A quasi-horizontal well fracturing technology for shale oil directional wells

Abstract

This invention discloses a quasi-horizontal well fracturing process for directional shale oil wells. It includes the following steps: S1: Based on the geological and engineering data of the fault-block shale oil reservoir, combined with the fracture parameters of previous fracturing wells in the block, determine the three-dimensional stratification and clustering of the directional well and the main parameters of the fracturing process; S2: Inject acid into the reservoir at a high flow rate for acid pretreatment; S3: Switch to low-viscosity fracturing fluid injection and rapidly increase the flow rate; S4: Inversely design with different construction pressure windows as the core, adopt a three-stage pressure control, flow rate adjustment, and pressure stabilization sand addition mode to complete single-layer fracturing and sand addition; S5: Referring to the above steps, complete the fracturing and sand addition of the remaining layers in the single well. The advantages are: significantly increasing the fracturing fracture length of directional shale oil wells, improving the fracture network support effect and fracture network-controlled reserves, high test production after fracturing, long stable production time, and achieving high-efficiency development of directional wells in structurally complex areas.

Description

Technical Field

[0001] This invention relates to an unconventional oil and gas production enhancement technology, specifically a shale oil directional well fracturing process that mimics a horizontal well, belonging to the field of petroleum extraction technology. Background Technology

[0002] Currently, the theory and technology for developing continental shale oil in China are both in their initial stages, and there is no mature development model yet. The eastern and western flanks of the Qintong Depression in the Subei Basin are structurally complex areas with well-developed faults, large stratigraphic dips, and fault blocks that are generally less than 2 km long, 1 km wide, and less than 2 km² in area. 2 The presence of small faults and natural fractures makes horizontal wells exceeding 1000m unsuitable. Well placement along the fault strike, parallel to the direction of maximum horizontal principal stress, makes it difficult to guarantee the effectiveness of the fracture network. Well placement across faults results in low sweet spots and requires fracturing sections to avoid fault locations, impacting economic efficiency. Horizontal well development involves long drilling and completion cycles and high investment, with fracture heights around 30m, resulting in low vertical resource utilization and unsatisfactory development benefits. Given the characteristics of fault-block shale reservoirs—steep formation dips, narrow fault blocks, well-developed laminae and fractures, small stress difference coefficients, and high brittleness indices—the efficient development of continental fault-block shale reservoirs faces numerous challenges. There is currently no mature development method for this type of reservoir; therefore, developing a quasi-horizontal well fracturing technology for directional shale oil is of great significance. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a shale oil directional well quasi-horizontal well fracturing process that can effectively increase the fracture length, improve the fracture mesh support effect and fracture mesh quality, and improve the shale oil production effect.

[0004] To solve the above-mentioned technical problems, the shale oil directional well pseudo-horizontal well fracturing process of the present invention includes the following steps:

[0005] S1: Based on the geological and engineering data of the fault-block shale reservoir, and combined with the fracture parameters of the previous fracturing in the block, determine the three-dimensional layering and clustering of directional wells and the main parameters of the fracturing process;

[0006] Furthermore, in this step, based on the existing reservoir properties and engineering parameters in the area, and combined with the fracture height data monitored by the fractured wells, the three-dimensional stratification and clustering parameters of the directional wells are determined;

[0007] Furthermore, in this step, the directional well preferably consists of 3-4 clusters of single-layer perforations.

[0008] S2: Acid pretreatment is performed by injecting acid into the reservoir at a large rate.

[0009] Furthermore, in this step, the amount of acid used per layer is 20-30 mg / L. 3 Pumping displacement 3-5m3 / min;

[0010] Furthermore, the acid solution in this step includes hydrochloric acid, high-temperature corrosion inhibitor, drainage aid, clay stabilizer, and iron ion stabilizer;

[0011] S3: Switch to low-viscosity fracturing fluid injection and quickly increase the flow rate;

[0012] Furthermore, in this step, the injection of low-viscosity fracturing fluid is switched, and the discharge rate is rapidly increased under the construction pressure limit to form a high fracturing pressure, which prompts multiple perforation clusters to fracture and inject fluid simultaneously.

