Background
Along with the exploration discovery of unconventional oil and gas resources and the rapid progress of exploitation technologies, hydraulic fracturing gradually becomes an important technology for leading the global unconventional oil and gas large-scale development, and the performance of fracturing fluid directly influences the effect of hydraulic fracturing operation.
In the hydraulic fracturing process, a pumping device injects fracturing fluid into an artificial fracture from a liquid storage tank through a ground pipeline, a shaft and a perforation hole at a high pumping speed, the fracturing fluid plays the roles of transferring pressure, forming and extending the fracture and carrying a propping agent, and the viscosity, the viscoelasticity and the sand carrying performance are important performance indexes of the fracturing fluid. At the wellbore and perforations, the fracturing fluid is subjected to high shear, which diminishes as the fracturing fluid flows into the artificial fractures. The conventional fracturing fluid takes vegetable gum or polymer as a thickening agent, under the action of high-speed shearing, the internal net structure of the fracturing fluid is irreversibly damaged, the viscosity and the viscoelasticity are greatly reduced, the sand carrying performance of the fracturing fluid is weakened, so that the propping agent cannot be conveyed to a preset position, even sand blockage occurs in a near-wellbore area, and the hydraulic fracturing construction effect is seriously influenced.
Therefore, the research and development of the fracturing fluid with good self-repairing performance is urgent, the viscosity, the viscoelasticity and the sand carrying performance of the fracturing fluid subjected to high-speed shearing can be quickly recovered after the fracturing fluid enters the artificial fracture, the propping agent is prevented from being quickly settled in a near-wellbore area, the propping agent is conveyed to the far end of the fracture, and the hydraulic fracturing construction is ensured to be smoothly carried out. An organic boron crosslinking fracturing fluid system commonly used for fracturing construction has certain shearing recovery property, but has the defects of low temperature resistance (less than 120 ℃), suitability for alkaline environment (pH is more than 8), high residue content and great damage to a reservoir stratum.
In recent years, based on the supramolecular chemistry concept, "dynamic reversible" self-healing systems have received much attention. The structure changes along with shearing disturbance, and can be restored to the initial structure again after the shearing disturbance is eliminated, and the self-repairing performance can compensate the loss of viscosity of the fracturing fluid system in the conveying process, so that the system can keep a high-viscosity state.
At present, a great deal of research is carried out on the supermolecule fracturing fluid formed by a polymer and a surfactant, but the defects of high cost and low temperature resistance of the surfactant limit the wide application of the supermolecule fracturing fluid, the research on the self-repairing performance of the fracturing fluid after being damaged is few, and whether the supermolecule fracturing fluid has the self-repairing performance is not clear.
Disclosure of Invention
In view of the above, the present application provides a supramolecular fracturing fluid with self-repairing performance and a preparation method thereof, aiming at the problem of poor self-repairing performance of the existing supramolecular fracturing fluid.
In order to solve the technical problem, the application discloses a supermolecule fracturing fluid with self-repairing performance, which consists of the following components in percentage by mass:
nonionic monomer: 2% -5%;
functional monomer: 0.1 to 0.6 percent;
and calculating other components according to the mass percent of the nonionic monomer:
a crosslinking agent: 0.05 percent to 0.08 percent;
initiator: 1% -5%;
the balance being deionized water.
Further, the nonionic monomer is acrylamide or modified acrylamide.
Further, the functional monomer is hydroxypropyl guar gum or carboxymethyl hydroxypropyl guar gum.
Further, the crosslinking agent is N, N' -methylene bisacrylamide.
Further, the initiator is ammonium persulfate.
The application also discloses a preparation method of the supermolecule fracturing fluid with self-repairing performance, which specifically comprises the following steps:
step 1, weighing the following components in percentage by mass:
nonionic monomer: 2% -5%;
functional monomer: 0.1 to 0.6 percent;
and calculating other components according to the mass percent of the nonionic monomer:
a crosslinking agent: 0.05 percent to 0.08 percent;
initiator: 1% -5%;
the balance of deionized water;
step 2, adding deionized water and a functional monomer into the reaction kettle, and stirring for 18-22 min;
step 3, adding a nonionic monomer under the stirring condition, stirring for 8-15 min, adding a cross-linking agent, stirring for 10-12 min, adding an initiator, and continuously stirring for 20-25 min to enable the mixed solution to reach a uniform state;
and 4, increasing the temperature of the reaction kettle to 35-45 ℃, and reacting for 11.5-12.5 hours to obtain the supermolecule fracturing fluid.
Further, the nonionic monomer in step 1 is acrylamide or modified acrylamide.
Further, the functional monomer in the step 1 is hydroxypropyl guar gum or carboxymethyl hydroxypropyl guar gum.
Further, in the step 1, the cross-linking agent is N, N' -methylene bisacrylamide.
Further, in the step 1, the initiator is ammonium persulfate.
