A multifunctional fracturing fluid composition, its preparation method and application

Abstract

The present application relates to the technical field of fracturing fluid, in particular to a multifunctional fracturing fluid composition, a preparation method and application thereof, and belongs to the technical field of shale development. The fracturing fluid composition comprises a small-molecule long-chain fatty acid anionic surfactant, a structure connecting agent, a carbon dioxide additive and water. The present application realizes the needs of integration of fracturing, swelling prevention and displacement for enhanced oil recovery at one time. The viscosity requirements of the fracturing fluid are different at different stages in the fracturing construction process, and the viscosity change of conventional fracturing is less operable, mainly composed of polymer macromolecules, and the reservoir damage is large. The performance of the fracturing fluid of the present application can be adjusted according to the field requirements, the reservoir damage is low, and the fracturing and the later enhanced oil recovery are realized at one time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fracturing fluid, in particular to a multifunctional fracturing fluid composition, a preparation method and application thereof. BACKGROUND

[0002] Shale gas, as a kind of unconventional natural gas, accounts for half of the total natural gas production. Shale reservoirs are dense, and volume fracturing can effectively form large-scale fracture networks to improve shale gas percolation, thereby producing industrial gas flow. Fracturing fluid is the blood of fracturing engineering, which directly affects the effect of fracturing reconstruction. Shale gas fracturing mainly pumps fracturing fluid with large displacement, and according to the design requirements, the types of fracturing fluid usually include linear gel, variable viscosity slick water, conventional slick water, etc. In the process of reservoir reconstruction, fracturing fluid enters the shale matrix, on the one hand, because the components in the fracturing fluid are mainly large molecular polymers, which can easily cause damage to the physical properties of shale reservoirs; on the other hand, shale reservoirs have multi-scale micro-nano pore structure and are rich in clay minerals, which can swell and disperse when they come into contact with water, causing water sensitivity damage and seriously hindering the discharge of shale gas. In addition, conventional fracturing fluid has shortcomings in reducing reservoir damage, improving shale gas recovery and environmental protection, and is single in function. Therefore, the present application aims to highlight the multifunctionalization of fracturing fluid, and proposes a preparation method and application of a multifunctional fracturing fluid composition for shale reservoir fracturing, swelling prevention and replacement.

[0003] At present, different performance fracturing fluids are required in the design of shale gas volume fracturing process, and the greater the viscosity of the fracturing fluid required for construction, the more the amount of polymer macromolecules, and the more serious the damage to the reservoir. In order to reduce the damage to the shale reservoir caused by the entry of fracturing fluid, various additives such as clay inhibitors need to be added to the fracturing fluid, which increases the preparation process and material cost. SUMMARY

[0004] The present application aims to provide a multifunctional fracturing fluid composition, a preparation method and application thereof, which solves the problem that the fracturing fluid in the prior art only has fracturing effect and does not have the effect of protecting the reservoir and improving the recovery rate by imbibition replacement.

[0005] The present application discloses a multifunctional fracturing fluid composition, which comprises a small molecule long chain fatty acid anionic surfactant, a structure connecting agent, an additive and water.

[0006] Further, the carbon chain length C of the small molecule long chain fatty acid anionic surfactant is 8-20. 12 ~C 24 The carbon chain is a saturated fatty acid or an unsaturated fatty acid, and the anion in the structure is a sulfonate or a sulfate.

[0007] Further, the small molecule long-chain fatty acid anionic surfactant is sodium fatty acid methyl ester sulfonate, sodium stearate, sodium coco-hydroxyethyl sulfonate or sodium lauryl sulfonate. The small molecule long-chain fatty acid anionic surfactant plays a role in increasing viscosity and viscoelasticity in fracturing, and after fracturing, it acts as a wicking agent to play a role in displacement and production increase.

[0008] Further, the small molecule long-chain fatty acid anionic surfactant is added in an amount of 0.5% to 3% based on 100% of the mass of the fracturing fluid.

