CN111363533B - Normal-pressure sand mixing quasi-dry fracturing method, fracturing fluid used in method, preparation method and application - Google Patents
Normal-pressure sand mixing quasi-dry fracturing method, fracturing fluid used in method, preparation method and application Download PDFInfo
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Abstract
Normal-pressure sand mulling quasi-dry fracturing method, fracturing fluid used in same, preparation method and application thereofThe method is characterized in that water-based fracturing fluid thickened by a water-based fracturing fluid thickener system material is simultaneously carried with a carbon dioxide dry fracturing fluid thickener system material, then normal-pressure sand mixing is carried out, and then the water-based fracturing fluid is combined with liquid carbon dioxide in carbon dioxide dry fracturing fluid according to a designed proportion, and liquid CO is obtained2After thickening, the two phases act synergistically to form a mixed liquid phase with enough viscosity and structure to become normal-pressure sand-mixing quasi-dry fracturing fluid, and the drag-reduction sand-carrying integrated fracturing construction is carried out. The normal-pressure sand mulling quasi-dry fracturing method and the normal-pressure sand mulling quasi-dry fracturing fluid do not need special closed mulling equipment, and are convenient to prepare; the drag reduction and sand carrying integrated application comprises the steps of preparing drag reduction liquid and sand carrying liquid at the same time; low damage or even no damage, which is beneficial to reservoir protection; the yield increasing effect is excellent, and the cost performance is high.
Description
Technical Field
The invention belongs to the technical field of fracturing yield increase, and particularly relates to a fracturing method organically combining water-based fracturing and carbon dioxide dry fracturing, namely an atmospheric sand mulling quasi-dry fracturing method, an atmospheric sand mulling quasi-dry fracturing fluid, a preparation method thereof and application thereof in an oil-gas field.
Background
The purpose of fracturing is to form fractures with conductivity in the reservoir, and the fracturing fluid used determines the fracturing effect to a large extent. Meanwhile, certain requirements are placed on the viscosity of the fracturing fluid, so that the fracturing fluid can become low-viscosity fluid after fracturing and is easy to flow back, and damage to an oil-gas layer in a reservoir stratum is avoided.
The conventional fracturing methods adopted at present mainly include oil-based fracturing, water-based fracturing, carbon dioxide dry fracturing (hereinafter referred to as "dry fracturing"), and the like. The oil-based fracturing has high cost, poor safety and prominent environmental protection problems, and occupies a lower proportion in the fracturing mode; the water-based fracturing has the advantages of low cost, high safety, convenient construction and the like, is most widely used at present, but has generally high damage to the stratum and unsatisfactory yield increasing effect due to the influences of water sensitivity, water lock effect and the like; the dry fracturing has the advantages of no water phase pollution, no residue, low damage or even no damage, energizing effect and the like, but the popularization and the application of the dry fracturing are limited because special high-pressure sand mixing equipment is needed and a large amount of sand cannot be carried because the dry fracturing cannot be thickened efficiently.
The preparation method and the process of the water-based fracturing fluid at home and abroad at the present stage are relatively mature, and the scale connection of related matched equipment such as a fluid distribution vehicle, a fracturing truck group and the like is realizedThe development and application of fracturing equipment and corollary equipment are realized in the continuous operation construction, in particular to the large-scale volume transformation of unconventional oil and gas reservoirs such as the segmented large-scale fracturing construction of a shale gas horizontal well. However, in unconventional oil and gas reservoirs such as shale oil and gas, dense oil and gas, coal bed gas and other reservoirs, the three-low characteristics of low pore, low pressure and low permeability are shown, the reservoir sensitivity is strong, such as water sensitivity, water lock, stress sensitivity, temperature sensitivity and the like, after the water-based fracturing fluid enters the reservoir, the water-based fracturing fluid inevitably generates damage to the reservoir in different degrees, so that the oil and gas yield is greatly reduced, and the final yield increasing effect is not satisfactory. On the other hand, in dry fracturing, conventional dry fracturing equipment cannot be used in a matched manner, special closed sand mixing equipment is needed, but high cost is required for development, use and maintenance, and only a few large equipment production enterprises at home and abroad have the design and manufacturing capacity of related professional equipment at present. The dry fracturing fluid cannot be thickened efficiently, so that liquid carbon dioxide (hereinafter referred to as liquid CO)2") low viscosity, low sand ratio, low sand volume, difficulty in carrying sand in sufficient quantity, and high pumping friction resistance, difficulty in forming effective fractures in the reservoir. Therefore, various factors such as equipment, materials and cost also limit the development of dry fracturing, which cannot be popularized and applied in a large scale even if the dry fracturing has performance advantages.
Disclosure of Invention
In view of the above, the main objective of the present invention is to provide an atmospheric sand-mulling quasi-dry fracturing method and an atmospheric sand-mulling quasi-dry fracturing fluid (hereinafter referred to as "quasi-dry fracturing fluid"), and a preparation method and applications thereof, so as to at least partially solve at least some of the technical problems in the related art.