Compared with the prior art, the application can obtain the following technical effects:
1) the supermolecule chemical concept is introduced, the double-network reversible structure is adopted for fracturing fluid design, so that the structure of the supermolecule fracturing fluid can be recovered after the supermolecule fracturing fluid is damaged by high-speed shearing, the performance of the supermolecule fracturing fluid can be recovered to the level before the damage to a certain degree, the viscosity repairing rate reaches more than 81%, the viscoelastic energy repairing rate reaches more than 95%, better sand carrying performance is kept, and the good self-repairing performance is achieved.
2) Under the condition that no temperature stabilizer is added, the supramolecular fracturing fluid has good temperature resistance and shearing resistance, the viscosity is kept above 70mPa & s after shearing for 90 minutes at 90 ℃, and the requirements of industrial standards are met.
3) Because the supermolecule fracturing fluid can still keep higher viscosity and good viscoelasticity after being damaged by high-speed shearing, the supermolecule fracturing fluid can keep excellent sand carrying performance in the whole process of entering a stratum from a pipeline through a perforation hole, the propping agent can be guaranteed to be conveyed to a preset position, a crack with high flow conductivity is formed, and the fracturing operation effect is improved.
Of course, it is not necessary for any one product to achieve all of the above-described technical effects simultaneously.
Detailed Description
Embodiments of the present application will be described in detail with reference to the drawings and examples, so that how to implement technical means to solve technical problems and achieve technical effects of the present application can be fully understood and implemented.
Example 1
A supermolecule fracturing fluid with self-repairing performance and a preparation method thereof are prepared from the following raw materials in percentage by mass:
acrylamide: 3 percent;
carboxymethyl hydroxypropyl guar: 0.5 percent;
and the other components are calculated according to the mass percentage of acrylamide:
n, N' -methylenebisacrylamide: 0.06 percent;
ammonium persulfate: 5 percent;
the balance being deionized water.
The preparation method comprises the following steps: adding deionized water and carboxymethyl hydroxypropyl guar gum into a reaction kettle, and stirring for 20 min; adding acrylamide under stirring, stirring for 10min, adding N, N' -methylene bisacrylamide, stirring for 10min, adding ammonium persulfate, and continuously stirring for 20min to make the mixture solution reach a uniform state; after stirring, the temperature of the reaction kettle is increased to 40 ℃, and the supermolecule fracturing fluid can be obtained after reaction for 12 hours.
Utilizing an HAAKE MARS III rheometer to carry out viscosity test on the supermolecule fracturing fluid and Polyacrylamide (PAM) with equal concentration; then, the shear failure of the fracturing fluid during injection was simulated, and the viscosity change of the two fluids after shear failure was tested, and the results are shown in fig. 1. After shearing for 1h under normal temperature, the viscosity of the supermolecule fracturing fluid is stabilized at 465 mPas, and the viscosity of the polyacrylamide is kept at about 306 mPas. Compared with polyacrylamide, the supramolecular fracturing fluid has higher initial viscosity, which shows that the supramolecular fracturing fluid has better thickening performance. After shearing failure, the viscosity of the polyacrylamide is 168mPa & s, which is 55% of the initial viscosity; the viscosity of the supramolecular fracturing fluid is 377 mPas, and the viscosity is recovered to 81 percent of the initial value, which shows that the supramolecular fracturing fluid has more excellent self-repairing performance.
Example 2
A supermolecule fracturing fluid with self-repairing performance and a preparation method thereof are prepared from the following raw materials in percentage by mass:
acrylamide: 2.5 percent;
carboxymethyl hydroxypropyl guar: 0.5 percent;
and the other components are calculated according to the mass percentage of acrylamide:
n, N' -methylenebisacrylamide: 0.07 percent;
ammonium persulfate: 4 percent;
the balance being deionized water.
The preparation is as in example 1.
The shear failure of the fracturing fluid during the injection process is simulated, and the HAAKE MARS III rheometer is used for testing the change relationship of the storage modulus and the energy consumption modulus of the supramolecular fracturing fluid and polyacrylamide with equal concentration before and after the shear failure, and the results are shown in fig. 2 and fig. 3. After the polyacrylamide is subjected to shear failure, the storage modulus and the energy consumption modulus of the polyacrylamide are greatly reduced compared with those before the polyacrylamide is damaged, and the yield stress is reduced from 10Pa to 2 Pa; the energy consumption modulus of the supermolecule fracturing fluid can be restored to the level before damage, the storage modulus is slightly reduced, the yield stress basically keeps unchanged, and the viscoelasticity repair rate reaches more than 95%, so that the supermolecule fracturing fluid has good self-repairing performance.
Example 3
A supermolecule fracturing fluid with self-repairing performance and a preparation method thereof are prepared from the following raw materials in percentage by mass:
acrylamide: 2.5 percent;
carboxymethyl hydroxypropyl guar: 0.45 percent;
and the other components are calculated according to the mass percentage of acrylamide:
n, N' -methylenebisacrylamide: 0.07 percent;
ammonium persulfate: 4 percent;
the balance being deionized water.