[0009] Further, the structural connecting agent is a compound containing two or three or more primary amine / tertiary amine structures. The structure can produce a supramolecular effect with the small molecule long-chain fatty acid anionic surfactant to jointly improve the performance of the fracturing fluid. The structural connecting agent can also play a role in preventing shale swelling after the fracturing fluid is broken, without the need to add an anti-swelling agent to the fracturing fluid.

[0010] Further, the multi-tertiary amine chemical structure is tetramethyl ethylenediamine, tetramethyl propylenediamine, pentamethyl diethylenetriamine, N-[3-(dimethylamino)propyl]-trimethyl-1,3 propanediamine, hexamethyl triethylene tetramine or tris(2-dimethylaminoethyl)amine, and the structural formulas are as follows,

[0011]

[0012] Further, the multi-primary amine chemical structure is diethylenetriamine, triethylenetetramine, tetraethylenepentamine or pentaethylenehexamine, and the structural formulas are as follows,

[0013] (1)

[0014] (2)

[0015] (3)

[0016] (4)

[0017] Further, the amount of the structural connecting agent added is 1 / 4 to 1 / 2 of the total amount of moles of the small molecule long-chain fatty acid anionic surfactant.

[0018] Further, the additive is carbon dioxide.

[0019] The long carbon chain anionic surfactant and the polyamine / tertiary amine structure connecting agent in a specific molar ratio form a supramolecular assembly in the environment of carbon dioxide and water, change the solution viscosity and viscoelasticity, and meet the performance requirements of the fracturing fluid.

[0020] Further, the water is fresh water or low salinity formation produced water.

[0021] A preparation method of the multifunctional fracturing fluid composition comprises the following steps: slowly adding a small molecule long chain fatty acid anionic surfactant and a structure connecting agent into water in a mechanical stirring process, dissolving, reducing the stirring speed, and passing carbon dioxide into the solution until the excess carbon dioxide gas overflows.

[0022] The multifunctional fracturing fluid composition is applied to a shale oil and gas fracturing reconstruction and yield increasing process, the small molecule long chain fatty acid anionic surfactant plays a role in increasing the viscosity and viscoelasticity in fracturing, and plays a role in replacement and yield increase after fracturing as a imbibition agent, and the structure connecting agent plays a role in anti-swelling of shale after the fracturing fluid is broken.

[0023] Compared with the prior art, the multifunctional fracturing fluid composition has the beneficial effects that:

[0024] 1. The multifunctional fracturing fluid composition comprises a main agent of a small molecule surfactant and a structure connecting agent, and carbon dioxide or carbon dioxide-based waste gas as an additive, and the structure connecting agent and the small molecule surfactant form a supramolecular structure under the stimulation of carbon dioxide, so that the solution performance is changed to meet the requirements of the fracturing fluid.

[0025] 2. The small molecule surfactant in the fracturing fluid composition not only has small reservoir damage but also can reduce water lock damage, the structure connecting agent plays a role in connecting and assembling the small molecule surfactant, so that the amount of the small molecule surfactant is reduced, and the structure connecting agent forms a quaternary amine structure after contacting with carbon dioxide, so as to have the effects of anti-swelling and damage reduction on shale.

[0026] 3. The viscosity of the fracturing fluid can be controlled by adjusting the amount of structural connecting agent or carbon dioxide additive, and after the fracturing fluid is broken in the reservoir, the extremely strong adsorption of carbon dioxide will enter the shale pore and replace the methane gas in the shale, thereby improving the shale gas recovery rate and achieving the environmental protection goal of carbon sequestration;

[0027] 4. The present application realizes the integrated needs of fracturing, swelling prevention, replacement and improved recovery rate at one time; the viscosity requirements of the fracturing fluid are different at different stages during the fracturing construction process, and the viscosity change of the conventional fracturing is less operable, mainly composed of polymer macromolecules, which causes greater damage to the reservoir, and the performance of the fracturing fluid of the present application can be adjusted according to the field requirements, and the reservoir damage is low, and the fracturing construction at one time realizes the dual purpose of fracturing and later improved recovery rate. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only represent some embodiments of the present application, and should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can be obtained without creative labor.

[0029] Figure 1 Rheological curve of the fracturing fluid in Example 2 of the present application.