In order to achieve the above object, according to an aspect of the present invention, there is provided a method for preparing an atmospheric mulling quasi-dry fracturing fluid, comprising the steps of:
step A, keeping the water temperature at 10-40 ℃, adding a water-based fracturing fluid thickener system material and a gel breaker according to a design proportion to prepare a water-based fracturing fluid, wherein the water-based fracturing fluid accounts for 10-40 wt% of the finally prepared normal-pressure sand-mixing quasi-dry-method fracturing fluid;
step B, adding dry fracturing fluid thickener system materials in a designed proportion into the water-based fracturing fluid prepared in the step A and uniformly mixing;
step C, adding a propping agent with a designed sand ratio into the product obtained in the step B, uniformly mixing sand, and pressurizing to a designed pressure;
step D, liquid CO accounting for 90-60 wt% of the finally prepared normal-pressure sand-mixing quasi-dry method fracturing fluid is used2Pressurizing to design pressure, then converging with the water-based fracturing fluid obtained in the step C, further pressurizing to design pressure, quickly mixing and exchanging heat, wherein the system temperature reaches-10-30 ℃, and simultaneously adding a dry fracturing fluid thickener system material into the mixture to enable the mixture to enter liquid CO2And (3) rapidly dissolving and thickening to prepare the final normal-pressure sand-mixing quasi-dry fracturing fluid.
As another aspect of the invention, the invention also provides the normal-pressure sand-mulling quasi-dry fracturing fluid prepared by the preparation method.
As another aspect of the present invention, there is provided a method for normal-pressure sand-mulling quasi-dry fracturing, comprising the steps of:
and (3) conveying the normal-pressure sand-mulling quasi-dry fracturing fluid to a reservoir, closing the well, stopping the pressure for a certain time, and finally breaking the gel and discharging back to complete the whole fracturing construction process.
As a further aspect of the invention, the application of the normal-pressure sand-mulling quasi-dry fracturing fluid as a resistance reducing fluid or a sand carrying fluid in an oil and gas field is provided.
Furthermore, the above preferred conditions may be arbitrarily changed and/or combined to obtain preferred embodiments of the present invention, based on the common knowledge in the art.
Based on the technical scheme, compared with the prior art, the technical scheme of the invention can achieve the following positive improvement effects:
(1) special closed sand mixing equipment is not needed, sand mixing is carried out under normal pressure, and preparation is convenient;
(2) the drag reduction and sand carrying integrated application is realized, the drag reduction liquid and the sand carrying liquid are prepared simultaneously, the sand ratio of the water-based fracturing liquid can reach 100 percent when the sand carrying liquid is prepared, and the sand ratio of the normal-pressure sand mixing quasi-dry method fracturing liquid can reach 45 percent;
(3) the two-phase thickener system has synergistic effect of materials;
(4) the quasi-dry method fracturing fluid has excellent temperature resistance and shearing resistance, and the overall viscosity of the formed quasi-dry method fracturing fluid reaches 50-200 mPa & s; the whole fracturing fluid is structural fluid, so that the viscoelasticity is good, and the shearing resistance is excellent; excellent heat resistance, 160 ℃ and 170s-1The viscosity is more than or equal to 20mPa & s after shearing for 2 h;
(5) the anti-swelling rate of the quasi-dry method fracturing fluid is more than or equal to 80%, the anti-swelling performance is excellent, the flowback rate is more than or equal to 50%, and the drainage-assisting performance is excellent;
(6) the material is less, and greenhouse gas is buried, so that the environment is protected;
(7) the damage rate of the rock core is less than or equal to 10 percent, which is beneficial to reservoir protection;
(8) the yield increasing effect is excellent, and the cost performance is high.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.
The research and development personnel of the invention gradually realize in the research and development process that: the water-based fracturing has the advantages of low cost, convenient preparation, perfect fracturing equipment and technical process and the like, but in unconventional oil and gas reservoirs such as shale oil and gas, compact oil and gas, conglomerate oil and gas, coal bed gas and the like, the three-low characteristics of low pore, low pressure and low permeability are shown, the reservoir sensitivity is strong, such as water sensitivity, water lock, stress sensitivity, temperature sensitivity and the like, and the water-based fracturing fluid inevitably causes damage to the reservoir in different degrees after entering the reservoir; meanwhile, an anti-swelling agent is additionally added to improve the stability of the clay, and a cleanup additive is added to improve the flowback effect after fracturing; the dry fracturing fluid has no water phase, no water sensitive water lock pollution, no residue, low or even no damage, easy energy increase and flowback, strong flowability, communicated reservoir stratum, CO2The viscosity reduction and oil gas replacement adsorption of the crude oil are achieved, but the viscosity is low, sand is difficult to carry, the friction is large, the crack is difficult to be formed, special closed sand mixing equipment is needed, the construction process is time-consuming and labor-consuming,the operation is inconvenient, the safety requirement is strict, the cost is high, and the overall cost performance is low.
