CN118145926B - Sea island fiber-based cement plugging agent for selective water plugging of gas wells and its application - Google Patents

Abstract

The invention discloses an island fiber-based cement plugging agent for selective water plugging of gas wells and application thereof, and relates to the technical field of oil and gas development. The plugging agent comprises the following components: 45-55% of G-grade oil well cement, 17-25% of hydrophobic quartz sand, 0.1-0.6% of island fiber, 1-2% of water reducer, 1-2% of dispersant, 1.5-2% of expander, 1.5-2.5% of waterproof lock agent, and 18-28% of water. The plugging agent is obtained by uniformly stirring the raw materials in a ball mill. The plugging agent is mainly used in gas reservoirs with a temperature range of 90-150°C. The island fiber-based cement plugging agent for selective water plugging of gas wells in the invention has a low initial consistency, ensures good pumping performance during construction, and ensures safe construction on site. The compressive strength of the plugging agent after curing can meet the strength requirement of a high-temperature deep well plugging layer, and has strong resistance to high-temperature strength attenuation and long-term plugging performance. The gas permeability of the plugging agent can be further adjusted by adjusting the composition of the hydrophobic island fiber, so as to achieve selective water plugging and gas drainage.

Description

Sea island fiber-based cement plugging agent for selective water plugging of gas wells and its application

Technical Field

The invention relates to the technical field of oil and gas development, and in particular to an island fiber-based cement plugging agent for selective water plugging of gas wells and an application thereof.

Background technique

Gas reservoirs are mainly mined by depletion, which has the characteristics of fast mining rate, high final recovery rate, etc. However, with the development of gas reservoirs, water production in gas wells is inevitable. The two-phase flow of water and gas in the seepage channel and the focus reduces the gas phase permeability, which seriously affects the gas production rate. As the development of gas fields gradually enters the middle and late stages, gas well water control and production increase have become an important research direction. At present, there are two main treatment methods for water-producing gas reservoirs: one is drainage gas production, that is, to remove the accumulated liquid in the wellbore and the formation near the bottom of the well, so that the gas well can resume normal production. Although drainage gas production has achieved obvious results, the construction is difficult, and separate drainage gas production is not conducive to the overall development of the gas field. The second is gas well plugging and water control, which increases the relative permeability of the gas phase by injecting plugging agents to plug the water-producing layer. Therefore, some scholars have proposed to use gas well water control agents to achieve water blocking without blocking gas. Gas water control agents can be divided into non-selective water control agents and selective water control agents according to the positional relationship between the gas layer and the water layer. Non-selective water control agents are mainly used for situations where the gas layer and the water layer have a clear interface. The treatment method is to place a non-permeable permanent barrier, such as cement slurry, solid particles, resin or high-strength gel, at the interface between the gas layer and the water layer to isolate the water layer. When the gas layer and the water layer are difficult to separate, it is necessary to use a water control agent with selective plugging effect, such as polymer gel, functional nanofluid, etc. The principle is that after the selective water control agent enters the formation, it establishes a water barrier in the water-gas layer. The barrier can greatly reduce the permeability of the water phase, while having little effect on the permeability of the gas phase, and finally achieves selective water plugging. Lin Renyi et al. prepared an acrylamide microgel system WJ-1 that can achieve secondary cross-linking under high temperature and high salt conditions, and conducted a series of water plugging performance evaluation experiments. The results show that the system has a certain effect of water plugging without gas plugging. It can be seen that the current selective water control agents generally have the problems of high cost, low plugging strength and poor selective water plugging effect.

Summary of the invention

In view of this, in order to solve the problem of poor effect of gas reservoir water plugging agents in the prior art, the present invention proposes an island fiber-based cement plugging agent for selective water plugging of gas wells and its application, which has the advantages of low price, high strength, long-term stability and selective water plugging.

The invention discloses a sea island fiber-based cement plugging agent for selective water plugging of gas wells, which comprises the following components by mass fraction:

G-grade oil well cement 45~55%

Hydrophobic quartz sand 17~25%

Sea-island fiber 0.1~0.6%

Water reducing agent 1~2%

Dispersant 1~2%

Expanding agent 1.5~2%

Waterproof lock agent 1.5~2.5%

Water 18~28%.

During preparation, the above raw materials are mixed in proportion and then put into a ball mill for uniform mixing. The speed range of the ball mill is 2000r/min~2500r/min. During specific implementation, further fine-tuning can be made based on the above formula according to the actual situation on site.

