A CO in a tight conglomerate reservoir 2 Instantaneous high-pressure energy storage fracturing system and fracturing method

Abstract

The present invention discloses a CO2 instantaneous high-pressure energy storage fracturing system and a fracturing method for a tight conglomerate reservoir, which relates to the technical field of oil and gas exploitation. The system used in the present invention includes an aqueous fracturing fluid pumping unit and a supercritical CO2 instantaneous high-pressure pumping unit. The present invention can effectively solve the problems of difficult oil and gas production and small swept range in "fine pore and fine throat" type tight conglomerate reservoirs. By injecting supercritical CO2 at instantaneous high pressure and pumping CO2 foam fracturing fluid at low pressure, the invasion ability of CO2 into fine pore throats is significantly enhanced, and the phase change is utilized to promote the formation of a complex micro-fracture network, expand the swept volume of CO2, achieve more efficient reservoir stimulation, and provide strong support for the long-term benefit development of tight conglomerate reservoirs.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and particularly to a CO 2 instantaneous high-pressure energy storage fracturing system and a fracturing method. Background Technique

[0002] A tight conglomerate reservoir refers to a reservoir with conglomerate as the reservoir rock, which has characteristics such as strong heterogeneity, low porosity and low permeability, and complex pore structure. These reservoirs are usually formed in the sedimentary environments of fan deltas and braided river deltas, with lithology mainly including conglomerate, sandy conglomerate, and gravel-bearing unequal-grained sandstone, and the components are mostly tuff, granite, rhyolite, etc. In contrast, ordinary reservoirs are usually formed in sandstone or carbonate rocks, with relatively uniform geological structures and higher porosity and permeability.

[0003] The main differences between conglomerate oilfields and ordinary oilfields lie in the reservoir type and development difficulty. The exploitation of tight conglomerate reservoirs is more difficult because of their low porosity. The crude oil is stored in the pores of the rock that are invisible to the naked eye, and it is necessary to improve the reservoir productivity through fracturing transformation. While the exploitation of ordinary reservoirs is relatively easy because of their higher porosity and permeability, and depletion development or conventional fracturing can meet the requirements. Due to the great difficulty in exploiting tight conglomerate reservoirs, the required investment and technical requirements are usually high, and the development cost is also relatively high.

[0004] Although the development cost of tight conglomerate reservoirs is high, their production potential is large, and the potential for production increase after effective fracturing transformation is great. While the production of conventional reservoirs is relatively stable, but the growth potential is limited.

[0005] Due to the poor physical properties of the reservoir in the Mahu tight conglomerate reservoir, strong heterogeneity, complex reservoir distribution law, and high gravel content, the transformation effect of the conventional hydraulic fracturing method is not ideal, and it is easy to have problems such as high initial productivity and rapid decline in the middle and later stages. There is an urgent need for a suitable transformation means to realize the efficient development of tight conglomerate reservoirs. At present, large-scale CO 2 pre-fracturing horizontal well experiments have been carried out in the Mahu Oilfield, and good results have been achieved in some Class I and Class II conglomerate reservoirs. The quarterly cumulative oil production of the well groups using carbon dioxide pre-fracturing has increased by nearly 23.5% compared with the conventional fracturing well groups in the same block. However, in some Class II and Class III conglomerate reservoirs with relatively poor reservoir physical properties, the cumulative oil production is low after the CO 2 pre-storage energy fracturing transformation, and the effect of improving the recovery rate is not obvious.

[0006] Since the pores between gravel debris are filled with a large amount of clay minerals and matrix, some Class II and Class III conglomerate reservoirs have typical "fine pores and fine throats" characteristics. During the conventional carbon dioxide pre-fracturing process, CO 2The invasion range of the fine pore throats is limited, and it can only play a local energy storage role, unable to effectively transform the reservoir in combination with the subsequent main fracturing operation. In addition, in reservoirs with well-developed fractures, CO 2 is prone to channeling along the interfaces of gravel particles, resulting in waste of CO 2 and engineering resources. The above problems lead to the lack of effective development means for such reservoirs. After the transformation by the conventional carbon dioxide pre-fracturing method, the production increase effect compared with adjacent wells is not good. There is an urgent need to propose a more practical reservoir transformation method for tight conglomerate reservoirs with the characteristics of "fine pores and fine throats" and "low formation-fluid saturation pressure difference" to provide strong support for the efficient development of tight conglomerate oil reservoirs. Summary of the Invention

[0007] The purpose of the present invention is to provide a CO 2 instantaneous high-pressure energy storage fracturing system and fracturing method for tight conglomerate oil reservoirs to solve the problems existing in the above-mentioned prior art.