The inherent properties of water-based fracturing and dry fracturing limit the further popularization and application of the fracturing. The applicant of the invention, Beijing Aipu polymerization science and technology Limited, concentrates on the research and development of oil field fracturing fluid thickener system products for a long time, concentrates on the research of the technology and application of the fracturing field technology, and accumulates abundant experiences after years of technical innovation. The inventor considers the advantages of combining water-based fracturing and dry fracturing in the aspects of fracturing methods and fracturing fluids, achieves normal-pressure sand mixing without special closed sand mixing equipment, and the fracturing fluid obtained by mixing two phases of a high-pressure manifold has excellent resistance-reducing effect as a resistance-reducing fluid, has the advantages of good crack formation, sufficient sand amount, low damage and high energy as a sand carrying fluid, and can increase the yield substantially. Therefore, the invention creatively provides a novel fracturing method of normal-pressure sand-mulling quasi-dry fracturing, and forms the matched normal-pressure sand-mulling quasi-dry fracturing fluid, and the preparation and the application thereof. The normal-pressure sand mixing quasi-dry fracturing method organically combines a water-based fracturing method and a dry fracturing method, has various technical advantages of the two methods, is combined into a whole, makes good use of the advantages and avoids the disadvantages, and has more unique advantages. The normal-pressure sand-mixing quasi-dry fracturing fluid as the drag reduction fluid has excellent drag reduction effect, has the unique advantages of good crack formation, sufficient sand amount, low damage and high energy as the sand carrying fluid, has excellent performance, and can certainly increase the yield greatly.
Specifically, the normal-pressure sand-mulling quasi-dry fracturing method disclosed by the invention is an innovative fracturing method which organically combines a water-based fracturing method and a dry fracturing method, has various technical advantages of the water-based fracturing method and the dry fracturing method, is combined into a whole, makes good use of the advantages and avoids the disadvantages, and has more unique advantages. The method is different from the conventional water-based fracturing method and the conventional dry fracturing method, and is named as the normal-pressure sand-mixing quasi-dry fracturing method. In the fracturing method, the water-based fracturing fluid thickened by the water-based fracturing fluid thickener system material is used, meanwhile, the dry fracturing fluid thickener system material is carried, then normal-pressure sand mixing is carried out, and then the mixed sand is mixed with liquid CO in the dry fracturing fluid according to the design proportion2Bound, liquid CO2After thickening, the two phases act synergistically to form a viscous enough productAnd (3) carrying out resistance reduction and sand carrying integrated fracturing construction on the mixed liquid phase with the structure, namely the normal-pressure sand mixing quasi-dry fracturing fluid.
The normal-pressure sand mulling quasi-dry fracturing fluid prepared by the fracturing method comprises the following material components: the water phase and the liquid CO are measured according to the mass percentage2The phase ratio is (10-40%) to (90-60%), wherein, when the retarder is used, the water-based fracturing fluid thickener system material accounts for 0.1-0.5% of the mass fraction of the water phase, and the dry-method fracturing fluid thickener system material accounts for liquid CO2The phase mass fraction is 0.1-0.5%; when the water-based fracturing fluid thickening agent system material is used as a sand carrying fluid, the water-based fracturing fluid thickening agent system material accounts for 0.5-3% of the mass fraction of the water phase, and the dry-method fracturing fluid thickening agent system material accounts for liquid CO2The phase mass fraction is 0.5-3%.
Preferably, the aqueous phase is CO liquid2The ratio of the phases is (20-30%): 80-70%);
preferably, when the retarder is used as a resistance reducing liquid, the water-based fracturing fluid thickener system material accounts for 0.2-0.3% of the mass fraction of the water phase, and the dry-method fracturing fluid thickener system material accounts for liquid CO2The phase mass fraction is 0.2-0.3%;
preferably, when the sand-carrying fluid is used as the sand-carrying fluid, the water-based fracturing fluid thickener system material accounts for 1-2% of the mass fraction of the water phase, and the dry-method fracturing fluid thickener system material accounts for liquid CO2The phase mass fraction is 1-2%.
The invention also provides an application step of the normal-pressure sand mulling quasi-dry fracturing method, which comprises the following steps:
(1) dissolving the water-based fracturing fluid thickener system materials in water:
keeping the water temperature at 10-40 ℃, adding a water-based fracturing fluid thickener system material and a gel breaker according to a design proportion by using a liquid preparation vehicle to prepare a water-based fracturing fluid, wherein the water-based fracturing fluid accounts for 10-40% of the normal-pressure sand-mulling quasi-dry method fracturing fluid; meanwhile, adding dry fracturing fluid thickener system materials in a designed proportion into the other parallel liquid adding port to be uniformly mixed in the water-based fracturing fluid; then the water-based fracturing fluid enters a normal-pressure sand mixing truck, a propping agent with a designed sand ratio is added, and the mixed sand is pressurized to the designed pressure by a booster pump after being uniform.
(2) Dry fracturing fluid thickener system materialWith liquid CO2Mixing and dissolving:
liquid CO accounting for 90-60% of quasi-dry method fracturing fluid in another parallel manifold2Pressurizing to design pressure by a booster pump, converging with water-based fracturing fluid at the joint of two high-pressure manifolds, further pressurizing to design pressure, rapidly mixing and exchanging heat, enabling the temperature of the system to reach-10-30 ℃, and enabling the dry fracturing fluid thickener system material to enter liquid CO2The intermediate solution is quickly dissolved, thickened and acted synergistically to form the quasi-dry fracturing fluid.