An embodiment of the present invention is that the G-grade oil well cement is an acid-resistant and high-sulfur-resistant oil well cement with a mesh size of 70-150.

One embodiment of the present invention is that the sea phase component of the sea island fiber is soluble polyvinyl alcohol fiber, the island phase component is insoluble polyester fiber, the fiber specification is 95D/36F, and the soluble polyvinyl alcohol fiber as the sea phase is easily dissolved in an alkaline water environment to form a permeable interconnecting channel.

One embodiment of the present invention is that the sea-island fibers are modified by soaking in a hydrophobic surfactant at 25° C. for 24 hours.

Furthermore, the hydrophobic surfactant is n-octyltriethoxysilane.

In one embodiment of the present invention, the water reducing agent is a combination of one or more of sodium lignin sulfonate, polyester polycarboxylic acid and sodium tannate.

An embodiment of the present invention is that the dispersant is a combination of one or more of polyethylene glycol and sodium alginate.

In one embodiment of the present invention, the expansion agent is ettringite, and the waterproof lock agent is hygroscopic nano-SiO ₂ .

In addition, the present invention also discloses the application of the island fiber-based cement plugging agent for selective water plugging of gas wells, which can be used to solve the problem of water gushing out from the bottom of vertical cracks and the tip of micro cracks after fracturing.

Furthermore, the gas reservoir temperature range for application of the island fiber-based cement plugging agent is 90-150°C.

The technical effects of the present invention are:

(1) The sea island fiber cement-based plugging agent for selective water plugging of gas wells provided by the present invention has a low initial consistency and low-temperature fluidity, which ensures good pumping performance during the construction process, and the thickening time can be more than 4 hours, which ensures safe construction on site.

(2) The compressive strength of the sea island fiber cement-based plugging agent for selective water plugging of gas wells in the present invention after curing can be greater than 23 MPa, which meets the strength requirements of the plugging layer of high-temperature deep wells and has long-term plugging performance.

(3) The sea island fiber cement-based plugging agent for selective water plugging of gas wells in the present invention has a strong ability to resist high temperature strength attenuation.

(4) The sea-island fiber cement-based plugging agent for selective water plugging of gas wells in the present invention constructs a gas channel by mixing hydrophobic sea-island fibers, and mixes gas-wet nano- _SiO2 to improve the hydrophobicity of the plugging agent, thereby preventing the air inlet end face from being affected by water sensitivity. The gas permeability of the plugging agent can be adjusted by adjusting the hydrophobic sea-island fibers, thereby achieving selective water plugging and gas drainage.

Detailed ways

The present invention will be further described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used therein are all commercially available unless otherwise specified.

Example 1: In parts by weight, 45.1 parts of G-grade oil well cement, 24.7 parts of hydrophobic quartz sand, 0.13 parts of sea island fiber, 1.2 parts of water reducer, 1.1 parts of dispersant, 1.5 parts of expansion agent, 1.9 parts of waterproof lock agent, and the balance of water are weighed, and the sum of the weight parts of each substance is 100 parts, and stirred evenly in a ball mill at a speed of 2000r/min.

The G-grade oil well cement and hydrophobic quartz sand are both of 70-150 mesh specifications. The sea-island fiber is of 95D/36F specifications, the sea phase component is soluble polyvinyl alcohol fiber, the island phase component is insoluble polyester fiber, the water reducer is sodium lignin sulfonate, the dispersant is polyethylene glycol, the expansion agent is ettringite, and the waterproof lock agent is hygroscopic nano-SiO ₂ .

Example 2: In parts by weight, 47.3 parts of G-grade oil well cement, 21.6 parts of hydrophobic quartz sand, 0.22 parts of sea island fiber, 1.9 parts of water reducer, 1.3 parts of dispersant, 1.8 parts of expander, 1.6 parts of waterproof lock agent, and the balance of water are weighed, and the sum of the weight parts of each substance is 100 parts, and stirred evenly in a ball mill at a speed of 2000r/min.

The G-grade oil well cement and quartz sand are of 70-150 mesh specifications. The sea-island fiber is of 95D/36F specifications, the sea phase component is soluble polyvinyl alcohol fiber, the island phase component is insoluble polyester fiber, the water reducer is polyester polycarboxylic acid, the dispersant is sodium alginate, the expansion agent is ettringite, and the waterproof lock agent is air-wet nano-SiO ₂ .