[0013] S4: Reverse design, with different construction pressure windows as the core, adopts a three-stage control of construction pressure, adjustment of discharge volume and pressure stabilization sand addition mode to complete single-layer fracturing sand addition;

[0014] In this step, the first phase mode is as follows:

[0015] Adjust the pump flow rate to control the pressure window of 4-5 MPa;

[0016] a. Pump in low-viscosity fracturing fluid carrying small-diameter proppant to fill microfractures, while simultaneously adding a low concentration of 0.1% synergist via slug injection, with a proppant-to-fluid ratio of 2%-10%;

[0017] b. Pump in medium-viscosity fracturing fluid carrying medium-sized proppant to fill branched fractures, with a proppant-to-fluid ratio of 2%-10%;

[0018] c. During the pumping process, the automatic pressure stabilizing pumping system is activated, and the pressure fluctuation range is set. When the pressure fluctuation reaches the upper or lower limit, the step adjustment of the discharge capacity is triggered to maintain stable pressure.

[0019] d. Complete 1 / 3 of the total liquid volume;

[0020] Second-phase mode:

[0021] Adjust the pump discharge rate to reduce the construction pressure and control the pressure window to 10-14 MPa;

[0022] a. Pump in medium-viscosity fracturing fluid carrying medium-sized proppant to fill microfractures, with a proppant-to-fluid ratio of 7%-10%;

[0023] b. Pump in medium- to high-viscosity fracturing fluid carrying medium- to large-diameter proppant to fill the main fracture, with a proppant-to-fluid ratio of 2%-5%;

[0024] c. During the pumping process, the automatic pressure stabilizing pumping system is activated, and the pressure fluctuation range is set. When the pressure fluctuation reaches the upper or lower limit, the step adjustment of the discharge capacity is triggered to maintain stable pressure.

[0025] d. Complete 2 / 3 of the total liquid volume;

[0026] Third-stage model:

[0027] Adjust the pump discharge rate to reduce the construction pressure and control the pressure window to 17-20 MPa;

[0028] a. Pump in medium- to high-viscosity fracturing fluid to carry medium-sized proppant and fill the main fracture, with a proppant-to-fluid ratio of 4%-5%;

[0029] b. Pump in high-viscosity fracturing fluid and follow it with ceramic proppant to establish a high-conductivity channel at the fracture opening, with a sand-to-fluid ratio of 4%-5%;

[0030] c. During the pumping process, the automatic pressure stabilizing pumping system is activated, and the pressure fluctuation range is set. When the pressure fluctuation reaches the upper or lower limit, the step adjustment of the discharge capacity is triggered to maintain stable pressure.

[0031] d. Complete the single-layer sand volume and liquid volume.

[0032] S5: Following the steps above, complete the fracturing and sand addition for the remaining sections of the single well.

[0033] Furthermore, the proppant in step S4 is a multi-sized proppant, including 100 / 200 mesh proppant, 70 / 140 mesh proppant, 40 / 70 mesh proppant, 30 / 50 mesh or larger 20 / 40 mesh proppant.

[0034] Furthermore, the proportion of proppant for each particle size is as follows: small particle size proppant volume : medium particle size proppant volume : large particle size proppant volume = 2 : 3 : 5.

[0035] Furthermore, the low-viscosity fracturing fluid is a drag-reducing agent with a concentration of 0.08-0.12%; the medium-viscosity fracturing fluid is a drag-reducing agent with a concentration of 0.13-0.18%; the medium-to-high viscosity fracturing fluid is a drag-reducing agent with a concentration of 0.19-0.24%; and the high-viscosity fracturing fluid is a drag-reducing agent with a concentration of 0.25-0.30%.

[0036] The advantages of this invention are:

[0037] By employing multi-stage pressure reduction and stabilization, variable viscosity proppant-carrying technology for efficient sand transport, and continuous construction with fully electric equipment, a novel "quasi-horizontal well" fracturing process for shale oil directional wells has been developed. This process, which utilizes a fully automated pressure-stabilizing pump injection system, slug-type accompanying injection of functional fracturing fluid, and low-sand-ratio long-range proppant transport, effectively increases the fracture length in shale oil directional well fracturing, enhances the fracture network support effect and quality, and significantly improves the fracture-controlled reserves of shale oil directional wells. The high test yield after fracturing in the quasi-horizontal well enables high-efficiency development of directional wells in structurally complex areas, thereby improving shale oil production efficiency. Attached Figure Description