[0008] To achieve the above purpose, the present invention provides the following solutions:

[0009] The present invention provides a CO 2 instantaneous high-pressure energy storage fracturing system for tight conglomerate oil reservoirs, including a water-based fracturing fluid pumping unit and a supercritical CO 2 instantaneous high-pressure pumping unit;

[0010] The water-based fracturing fluid pumping unit includes a first fracturing pump truck group, a first high-pressure manifold, a first low-pressure pipeline, a blender truck, a sand tank truck, and a liquid tank truck; wherein, the blender truck, the first low-pressure pipeline, the first fracturing pump truck group are sequentially connected to the first high-pressure manifold; the sand tank truck and the liquid tank truck are connected to the blender truck in parallel;

[0011] The supercritical CO 2 instantaneous high-pressure pumping unit includes a second fracturing pump truck group, a second high-pressure manifold, a second low-pressure pipeline, a CO 2 tank truck, and a CO 2 boosting pump truck; wherein, the CO 2 tank truck, the CO 2 boosting pump truck, the second low-pressure pipeline, the second fracturing pump truck group are sequentially connected to the second high-pressure manifold;

[0012] The first high-pressure manifold is connected to the wellhead through the first high-pressure pipeline, and the second high-pressure manifold is connected to the wellhead through the second high-pressure pipeline; a first instrument truck is used to monitor the water-based fracturing fluid pumping unit; a second instrument truck is used to monitor the supercritical CO 2 instantaneous high-pressure pumping unit.

[0013] Among them, the sand tank truck is used for transporting proppants (materials used to fill reservoir fractures during the fracturing process); the liquid tank truck is used for transporting liquids and preparing fracturing fluids.

[0014] As a further preference of the present invention, the tight conglomerate reservoir CO 2 The instantaneous high-pressure energy storage fracturing system further includes a heating device for wellhead heating.

[0015] Specifically, in the fracturing system of the present invention, the first instrument truck and the second instrument truck serve as the command and control centers. The first instrument truck is used for remotely controlling the first fracturing pump truck and the blender truck, and simultaneously recording the construction curve; the second instrument truck is used for remotely controlling the second fracturing pump truck group and simultaneously recording the construction curve.

[0016] The instrument truck mainly remotely controls and receives digital signals to form a construction curve image.

[0017] As a further preference of the present invention, the water-based fracturing fluid pumping unit further includes a first blower for cooling the first fracturing pump truck group; the supercritical CO 2 The instantaneous high-pressure pumping unit further includes a second blower for cooling the second fracturing pump truck group.

[0018] The present invention also provides a tight conglomerate reservoir CO 2 Instantaneous high-pressure energy storage fracturing method, using the above-mentioned tight conglomerate reservoir CO 2 Instantaneous high-pressure energy storage fracturing system, including the following steps:

[0019] (1) Pumping energy storage preflush: Using the supercritical CO 2 Instantaneous high-pressure pumping unit to pump supercritical CO 2 As the energy storage preflush;

[0020] (2) Pumping preflush: Using the supercritical CO 2 Instantaneous high-pressure pumping unit to pump supercritical CO 2 Fluid as the preflush;

[0021] (3) Pumping CO 2 Foam fracturing fluid: Using the supercritical CO 2 Instantaneous high-pressure pumping unit and the water-based fracturing fluid pumping unit to alternately pump CO 2 Foam fracturing fluid;

[0022] (4) Repeating steps (2) and (3);

[0023] (5) Conduct sand-carrying operation using the water-based fracturing fluid pumping unit: Use low-viscosity slickwater to carry 70-140 mesh proppants to fill the microfractures, gradually increase the viscosity of the slickwater to expand the main fracture, and successively carry 40-70 mesh and 20-40 mesh proppants to support the main fracture to complete the main fracturing construction.

[0024] Further, the proppant is quartz sand.