Example 3: In parts by weight, 49.1 parts of G-grade oil well cement, 19.3 parts of hydrophobic quartz sand, 0.34 parts of sea island fiber, 1.1 parts of water reducer, 1.5 parts of dispersant, 1.6 parts of expander, 1.7 parts of waterproof lock agent, and the remainder of water are weighed, and the sum of the weight parts of each substance is 100 parts, and stirred evenly in a ball mill at a speed of 2000r/min.

The G-grade oil well cement and quartz sand are of 70-150 mesh specifications. The sea-island fiber is of 95D/36F specifications, the sea phase component is soluble polyvinyl alcohol fiber, the island phase component is insoluble polyester fiber, the water reducer is sodium tannate, the dispersant is polyethylene glycol, the expansion agent is ettringite, and the waterproof lock agent is hygroscopic nano-SiO ₂ .

Example 4: In parts by weight, 52.3 parts of G-grade oil well cement, 18.4 parts of hydrophobic quartz sand, 0.41 parts of sea island fiber, 2.0 parts of water reducer, 1.7 parts of dispersant, 1.6 parts of expansion agent, 1.5 parts of waterproof lock agent, and the remainder of water are weighed, and the sum of the weight parts of each substance is 100 parts, and stirred evenly in a ball mill at a speed of 2000r/min.

The G-grade oil well cement and quartz sand are of 70-150 mesh specifications. The sea-island fiber is of 95D/36F specifications, the sea phase component is soluble polyvinyl alcohol fiber, the island phase component is insoluble polyester fiber, the water reducer is sodium lignin sulfonate, the dispersant is sodium alginate, the expansion agent is ettringite, and the waterproof lock agent is air-wetting nano-SiO ₂ .

Example 5: In parts by weight, 53.4 parts of G-grade oil well cement, 17.9 parts of hydrophobic quartz sand, 0.49 parts of sea island fiber, 1.0 parts of water reducer, 1.9 parts of dispersant, 1.5 parts of expansion agent, 2.0 parts of waterproof lock agent, and the remainder of water are weighed, and the sum of the weight parts of each substance is 100 parts, and stirred evenly in a ball mill at a speed of 2000r/min.

The G-grade oil well cement and quartz sand are of 70-150 mesh specifications. The sea-island fiber is of 95D/36F specifications, the sea phase component is soluble polyvinyl alcohol fiber, the island phase component is insoluble polyester fiber, the water reducer is polyester polycarboxylic acid, the dispersant is polyethylene glycol, the expansion agent is ettringite, and the waterproof lock agent is air-wet nano-SiO ₂ .

Example 6: In parts by weight, 54.9 parts of G-grade oil well cement, 17.2 parts of hydrophobic quartz sand, 0.6 parts of sea island fiber, 2.0 parts of water reducer, 2.0 parts of dispersant, 1.8 parts of expansion agent, 1.5 parts of waterproof lock agent, and the remainder of water are weighed, and the sum of the weight parts of each substance is 100 parts, and stirred evenly in a ball mill at a speed of 2000r/min.

The G-grade oil well cement and quartz sand are of 70-150 mesh specifications. The sea-island fiber is of 95D/36F specifications, the sea phase component is soluble polyvinyl alcohol fiber, the island phase component is insoluble polyester fiber, the water reducer is sodium tannate, the dispersant is sodium alginate, the expansion agent is ettringite, and the waterproof lock agent is hygroscopic nano-SiO ₂ .

Comparative Example 1: The raw material dosage and implementation method of this comparative example are basically the same as those of Example 1, the difference being that no sea island fiber is added in this comparative example, and other raw material components, dosages and conditions during the implementation process are the same as those of Example 1.

In order to better illustrate the technical effects of the present invention, performance evaluations are provided below for relevant embodiments or comparative examples.

1. Thickening performance test

The thickening time of the plugging agent prepared in the above-mentioned Examples 1-6 was measured, and the specific test method was as follows: the island fiber cement-based selective gas well plugging agent prepared in the above-mentioned Examples 1-6 was stirred evenly, and placed in a DFC-0712B high temperature and high pressure double cylinder thickener under the conditions of a temperature range of 90-150°C and a pressure of 30 MPa, and the temperature and pressure were kept at 30 minutes. The thickening time of each example was measured respectively, and the specific results are shown in Table 1:

Table 1 Thickening schedule of island fiber cement-based selective gas well plugging agent

As can be seen from Table 1, the oilfield heat-resistant plugging agent provided by Examples 1-6 of the present invention has a low initial consistency, can maintain good fluidity, ensures good pumping performance on site, and has a thickening time of more than 4 hours under the conditions of a temperature range of 90-150°C and a pressure of 30 MPa, which can ensure the safety of on-site construction.