[0038] Figure 1This is a single-layer fracturing construction curve diagram of shale oil directional well A in this invention. Detailed Implementation

[0039] The fracturing process for shale oil directional wells with pseudo-horizontal wells of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. In this embodiment of the present invention, the fracturing equipment unit is preferably a fully electric pump injection system; a fully electric pump, an online lubrication system, and a fully automatic sand conveying equipment are selected, and an automatic pressure stabilizing pump injection system is put into operation to meet the requirements of large single-stage fluid volume (>12,000 cubic meters), long operation time (>14 hours), large construction displacement (>16 cubic meters / minute), and continuous fluid injection for directional well fracturing.

[0040] The fracturing process for shale oil directional wells with a pseudo-horizontal well according to the present invention includes the following steps:

[0041] S1: Based on the geological and engineering data of shale reservoirs in structurally complex areas, and combined with the fracture parameters of the block in the early stage of fracturing, simulation software was used to optimize and determine the three-dimensional layering and clustering of directional wells and the main parameters of fracturing process;

[0042] Furthermore, in this step, based on the reservoir properties and engineering parameters of the structurally complex area, and combined with the fracture height data monitored by the fractured wells, the three-dimensional stratification and clustering parameters of the directional well are determined;

[0043] Furthermore, in this step, the directional well has 3-4 perforations per layer, which is 2-4 fewer perforations per section compared to the horizontal well, thus increasing the flow rate per perforation and promoting the extension of fracture length.

[0044] Meanwhile, in this step, conventional reservoir geological modeling and fracture propagation simulation software is used to import geological and engineering data, simulate the fracture system, obtain the fracture propagation distribution corresponding to different pumping stages, and combine the fracture length data monitored by the fractured wells to optimize the main fracturing process parameters, including the construction flow rate, single-layer fluid volume, proppant dosage, etc. The specific operation of the simulation using mature professional software is known to those skilled in the art and will not be described in detail here.

[0045] S2: Acid pretreatment is performed by injecting acid into the reservoir at a large rate through the wellbore.

[0046] Furthermore, in this step, the amount of acid used per layer is 20-30 mg / L. 3 Pumping displacement 3-5m 3 / min;

[0047] Furthermore, the acid solution in this step includes hydrochloric acid, high-temperature corrosion inhibitor, drainage aid, clay stabilizer, and iron ion stabilizer;

[0048] S3: Switch to low-viscosity fracturing fluid injection and quickly increase the flow rate;

[0049] Furthermore, in this step, the discharge rate is rapidly increased under the construction pressure limit to form a high fracturing pressure. Under the high fracturing pressure, the shale reservoir is opened, which promotes the simultaneous fracturing and fluid injection of multiple perforation clusters. Compared with the tortuous and complex fractures formed under low fracturing pressure, the generation of the main fracture under high fracturing conditions will reduce the construction pressure and the difficulty of sand addition.

[0050] S4: The reverse design takes different construction pressure windows as the core and adopts a three-stage pressure control and pressure stabilization sand addition mode to complete single-layer fracturing sand addition;

[0051] In this step, the first phase mode is as follows:

[0052] Adjust the pump flow rate to control the pressure window of 4-5 MPa;

[0053] a. Pump in low-viscosity fracturing fluid carrying small-diameter proppant to fill microfractures, while simultaneously adding a low concentration of 0.1% synergist via slug injection, with a proppant-to-fluid ratio of 2%-10%;

[0054] b. Pump in medium-viscosity fracturing fluid carrying medium-sized proppant to fill branch fractures, with a sand-to-fluid ratio of 2%-10%;

[0055] c. During the pumping process, the automatic pressure stabilizing pumping system is activated, and the pressure fluctuation range is set. When the pressure fluctuation reaches the upper or lower limit, the step adjustment of the discharge capacity is triggered to maintain stable pressure.

