Compact conglomerate oil reservoir CO2 instantaneous high-pressure energy storage fracturing system and fracturing method

Abstract

The invention discloses a compact conglomerate oil reservoir CO2 instantaneous high-pressure energy storage fracturing system and method, and relates to the technical field of oil and gas exploitation. The system comprises a water-based fracturing fluid pumping unit and a supercritical CO2 instantaneous high-pressure pumping unit. By means of the method, the problems that the'thin-hole and thin-throat 'type compact conglomerate oil reservoir is large in oil and gas utilization difficulty and small in sweep range can be effectively solved, the invasion capacity of CO2 to a thin-hole throat is remarkably enhanced through instantaneous high-pressure injection of supercritical CO2 and low-pressure pumping of CO2 foam fracturing fluid, formation of a complex micro-crack net is promoted through phase state change, the sweep volume of CO2 is increased, and the fracturing efficiency is improved. And more efficient reservoir transformation is achieved, and powerful support is provided for long-term benefit development of the compact conglomerate oil reservoir.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and in particular to a CO2 instantaneous high-pressure energy storage fracturing system and a fracturing method for a dense conglomerate reservoir. Background Art

[0002] Tight conglomerate reservoirs refer to reservoirs with conglomerate as the reservoir layer, which are characterized by strong heterogeneity, low porosity and low permeability, and complex pore structure. These reservoirs are usually formed in the sedimentary environment of fan delta and braided river delta, and the lithology is mainly conglomerate, sandy conglomerate and gravelly unequal grained sandstone, and the composition is mostly tuff, granite, rhyolite, etc. In contrast, ordinary reservoirs are usually formed in sandstone or carbonate rock, with relatively uniform geological structure, high porosity and permeability.

[0003] The main differences between gravel oil fields and ordinary oil fields are the reservoir type and development difficulty. The development of tight gravel reservoirs is more difficult because of their low porosity. Crude oil is hidden in rock pores that are invisible to the naked eye. Fracturing is required to increase reservoir production capacity. The development of ordinary reservoirs is relatively easy because of their high porosity and permeability. Depletion development or conventional fracturing can meet the needs. Due to the difficulty of developing tight gravel reservoirs, the investment and technical requirements are usually high, and the development cost is also relatively high.

[0004] Although tight conglomerate reservoirs have high development costs, they have great production potential, and the potential for increased production after effective fracturing and transformation is large, while the production of conventional reservoirs is relatively stable, but the growth potential is limited.

[0005] Due to the poor reservoir properties, strong heterogeneity, complex reservoir distribution and high gravel content of the Mahu tight conglomerate reservoir, the conventional hydraulic fracturing method has an unsatisfactory transformation effect, and is prone to problems such as high initial production capacity and rapid decline in the middle and late stages. Appropriate transformation methods are urgently needed to achieve the efficient development of tight conglomerate reservoirs. At present, the Mahu Oilfield has carried out large-scale CO2 pre-fracturing horizontal well experiments, and has achieved good results in some Class I and Class II conglomerate reservoirs. The quarterly cumulative oil production of the well group using carbon dioxide pre-fracturing has increased by nearly 23.5% compared with the conventional fracturing well group in the same block. However, in some Class II and Class III conglomerate reservoirs with poor reservoir properties, the cumulative oil production after CO2 pre-storage fracturing is low, and the effect of improving the recovery factor is not obvious.

[0006] Since the pores between gravel fragments 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 conventional CO2 pre-fracturing, the scope of CO2 invading fine pores and throats is limited, and it can only play a local energy storage role, and cannot be combined with subsequent main fracturing operations to achieve effective reservoir transformation. In addition, in reservoirs with relatively developed fractures, CO2 may easily flow along the interface of gravel particles, resulting in a waste of CO2 and engineering resources. The above problems have led to the lack of effective development methods for this type of reservoir. The conventional CO2 pre-fracturing method has a poor effect on improving the production compared with adjacent wells after transformation. It is urgent to propose a reservoir transformation method with more practical application effects for tight conglomerate reservoirs with the characteristics of "fine pores and fine throats" and "low saturation pressure difference", so as 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 CO2 instantaneous high-pressure energy storage fracturing system and a fracturing method for a dense conglomerate reservoir, so as to solve the problems existing in the above-mentioned prior art.

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

[0009] The present invention provides a CO2 instantaneous high-pressure energy storage fracturing system for a dense conglomerate reservoir, comprising a water-based fracturing fluid pumping unit and a supercritical CO2 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 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;

[0011] 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;

[0012] The first high-pressure manifold is connected to the wellhead via the first high-pressure pipeline, and the second high-pressure manifold is connected to the wellhead via the 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.