[0030] Figure 2 The viscosity of the fracturing fluid system in Example 2 of the present application is injected into carbon dioxide and the viscosity of the liquid after gel breaking with respect to shear rate.

[0031] Figure 3 The swelling prevention effect of the fracturing fluid system in Examples 1-4 of the present application on shale.

[0032] Figure 4 The efficiency of the system in Example 4 of the present application for replacing methane gas in shale. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below, and obviously, the described embodiments are part of the embodiments of the present application, but not all the embodiments.

[0034] The viscosity and swelling rate experiment in the embodiments is carried out according to SY / T 6376-2008 General Technical Conditions for Fracturing Fluid and NB / T14003.3-2017 Shale Gas Fracturing Fluid.

[0035] Example 1

[0036] A multifunctional fracturing fluid composition and a preparation method thereof are disclosed in the embodiment, which comprises the following steps:

[0037] A small-molecule long-chain fatty acid anionic surfactant sodium fatty acid methyl ester sulfonate is stirred and dissolved in tap water according to a mass ratio of 97:3, then 1 / 3 of the total amount of sodium fatty acid methyl ester sulfonate is added to a multi-tertiary amine structure linker N-[3-(dimethylamino)propyl]-trimethyl-1,3 propanediamine, and after stirring, carbon dioxide solution is introduced, the viscosity starts to rapidly rise until the liquid viscosity changes little and stops.

[0038] According to the fracturing fluid evaluation standard, the solution viscosity is measured to be 33-35 mPa·s at 90℃, 170s -1 under the condition of a rheometer, the viscoelastic modulus increases with the increase of the oscillation frequency, there is a cross point, the elastic modulus of the fracturing fluid is 8-10 Pa at a fixed frequency of 1.0 Hz, the viscoelasticity is good, which is helpful for sand carrying. After breaking the gel by introducing methane gas, the shale clay anti-swelling experiment is carried out on the broken gel, and the anti-swelling rate reaches 92%. The columnar shale is split into two halves to simulate artificial fracturing, and the core displacement device is used to simulate the reservoir environment. The rock sample is saturated with methane gas, and then the fracturing fluid composition is injected, the gel breaking and flowback during well shut-in are simulated, and the gas production is recorded. The results show that the fracturing fluid composition in Example 1 can increase the recovery degree to 8%.

[0039] Comparative Example 1

[0040] In this embodiment, only the injected fracturing fluid is changed to conventional slick water based on Example 1, and the results show that the shale appears to swell, the conventional fracturing fluid has no anti-swelling effect, and additional anti-swelling agent needs to be added in actual application. The recovery degree after the conventional slick water measure is 1%-2%.

[0041] Example 2

[0042] A multifunctional fracturing fluid composition and a preparation method thereof are disclosed in the embodiment, which comprises the following steps:

[0043] A small-molecule long-chain fatty acid anionic surfactant sodium stearate is stirred and dissolved in tap water according to a mass ratio of 98:2, then 1 / 4 of the total amount of sodium stearate is added to a multi-tertiary amine structure linker hexamethyl triethylene tetramine, and after stirring, carbon dioxide solution is introduced, the viscosity starts to rapidly rise until the liquid viscosity changes little and stops.

[0044] According to the fracturing fluid evaluation standard, the solution viscosity is measured to be 33-35 mPa·s at 90℃, 170s -1The viscosity of the solution was measured to be 25-28 mPa-s under the conditions, the viscoelastic modulus increased with the increase of the oscillation frequency, there was a cross point, the elastic modulus of the fracturing fluid was 7-8 Pa at a fixed frequency of 1.0 Hz, the viscoelasticity was good, which was helpful for sand carrying. After the gel breaking by the methane gas, the shale clay anti-swelling experiment was performed on the gel breaking liquid, and the anti-swelling rate reached 89%. The columnar shale was split into two halves to simulate artificial fracturing, the core displacement device was used to simulate the reservoir environment, the rock sample was saturated with methane gas, and then the fracturing fluid composition was injected, the gel breaking and flowback in the simulated well was simulated, and the gas production was recorded. The results showed that the fracturing fluid composition in Example 2 could reach a recovery degree of 6%.