[0056] d. Complete 1 / 3 of the total liquid volume;

[0057] Second-phase mode:

[0058] Adjust the pump discharge rate to reduce the construction pressure and control the pressure window to 10-14 MPa;

[0059] a. Pump in medium-viscosity fracturing fluid carrying medium-sized proppant to fill microfractures, with a proppant-to-fluid ratio of 7%-10%;

[0060] b. Pump in medium- to high-viscosity fracturing fluid carrying medium- to large-diameter proppant to fill the main fracture, with a proppant-to-fluid ratio of 2%-5%;

[0061] c. During the pumping process, the automatic pumping system based on the intelligent adjustment algorithm performs precise control to keep the construction pressure relatively stable;

[0062] d. Complete 2 / 3 of the total liquid volume;

[0063] Third-stage model:

[0064] Adjust the pump discharge rate to reduce the construction pressure and control the pressure window to 17-20 MPa;

[0065] a. Pump in medium- to high-viscosity fracturing fluid to carry medium-sized proppant and fill the main fracture, with a proppant-to-fluid ratio of 4%-5%;

[0066] b. Pump in high-viscosity fracturing fluid and follow it with ceramic proppant to establish a high-conductivity channel at the fracture opening, with a sand-to-fluid ratio of 4%-5%;

[0067] c. During the pumping process, the automatic pumping system based on the intelligent adjustment algorithm performs precise control to keep the construction pressure relatively stable;

[0068] d. Complete the single-layer sand volume and liquid volume.

[0069] Furthermore, the fracturing fluid in step S4 includes a high-efficiency drag reducer, a composite anti-swelling agent, a bactericide, and a surfactant. The proppant in step S4 can be multi-sized proppant, including 100 / 200 mesh proppant, 70 / 140 mesh proppant, 40 / 70 mesh proppant, 30 / 50 mesh proppant, or larger 20 / 40 mesh proppant. Based on the differences in the fracture network, the preferred proportion of each proppant size is: small proppant volume: medium proppant volume: large proppant volume = 2:3:5.

[0070] Furthermore, the low-viscosity fracturing fluid contains a drag-reducing agent at a concentration of 0.08-0.12%; the medium-viscosity fracturing fluid contains a drag-reducing agent at a concentration of 0.13-0.18%; the medium-to-high viscosity fracturing fluid contains a drag-reducing agent at a concentration of 0.19-0.24%; and the high-viscosity fracturing fluid contains a drag-reducing agent at a concentration of 0.25-0.30%. Simultaneously, a plug-type synergist is injected to effectively expand the range of synergistic effects of the fracturing fluid.

[0071] Furthermore, in step S4, an automated pressure-stabilizing pumping system is activated, and a pressure fluctuation amplitude value of ±0.5MPa is set based on changes in construction pressure; when the pressure fluctuation reaches the upper or lower limit, a step adjustment of the discharge rate of 0.1m is triggered. 3 The construction pressure fluctuates within a narrow range and tends to stabilize at a constant rate of / min.

[0072] As described above, in the first stage of fracturing, the pumped fracturing fluid volume is approximately 33% of the total designed volume for a single layer. In the second stage, pumping completes approximately 66% of the designed volume for a single layer. The third stage of fracturing continues until the designed volume for a single layer is reached. The high pressure and large flow rate in the first stage can extend the intra-layer fracture height of the directional well. In the second and third stages, the construction pressure is gradually reduced, and the pressure is stabilized to control the fracture complexity, which is conducive to the extension of the main fracture to the far end. This achieves the fracturing concept of creating long fractures in directional wells, similar to creating horizontal wells. This innovative three-stage pressure control mode gradually reduces the construction pressure, adjusts the flow rate, stabilizes the pressure, and adds sand, ensuring the transformation effect while saving energy and reducing consumption. At the same time, it reduces the failure rate of fracturing equipment under high volume and high pressure for a long time.

[0073] S5: Following the steps above, complete the fracturing and sand addition for the remaining sections of the single well.

[0074] This solution employs a three-stage pressure control mode, utilizing an automatic pressure-stabilizing pump injection system for real-time pressure adjustment and stabilization, preventing the activation of more bedding fractures and microfracture systems. It also utilizes a low-cluster perforation mode, allowing for large-scale fluid injection to promote the extension of the main fracture length. The construction pressure is reduced by 5-8 MPa, the discharge rate by 2-3 cubic meters per minute, and the power consumption per cubic meter of fluid is lowered, ensuring the effectiveness of the modification while saving energy. Furthermore, based on the fully electric fracturing equipment, an online lubrication system and a fully automatic sand conveying device are added, enabling centralized remote control and one-button fracturing throughout the entire process. This meets the needs of large-volume, long-term continuous fluid injection, increasing fracture length by 8-9% compared to diesel generator fracturing with multiple start-stop cycles, significantly improving construction efficiency and reducing construction costs.

