can easily deposit with the fractures to form slugs to prevent kill fluid leakage. However, chemical plugging often suffers from insufficient pressure resistance.

[0004] Currently, chemical plugging agents are the preferred method for controlling fluid loss during well testing in complex fractured reservoirs. However, for deep fractured reservoirs, where temperatures often exceed 100°C, the harsh high-temperature environment weakens the strength of gel materials, further exacerbating their insufficient pressure-bearing capacity. Domestic literature reviews indicate that the low pressure-bearing capacity of gel plugging materials forming slugs in fractures remains a significant challenge. Improving the pressure-bearing capacity of fracture sealing layers remains a crucial and urgent problem in the field of working fluid loss control. Summary of the Invention

[0005] The purpose of this invention is to provide a chemical temporary plugging agent for oil testing of leaking reservoirs, its preparation method, and its application, in order to solve the technical problem that the pressure-bearing capacity of gel temporary plugging materials forming slugs in fractures is low in the prior art.

[0006] To achieve the above objectives, one embodiment of the present invention provides a chemical temporary plugging agent for oil testing of leaking reservoirs, comprising the following raw materials in weight percentages: 80%-90% acid-soluble gel material and 10%-20% acid-soluble particulate material.

[0007] One preferred embodiment of the present invention is a chemical temporary plugging agent comprising the following raw materials in weight percentages: 81%-88% acid-soluble gel material and 12%-19% acid-soluble particulate material.

[0008] One preferred embodiment of the present invention is a chemical temporary plugging agent comprising the following raw materials in weight percentages: 83%-87% acid-soluble gel material and 13%-16% acid-soluble particulate material.

[0009] In one preferred embodiment of the present invention, the acid-soluble gel material includes SMG gel.

[0010] In one preferred embodiment of the present invention, the acid-soluble particulate material includes at least one of calcium carbonate and oyster shell.

[0011] In one preferred embodiment of the present invention, the particle size of the acid-soluble particulate material is 1 / 3 to 2 / 3 of the crack width.

[0012] Based on the chemical plugging agent for oil testing of leaking reservoirs disclosed in this invention, this invention also discloses a method for preparing the chemical plugging agent for oil testing of leaking reservoirs, wherein acid-soluble gel material and acid-soluble particulate material are stirred and mixed to obtain the chemical plugging agent.

[0013] In one preferred embodiment of the present invention, acid-soluble particulate material is added to acid-soluble gel material and stirred evenly to obtain a chemical temporary plugging agent.

[0014] In one preferred embodiment of the present invention, the stirring speed is 300 r / min-500 r / min and the stirring time is 0.5 h-1.5 h.

[0015] This invention also discloses the application of a chemical temporary plugging agent in oil testing operations for leaking reservoirs, applying it to well-killing fluid leakage during oil testing operations in complex fractured reservoirs.

[0016] In summary, the beneficial effects of the present invention are as follows:

[0017] 1. The chemical plugging agent of the present invention includes acid-soluble gel material and acid-soluble particulate material. Compared with a single gel material: the slug formed by a single gel material in the fracture has weakened pressure resistance under high temperature conditions. However, after adding acid-soluble particulate material, the gel solution carries the particulate material to stay, accumulate and bridge at a suitable position in the fracture, forming a skeleton structure of the plugging layer. After the gel solution is cross-linked or cured, the plugging layer skeleton formed by the bridging of the particles can assist the gel in bearing part of the shear force (pressure difference between the wellbore and the fracture). At the same time, the plugging layer skeleton formed by the bridging of the particulate material is equivalent to transforming the fracture leakage channel into a porous leakage channel, which greatly helps to improve the pressure resistance of the gel material, thereby improving the pressure resistance of the fracture plugging.

[0018] 2. The chemical plugging agent proposed in this invention is mainly made of gel, so it can easily enter the fracture regardless of the fracture width, quickly form a slug, and prevent the loss of kill fluid.

[0019] 3. The chemical temporary plugging agent provided by the present invention can significantly improve the pressure bearing capacity of the crack sealing layer formed by gel, and can improve the pressure bearing capacity by up to 164% compared with the crack sealing layer formed by using the same type of gel alone.