[0013] Among them, sand tank trucks are used to transport proppants (materials used to fill reservoir cracks during the fracturing process); liquid tank trucks are used to transport liquids and prepare fracturing fluids.

[0014] As a further preferred embodiment of the present invention, the tight conglomerate reservoir CO2 instantaneous high-pressure energy storage fracturing system also includes a heating device for wellhead heating.

[0015] Specifically, in the fracturing system of the present invention, the first instrument vehicle and the second instrument vehicle are the command and control centers. The first instrument vehicle is used to remotely control the first fracturing pump truck and the sand mixing truck, and record the construction curve at the same time; the second instrument vehicle is used to remotely control the second fracturing pump truck group, and record the construction curve at the same time.

[0016] The instrument vehicle is mainly used for remote control and receiving digital signals to form construction curve images.

[0017] As a further preferred embodiment of the present invention, 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.

[0018] The present invention also provides a method for fracturing a dense conglomerate reservoir using CO2 instantaneous high-pressure energy storage, which uses the above-mentioned dense conglomerate reservoir CO2 instantaneous high-pressure energy storage fracturing system and comprises the following steps:

[0019] (1) Pumping energy storage pre-fluid: using the supercritical CO2 instantaneous high-pressure pumping unit to pump supercritical CO2 as energy storage pre-fluid;

[0020] (2) Pumping the pre-fluid: using the supercritical CO2 instantaneous high-pressure pumping unit to pump the supercritical CO2 fluid as the pre-fluid;

[0021] (3) Pumping CO2 foam fracturing fluid: using the supercritical CO2 instantaneous high-pressure pumping unit and the water-based fracturing fluid pumping unit to alternately pump CO2 foam fracturing fluid;

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

[0023] (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, 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.

[0024] Furthermore, the proppant is quartz sand.

[0025] Furthermore, the method comprises the following steps:

[0026] (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;

[0027] (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;

[0028] (3) Pumping CO2 foam fracturing fluid:

[0029] 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;

[0030] 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;

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

[0032] (5) Using the water-based fracturing fluid pumping unit to carry out sand-carrying operations: using slick water to carry 70-140 mesh proppant 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 proppant to support the main fractures to complete the main fracturing construction.

[0033] Furthermore, in step (1), the amount of supercritical CO2 fluid injected is 1.2 times the wellbore volume.

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

[0035] Furthermore, 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.

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

[0037] Furthermore, the total amount of supercritical carbon dioxide fluid pumped in is 20% of the total amount of injected liquid.

[0038] Based on comprehensive consideration of the transformation effect and construction cost, steps (2) and (3) shall be repeated no more than three times.

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

[0040] 1. The present invention can effectively solve the problem of difficulty in producing oil and gas in the "fine pores and fine throats" of dense conglomerate reservoirs. Through the instantaneous high-pressure injection of supercritical CO2, while reducing the lower limit of pore throat production in conglomerate reservoirs, the radius of fine conglomerate pore throats is effectively increased, and the dynamic critical production of dense conglomerate reservoirs is achieved through "one reduction and one increase", which improves the recovery effect of CO2 pre-energy storage fracturing within its range of action.

[0041] 2. The present invention can effectively solve the problem of small sweep range of conventional CO2 pre-storage in dense conglomerate reservoirs. By injecting supercritical CO2 at high pressure, micro-fractures in the reservoir can be effectively expanded and extended. By injecting CO2 foam fracturing fluid at low pressure, the foam can be used to enter the main fracture and slowly penetrate into the gaps along the way by utilizing its high viscosity and low filtration loss. By utilizing the difference in the ability of the two fluids to invade the reservoir, the gas can be effectively blocked while increasing the formation pressure, the occurrence of gas fingering can be suppressed, the occurrence time of CO2 gas channeling can be extended, the degree of gas channeling can be reduced, and the sweep efficiency of CO2 pre-storage can be improved.

[0042] 3. The present invention can promote the formation and expansion of complex fracture networks, improve crude oil properties, and increase crude oil recovery. Gravel reservoirs have strong heterogeneity. Instantaneous high-pressure CO2 injection can easily form "around gravel" and "through gravel" advantageous channels, and then the pressure reduction and injection of CO2 foam fracturing fluid can effectively block the advantageous channels. A complex fracture network can be formed by changing the displacement and fluid properties. As the pressure increases, the miscibility of CO2 and crude oil will increase, improving the solubilization effect on crude oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 This is a field layout diagram of the CO2 instantaneous high-pressure energy storage fracturing system for tight conglomerate reservoirs of the present invention;

[0045] Figure 2The present invention is a process flow chart of the CO2 instantaneous high-pressure energy storage fracturing method for tight conglomerate reservoirs. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0049] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0050] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0051] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in the art and are not the focus of the present invention.