[0075] The following example from a region in Jiangsu Province will be used to verify its effectiveness:

[0076] The Fu-2 section of a shale oil field in Jiangsu Province has a complex geological structure with significant formation undulations and dip angles ranging from 8.5° to 18°. Taking directional well A as an example, the well inclination angle ranges from 4 to 30 degrees. The Fu-2 section encountered during drilling has a thickness of 451m, including 251m of high-quality Class I and II reservoirs. Gas logging shows a total hydrocarbon content of 52%, with well-developed laminae and fractures, a small stress difference coefficient, and a high brittleness index of 65.8%, which is conducive to fracturing and the formation of a complex fracture network. The near-wellbore zone is prone to excessive complexity, making fracture propagation and propagation difficult.

[0077] The fracturing method provided by this invention was used to perform quasi-horizontal well fracturing, and its effectiveness was verified. The specific steps are as follows:

[0078] Step 1: Using the basic data from this well, design the fracturing process parameters;

[0079] Based on the monitoring data of fractures in adjacent wells within the block, the test section of subsection I-II is 256m long, divided into 4 layers with an average section length of 64m. Each section has 4 clusters of perforations with a cluster spacing of 12.8m. Using mature simulation software to simulate fracturing operation data, the main fracturing process parameters required to achieve fracture parameters of 255m fracture half-length and 55m fracture height were determined. The design fluid volume for each section is 12000m³, sand volume is 500m³, and displacement is 14-18m³ / min.

[0080] The site is equipped with fully electric equipment, including a 6000-type electric pump, an electric sand mixing skid, and an automatic sand conveying device, and is equipped with an automatic pressure-stabilizing pump injection system. The fracturing wellhead pressure is 105 MPa, and the fracturing operation pressure limit is 84 MPa.

[0081] Step 2, First stage pumping 20m 3 Acid is delivered at a rate of 4 m³ / min. After the acid enters the formation, the construction pressure drops from 42.07 MPa to 38.19 MPa. In the remaining fracturing sections, the pumping acid volume can be adjusted according to the pumping pressure of each section.

[0082] Step 3: Inject low-viscosity fracturing fluid, quickly increase the flow rate to 14 m³ / min, fracture pressure 82.2 MPa, after fracture increase the flow rate to 17.85 m³ / min, and inject pre-fracturing fluid.

[0083] Step 4: First stage fracturing, control pressure window 4MPa, construction pressure benchmark value 80MPa; put into operation automatic pressure stabilizing pump injection system, set fluctuation range ±0.5MPa, step adjustment of electric pump construction discharge rate, discharge rate step adjustment range is 0.1m³ / min;

[0084] A. Pump in 300 ml of low-viscosity fracturing fluid with a concentration of 0.1%. 3 ;

[0085] b. Pump in 0.12% low-viscosity fracturing fluid carrying 100 / 200 mesh proppant, and continuously add 100 m³ of 100 / 200 mesh proppant to fill the propping layer fractures and microfractures; at the same time, add 0.1% wash oil agent (600 m³ of fracturing fluid between slugs) via slug injection.

[0086] c. Pump in 0.15% medium-viscosity fracturing fluid carrying 70 / 140 mesh proppant, and continuously add 90 m³ of 70 / 140 mesh proppant to fill the branch fracture;

[0087] D. Pump in 4090 m³ of total fracturing fluid and 190 m³ of sand to complete the first stage of construction.

[0088] In the second stage of fracturing, the pressure window was controlled at 11 MPa, the pump flow rate was reduced to 15.65 m³ / min, and the benchmark construction pressure was 73 MPa; relying on the automatic pressure stabilizing pump system, the pressure fluctuation range was ±0.5 MPa.