[0025] Further, the method includes the following steps:

[0026] (1) Pump the energy storage preflush fluid: Use the CO 2 booster pump truck to pressurize the CO 2 fluid in the CO 2 tank truck, and successively transport the supercritical CO 2 fluid to the wellhead through the second low-pressure pipeline, the second fracturing pump truck group, the second high-pressure manifold and the second high-pressure pipeline;

[0027] (2) Pump the preflush fluid: Use the CO 2 booster pump truck to pressurize the CO 2 fluid in the CO 2 tank truck, and successively transport the supercritical CO 2 fluid to the wellhead through the second low-pressure pipeline, the second fracturing pump truck group, the second high-pressure manifold and the second high-pressure pipeline by means of instantaneous high pressure;

[0028] (3) Pump the CO 2 foam fracturing fluid:

[0029] Take the water-based fracturing fluid in the blender truck as the base fluid and successively transport it to the wellhead through the first low-pressure pipeline, the first fracturing pump truck group, the first high-pressure manifold and the first high-pressure pipeline. While injecting the water-based fracturing fluid, use the CO 2 booster pump truck to pressurize the CO 2 fluid in the CO 2 tank truck, and transport the supercritical CO 2 fluid to the wellhead through the second low-pressure pipeline, the second fracturing pump truck group, the second high-pressure manifold and the second high-pressure pipeline to form the CO 2 foam fracturing fluid;

[0030] The components of the water-based fracturing fluid include drag reducer, foaming agent, crosslinking agent, breaker and ammonium persulfate;

[0031] (4) Repeat steps (2) and (3);

[0032] (5) Conduct sand-carrying operation using the water-based fracturing fluid pumping unit: Use slickwater to carry proppant with a mesh size of 70 - 140 to fill the microfractures, then gradually increase the viscosity of the slickwater to expand the main fracture, and gradually carry proppant with a mesh size of 40 - 70 and 20 - 40 to support the main fracture, completing the main fracturing construction.

[0033] Further, in step (1), the injection volume of the supercritical CO 2 fluid is 1.2 times the wellbore volume.

[0034] Further, the construction displacement in step (1) is 2 - 4 m³ / min; the construction displacement of the instantaneous high pressure in step (2) is 8 - 20 m³ / min.

[0035] Further, in step (3), the total pumping displacement of the water-based fracturing fluid and the supercritical CO 2 fluid is 2 - 3 m³ / min; the pumping displacement ratio of the water-based fracturing fluid and the supercritical carbon dioxide fluid is 1:1; the construction displacement in step (5) is 8 - 20 m³ / min.

[0036] In the present invention, the displacement during the main fracturing construction is usually determined according to reservoir characteristics, fracture design, equipment capacity, and wellbore structure. The displacement range for casing fracturing is generally 8 - 20 m³ / min.

[0037] Further, the total pumped-in volume of the supercritical carbon dioxide fluid is 20% of the total injected fluid volume.

[0038] On the basis of comprehensively considering the transformation effect and construction cost, the number of times of repeating step (2) and step (3) does not exceed 3 times.

[0039] The present invention discloses the following technical effects:

[0040] 1. The present invention can effectively solve the problem of difficult mobilization of oil and gas in the "fine pores and fine throats" of tight conglomerate reservoirs. Through the instantaneous high-pressure injection of supercritical CO 2 while reducing the lower limit of pore-throat mobilization in the conglomerate reservoir, the radius of the fine conglomerate pore-throat is effectively increased. Through "one reduction and one increase", the dynamic critical mobilization of the tight conglomerate reservoir is realized, and the enhanced oil recovery effect of the pre-storage energy fracturing within its action range is improved. 2

[0041] 2. The present invention can effectively solve the problem of small sweep range of conventional CO 2 pre-storage energy in tight conglomerate reservoirs. Through high-pressure injection of supercritical CO 2 the microfractures in the reservoir can be effectively expanded and extended. Through low-pressure injection of CO 2Foam fracturing fluid can utilize its characteristics of high viscosity and low filtration loss. When entering the main fracture, it slowly infiltrates the along - the - way fractures. By taking advantage of the difference in the invasion ability of the two fluids into the reservoir, while increasing the formation pressure, it can effectively block gas, inhibit the occurrence of gas fingering, extend the gas channeling occurrence time of CO 2 and reduce the degree of gas channeling, thereby improving the sweep efficiency of pre - placed energy storage. 2