[0020] 4. The chemical plugging agent of this invention uses acid-soluble gel and acid-soluble particulate materials. After the construction operation is completed, the plugging layer can be removed by acidification, thereby protecting the reservoir.

[0021] 5. The chemical temporary plugging agent of the present invention includes an acid-soluble gel material and an acid-soluble particulate material. The acid-soluble particulate material is preferably calcium carbonate. Adding light calcium carbonate to the gel material increases the weight of the gel solution, enhancing the suspension ability of the particles in the gel solution. Furthermore, adding an appropriate amount of light calcium carbonate powder can improve the strength of the gel after cross-linking or curing, because light calcium carbonate assists the gel material in physical cross-linking, increasing the cross-linking density. Attached Figure Description

[0022] Figure 1 The figure shows the test results of the crack sealing layer pressure bearing capacity of the chemical temporary plugging agent prepared in Example 1 of the present invention;

[0023] Figure 2 The figure shows the test results of the crack sealing layer pressure bearing capacity of the chemical temporary plugging agent prepared in Example 2 of the present invention;

[0024] Figure 3 The image shows the test results of the crack sealing layer bearing capacity of the chemical temporary plugging agent prepared in Comparative Example 1 of this invention.

[0025] Figure 4 The figure shows the test results of the crack sealing layer pressure bearing capacity of the chemical temporary plugging agent prepared in Comparative Example 2 of this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0027] This invention provides a chemical temporary plugging agent for oil testing of leaking reservoirs, comprising the following raw materials in the following weight percentages: 80%-90% acid-soluble gel material and 10%-20% acid-soluble particulate material;

[0028] Preferably, the chemical plugging agent comprises the following raw materials in the following weight percentages: 81%-88% acid-soluble gel material and 12%-19% acid-soluble particulate material; further, the chemical plugging agent comprises the following raw materials in the following weight percentages: 83%-87% acid-soluble gel material and 13%-16% acid-soluble particulate material; the present invention limits the weight ratio of acid-soluble gel material to acid-soluble particulate material. When the proportion of acid-soluble particulate material is too low, the gel solution carries particles into the crack, resulting in a low particle concentration, making it difficult for the particles to remain, accumulate, or bridge in the crack. Alternatively, due to the low particle concentration, the bridging layer skeleton structure is loose and cannot assist the gel material in bearing pressure. When the proportion of acid-soluble particulate material is too high, the addition of a large amount of particulate material will affect the overall rheological properties of the gel-particle system. The use of gel polymer for plugging is based on the adaptive leakage channel characteristics of the gel, and the addition of too many particles will affect this adaptive plugging characteristic.

[0029] Among them, the acid-soluble gel material includes SMG gel, which is from Xinjiang Greedis Petroleum Technology Co., Ltd.; the acid-soluble particulate material includes at least one of calcium carbonate and oyster shell, and the particle size of the acid-soluble particulate material is 1 / 3-2 / 3 of the crack width.

[0030] The chemical plugging agent prepared by this invention retains the properties of a gel material as a whole. Since the properties of a gel-particle system are largely related to the amount of particles added, adding a small amount of inert particles to the gel solution before the gel material crosslinks or solidifies will not significantly affect the rheological properties of the gel solution, nor will it affect the pumping of the gel solution into the leaking layer, as long as the particles do not agglomerate and can be dispersed. After the gel material crosslinks or solidifies, it often exhibits a rubbery or viscous flow state. In this case, if the amount of particles added is small, the product after crosslinking or solidification should also tend towards a gel.

[0031] A method for preparing a chemical plugging agent for oil testing of a leaking reservoir involves mixing an acid-soluble gel material and an acid-soluble particulate material to obtain the chemical plugging agent. Specifically, the acid-soluble particulate material is added to the acid-soluble gel material and stirred evenly to obtain the chemical plugging agent. The stirring speed is 300 r / min-500 r / min and the stirring time is 0.5 h-1.5 h.