[0045] Comparative Example 2

[0046] In this embodiment, only the injected fracturing fluid was changed to conventional slick water based on Example 2, and the results showed that the shale appeared swelling phenomenon, the conventional fracturing fluid had no anti-swelling effect, and additional anti-swelling agent was needed in actual application, and the recovery degree after the conventional slick water treatment was basically 0.

[0047] Example 3

[0048] In this embodiment, a multifunctional fracturing fluid composition and a preparation method thereof are disclosed, which comprises the following steps:

[0049] The small molecule long-chain fatty acid anionic surfactant sodium cocoyl isethionate was dissolved and prepared by stirring with tap water at a mass ratio of 100:2, then 1 / 2 of the total amount of sodium cocoyl isethionate was added to the triethylenetetramine, and the stirring was uniform. Then carbon dioxide was introduced, and the viscosity of the solution began to rise rapidly until the change of the liquid viscosity was small.

[0050] According to the fracturing fluid evaluation standard, the rheometer was used at 100℃, 170s -1 The viscosity of the solution was measured to be 25-28 mPa-s under the conditions, the viscoelastic modulus increased with the increase of the oscillation frequency, there was a cross point, the elastic modulus of the fracturing fluid was 7-8 Pa at a fixed frequency of 1.0 Hz, the viscoelasticity was good, which was helpful for sand carrying. After the gel breaking by the methane gas, the shale clay anti-swelling experiment was performed on the gel breaking liquid, and the anti-swelling rate reached 89%. The columnar shale was split into two halves to simulate artificial fracturing, the core displacement device was used to simulate the reservoir environment, the rock sample was saturated with methane gas, and then the fracturing fluid composition was injected, the gel breaking and flowback in the simulated well was simulated, and the gas production was recorded. The results showed that the fracturing fluid composition in Example 2 could reach a recovery degree of 6%.

[0051] Comparative Example 3

[0052] The only change in the present embodiment is to replace the injected fracturing fluid with conventional slick water based on Example 3, and the result shows that shale appears to expand, the conventional fracturing fluid has no anti-swelling effect, and an additional anti-swelling agent needs to be added in practical application. The recovery degree after the conventional slick water measure is basically 2% to 3%.

[0053] Example 4

[0054] The present embodiment discloses a multifunctional fracturing fluid composition and a preparation method thereof, comprising the following steps:

[0055] The small-molecule long-chain fatty acid anionic surfactant sodium lauryl sulfonate is stirred and dissolved with tap water according to a mass ratio of 98.5:1.5, then 1 / 2 of the total amount of sodium lauryl sulfonate is added to the tetraethylene pentamine of the poly tertiary amine structure linker, and after uniform stirring, carbon dioxide solution is introduced, the viscosity starts to rapidly rise until the liquid viscosity changes little and stops.

[0056] According to the fracturing fluid evaluation standard, the solution viscosity is measured to be 35-38 mPa·s under the condition of 70℃, 170s -1 The viscoelastic modulus increases with the increase of oscillation frequency, there is a cross point, the elastic modulus of the fracturing fluid is 5-7 Pa at a fixed frequency of 1.0 Hz, the viscoelasticity is good, which is helpful for sand carrying. After breaking the gel by introducing methane gas, the shale clay anti-swelling experiment is carried out on the broken gel, and the anti-swelling rate reaches 91%. The columnar shale is split into four halves along the radial direction to simulate artificial fracturing, and the core displacement device is used to simulate the reservoir environment. The rock sample is saturated with methane gas, and then the fracturing fluid composition is injected. The gas production is recorded after the simulated well killing and gel breaking and flowback. The result shows that the recovery degree of the fracturing fluid composition in Example 4 is 15%.

[0057] Comparative Example 4

[0058] The only change in the present embodiment is to replace the injected fracturing fluid with conventional slick water based on Example 3, and the result shows that shale appears to expand, the conventional fracturing fluid has no anti-swelling effect, and an additional anti-swelling agent needs to be added in practical application. The recovery degree after the conventional slick water measure is basically 2% to 3%.