[0042] 3. The present invention can promote the formation and expansion of complex fracture networks, improve the physical properties of crude oil, and increase the oil recovery rate. The conglomerate reservoir has strong heterogeneity. Injecting CO instantaneously under high pressure by a pump 2 is likely to form "bypassing gravel" and "penetrating gravel" preferential channels. Then, when injecting CO by a pump under reduced pressure 2 foam fracturing fluid can effectively block the preferential channels. By varying the displacement and fluid properties, complex fracture networks can be formed. As the pressure increases, the miscibility degree of CO 2 with crude oil will increase to some extent, enhancing the solubilization effect on crude oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0044] Figure 1 FIG. 2 is the on - site layout diagram of the instantaneous high - pressure energy - storage fracturing system for the tight conglomerate reservoir of CO in the present invention;

[0045] Figure 2 FIG. 2 is the process flow diagram of the instantaneous high - pressure energy - storage fracturing method for the tight conglomerate reservoir of CO in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. For any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0048] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to those documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0049] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this invention are merely exemplary.

[0050] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0051] It should be noted that the aspects not described in detail in this invention are all conventional operating means in the art and are not the focus of this invention.

[0052] Example 1

[0053] For a certain tight conglomerate reservoir, the mid-depth of the reservoir in Well H026 is 3040 meters. The reservoir characteristics of the target layer are divided into five aspects: reservoir quality, natural energy, sensitivity, fluid properties, and engineering quality. Among them, in terms of reservoir quality, the porosity of this reservoir is 5.1% - 14.8%, and the average porosity is 8.82%. The permeability mainly ranges from 0.1 to 422 mD, and the average permeability is 6.06 mD; the porosity of the oil layer is 6.4% - 14.8%, and the average porosity is 10.53%. The permeability mainly ranges from 0.474 to 422 mD, with an average of 9.94 mD, belonging to a low-porosity and extra-low-permeability conglomerate reservoir; in terms of natural energy, the pressure coefficient is about 1.2; in terms of sensitivity, there is no obvious velocity sensitivity in the reservoir, and it has medium salt sensitivity and strong water sensitivity; in terms of fluid properties, the density of the formation crude oil is 0.755 g / cm 3 , the viscosity is 8.5 mPa·s, the gas-oil ratio is 138 m 3 / m 3 , the volume coefficient is 1.311, and the compressibility coefficient is 14×10 -4 / MPa; in terms of engineering quality, the natural fractures in the reservoir are not well-developed, and construction can be carried out by the method provided in this invention.

[0054] Step 1: Standardized layout of the pumping equipment.

[0055] Figure 1 For the in-situ layout diagram of the instantaneous high-pressure energy storage fracturing system for the tight conglomerate oil reservoir of the present invention and CO 2 instantaneous high-pressure energy storage fracturing system.

[0056] For the CO 2 The system adopted for instantaneous high-pressure energy storage fracturing includes two relatively independent units arranged on-site: the water-based fracturing fluid pumping unit and the supercritical CO 2 instantaneous high-pressure pumping unit.

[0057] The water-based fracturing fluid pumping unit includes a first fracturing pump truck group, a first high-pressure pipeline network, a first low-pressure pipeline, a first blower, a sand mixing truck, a sand tank truck, and a liquid tank truck; among them, the sand mixing truck, the first low-pressure pipeline, the first fracturing pump truck group, and the first high-pressure pipeline network are connected in sequence; the sand tank truck and the liquid tank truck are connected to the sand mixing truck in parallel; the first blower is connected to the first fracturing pump truck group to cool the first fracturing pump truck group;

[0058] The supercritical CO 2 The instantaneous high-pressure pumping unit includes a second fracturing pump truck group, a second high-pressure pipeline network, a second low-pressure pipeline, a second blower, a CO 2 tank truck, and a CO 2 boosting pump truck; among them, the CO 2 tank truck, the CO 2 boosting pump truck, the second low-pressure pipeline, the second fracturing pump truck group, and the second high-pressure pipeline network are connected in sequence; the second blower is connected to the second fracturing pump truck group to cool the second fracturing pump truck group;

[0059] The first high-pressure pipeline network is connected to the wellhead through a first high-pressure pipeline, and the second high-pressure pipeline network is connected to the wellhead through a second high-pressure pipeline; the water-based fracturing fluid pumping unit and the supercritical CO 2 instantaneous high-pressure pumping unit are respectively connected to a first instrument vehicle and a second instrument vehicle.