(3) The quasi-dry method fracturing fluid enters a reservoir and is subjected to the processes of fracturing, flowback and the like:
the quasi-dry method fracturing fluid sequentially passes through a ground high-pressure pipeline, an oil pipe or a sleeve pipe in the well and a blast hole to enter a reservoir, a propping agent is brought into a main crack and a branch crack of the reservoir to perform joint forming and sand filling, the reservoir is energized at the same time, the well is closed and the pressure is kept for a certain time, and finally the gel is broken and the fracturing construction overall process is completed.
Wherein the water used is conventional source water, including one or more of tap water, surface water, underground water, fracturing fluid flowback fluid or crude oil separation water;
wherein the liquid CO is2As gaseous CO2Liquid CO which is pressurized to 1.5-2.5 MPa by a pressure pump truck, cooled to-25-15 ℃ and stored in a special tank car or a storage tank2Wherein the gas is CO2Sources include CO captured after combustion of fossil fuels2Or CO2CO produced by gas wells2；
Wherein the used water-based fracturing fluid thickener system material comprises one of vegetable gum and modified vegetable gum thickener system material, viscoelastic surfactant system material and synthetic polymer system material;
wherein the dry fracturing fluid thickener system material comprises fluorine-containing CO2Thickener, silicon-containing CO2Thickener, and hydrocarbon polymer thickener.
Wherein, the design proportion of the dry fracturing fluid thickener material is that the dry fracturing fluid thickener material occupies liquid CO when being used as a resistance reducing fluid2The phase mass fraction is 0.1About 0.5%, when used as sand carrier, it occupies CO in liquid2The phase mass fraction is 0.5-3%.
The gel breaker used in the method comprises one or more than two of ammonium persulfate, capsule gel breaker and enzyme gel breaker.
Wherein the design proportion of the gel breaker accounts for 0.005-0.3% of the mass fraction of the quasi-dry fracturing fluid.
The proppant includes but is not limited to one or more of quartz sand, ceramsite and resin-coated sand.
The proppant is designed to have a sand ratio of 0-10% when used as a resistance reducing liquid and 5-45% when used as a sand carrying liquid.
The design pressure of the pressurized water-based fracturing fluid can be designed by combining the actual conditions of the inlet and the outlet of the booster pump, including but not limited to 10-40 MPa, and preferably 20-30 MPa.
Wherein the liquid CO is2The design pressure after pressurization is designed by combining the actual conditions of the inlet and the outlet of the booster pump, and comprises but is not limited to 10-40 MPa, preferably 20-30 MPa, and is consistent with the design pressure after pressurization of the water-based fracturing fluid.
The design pressure of the quasi-dry fracturing fluid is designed by combining actual conditions such as formation fracture pressure and the like, and includes but is not limited to 40-120 MPa, and preferably 50-70 MPa.
The well closing and pressure closing time can be designed by combining actual conditions such as field construction conditions, stratum conditions, post-fracturing production requirements and the like, and the well closing and pressure closing time comprises but is not limited to 1 h-7 d, and preferably 2-24 h.
In the following, specific embodiments are shown to illustrate the technical solution of the present invention in more detail. It should be noted that the specific values and amounts in the following embodiments are only for illustration, and can be scaled according to the ratio relationship in specific applications.
Example 1
Indoor application and performance test of the normal-pressure sand-mulling quasi-dry fracturing method:
keeping the water temperature at 10 ℃, adding 99.8g of tap water into the liquid preparation equipment, keeping stirring, sequentially adding 0.2g of water-based fracturing fluid thickener system material, 0.05g of ammonium persulfate and 1.8g of dry-method fracturing fluid thickener system material, and uniformly stirring and mixing; then 50cm of the solution was added3And (3) uniformly mixing the ceramsite and the sand, pressurizing to 10MPa by a booster pump, and entering a high-pressure manifold. Holding liquid CO in another parallel manifold2At-20 ℃ 898.2g of liquid CO were added2Pressurizing to 10MPa by a booster pump, converging with the water-based fracturing fluid at the joint of the two high-pressure manifolds, further pressurizing to 40MPa, and stirring and mixing uniformly to obtain the quasi-dry-method fracturing fluid. And (4) heating to 90 ℃, closing the pressure for 2 hours, and finally breaking the gel and discharging the gel again to finish the indoor evaluation process.
Wherein, the water-based fracturing fluid thickener system material adopts an integrated self-crosslinking emulsion type fracturing fluid thickener disclosed in CN201811402402.9 embodiment 4, and the dry fracturing fluid thickener system material adopts a dry fracturing fluid drag reduction thickener disclosed in CN201611251858.0 embodiment 1.
The prepared quasi-dry fracturing fluid is used as drag reduction fluid, and the temperature is-5 ℃ and the density is 0.95g/cm through tests3The pH value is 3, the viscosity is 3 mPa.s, the drag reduction rate is 71 percent, and the sand ratio is 5 percent.