[0059] Comparative Example 5

[0060] In the present embodiment as a pair of examples of the present application, only the total amount of sodium fatty acid methyl ester sulfonate is changed to 1 / 4 of the total amount of N-[3-(dimethylamino)propyl]-trimethyl-1,3 propanediamine of the poly tertiary amine structure linker in Example 1. The viscosity is reduced by 12-15 mPa·s, the elastic modulus is reduced to 6 Pa, which obviously affects the sand carrying effect in the fracturing process, and the anti-swelling effect is slightly reduced, reaching 72%.

[0061] From Figure 1As can be seen from the above, the fracturing fluid system of the present application can keep viscosity stable under the action of long-time rheological shear and high temperature, thereby providing stable guarantee for fracturing sand carrying and fracture forming. Figure 2 As can be seen from the above, the fracturing fluid system of the present application can keep viscosity stable under the action of long-time rheological shear and high temperature, thereby providing stable guarantee for fracturing sand carrying and fracture forming. Figure 3 As can be seen from the above, the fracturing fluid system of the present application can keep viscosity stable under the action of long-time rheological shear and high temperature, thereby providing stable guarantee for fracturing sand carrying and fracture forming. Figure 4 As can be seen from the above, the fracturing fluid system of the present application can keep viscosity stable under the action of long-time rheological shear and high temperature, thereby providing stable guarantee for fracturing sand carrying and fracture forming.

[0062] The above is the embodiment listed in the present embodiment, but the present embodiment is not limited to the above optional embodiment, and those skilled in the art can obtain other various embodiments by arbitrarily combining the above modes with each other, and anyone can obtain other various forms of embodiments under the inspiration of the present embodiment. The above specific embodiments should not be understood as limiting the protection scope of the present embodiment, and the protection scope of the present embodiment should be defined by the claims, and the specification can be used to explain the claims.

Claims

1. A multifunctional fracturing fluid composition, characterized in that: It includes small molecule long chain fatty acid anionic surfactant, structural linker, additives and water; The structural linker is a compound containing a polyprimary amine or polytertiary amine structure; The chemical structure of the poly-tertiary amine is: tetramethylethylenediamine, tetramethylpropylenediamine, pentamethyldiethylenetriamine, N-[3-(dimethylamino)propyl]-trimethyl-1,3-propylenediamine, hexamethyltriethylenetetramine or tris(2-dimethylaminoethyl)amine, and the structural formula is as follows: ； The chemical structure of the polyamine is: diethylenetriamine, triethylenetetramine, tetraethylenepentamine or pentaethylenehexamine, and the structural formula is as follows: ； The small molecule long chain fatty acid anionic surfactant is sodium fatty acid methyl ester sulfonate, sodium stearate, sodium coconut oil isethionate or sodium lauryl sulfonate; The additive is carbon dioxide.

2. The multifunctional fracturing fluid composition according to claim 1, characterized in that: Based on 100% of the mass of the fracturing fluid, the addition amount of the small molecule long-chain fatty acid anionic surfactant is 0.5% to 3%.

3. The multifunctional fracturing fluid composition according to claim 1, characterized in that: The amount of the structural linker added is 1 / 4 to 1 / 2 of the total molar amount of the small molecule long chain fatty acid anionic surfactant.

4. The method for preparing a multifunctional fracturing fluid composition according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: slowly adding a small molecule long-chain fatty acid anionic surfactant and a structural linker into water during mechanical stirring; after dissolution, reducing the stirring rate and introducing carbon dioxide into the solution until excess carbon dioxide gas overflows, thereby preparing a fracturing fluid composition for use.

5. An application of a multifunctional fracturing fluid composition, characterized in that: A multifunctional fracturing fluid composition according to any one of claims 1 to 3 or a multifunctional fracturing fluid composition prepared according to claim 4 is used in a shale oil and gas fracturing, transformation and production increase process. The small molecule long-chain fatty acid anionic surfactant increases viscosity and viscoelasticity during fracturing, and acts as an imbibition agent after fracturing to exert a displacement and production increase effect. The structural connector prevents shale from swelling after the fracturing fluid breaks.

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