[0052] Example 1

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

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

[0055] Figure 1 This is a field layout diagram of the CO2 instantaneous high-pressure energy storage fracturing system for tight conglomerate reservoirs of the present invention.

[0056] The system used for CO2 instantaneous high-pressure energy storage fracturing includes two relatively independent units arranged on site: a water-based fracturing fluid pumping unit and a supercritical CO2 instantaneous high-pressure pumping unit.

[0057] 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 first blower, 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 first blower is connected to the first fracturing pump truck group to cool the first fracturing pump truck group;

[0058] The supercritical CO2 instantaneous high-pressure pumping unit includes a second fracturing pumping vehicle group, a second high-pressure manifold, a second low-pressure pipeline, a second blower, a CO2 tanker and a CO2 booster pumping vehicle; wherein the CO2 tanker, the CO2 booster pumping vehicle, the second low-pressure pipeline, the second fracturing pumping vehicle group and the second high-pressure manifold are connected in sequence; the second blower is connected to the second fracturing pumping vehicle group to cool down the second fracturing pumping vehicle group;

[0059] The first high-pressure manifold is connected to the wellhead via the first high-pressure pipeline, and the second high-pressure manifold is connected to the wellhead via the second high-pressure pipeline; the water-based fracturing fluid pumping unit and the supercritical CO2 instantaneous high-pressure pumping unit are connected to the first instrument vehicle and the second instrument vehicle respectively.

[0060] At the same time, a heater is provided for wellhead heating.

[0061] Among them, the two groups of fracturing pump trucks include multiple fracturing trucks. The model parameters of each fracturing truck are as follows: YLC105-1490 model, output power is 2500HP, maximum construction pressure is 103MPa, and the maximum single vehicle displacement is 2.46m 3 / min. The sand mixer adopts HSC20 model, the maximum clean water displacement of the sand pump is 20m³ / min, the maximum working pressure is 0.7MPa, the maximum sand conveyor conveying capacity is 12000kg / min, the mixing tank volume is 2.0m³, the engine model is Detroit S60 diesel engine, and the engine power is 650hp. The CO2 booster pump truck adopts TZQ08D model, the maximum working pressure is 2.5MPa, the maximum displacement is 12m³ / min, and the power is 180hp. The instrument truck adopts 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, sand ratio, etc., 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, acidic 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 a sand mixer through a 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 pipelines are pressure tested and circulated to ensure that there is no residual air in the pipelines and fracturing pump trucks. The wellhead heater is turned on at a heating temperature of 80°C. The CO2 fluid in the CO2 tank truck is pressurized at a displacement of 4m³ / min through the CO2 booster pump truck and transported to the wellhead through the second low-pressure pipeline, the second fracturing pump truck and the second high-pressure manifold. The total amount of supercritical CO2 continuously pumped reaches 100m³, which is about 1.2 times the wellbore volume, and is used to supplement the bottom energy. The specific construction process is shown in Table 1.

[0065] Step 3: Alternately pump high-pressure supercritical CO2 and low-pressure CO2 foam fracturing fluid.

[0066] (1) The CO2 fluid in the CO2 tank truck is pressurized by the CO2 booster pump truck, and transported to the wellhead through the second low-pressure pipeline, the second fracturing pump truck group and the second high-pressure manifold. The CO2 fluid is pumped at a high displacement of 10 m³ / min for 3 minutes, and the total amount of supercritical CO2 pumped reaches 30 m³;

[0067] (2) Add water-based fracturing fluid at 1.5 m 3 / min displacement as the base fluid injected into the wellhead, where the water-based fracturing fluid composition is: drag reducer (WF924) 4‰, foaming agent 4‰, ammonium persulfate capsule breaker 1‰, acid cross-linking agent 5‰ (i.e., the cross-linking ratio is 100:0.5), and the balance is water; at the same time, CO2 instantaneous high-pressure pumping equipment is at 1.5m 3 / min displacement of CO2 into the wellhead to form a small displacement of CO2 foam fracturing fluid, which is pumped continuously for 10 minutes until the total amount of pumped CO2 foam fracturing fluid reaches 30m³.