Example 2
Indoor application and performance test of the normal-pressure sand-mulling quasi-dry fracturing method:
keeping the water temperature at 20 ℃, adding 388g of surface water into the liquid preparation equipment, keeping stirring, sequentially adding 12g of the water-based fracturing fluid thickening agent system material, 0.8g of the capsule gel breaker and 3g of the dry fracturing fluid thickening agent system material, and uniformly stirring and mixing; then adding 450cm3And (4) uniformly mixing the ceramsite and the sand, pressurizing to 40MPa by a booster pump, and entering a high-pressure manifold. Holding liquid CO in another parallel manifold2At-15 ℃ 597g of liquid CO are introduced2Pressurizing to 40MPa by a booster pump, converging with the water-based fracturing fluid at the joint of the two high-pressure manifolds, further pressurizing to 60MPa, and stirring and mixing uniformly to obtain the quasi-dry-method fracturing fluid. And (4) heating to 120 ℃, closing the pressure for 8h, and finally breaking the gel and discharging the gel again to finish the indoor evaluation process.
Wherein, the water-based fracturing fluid thickener system material adopts an integrated self-crosslinking emulsion type fracturing fluid thickener disclosed in CN201811402402.9 embodiment 4, and the dry fracturing fluid thickener system material adopts a dry fracturing fluid drag reduction thickener disclosed in CN201611251858.0 embodiment 1.
The prepared quasi-dry method fracturing fluid is used as a sand carrying fluid, and the temperature is 16 ℃, and the density is 0.91g/cm through tests3pH 5, viscosity 150 mPas, 160 DEG C&170s-1The viscosity after 2h of shearing is 25 mPa.s, the damage rate of the rock core is 3%, the anti-swelling rate is 85%, and the flowback rate is 64%.
Example 3
Indoor application and performance test of the normal-pressure sand-mulling quasi-dry fracturing method:
keeping the water temperature at 25 ℃, adding 298.5g of underground water into the liquid preparation equipment, keeping stirring, sequentially adding 1.5g of water-based fracturing fluid thickener system material, 0.3g of ammonium persulfate and 21g of dry-method fracturing fluid thickener system material, and stirring and mixing uniformly; then adding 200cm3And (4) uniformly mixing the ceramsite and the sand, pressurizing to 40MPa by a booster pump, and entering a high-pressure manifold. Holding liquid CO in another parallel manifold2At-20 deg.C, 679g of liquid CO2Pressurizing to 40MPa by a booster pump, converging with water-based fracturing fluid at the interface of two high-pressure manifolds, and further pressurizing to 60MPaAnd uniformly stirring and mixing to obtain the quasi-dry method fracturing fluid. And (4) heating to 160 ℃, closing the pressure for 4 hours, and finally breaking the gel and discharging again to finish the indoor evaluation process.
Wherein, the water-based fracturing fluid thickener system material adopts an integrated self-crosslinking emulsion type fracturing fluid thickener disclosed in CN201811402402.9 embodiment 4, and the dry fracturing fluid thickener system material adopts a dry fracturing fluid drag reduction thickener disclosed in CN201611251858.0 embodiment 1.
The prepared quasi-dry method fracturing fluid is used as a sand carrying fluid, and the temperature is 14 ℃ and the density is 0.85g/cm through tests3pH 4, viscosity 180mPa s, 160 DEG C&170s-1The viscosity is 35 mPa.s after shearing for 2h, the damage rate of the rock core is-5%, the anti-swelling rate is 89%, and the flowback rate is 69%.
Example 4
The field application and performance test of the normal-pressure sand-mulling quasi-dry fracturing method are as follows:
the field application of a certain shale gas well in a certain oil field in northern Shaanxi is as follows:
preparing 171.5t of surface water in a water tank, keeping the water temperature at 15 ℃, continuously adding 3.5t of water-based fracturing fluid thickener system material by using one liquid adding port of a continuous liquid preparation vehicle, continuously adding 0.035t of capsule gel breaker by using a dry powder charging port, and simultaneously continuously adding 6.5t of dry fracturing fluid thickener system material in the other parallel liquid adding port, and uniformly mixing in the water-based fracturing fluid; then the water-based fracturing fluid enters a normal-pressure sand mixing truck and is added into the sand mixing truck with the volume of 150m3And (3) uniformly mixing the ceramsite and the sand, and pressurizing to 30MPa by a booster pump.
318.5t liquid CO at-18 ℃ in another parallel manifold2Pressurizing to 30MPa by a booster pump, converging with the water-based fracturing fluid at the joint of the two high-pressure manifolds, further pressurizing to 65MPa, and quickly and uniformly mixing to obtain the quasi-dry method fracturing fluid.
And (3) allowing the quasi-dry method fracturing fluid to enter a reservoir layer through a ground high-pressure pipeline, an in-well casing and a blast hole in sequence, bringing a propping agent into a main crack and a branch crack of the reservoir layer to perform joint forming and sand filling, energizing the reservoir layer, closing the well, performing pressure closing for 12h, and finally performing gel breaking and flowback to complete the whole fracturing construction process.
Wherein, the water-based fracturing fluid thickener system material adopts an integrated self-crosslinking emulsion type fracturing fluid thickener disclosed in CN201811402402.9 embodiment 4, and the dry fracturing fluid thickener system material adopts a dry fracturing fluid drag reduction thickener disclosed in CN201611251858.0 embodiment 1.