[0060] A heater for heating the wellhead is also provided.

[0061] Among them, the two fracturing pump truck groups include multiple fracturing trucks, and the model parameters of each fracturing truck are as follows: adopting the YLC105-1490 model, with an output power of 2500 HP, a maximum construction pressure of 103 MPa, and a maximum single-truck displacement of 2.46 m 3 / min. The sand mixing truck adopts the HSC20 model, with a maximum clear water displacement of the sand pump of 20 m³ / min, a maximum working pressure of 0.7 MPa, a maximum sand transportation volume of the sand transporter of 12000 kg / min, a mixing tank volume of 2.0 m³, and an engine model of Detroit S60 diesel engine with an engine power of 650 hp. CO 2The booster pump truck adopts the TZQ08D model, with a maximum working pressure of 2.5MPa, a maximum displacement of 12m³ / min, and a power of 180hp. The instrument truck adopts the JR5140TBC model, which is equipped with data acquisition software, pump control software, sand mixing monitoring software, comprehensive management software, etc. It has the data acquisition and processing functions of parameters such as pressure, displacement, and sand ratio, and can timely, sensitively, accurately, and reliably collect and display the parameters and curve changes of each period, and can comprehensively monitor, control and manage the construction process. The fracturing fluid additives (including drag reducers, foaming agents, acid cross-linking agents, capsule breakers and ammonium persulfate, which are solid at room temperature) are stored in polypropylene container bags and mixed with water in the sand mixing truck through the feed pipe to form a water-based fracturing fluid.

[0062] Step 2: Pump the energy storage pre-fluid.

[0063] The assembled perforating gun is lowered to the preset perforating depth via a cable; the perforating gun is accurately positioned using logging data and wellhead marks; the explosives are detonated through the ground control system to fire the perforating bullets to form blastholes in the casing and formation.

[0064] After connecting the above systems, low-viscosity slick water (low-viscosity water-based fracturing fluid) is pumped to push the bridge plug to the target depth. After the plugging ball is seated, the equipment and pipeline are pressure tested and circulated to ensure that there is no residual air in the pipeline and fracturing pump truck. Then, the wellhead heater is turned on at a heating temperature of 80°C and the CO 2 The booster pump truck displaces CO at a rate of 4m³ / min. 2 CO in tank trucks 2 The fluid is pressurized and transported to the wellhead through the second low-pressure pipeline, the second fracturing pump truck and the second high-pressure manifold. Continuous pumping of supercritical CO 2 The total amount reaches 100m³, which is about 1.2 times the wellbore volume, and is used to supplement the bottom layer energy. The specific construction process is shown in Table 1.

[0065] Step 3: Alternately pump high-pressure supercritical CO 2 and low pressure CO 2 Foam fracturing fluid.

[0066] (1) Through CO 2 Booster pump trucks convert CO 2 CO in tank trucks 2 The fluid is pressurized and transported to the wellhead through the second low-pressure pipeline, the second fracturing pump truck and the second high-pressure manifold. It is pumped at a high displacement of 10m³ / min for 3 minutes to inject supercritical CO 2 The total volume reaches 30m³;

[0067] (2) Add water-based fracturing fluid at 1.5 m 3The base fluid with a displacement of / min is injected into the wellhead. The composition of the water-based fracturing fluid is as follows: drag reducer (WF924) 4‰, foaming agent 4‰, ammonium persulfate capsule breaker 1‰, acidic crosslinking agent 5‰ (i.e., the crosslinking ratio is 100:0.5), and the balance is water; meanwhile, CO 2 The instantaneous high-pressure pumping equipment injects CO 3 into the wellhead at a displacement of 1.5 m 2 / min to form a small-displacement CO 2 foam fracturing fluid, and continuously pumps for 10 min. The total amount of the pumped CO 2 foam fracturing fluid reaches 30 m³.

[0068] (3) Repeat steps (1) and (2) twice to complete the pre-charging energy storage stage. The technological process of the entire pre-charging energy storage stage is as shown in steps ①-④ in Figure 2 the figure.

[0069] Step Four: The water-based fracturing fluid carries sand to support the fracture network.