[0068] (3) Repeat steps (1) and (2) twice to complete the pre-energy storage stage. The entire pre-energy storage stage process flow is as follows: Figure 2 As shown in steps ①-④.

[0069] Step 4: Water-based fracturing fluid carries sand to support the fracture network.

[0070] After the CO2 pre-storage is completed, the CO2 booster pump is turned off. The displacement is increased to 10m3 by the first fracturing pump unit in the water-based fracturing fluid pumping unit. 3 / min, at this time, the drag reducer ratio was adjusted to 6‰, and 93.3m of water-based fracturing fluid was pumped in. 3 . Then, with the construction displacement unchanged, proceed as follows:

[0071] a. The drag reducer ratio is adjusted to 1‰, and 70-140 mesh silt sand is added in 2%, 3% and 4% sand ratios in sequence;

[0072] b. The drag reducer ratio is increased to 2‰, and 70-140 mesh silt sand is added at a 5% sand ratio;

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

[0074] d. The drag reducer ratio is increased to 3‰, and 20-40 mesh coarse sand is added at a sand ratio of 10%; after that, the 20-40 mesh coarse sand is kept unchanged, the drag reducer ratio is increased by a gradient of 1‰, and the sand ratio is increased by 1% accordingly, until the final drag reducer ratio is 7‰ and the sand ratio is 14%.

[0075] The main fracture is expanded by gradually increasing the viscosity of the water-based fracturing fluid, and the micro-fracture network is supported by 70-140 mesh silt sand and 40-70 mesh fine sand, and the main fracture is supported by 40-70 mesh quartz sand and 20-40 mesh quartz sand to complete the main fracturing construction. The process flow of the entire main fracturing construction stage is as follows: Figure 2 As shown in steps ⑤-⑥.

[0076] Step 5: After the sand-carrying fluid is injected, in order to ensure that there is no proppant residue in the wellbore, high-viscosity slippery water is injected first, and then low-viscosity slippery water is injected. The total amount of displacement fluid injected is about one wellbore.

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

[0078] Table 1: The whole process of fracturing.

[0079]

[0080] Table 1 is a process table of the entire fracturing process, wherein step 1 is pumping the energy storage pre-fluid; steps 2 to 5 are circulating injection; and steps 6 to 21 are the main fracturing construction stages.

[0081] The central depth of the H026 well reservoir is 3040 meters, and the total amount of sand entering the well is 1620m 3 , total fluid volume entering the well is 22112.7m 3 The instantaneous high-pressure front CO2 pump injection volume is 2800~3500t. The CO2 instantaneous high-pressure energy storage fracturing improves the injection capacity of water-based fracturing fluid. The difficulty of adding sand in the main construction stage is lower than that of adjacent wells. The construction process is relatively smooth. The average single-stage liquid volume is 762.5m³ and the single-stage sand volume is 55.9m 3 The annual cumulative oil production is 8816.7t, the annual average oil pressure is 5.568MPa, and the daily oil production is 23.2t as of January 2025, with an oil pressure of 4.9MPa. Compared with the Linjing H025 well, the production has increased by about 12.9%, and the oil pressure has increased significantly.

[0082] Comparative Example 1

[0083] The middle depth of the H025 reservoir is 3040 meters. The construction scale is the same as that of the instantaneous high-pressure CO2 pre-fracturing experimental well H026. The reservoir quality, natural energy, sensitivity, fluid properties and engineering quality of the target layer of this well are similar to those of the H026 well. Affected by the formation development conditions, the formation fracture pressure along the perforation holes is uneven, and the fluid pressure in the perforation holes is repeatedly greater than the formation fracture pressure to form multiple branch fractures. When the net pressure in the hydraulic jet hole is greater than the formation fracture pressure, the formation is compressed to produce fractures. Therefore, the sand filling process is combined with the oil-casing co-injection process to convert the energy of the fluid in the annulus into the branch fractures and continue to extend, thereby forming a more complex volume fracture network. This section is the 20th section of the H025 well construction, and the two clusters are perforated separately. The steps are as follows:

[0084] (1) Preparation before construction. Complete the placement, connection and preparation of fracturing equipment, high and low pressure manifolds, fracturing wellheads and related gates. The fracturing fluid uses a variable viscosity fracturing fluid without mixing. It is required to add 4% KCl or other anti-swelling fluids with anti-swelling performance that meets the requirements in the fracturing fluid formula. Fracturing fluid formula: ① Low viscosity slippery water formula: 0.10%~0.2% emulsion drag reducer + 0.05%~0.1% gel breaker. ② Medium viscosity fracturing fluid formula: 0.2%~0.6% emulsion drag reducer + 0.08%~0.13% gel breaker. ③ High viscosity fracturing fluid formula: 0.6%~1% emulsion drag reducer + 0.10%~0.2% gel breaker. The proppant uses 40-70 mesh quartz sand with a pressure rating of not less than 28MPa.