The prepared quasi-dry method fracturing fluid is used as a sand carrying fluid, and the temperature is 18 ℃ and the density is 0.87g/cm through tests3pH 4.5, viscosity 168mPa s at 160 deg.C&170s-1The viscosity after 2h shearing is 28 mPa.s, the damage rate of the core is 4%, the anti-swelling rate is 91%, and the flowback rate is 58%.
Comparative example 1
Comparative example 1 indoor application and performance testing of fracturing fluids:
keeping the water temperature at 10 ℃, adding 99.95g of tap water into the liquid preparation equipment, keeping stirring, sequentially adding 0.05g of water-based fracturing fluid thickener system material,0.05g of ammonium persulfate and 0.45g of dry fracturing fluid thickener system material are stirred and mixed uniformly; then 50cm of the solution was added3And (3) uniformly mixing the ceramsite and the sand, pressurizing to 10MPa by a booster pump, and entering a high-pressure manifold. Holding liquid CO in another parallel manifold2At-20 ℃ 899.55g of liquid CO were added2Pressurizing to 10MPa by a booster pump, converging with the water-based fracturing fluid at the junction of two high-pressure pipes, further pressurizing to 40MPa, and stirring and mixing uniformly to obtain the fracturing fluid of comparative example 1. And (4) heating to 90 ℃, closing the pressure for 2 hours, and finally breaking the gel and discharging the gel again to finish the indoor evaluation process.
Wherein, the water-based fracturing fluid thickener system material adopts an integrated self-crosslinking emulsion type fracturing fluid thickener disclosed in CN201811402402.9 embodiment 4, and the dry fracturing fluid thickener system material adopts a dry fracturing fluid drag reduction thickener disclosed in CN201611251858.0 embodiment 1.
The fracturing fluid prepared in the comparative example 1 is tested to have the temperature of-5 ℃ and the density of 0.95g/cm3The pH value is 3, the viscosity is 0.5 mPas, the drag reduction rate is 32 percent, and the sand ratio is 0 percent.
Comparative example 2
Comparative example 2 indoor application and performance testing of fracturing fluids:
keeping the water temperature at 20 ℃, adding 436.5g of surface water into the liquid preparation equipment, keeping stirring, sequentially adding 13.5g of the water-based fracturing fluid thickening agent system material, 0.9g of the capsule gel breaker and 2.75g of the dry fracturing fluid thickening agent system material, and uniformly stirring and mixing; then adding 450cm3And (4) uniformly mixing the ceramsite and the sand, pressurizing to 40MPa by a booster pump, and entering a high-pressure manifold. Holding liquid CO in another parallel manifold2At-15 ℃ 547.25g of liquid CO were added2Pressurizing to 40MPa by a booster pump, converging with the water-based fracturing fluid at the joint of the two high-pressure manifolds, further pressurizing to 60MPa, and stirring and mixing uniformly to obtain the quasi-dry-method fracturing fluid. And (4) heating to 120 ℃, closing the pressure for 8h, and finally breaking the gel and discharging the gel again to finish the indoor evaluation process.
Wherein, the water-based fracturing fluid thickener system material adopts an integrated self-crosslinking emulsion type fracturing fluid thickener disclosed in CN201811402402.9 embodiment 4, and the dry fracturing fluid thickener system material adopts a dry fracturing fluid drag reduction thickener disclosed in CN201611251858.0 embodiment 1.
The fracturing fluid of comparative example 2, prepared as described above, was tested to have a temperature of 20 deg.C and a density of 0.93g/cm3pH 6, viscosity 120mPa s, 160 DEG C&170s-1The viscosity after 2h shearing is 15 mPa.s, the damage rate of the core is 24%, the anti-swelling rate is 71%, and the flowback rate is 52%.
The main materials, compounding ratios, two-phase ratios and performance test results of the above examples and comparative examples are shown in table 1 below.
TABLE 1 statistics of main materials, compounding ratios, two-phase ratios and performance test results for examples and comparative examples
The normal-pressure sand mulling quasi-dry fracturing method implemented in the embodiment has the following remarkable advantages through practical application:
1. special airtight sand mixing equipment and normal-pressure sand mixing are not needed, and the preparation is convenient: the normal pressure sand mixing quasi-dry method fracturing method only needs the existing water-based fracturing matching equipment and liquid CO2The high-pressure manifold does not need special closed sand mixing equipment required by dry fracturing; the water-based fracturing fluid can be prepared by adopting part of water only by using the water-based fracturing fluid thickening agent system material and the dry-method fracturing fluid thickening agent system material, and normal-pressure sand mixing can be carried out only by using a water-based fracturing matched sand mixing truck, so that the preparation is convenient.
2. The drag reduction and sand carrying integrated application comprises the following steps of preparing drag reduction liquid and sand carrying liquid: preparing a resistance reducing liquid by using a low-concentration water-based fracturing fluid thickener system material and a dry-method fracturing fluid thickener system material, and efficiently reducing resistance; the sand carrying fluid is prepared from the water-based fracturing fluid thickening agent system material with higher concentration and the dry-method fracturing fluid thickening agent system material, the sand amount is not limited by the capacity of sand adding equipment, sand can be added at will at one time, the sand ratio of the water-based fracturing fluid can reach 100%, the overall sand ratio after two phases are mixed can reach 45%, the sand amount is sufficient, the sand ratio is high, and the joint forming effect is excellent.