[0070] After completing the CO 2 pre-charging energy storage, turn off the CO 2 booster pump. Increase the displacement to 10 m 3 / min through the first fracturing pump truck group in the water-based fracturing fluid pumping unit. At this time, adjust the proportion of the drag reducer to 6‰, and pump 93.3 m 3 of the water-based fracturing fluid. Then, under the condition of unchanged construction displacement, perform the following steps:

[0071] a. Adjust the proportion of the drag reducer to 1‰, and sequentially add 70-140 mesh pulverized sand at sand ratios of 2%, 3%, and 4%;

[0072] b. Increase the proportion of the drag reducer to 2‰, and add 70-140 mesh pulverized sand at a sand ratio of 5%;

[0073] c. Keep the proportion of the drag reducer at 2‰, and sequentially add 40-70 mesh fine sand at sand ratios of 6%, 7%, 8%, and 9%;

[0074] d. Increase the proportion of the drag reducer to 3‰, and add 20-40 mesh coarse sand at a sand ratio of 10%; then, keep the 20-40 mesh coarse sand unchanged, and increase the proportion of the drag reducer by a gradient of 1‰, and the sand ratio increases correspondingly by a ratio of 1% until the final proportion of the drag reducer is 7‰ and the sand ratio is 14%.

[0075] Expand the main fracture by gradually increasing the viscosity of the water-based fracturing fluid, carry 70-140 mesh pulverized sand and 40-70 mesh fine sand to support the micro-fracture network, carry 40-70 mesh quartz sand and 20-40 mesh quartz sand to support the main fracture, and complete the main fracturing construction. The technological process of the entire main fracturing construction stage is as shown in steps ⑤-⑥ in Figure 2 the figure.

[0076] Step 5: After the injection of the proppant-carrying fluid is completed, to ensure that there is no residual proppant in the wellbore, high-viscosity slickwater is injected first, and then low-viscosity slickwater is injected. The total volume of the displacement fluid injected is approximately one wellbore.

[0077] Among them, the main formula of the water-based fracturing fluid is as follows: ① Low-viscosity slickwater formula: 0.1% - 0.2% drag reducer + 0.05% - 0.1% ammonium persulfate capsule breaker + 0.2 - 0.6% acidic crosslinking agent + the balance of water; ② Medium-viscosity fracturing fluid formula: 0.2% - 0.6% drag reducer + 0.08% - 0.13% ammonium persulfate capsule breaker + 0.2 - 0.6% acidic crosslinking agent + the balance of water; ③ High-viscosity fracturing fluid formula: 0.6% - 1% drag reducer + 0.10% - 0.2% ammonium persulfate capsule breaker + 0.2 - 0.6% acidic crosslinking agent + the balance of water.

[0078] Table 1 Fracturing full-process operation table.

[0079]

[0080] Table 1 is the fracturing full-process operation table. Among them, Step 1 is to pump and inject the energy storage preflush fluid; Steps 2 - 5 are cyclic injection; Steps 6 - 21 are the main fracturing construction stage.

[0081] The mid-reservoir depth of Well H026 is 3040 meters, the total sand volume injected into the well is 1620 m 3 , and the total fluid volume injected into the well is 22112.7 m 3 , the instantaneous high-pressure preflush CO 2 The pumping volume is 2800 - 3500 t, and the CO 2 The instantaneous high-pressure energy storage fracturing improves the injection capacity of the water-based fracturing fluid. The difficulty of adding sand in the main construction stage is reduced compared with the adjacent well, and the construction process is relatively smooth. The average single-stage fluid volume is 762.5 m³, and the single-stage sand volume is 55.9 m 3 . The annual cumulative oil production is 8816.7 t, the annual average oil pressure is 5.568 MPa. As of January 2025, the daily oil production is 23.2 t, and the oil pressure is 4.9 MPa. Compared with the adjacent well H025, the production has increased by about 12.9%, and at the same time, the oil pressure has increased significantly.