The preparation is as in example 1.
The shear failure of the fracturing fluid in the injection process is simulated, the static settlement rate of the proppant before and after shear failure of the supermolecular fracturing fluid and polyacrylamide with equal concentration is tested, the sand carrying performance of the fracturing fluid is represented, and the result is shown in fig. 4. The static settling rate of the proppant in the supramolecular fracturing fluid before shear failure is 1.8cm/h, which is less than the settling rate (4cm/h) of the proppant in polyacrylamide. After shear failure, the static settling rate of the proppant in the supramolecular fracturing fluid is 3cm/h, and the polyacrylamide after shear failure almost loses the sand carrying performance. The contrast shows that the shear action destroys the structure of the supermolecule fracturing fluid, after the shear action disappears, the supermolecule fracturing fluid can finish self-repairing of the structure, and keeps better sand carrying performance, and the polyacrylamide has no self-repairing performance.
Example 4
A supermolecule fracturing fluid with self-repairing performance and a preparation method thereof are prepared from the following raw materials in percentage by mass:
acrylamide: 3.5 percent;
carboxymethyl hydroxypropyl guar: 0.5 percent;
and the other components are calculated according to the mass percentage of acrylamide:
n, N' -methylenebisacrylamide: 0.067%;
ammonium persulfate: 5 percent;
the balance being deionized water.
The preparation is as in example 1.
The supramolecular fracturing fluid is placed at 90 ℃ to be sheared for 90 minutes, and the temperature resistance and the shearing resistance of the fracturing fluid are tested, and the result is shown in figure 5. The viscosity of the supermolecule fracturing fluid is rapidly reduced along with the rise of the temperature; after 30 minutes of shearing, the viscosity dropped to 164 mPas, and then the fracturing fluid viscosity dropped slowly. After shearing for 90 minutes, the viscosity of the supermolecule fracturing fluid is kept at 71mPa & s, which shows that the fracturing fluid has good temperature resistance and shearing resistance.
Example 5
A supermolecule fracturing fluid with self-repairing performance and a preparation method thereof are prepared from the following raw materials in percentage by mass:
modified acrylamide: 2 percent;
hydroxypropyl guar gum: 0.1 percent;
and the other components are calculated according to the mass percentage of the modified acrylamide:
n, N' -methylenebisacrylamide: 0.08 percent;
ammonium persulfate: 2 percent;
the balance being deionized water.
The preparation method comprises the following steps: adding deionized water and hydroxypropyl guar gum into a reaction kettle, and stirring for 18 min; adding modified acrylamide under stirring, stirring for 15min, adding N, N' -methylene bisacrylamide, stirring for 10min, adding ammonium persulfate, and continuing stirring for 22min to make the mixture solution reach a uniform state; after stirring, the temperature of the reaction kettle is increased to 45 ℃, and the reaction is carried out for 11.5 hours to obtain the supermolecule fracturing fluid.
Example 6
A supermolecule fracturing fluid with self-repairing performance and a preparation method thereof are prepared from the following raw materials in percentage by mass:
acrylamide: 5 percent;
hydroxypropyl guar gum: 0.6 percent;
and the other components are calculated according to the mass percentage of acrylamide:
n, N' -methylenebisacrylamide: 0.05 percent;
ammonium persulfate: 1 percent;
the balance being deionized water.
The preparation method comprises the following steps: adding deionized water and hydroxypropyl guar gum into a reaction kettle, and stirring for 22 min; adding acrylamide under stirring, stirring for 12min, adding N, N' -methylene bisacrylamide, stirring for 11min, adding ammonium persulfate, and continuously stirring for 25min to make the mixture solution reach a uniform state; after stirring, the temperature of the reaction kettle is increased to 35 ℃, and the reaction is carried out for 12.5 hours to obtain the supermolecule fracturing fluid.
Example 7
A supermolecule fracturing fluid with self-repairing performance and a preparation method thereof are prepared from the following raw materials in percentage by mass:
modified acrylamide: 4 percent;
carboxymethyl hydroxypropyl guar: 0.3 percent;
and the other components are calculated according to the mass percentage of the modified acrylamide:
n, N' -methylenebisacrylamide: 0.06 percent;
ammonium persulfate: 3 percent;
the balance being deionized water.
The preparation method comprises the following steps: adding deionized water and carboxymethyl hydroxypropyl guar gum into a reaction kettle, and stirring for 21 min; adding modified acrylamide under stirring, stirring for 8min, adding N, N' -methylene bisacrylamide, stirring for 12min, adding ammonium persulfate, and continuously stirring for 24min to make the mixture solution reach a uniform state; after stirring, the temperature of the reaction kettle is increased to 40 ℃, and the supermolecule fracturing fluid can be obtained after reaction for 12 hours.
While the foregoing description shows and describes several preferred embodiments of the invention, it is to be understood, as noted above, that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.