3. Two-phase thickener system materials synergy: thickener system using water-based fracturing fluidThe material thickens water-based fracturing fluid, the water-based fracturing fluid can carry thickening agent system material of dry fracturing fluid, and the thickening agent system material of the dry fracturing fluid can thicken liquid CO2The two-phase thickener system has synergistic effect; the prepared quasi-dry method fracturing fluid has two phases which act synergistically to form a mixed liquid phase with sufficient viscosity and structure.
4. The quasi-dry method fracturing fluid has excellent temperature resistance and shear resistance: the overall viscosity of the formed quasi-dry fracturing fluid reaches 50-200 mPa & s; the whole fracturing fluid is structural fluid, so that the viscoelasticity is good, and the shearing resistance is excellent; excellent heat resistance, 160 ℃ and 170s-1The viscosity is more than or equal to 20 mPas after shearing for 2 h.
5. Excellent anti-swelling and drainage-assisting performance: liquid CO at high pressure2The solubility in water is greatly improved, so that in the quasi-dry method fracturing fluid, most of water and liquid CO2The water-based fracturing fluid exists in a saturated carbonic acid solution form, free water hardly exists, the activity of the water is greatly reduced, and the hydration expansion and migration effects of the clay are far lower than those of a water-based fracturing fluid, so that the natural anti-swelling property is excellent; the quasi-dry method fracturing fluid has liquid CO2The surface tension is ultralow, and a large amount of energy is supplemented for the reservoir, so that the drainage assisting effect is excellent, and the flowback rate is high.
6. The material is few, and the greenhouse gas is buried, so that the environment is protected: the prepared quasi-dry method fracturing fluid does not need to use auxiliary agents such as an anti-swelling agent, a cleanup additive and the like, so that the pollution of the fracturing fluid to the ground surface and the environment is effectively reduced, and simultaneously, a large amount of greenhouse gas can be buried to reduce the greenhouse effect, thereby being beneficial to environmental protection.
7. Low damage or even no damage, and is beneficial to reservoir protection: the quasi-dry method fracturing fluid is easy to break gel and thorough in gel breaking, and has low or even no damage to a reservoir because of high flowback rate, few reservoir residues and no damage of a water-sensitive water lock and the like, thereby being beneficial to reservoir protection.
8. The yield increasing effect is excellent, and the cost performance is high: the normal-pressure sand-mulling quasi-dry fracturing method has the outstanding advantages and characteristics which are confirmed by field application, and compared with adjacent well water-based fracturing and dry fracturing, the yield is increased by more than ten times, the yield increasing effect is excellent, and the cost performance is high. The technology is not only applied to conventional oil and gas reservoirs, but also particularly suitable for unconventional oil and gas reservoirs such as shale oil and gas, compact oil and gas, conglomerate oil and gas, coal bed gas and the like.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (11)
1. A preparation method of normal-pressure sand-mulling quasi-dry fracturing fluid is characterized by comprising the following steps:
step A, keeping the water temperature at 10-40 ℃, adding a water-based fracturing fluid thickener system material and a gel breaker according to a design proportion to prepare a water-based fracturing fluid, wherein the water-based fracturing fluid accounts for 10-40 wt% of the finally prepared normal-pressure sand-mixing quasi-dry-method fracturing fluid;
step B, adding dry fracturing fluid thickener system materials in a designed proportion into the water-based fracturing fluid prepared in the step A and uniformly mixing;
c, adding a propping agent with a designed sand ratio into the product obtained in the step B, uniformly mixing sand, and pressurizing to a designed pressure of 10-40 MPa;
step D, liquid CO accounting for 90-60 wt% of the finally prepared normal-pressure sand-mixing quasi-dry method fracturing fluid is used2And D, pressurizing to a design pressure of 10-40 MPa, then converging with the water-based fracturing fluid obtained in the step C, further pressurizing to a design pressure of 40-120 MPa, quickly mixing and carrying out heat exchange, and enabling the system temperature to reach-10-30 ℃, thereby preparing the final normal-pressure sand-mixing quasi-dry fracturing fluid.
2. The production method according to claim 1,
according to the mass percentage, the water phase and the liquid CO in the final normal-pressure sand-mixing quasi-dry-method fracturing fluid2The phase ratio is (10-40%): (90-60%);
wherein the finally prepared normal-pressure sand mulling is quasi-dryWhen the fracturing fluid is used as a resistance reducing fluid, the mass fraction of the water-based fracturing fluid thickener system material in the water phase is 0.1-0.5%, and the mass fraction of the dry fracturing fluid thickener system material in the liquid CO2The mass fraction of the phases is 0.1-0.5%;
when the finally prepared normal-pressure sand-mixing quasi-dry fracturing fluid is used as a sand-carrying fluid, the mass fraction of the water-based fracturing fluid thickener system material in the water phase is 0.5-3%, and the mass fraction of the dry fracturing fluid thickener system material in the liquid CO2The mass fraction of the phases is 0.5-3%.