[0082] Comparative Example 1

[0083] The mid-reservoir depth of Well H025 is 3040 meters, and the construction scale is the same as that of the instantaneous high-pressure CO 2Similar to the pre - fracturing test well H026, the reservoir quality, natural energy, sensitivity, fluid properties and engineering quality of the target formation of this well are similar to those of H026. Affected by the formation development status, the formation fracture pressure along the perforation holes is uneven. There are multiple times when the fluid pressure in the perforation holes is greater than the formation fracture pressure to form multiple branched fractures. When the net pressure in the hydraulic jet perforation holes is greater than the formation fracture pressure, the formation is fractured to generate fractures. Therefore, a sand - filling process combined with an oil - casing co - injection process is adopted to enable the fluid in the annulus to undergo energy conversion and enter the branched fractures and continue to extend, thus forming a more complex volume - type fracture network. This section is the 20th section of the construction of Well H025, with two clusters of separate perforations, and the steps are as follows:

[0084] (1)Preparation before construction. Complete the placement, connection and preparation work of fracturing equipment, high - and low - pressure manifolds, fracturing wellheads and related gates. The fracturing fluid uses a variable - viscosity fracturing fluid that does not require mixing. It is required to add 4% KCl or other anti - swelling fluids with qualified anti - swelling performance to the fracturing fluid formula. Fracturing fluid formula: ① Low - viscosity slickwater formula: 0.10% - 0.2% emulsion drag reducer + 0.05% - 0.1% breaker. ② Medium - viscosity fracturing fluid formula: 0.2% - 0.6% emulsion drag reducer + 0.08% - 0.13% breaker. ③ High - viscosity fracturing fluid formula: 0.6% - 1% emulsion drag reducer + 0.10% - 0.2% breaker. The proppant is selected as 40 - 70 mesh quartz sand with a bearing pressure grade not less than 28 MPa.

[0085] (2)Formation fracture and initial fracture formation. Use 20 - 40 mesh quartz sand for perforation. After completing the sand filling at a low displacement, inject the pre - flush fluid into the formation through a high - pressure pump truck group. The pump - injection program for the example section is shown in Table 2. During the annulus reservoir reconstruction construction, the displacement is controlled at 4.0 - 7.0 m³ / min. Using a relatively large displacement and pressure, fracture the formation rock to form initial fractures; the coiled - tubing construction displacement is controlled at 0.7 - 0.9 m³ / min to ensure that the pre - flush fluid can be accurately injected into the target formation. During the injection process, closely monitor parameters such as wellhead pressure and displacement, and adjust the construction parameters in a timely manner according to the formation response.

[0086] (3)Carrying fluid injection. After the formation forms fractures of a certain scale, start injecting the carrying fluid. The carrying fluid is prepared according to the pre - designed medium - viscosity fracturing fluid formula, and the proppant is evenly suspended in it. Inject it into the fractures through a high - pressure pump group at a stable displacement. During the injection process, monitor the sand ratio change in real - time to ensure that the proppant can be smoothly carried to the deep part of the fractures and evenly distributed.

[0087] (4)Displacement fluid injection. After the proppant-carrying fluid injection is completed, the displacement fluid is injected. The function of the displacement fluid is to push all the proppant-carrying fluid in the wellbore and pipeline into the fracture, ensuring that all the proppants enter the fracture and are evenly distributed. The injection volume of the displacement fluid is accurately calculated according to the volume of the wellbore and pipeline. During the injection process, closely monitor the pressure change to prevent the fracturing effect from being affected by excessive or insufficient displacement. After the first cluster of construction is completed, perforate at the perforation point of the second cluster, and repeat the above steps according to the construction process table.

[0088] (5)Well shut-in and flowback. After the displacement fluid injection is completed, close the wellhead to allow the fracture to gradually close under the action of the closing stress. After the fracturing fluid is broken down underground for a certain period of time, open the wellhead for flowback. During the flowback process, closely monitor parameters such as the flow rate, pressure, and fluid properties of the flowback fluid, analyze the flowback situation in a timely manner, and evaluate the fracturing effect. After the entire fracturing construction process is completed, clean and maintain the equipment, and clean the site to prepare for subsequent production operations.

[0089] The average single-stage fluid volume of Well H025 is 817.3 m 3 , and the single-stage sand volume is 50 m 3 . The annual cumulative oil production is 7,810.9 t, the annual average oil pressure is 0.686 MPa, and as of January 2025, the daily oil production is 18.7 t and the oil pressure is 0.5 MPa.

[0090] Table 2 Pumping program for the 20th stage (sand addition scale 50.0 m 3 ).