[0089] a. Pump in 0.18% medium-viscosity fracturing fluid carrying 70 / 140 mesh proppant, and continuously add 60 m³ of 70 / 140 mesh proppant to fill the branch fracture;

[0090] b. Pump in 0.22% medium-high viscosity fracturing fluid carrying 40 / 70 mesh proppant into the main fracture, and add 90 m³ of 40 / 70 mesh proppant to fill the main fracture;

[0091] D. Pump in 8100 m³ of total fracturing fluid and 350 m³ of sand to complete the second stage of construction;

[0092] In the third stage of fracturing, the pressure window was controlled at 18 MPa, the pump flow rate was reduced to 13.62 m³ / min, and the benchmark construction pressure was 66 MPa; relying on the automatic pressure stabilizing pump system, the pressure fluctuation range was ±0.5 MPa.

[0093] a. Pump in medium-to-high viscosity fracturing fluid with a concentration of 0.24% carrying 40 / 70 mesh quartz sand proppant, and continuously add 140 m³ of 40 / 70 mesh proppant to fill the main fracture.

[0094] b. Pump in 0.28% high-viscosity fracturing fluid carrying 40 / 70 mesh ceramic proppant into the main fracture, add 20 m³ of 40 / 70 mesh proppant to establish a high-conductivity propped fracture at the fracture opening;

[0095] D. A total of 12005.78 m³ of fracturing fluid and 502.29 m³ of sand were pumped into the single layer, completing the third stage of construction, i.e., the single-layer construction was completed, with a single-layer overall sand-to-fluid ratio of 4.18%.

[0096] Step 5: Following the steps above, complete the fracturing and sand addition for the remaining sections.

[0097] In this embodiment, the main formulation of the pretreatment acid is 15% HCl + 2.0% high-temperature corrosion inhibitor + 1.5% drainage aid + 2.0% clay stabilizer + 1.5% iron ion stabilizer.

[0098] In this embodiment, during the fracturing fluid proppant carrying process, a 0.1% concentration of wash oil agent is added and injected along with the fracturing fluid, with a single slug volume of 600 m³ and a release fluid volume of 600 m³. The wash oil agent is used to change the wettability of the shale oil reservoir, reduce the oil-water interfacial tension, and improve the crude oil recovery rate.

[0099] In this embodiment, 100 / 200 mesh quartz sand proppant is selected for fracturing shale oil reservoirs to fill and support the bedding fractures and microfractures in the early stage. In the middle and late stages, 70 / 140 mesh + 40 / 70 mesh low-density ceramsite is selected as the proppant. By adopting a multi-size proppant plus sand method, the three-dimensional fracture network at all levels is effectively supported, the fracture conductivity is enhanced, and the production of shale oil directional wells after fracturing is effectively improved.

[0100] In this embodiment, the main formulation of the fracturing fluid is water + 0.1-0.28% drag reducer + 0.1% composite anti-swelling agent + 0.02% bactericide. The drag reducer dosage is prepared according to the technical solution, generally in a linear proportion. The viscosity variability of the fracturing fluid improves its proppant-carrying capacity.

[0101] After verification, by using the fracturing method of the present invention to carry out fracturing and stimulation operations on Well A, a total of 4 stages of fracturing operations were completed on Well A, with a total injection volume of 48,023 m³ of fluid into the formation. 3 A total of 2009m³ of sand was added. 3The average sand addition was 8.55 m³ / m, and the overall sand-to-fluid ratio in a single well was 4.18%. Fracture network monitoring data showed that the fracture half-fracture length and stimulated volume increased to 1.6 and 1.76 times that of horizontal wells, respectively, effectively improving fracture-controlled reserves. Post-fracturing 4mm nozzle testing achieved a maximum daily oil production of 64.5 m³ / d, marking a significant breakthrough in production. This pioneering model for directional well fracturing in shale oil production has led to efficient utilization of fault-block shale oil in structurally complex areas.