3. The production method according to claim 1 or 2,
the water is conventional source water and comprises one or more than two of tap water, surface water, underground water, fracturing fluid flowback fluid or crude oil separation water;
the liquid CO2As gaseous CO2Pressurizing to 1.5-2.5 MPa by a pressure pump truck, cooling to-25 to-15 ℃, and storing the liquid CO in a special tank car or a storage tank2Wherein the gas is CO2Sources include CO captured after combustion of fossil fuels2Or CO2CO produced by gas wells2；
The water-based fracturing fluid thickener system material comprises one of vegetable gum and modified vegetable gum thickener system material, viscoelastic surfactant system material and synthetic polymer system material;
the dry fracturing fluid thickener system material comprises fluorine-containing CO2Thickener, silicon-containing CO2Thickener, and hydrocarbon polymer thickener.
4. The production method according to claim 1,
the design proportion of the water-based fracturing fluid thickener system material is 0.1-0.5% of the mass fraction of the water phase when being used as a resistance reducing fluid and 0.5-3% of the mass fraction of the water phase when being used as a sand carrying fluid;
the design proportion of the dry fracturing fluid thickener material is that when the thickener material is used as a resistance reducing fluid, the thickener material occupies liquid CO2Phase quality0.1-0.5% of the total weight of the sand-carrying liquid, and the sand-carrying liquid occupies liquid CO20.5-3% of phase mass fraction;
the gel breaker comprises at least one of ammonium persulfate, a capsule gel breaker and an enzyme gel breaker;
the design proportion of the gel breaker accounts for 0.005-0.3% of the mass fraction of the finally prepared normal-pressure sand-mixing quasi-dry-method fracturing fluid;
the proppant comprises at least one of quartz sand, ceramsite and resin coated sand;
the designed sand ratio of the proppant is 0-10% when used as a resistance reducing liquid and 5-45% when used as a sand carrying liquid;
the design pressure of the water-based fracturing fluid after pressurization in the step C is 20-30 MPa;
liquid CO in step D2The design pressure after pressurization is 20-30 MPa, and is consistent with the design pressure after pressurization of the water-based fracturing fluid;
and D, increasing the final pressure to 50-70 MPa.
5. The normal-pressure sand-mixing quasi-dry fracturing fluid prepared by the preparation method according to any one of claims 1 to 4.
6. The normal-pressure sand-mixing quasi-dry fracturing fluid as claimed in claim 5, wherein the temperature of the normal-pressure sand-mixing quasi-dry fracturing fluid is-10 to 30 ℃, and the density of the normal-pressure sand-mixing quasi-dry fracturing fluid is 0.8 to 1.1g/cm3The pH value is 3.0-6.0.
7. The normal-pressure sand-mixing quasi-dry fracturing fluid as claimed in claim 5, wherein when used as a resistance reducing fluid, the viscosity of the normal-pressure sand-mixing quasi-dry fracturing fluid is 1-20 mPa.s, the resistance reducing rate is not less than 60%, and the sand ratio is 0-10%; when the normal-pressure sand-mixing quasi-dry fracturing fluid is used as a sand-carrying fluid, the viscosity of the normal-pressure sand-mixing quasi-dry fracturing fluid is 50-200 mPa.s and 160 DEG C&170s-1The viscosity is more than or equal to 20 mPa.s after shearing for 2 hours, the sand ratio is 5-45%, the core damage rate is less than or equal to 10%, the anti-swelling rate is more than or equal to 80%, and the flowback rate is more than or equal to 50%.
8. A normal-pressure sand mulling quasi-dry fracturing method is characterized by comprising the following steps:
the normal-pressure sand-mixing quasi-dry fracturing fluid as claimed in any one of claims 5 to 7 is conveyed to a reservoir, then a well is closed, the pressure is closed for a certain time, finally, gel is broken and flowback is carried out, and the whole fracturing construction process is completed.
9. The atmospheric mulling quasi-dry fracturing method as recited in claim 8,
and the well closing and pressure closing time is 1 h-7 d.
10. The atmospheric mulling quasi-dry fracturing method as recited in claim 9,
and the well closing and pressure closing time is 2-24 h.
11. The application of the normal-pressure sand-mixing quasi-dry fracturing fluid as defined in any one of claims 5 to 7 as a resistance reducing fluid or a sand carrying fluid in an oil and gas field.
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| CN85102151A (en) * | 1984-01-20 | 1987-02-18 | 哈利伯顿公司 | With carbon dioxide-base liquid Splitting Method with stimulation of wells |
| CN1890346A (en) * | 2003-12-05 | 2007-01-03 | 施蓝姆伯格技术公司 | Carbon dioxide foamed fluids |
| CN104152133A (en) * | 2013-05-13 | 2014-11-19 | 中国石油化工股份有限公司 | Carbon dioxide fracturing fluid and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN85102151A (en) * | 1984-01-20 | 1987-02-18 | 哈利伯顿公司 | With carbon dioxide-base liquid Splitting Method with stimulation of wells |
| CN1890346A (en) * | 2003-12-05 | 2007-01-03 | 施蓝姆伯格技术公司 | Carbon dioxide foamed fluids |
| CN104152133A (en) * | 2013-05-13 | 2014-11-19 | 中国石油化工股份有限公司 | Carbon dioxide fracturing fluid and preparation method thereof |
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