[0085] (2) Formation rupture and initial crack formation. Perforation was performed with 20-40 mesh quartz sand. After sand filling was completed at a low displacement, the pre-fluid was injected into the formation through a high-pressure pump truck. The pumping procedure for the example section is shown in Table 2. During the annular reservoir reconstruction construction, the displacement was controlled at 4.0-7.0 m³ / min. A larger displacement and pressure were used to rupture the formation rock and form initial cracks. The displacement of the continuous tubing construction was controlled at 0.7-0.9 m³ / min to ensure that the pre-fluid could be accurately injected into the target layer. During the injection process, the wellhead pressure, displacement and other parameters were closely monitored, and the construction parameters were adjusted in time according to the response of the formation.

[0086] (3) Sand-carrying fluid injection. After a certain scale of fractures are formed in the formation, the sand-carrying fluid is injected. The sand-carrying fluid is prepared according to the pre-designed medium-viscosity fracturing fluid formula, and the proppant is evenly suspended in it. It is then injected into the fractures at a stable displacement through a high-pressure pump group. During the injection process, the sand ratio change is monitored in real time to ensure that the proppant can be smoothly carried to the depth of the fracture and evenly distributed.

[0087] (4) Displacement fluid injection. After the sand-carrying fluid is injected, the displacement fluid is injected. The function of the displacement fluid is to push all the sand-carrying fluid in the wellbore and manifold into the fractures, ensuring that all the proppant enters the fractures and is evenly distributed. The injection volume of the displacement fluid is accurately calculated based on the volume of the wellbore and manifold. During the injection process, pay close attention to pressure changes to prevent the fracturing effect from being affected by excessive or insufficient displacement. After the first cluster 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 closure and flowback. After the displacement fluid is injected, the wellhead is closed to allow the fractures to gradually close under the action of the closing stress. After the fracturing fluid has broken down in the well for a certain period of time, the wellhead is opened for flowback. During the flowback process, the flow rate, pressure, liquid properties and other parameters of the flowback fluid are closely monitored, the flowback situation is analyzed in a timely manner, and the fracturing effect is evaluated. After the entire fracturing construction process is completed, the equipment is cleaned and maintained, and the site is cleaned to prepare for subsequent production operations.

[0089] The average single-stage liquid volume of H025 well is 817.3m 3 , single stage sand volume 50m 3 The annual cumulative oil production is 7810.9t, the annual average oil pressure is 0.686MPa, and as of January 2025, the daily oil production is 18.7t, and the oil pressure is 0.5MPa.

[0090] Table 2 Pumping procedure for stage 20 (sand injection scale 50.0m 3 ).

[0091] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A CO2 instantaneous high-pressure energy storage fracturing system for tight conglomerate reservoirs, characterized in that: It 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.

2. The CO2 instantaneous high-pressure energy storage fracturing system for tight conglomerate reservoirs according to claim 1 is characterized in that: Also included is a heating device for wellhead heating.

3. The CO2 instantaneous high-pressure energy storage fracturing system for tight conglomerate reservoirs according to claim 1 is 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.

4. 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 for tight conglomerate reservoirs according to claim 1 is characterized by comprising the following steps: (1) Pumping energy storage pre-fluid: using the supercritical CO2 instantaneous high-pressure pumping unit to pump supercritical CO2 as energy storage pre-fluid; (2) Pumping the pre-fluid: using the supercritical CO2 instantaneous high-pressure pumping unit to pump the supercritical CO2 fluid as the pre-fluid; (3) Pumping CO2 foam fracturing fluid: using the supercritical CO2 instantaneous high-pressure pumping unit and the water-based fracturing fluid pumping unit to alternately pump CO2 foam fracturing fluid; (4) Repeat steps (2) and (3); (5) Using the water-based fracturing fluid pumping unit to carry out sand-carrying operations: using slick water to carry 70-140 mesh proppant 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 proppant to support the main fractures to complete the main fracturing construction.

5. The method according to claim 4, characterized in that The following steps are involved: (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.

6. The method according to claim 5, characterized in that In step (1), the amount of supercritical CO2 fluid injected is 1.2 times the wellbore volume.

7. The method according to claim 5, 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.

8. The method according to claim 5, 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.

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

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