[0091] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for CO2 instantaneous high-pressure energy storage fracturing in a tight conglomerate reservoir, characterized in that: The CO2 instantaneous high-pressure energy storage fracturing system used in tight conglomerate reservoirs includes a water-based fracturing fluid pumping unit and a supercritical CO2 instantaneous high-pressure pumping unit; The water-based fracturing fluid pumping unit includes a first fracturing pump truck group, a first high-pressure manifold, a first low-pressure pipeline, a sand mixing truck, a sand tank truck, and a liquid tank truck; wherein the sand mixing truck, the first low-pressure pipeline, the first fracturing pump truck group and the first high-pressure manifold are connected in sequence; the sand tank truck and the liquid tank truck are connected to the sand mixing truck in parallel; The supercritical CO2 instantaneous high-pressure pumping unit comprises a second fracturing pump truck group, a second high-pressure manifold, a second low-pressure pipeline, a CO2 tanker and a CO2 booster pump truck; wherein the CO2 tanker, the CO2 booster pump truck, the second low-pressure pipeline, the second fracturing pump truck group and the second high-pressure manifold are connected in sequence; The first high-pressure manifold is connected to the wellhead via a first high-pressure pipeline, and the second high-pressure manifold is connected to the wellhead via a second high-pressure pipeline; The first instrument vehicle is used to monitor the water-based fracturing fluid pumping unit; the second instrument vehicle is used to monitor the supercritical CO2 instantaneous high-pressure pumping unit; The CO2 instantaneous high-pressure energy storage fracturing method for tight conglomerate reservoirs comprises the following steps: (1) Pumping the energy storage pre-fluid: using the CO2 booster pump truck to pressurize the CO2 fluid in the CO2 tank truck, and transporting the supercritical CO2 fluid to the wellhead via the second low-pressure pipeline, the second fracturing pump truck group, the second high-pressure manifold and the second high-pressure pipeline in sequence; (2) Pumping the pre-fluid: pressurizing the CO2 fluid in the CO2 tank truck by the CO2 booster pump truck, and transporting the supercritical CO2 fluid to the wellhead in sequence through the second low-pressure pipeline, the second fracturing pump truck group, the second high-pressure manifold and the second high-pressure pipeline by instantaneous high pressure; (3) Pumping CO2 foam fracturing fluid: The water-based fracturing fluid in the sand mixing truck is used as the base fluid and is sequentially transported to the wellhead through the first low-pressure pipeline, the first fracturing pump truck group, the first high-pressure manifold and the first high-pressure pipeline. While the water-based fracturing fluid is injected, the CO2 fluid in the CO2 tank truck is pressurized by the CO2 booster pump truck, and the supercritical CO2 fluid is transported to the wellhead through the second low-pressure pipeline, the second fracturing pump truck group, the second high-pressure manifold and the second high-pressure pipeline to form CO2 foam fracturing fluid; The components of the water-based fracturing fluid include a drag reducer, a foaming agent, a cross-linking agent, a gel breaker and ammonium persulfate; (4) Repeat steps (2) and (3); (5) Using the water-based fracturing fluid pumping unit to carry out sand-carrying operations: using low-viscosity slick water to carry 70-140 mesh proppants to fill micro fractures, then gradually increasing the viscosity of the slick water to expand the main fractures, and gradually carrying 40-70 mesh and 20-40 mesh proppants to support the main fractures to complete the main fracturing construction.

2. The method according to claim 1, characterized in that In step (1), the amount of supercritical CO2 fluid injected is 1.2 times the wellbore volume.

3. The method according to claim 1, characterized in that The construction displacement in step (1) is 2-4 m³ / min; the construction displacement of the instantaneous high pressure in step (2) is 8-20 m³ / min.

4. The method according to claim 1, characterized in that The total pumping rate of the water-based fracturing fluid and the supercritical CO2 fluid in step (3) is 2-3 m³ / min; the pumping rate ratio of the water-based fracturing fluid and the supercritical carbon dioxide fluid is 1:1; and the construction rate in step (5) is 8-20 m³ / min.

5. The method according to claim 1, characterized in that The total amount of supercritical CO2 fluid pumped in is 20% of the total injected liquid volume.

6. The method according to claim 1, characterized in that Also included is a heating device for wellhead heating.

7. The method according to claim 1, characterized in that The water-based fracturing fluid pumping unit also includes a first blower for cooling the first fracturing pumping vehicle group; the supercritical CO2 instantaneous high-pressure pumping unit also includes a second blower for cooling the second fracturing pumping vehicle group.

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