[0032] The application of a chemical temporary plugging agent for oil testing operations in leaking reservoirs, specifically for well-killing fluid leakage during oil testing operations in complex fractured reservoirs.

[0033] Example 1

[0034] The acid-soluble gel material used in Example 1 was SMG gel (from Xinjiang Greedis Petroleum Technology Co., Ltd.), and the acid-soluble particle material was calcium carbonate particles.

[0035] (1) Prepare a steel core module with a crack width of 3mm;

[0036] (2) Screen out calcium carbonate particles with a particle size range of 1mm-2mm;

[0037] (3) Add 126 ml of acid-soluble gel main agent, 126 ml of delayed crosslinking agent and 144 ml of other additives to 1800 mL of water, and stir at 300 r / min-500 r / min for 1 h to obtain the prepared acid-soluble gel material; then add 353 g of calcium carbonate granules to the prepared acid-soluble gel material, and continue to stir at 300 r / min-500 r / min for 1 h to obtain a chemical temporary plugging agent with a formula of 85 parts SMG gel + 15 parts calcium carbonate granules.

[0038] (4) The pressure bearing capacity of the fracture sealing layer of the prepared gel-particle composite chemical temporary plugging agent was tested using a simulated fracture test device. The steps are as follows: The gel-particle composite chemical temporary plugging agent was injected into the holder containing a steel fracture core model. After the injection was completed, the constant flow pump was turned on, and drilling fluid was slowly injected into the holder containing the steel fracture core model. The injection pressure was recorded in real time. The maximum pressure corresponding to the loss of drilling fluid was the pressure bearing capacity of the fracture sealing layer of the gel-particle composite chemical temporary plugging agent.

[0039] Test data such as Figure 1 As shown, the pressure-bearing capacity of the crack sealing layer of the gel-particle composite chemical temporary plug is 11.5 MPa.

[0040] Example 2

[0041] The acid-soluble gel material used in Example 2 was SMG gel (from Xinjiang Greedis Petroleum Technology Co., Ltd.), and the acid-soluble particle material was a mixture of calcium carbonate particles and oyster shell particles.

[0042] (1) Prepare a steel core module with a crack width of 2mm;

[0043] (2) Calcium carbonate particles and oyster shell particles with a particle size range of 0.67 mm to 1.34 mm were screened out;

[0044] (3) Add 126 ml of acid-soluble gel main agent, 126 ml of delayed crosslinking agent and 144 ml of other additives to 1800 mL of water, and stir at 300 r / min-500 r / min for 1 h to obtain acid-soluble gel material. Then add 100 g of calcium carbonate particles and 100 g of oyster shell particles to the prepared acid-soluble gel material, and continue to stir at 300 r / min-500 r / min for 1 h to obtain a chemical temporary plugging agent with a formula of 90 parts SMG gel + 5 parts calcium carbonate particles + 5 parts oyster shell particles.

[0045] (4) The pressure bearing capacity of the fracture sealing layer of the prepared gel-particle composite chemical temporary plugging agent was tested using a simulated fracture test device. The steps are as follows: The above-mentioned gel-particle composite chemical temporary plugging agent was injected into the holder containing a steel fracture core model. After injection, it was left to stand for 3 hours to allow the chemical temporary plugging agent to react completely in the fracture. The constant flow pump was turned on, and drilling fluid was slowly injected into the holder containing the steel fracture core model. The injection pressure was recorded in real time. The maximum pressure corresponding to the loss of drilling fluid was the pressure bearing capacity of the fracture sealing layer of the gel-particle composite chemical temporary plugging agent.

[0046] Test data such as Figure 2 As shown, the pressure-bearing capacity of the crack sealing layer of the gel-particle composite chemical temporary plug is 10.7 MPa.

[0047] Comparative Example 1

[0048] The acid-soluble gel material used in Comparative Example 1 was SMG gel.

[0049] (1) Prepare a steel core module with a crack width of 3mm;

[0050] (2) Prepare 2000 mL of gel chemical temporary plugging agent containing only acid-soluble gel material: Add 126 mL of acid-soluble gel main agent, 126 mL of delayed crosslinking agent and 144 mL of other additives to 1800 mL of water, and stir at a speed of 300 r / min-500 r / min for 1 h to obtain gel chemical temporary plugging agent containing only acid-soluble gel material.