2. Compressive strength test

The compressive strength of the plugging agent prepared in the above Examples 1-6 was measured, and the test method was as follows: the island fiber cement-based selective gas well plugging agent prepared in the above Examples 1-6 was stirred evenly, poured into a 5 cm×5 cm×5 cm mold, and then placed in an oven at 90~150°C for 3d and 30d, and the compressive strength of the prepared samples was measured at room temperature using a universal mechanical testing machine, as shown in Table 2:

Table 2 Compressive strength of island fiber cement-based selective gas well plugging agent

It can be seen from Table 2 that the oilfield heat-resistant plugging agents provided by Examples 1-6 of the present invention have a compressive strength greater than 20 MPa after being cured at a temperature range of 90-150° C. for 72 hours, which can meet the requirements of deep well sealing and channeling sealing strength.

3. Evaluation of Plugging Effect

In size 15cm × The samples of Examples 1-6 and Comparative Example 1 were placed in a 2.5 cm mold and placed in a constant temperature oven at 90-150°C for 72 hours. A 5 cm × 2.5 cm core drill was then used to drill a 5 cm × 2.5 cm core. The standard sample of 2.5 cm was prepared, and both ends were smoothed with sandpaper. The sample surface was cleaned and placed in a 60°C constant temperature blast drying oven for 72 hours. The end displacement pressure difference of the samples of Examples 1-6 and Comparative Example 1 during gas injection and water injection was tested by a core displacement device. The injection rates of nitrogen and water during the displacement process were set to 5 mL/min and 10 mL/min, respectively, and the back pressure was set to 20 MPa. The displacement temperature was kept the same as the curing temperature of each group of samples. The selective water plugging ability of the samples obtained by testing is shown in Table 3:

Table 3 Sea island fiber cement-based selective gas well plugging agent plugging effect table

As can be seen from Table 3, the oilfield heat-resistant plugging agent provided by Examples 1-6 of the present invention can block water while minimizing the impact on gas flow capacity after being cured for 72 hours under a temperature condition of 90-150°C, which indicates that the plugging agent has excellent water blocking but no gas blocking performance.

The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (6)

1. A sea island fiber-based cement plugging agent for selective water plugging of gas wells, characterized in that it comprises the following components by mass fraction: G-grade oil well cement 45~55% Hydrophobic quartz sand 17~25% Sea-island fiber 0.1~0.6% Water reducing agent 1~2% Dispersant 1~2% Expanding agent 1.5~2% Waterproof lock agent 1.5~2.5% Water 18~28%; The sea phase component of the sea island fiber is soluble polyvinyl alcohol fiber, the island phase component is insoluble polyester fiber, the fiber specification is 95D/36F, the sea island fiber is modified by soaking in a hydrophobic surfactant at 25°C for 24 hours, the expansion agent is calcium aluminate, the waterproof lock agent is air-wetting nano- _SiO2 , and the hydrophobic surfactant is n-octyltriethoxysilane. 2. The sea island fiber-based cement plugging agent for selective water plugging of gas wells according to claim 1, characterized in that the G-grade oil well cement is an acid-resistant and high-sulfur-resistant oil well cement with a mesh size of 70 to 150. 3. The sea island fiber-based cement plugging agent for selective water plugging of gas wells according to claim 1, characterized in that the water reducer is a combination of one or more of sodium lignin sulfonate, polyester polycarboxylic acid and sodium tannate. 4. The sea island fiber-based cement plugging agent for selective water plugging of gas wells according to claim 1, characterized in that the dispersant is a combination of one or more of polyethylene glycol and sodium alginate. 5. Use of the sea island fiber-based cement plugging agent for selective water plugging of gas wells as claimed in any one of claims 1 to 4. 6. The use of the sea island fiber-based cement plugging agent for selective water plugging of gas wells according to claim 5, characterized in that the gas reservoir temperature range in which the sea island fiber-based cement plugging agent is used is 90-150°C.