[0102] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A process for fracturing a directional well or a horizontal well in a shale oil field, characterized in that, The method comprises the following steps: S1: according to the geological and engineering data of the fault block type shale reservoir, combined with the fracture parameters of the previous fractured wells in the block, the three-dimensional layered clustering of the directional well and the main parameters of the fracturing process are determined; S2: acid pretreatment is carried out by injecting acid liquid into the reservoir at a large flow rate; S3: switch to low viscosity fracturing fluid injection, and increase the flow rate quickly; S4: reverse design with different construction pressure windows as the core, three-stage control construction pressure, adjust the flow rate to stabilize the pressure sand mode, complete single layer fracturing sand; In this step, First stage mode: Adjust the pump injection flow rate, control the pressure window 4-5MPa; a, pump in low viscosity fracturing fluid to carry small particle size proppant to fill micro cracks, sand liquid ratio 2%-10%, at the same time, add low concentration 0.1% synergist in plug type, complete small particle size proppant increase; b, pump in medium viscosity fracturing fluid to carry medium particle size proppant to fill branch cracks, sand liquid ratio 2%-10%; c, during the pumping process, the automatic pressure stabilizing pumping system is put into, the pressure fluctuation amplitude is set, when the pressure fluctuation reaches the upper and lower limit values, the step adjustment of the flow rate is triggered to keep the pressure stable; d, complete 1 / 3 of the total liquid volume; Second stage mode: Adjust the pump injection flow rate, reduce the construction pressure, control the pressure window 10-14MPa; a, pump in medium viscosity fracturing fluid to carry medium particle size proppant to fill micro cracks, sand liquid ratio 7%-10%; b, pump in medium-high viscosity fracturing fluid to carry medium-large particle size proppant to fill main cracks, sand liquid ratio 2%-5%; c, during the pumping process, the automatic pressure stabilizing pumping system is put into, the pressure fluctuation amplitude is set, when the pressure fluctuation reaches the upper and lower limit values, the step adjustment of the flow rate is triggered to keep the pressure stable; d, complete 2 / 3 of the total liquid volume; Third stage mode: Adjust the pump injection flow rate, reduce the construction pressure, control the pressure window 17-20MPa; a, pump in medium-high viscosity fracturing fluid to carry medium particle size proppant to fill main cracks, sand liquid ratio 4%-5%; b, pump in high viscosity fracturing fluid to chase after ceramic proppant to establish high conductivity channel, sand liquid ratio 4%-5%; c, during the pumping process, the automatic pressure stabilizing pumping system is put into, the pressure fluctuation amplitude is set, when the pressure fluctuation reaches the upper and lower limit values, the step adjustment of the flow rate is triggered to keep the pressure stable; d, complete single layer sand volume, liquid volume, comprehensive sand liquid ratio 3.0%-4.5%; S5: refer to the above steps, complete the fracturing sand of the remaining layer of single well.

2. The shale oil directional well, horizontal well fracturing process, according to claim 1, characterized in that: In the step S1, according to the existing reservoir physical properties and engineering parameters of the fault block area, combined with the fracture height data monitored by the fractured well, the three-dimensional layered clustering parameters of the directional well are determined.

3. The process for the shale oil directional well horizontal well fracturing according to claim 1 or 2, characterized in that: In the step S1, the directional well is preferably single layer perforation 3-4 clusters.

4. The shale oil directional well, horizontal well, fracturing process, according to claim 1, characterized by: In step S2, the amount of acid used for each layer is 20-30 mg. 3 Pumping displacement 3-5m 3 / min.

5. The shale oil directional well, horizontal well, fracturing process, according to claim 1, characterized by: The acid liquid in the step S2 includes hydrochloric acid, high temperature corrosion inhibitor, cleanup additive, clay stabilizer and iron ion stabilizer.

6. The process for shale oil directional well horizontal well fracturing according to claim 1 or 2, characterized in that: In the step S3, switch to low viscosity fracturing fluid injection, increase the flow rate under the construction pressure limit, form high fracture pressure.

7. The shale oil directional well, horizontal well, fracturing process, according to claim 6, characterized by: The proppant in the step S4 uses multi-grade proppant, specifically including 100 / 200 mesh proppant, 70 / 140 mesh proppant, 40 / 70 mesh proppant, 30 / 50 mesh or larger particle size 20 / 40 mesh proppant.

8. The shale oil directional well, horizontal well, fracturing process, according to claim 7, characterized by: The proportion of the proppant of each particle size is small particle size proppant volume: medium particle size proppant volume: large particle size proppant volume = 2:3:

5.

9. The shale oil directional well, horizontal well, fracturing process, according to claim 6, characterized by: The low viscosity fracturing fluid is a drag reducer with a concentration of 0.08-0.12%; the medium viscosity fracturing fluid is a drag reducer with a concentration of 0.13-0.18%; the medium-high viscosity fracturing fluid is a drag reducer with a concentration of 0.19-0.24%; and the high viscosity fracturing fluid is a drag reducer with a concentration of 0.25-0.30%.

Images