[0051] (3) The pressure bearing capacity of the fracture sealing layer of the prepared gel chemical temporary plugging agent was tested using a simulated fracture test device. The steps are as follows: inject the above-mentioned gel chemical temporary plugging agent into the holder containing the steel fracture core model; after the injection is completed, turn on the constant flow pump and slowly inject drilling fluid into the holder containing the steel fracture core model, record the injection pressure in real time, and the maximum pressure corresponding to the drilling fluid leakage is the pressure bearing capacity of the fracture sealing layer of the gel chemical temporary plugging agent.

[0052] Test data such as Figure 3 As shown, the pressure-bearing capacity of the crack sealing layer of the pure gel chemical temporary plug is 7 MPa.

[0053] Comparative Example 2

[0054] The acid-soluble gel material used in Comparative Example 2 was SMG gel, and the acid-soluble particle material was calcium carbonate particles.

[0055] (1) Prepare a steel core module with a crack width of 3mm;

[0056] (2) Screen out calcium carbonate particles with a particle size range of 1mm-2mm;

[0057] (3) Add 126 ml of acid-soluble gel main agent, 126 ml of delayed crosslinking agent and 144 ml of other additives to 1800 mL of water, and stir at 300 r / min-500 r / min for 1 h to obtain acid-soluble gel material. Then add 100 g of calcium carbonate granules to the prepared acid-soluble gel material and continue to stir at 300 r / min-500 r / min for 1 h to obtain a chemical temporary plugging agent with a formula of 90 parts SMG gel + 5 parts calcium carbonate granules.

[0058] (4) The pressure bearing capacity of the fracture sealing layer of the prepared gel-particle composite chemical temporary plugging agent was tested using a simulated fracture test device. The steps are as follows: The above-mentioned gel-particle composite chemical temporary plugging agent was injected into the holder containing a steel fracture core model. After injection, it was left to stand for 3 hours to allow the chemical temporary plugging agent to react completely in the fracture. The constant flow pump was turned on, and drilling fluid was slowly injected into the holder containing the steel fracture core model. The injection pressure was recorded in real time. The maximum pressure corresponding to the loss of drilling fluid was the pressure bearing capacity of the fracture sealing layer of the gel-particle composite chemical temporary plugging agent.

[0059] Test data such as Figure 4 As shown, the crack sealing layer of the gel-particle composite chemical temporary plug has a pressure bearing capacity of 4.8 MPa.

[0060] Comparative Example 3

[0061] The acid-soluble gel material used in Comparative Example 3 was SMG gel, and the acid-soluble particle material was calcium carbonate particles.

[0062] (1) Prepare a steel core module with a crack width of 3mm;

[0063] (2) Screen out calcium carbonate particles with a particle size range of 1mm-2mm;

[0064] (3) Add 126 ml of acid-soluble gel main agent, 126 ml of delayed crosslinking agent and 144 ml of other additives to 1800 mL of water, and stir at 300-500 r / min for 1 h to obtain acid-soluble gel material. Then add 600 g of calcium carbonate granules to the prepared acid-soluble gel material and continue to stir at 300 r / min-500 r / min for 1 h to obtain a chemical temporary plugging agent with a formula of 70 parts SMG gel + 30 parts calcium carbonate granules.

[0065] (4) The pressure bearing capacity of the fracture sealing layer of the prepared gel-particle composite chemical temporary plugging agent was tested using a simulated fracture test device. The steps are as follows: The above-mentioned gel-particle composite chemical temporary plugging agent was injected into the holder containing a steel fracture core model. After injection, it was left to stand for 3 hours to allow the chemical temporary plugging agent to react completely in the fracture. The constant flow pump was turned on, and drilling fluid was slowly injected into the holder containing the steel fracture core model. The injection pressure was recorded in real time. The maximum pressure corresponding to the loss of drilling fluid was the pressure bearing capacity of the fracture sealing layer of the gel-particle composite chemical temporary plugging agent.

[0066] This formulation exhibits a sealing phenomenon, with a large amount of granular material accumulating at the fracture opening and preventing subsequent materials from entering the fracture. Although the pressure-bearing capacity can be measured, this pressure-bearing capacity is meaningless. When the working fluid circulates inside the wellbore, the sealing material at the fracture opening is washed away, failing to isolate the wellbore pressure from the pressure inside the fracture.

[0067] The test results of Example 1 and Comparative Example 1 show that the method of improving the pressure-bearing capacity by mixing acid-soluble particulate material into the acid-soluble gel material is feasible. The test results of Example 1 and Comparative Example 2 show that if the ratio of acid-soluble gel material to acid-soluble particulate material is higher than the ratio described in the technical solution of this invention, the particulate material will not be able to bridge and form a skeleton in the crack, or only a few particles can form a sealing layer skeleton. Therefore, this formula has limited effect on improving the sealing pressure-bearing capacity. The test results of Example 1 and Comparative Example 3 show that if the ratio of acid-soluble gel material to acid-soluble particulate material is lower than the ratio in the claims, too much acid-soluble particulate material will lead to a sealing phenomenon, which is also not conducive to sealing cracks.

[0068] In summary, the chemical temporary plugging agent for lost reservoir testing provided by this invention can significantly improve the pressure-bearing capacity of the fracture plugging layer. Compared with the pressure-bearing capacity of the fracture plugging layer formed by simply using gel chemical temporary plugging agents, it can be increased by up to 164%. After the operation, the plugging layer can be completely removed by acidizing, thus achieving the purpose of reservoir protection. Therefore, this invention proposes a chemical temporary plugging agent for lost reservoir testing, which has broad application prospects and market potential in the development of gas fields such as Sichuan and Tarim.

[0069] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A chemical temporary plugging agent for oil testing operations in leaking reservoirs, characterized in that, It includes the following raw materials in weight percentages: 80%-90% acid-soluble gel material and 10%-20% acid-soluble particulate material.

2. The chemical temporary plugging agent for oil testing of a leaking reservoir as described in claim 1, characterized in that: The chemical temporary plugging agent comprises the following raw materials in the following weight percentages: 81%-88% acid-soluble gel material and 12%-19% acid-soluble particulate material.

3. The chemical temporary plugging agent for oil testing of a leaking reservoir as described in claim 1, characterized in that: The chemical temporary plugging agent comprises the following raw materials in the following weight percentages: 83%-87% acid-soluble gel material and 13%-16% acid-soluble particulate material.

4. A chemical temporary plugging agent for oil testing operations in leaking reservoirs as described in any one of claims 1-3, characterized in that: The acid-soluble gel material includes SMG gel.

5. A chemical temporary plugging agent for oil testing operations in leaking reservoirs as described in any one of claims 1-3, characterized in that: The acid-soluble particulate material includes at least one of calcium carbonate and oyster shell.

6. A chemical temporary plugging agent for oil testing operations in leaking reservoirs as described in any one of claims 1-3, characterized in that: The particle size of the acid-soluble particulate material is 1 / 3 to 2 / 3 of the crack width.

7. A method for preparing a chemical temporary plugging agent for oil testing operations in a leaking reservoir according to any one of claims 1-6, characterized in that: A chemical temporary plugging agent is obtained by stirring and mixing acid-soluble gel materials and acid-soluble particulate materials.

8. The preparation method of the chemical temporary plugging agent for oil testing of a leaking reservoir as described in claim 7, characterized in that: Acid-soluble particulate material is added to acid-soluble gel material and stirred evenly to obtain a chemical temporary plugging agent.

9. The preparation method of the chemical temporary plugging agent for oil testing of a leaking reservoir as described in claim 8, characterized in that: The stirring speed is 300 r / min-500 r / min, and the stirring time is 0.5 h-1.5 h.

10. The application of a chemical temporary plugging agent for oil testing operations in a leaking reservoir according to any one of claims 1-6, characterized in that: It was applied to well-killing fluid loss during oil testing operations in complex fractured reservoirs.

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