Shale oil and gas horizontal well layer-crossing expansion fracturing method and application

Abstract

The invention discloses a shale oil and gas horizontal well layer-crossing expansion fracturing method and application. The fracturing method comprises a pre-fracturing step and a fracture forming step. The displacement of fracturing fluid used in the pre-fracturing step is gradually increased, and the displacement increasing amplitude is gradually increased; the fracture forming step comprises a four-stage reinforced temporary plugging construction step, and variable displacement temporary plugging construction is adopted when temporary plugging balls are delivered for temporary plugging construction. According to the fracturing method, the space-time form of fracture expansion is reasonably regulated and controlled, fracture diversion and reservoir matrix serious damage caused by too high viscosity of fracturing fluid are avoided while the fracture height completely penetrates through a target small layer, the problems that the fracture is excessively expanded in a non-target layer, centralized transformation and repeated transformation are conducted near a shaft and the like are solved, and the fracturing efficiency is improved. The fracture length is greatly increased, the size and the drainage area are effectively transformed, and the fracturing targets of promoting generation of complex fractures and improving the yield and the efficiency through layer-penetrating body expansion are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum exploration and development fracturing engineering, and more particularly to a method and application of shale oil and gas horizontal well cross-layer expansion fracturing. Background Art

[0004] In order to solve the problem of insufficient fracture penetration height, the industry has carried out large-volume pre-gel or ultra-high viscosity slick water reverse fracturing tests, which have improved the penetration ability and fracturing effect to a certain extent. The production of some deep shale oil and gas wells has increased significantly, but the effective transformation volume of most wells is still relatively small, the production decreases rapidly, the EUR is relatively low, and the barrel of oil equivalent cost is relatively high. The relevant technology is not universal and cannot be promoted and replicated.

[0005] Due to different theories and cognitions on the dynamic expansion of shale oil and gas fracturing cracks, the inventors of the present invention found that the prior art generally has the following phenomena: too fast increase in displacement in the pre-fracture making stage, unreasonable net pressure control, poor crack distribution morphology, concentrated transformation near the wellbore, unbalanced transformation, excessive expansion of cracks in non-target layers, and short support fracture length. For example, in the high-quality shale of the Silurian Longmaxi Formation in the Sichuan Basin, decimeter-level dolomite and Guanyinqiao dense dolomite, Jurassic shell limestone and dense sandstone, and Paleogene mudstone in the old eastern area, interlayers and other interlayers obviously block the penetration of cracks, and the cracks present unfavorable shapes such as "T"-shaped, "I"-shaped, "Tu"-shaped and terraced, which affect the effect and high-quality development of shale oil and gas fracturing.

[0006] Therefore, there is an urgent need to invent a new method for efficient fracturing suitable for shale oil and gas horizontal well penetration and expansion. Summary of the invention

[0007] In order to solve the problems in the prior art, the present invention proposes a method and application of shale oil and gas horizontal well penetration and expansion fracturing. The shale oil and gas horizontal well penetration and expansion high-efficiency fracturing method of the present invention systematically optimizes the viscosity, scale, displacement step duration and lifting amplitude of the pre-fluid, controls the near expansion, slow first and then fast, and changes the displacement in a long step, forming a "2543" fracturing mode with two viscosity integrated fracturing fluids, five pre-fluid displacement steps, four-level enhanced temporary plugging, three obvious construction pressure steps and batch fracturing as the main features, optimizing the net pressure in real time, and reasonably regulating the spatiotemporal morphology of fracture expansion. While achieving full penetration of the target small layer of fracture height, it avoids the fracture diversion and serious damage to the reservoir matrix caused by excessive viscosity of the fracturing fluid, solves the problems of excessive expansion of fractures in non-target layers, concentrated transformation near the wellbore and repeated transformation, and greatly increases the fracture length, effective transformation volume and drainage area, so as to achieve the fracturing goals of penetration and expansion to promote complex fractures and increase production and efficiency.

[0008] One of the purposes of the present invention is to provide a method for shale oil and gas horizontal well cross-layer expansion fracturing, the fracturing method comprising a pre-fracturing step and a fracture creation step;

[0009] The displacement of the fracturing fluid used in the pre-fracturing step is gradually increased, and the displacement increase amplitude is gradually increased; the fracture making step includes 4 levels of enhanced temporary plugging construction steps, and when temporary plugging balls are delivered for temporary plugging construction, variable displacement temporary plugging construction is adopted.

[0010] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably, the following steps are included:

[0011] Pre-fracturing steps:

[0012] ① Low-displacement pump to inject acid;

[0013] ② Low-volume, long-term, high-viscosity fracturing fluid pre-placement;

[0014] ③ Medium-to-high displacement and high-viscosity fracturing fluid stably expands the horizontal section and penetrates the small layer cracks;

[0015] ④ Use high-viscosity fracturing fluid with a relatively high displacement to perform fracturing through all target small layers; use medium- and low-viscosity fracturing fluid with a relatively high displacement and sand fracturing;

[0016] Seam making steps:

[0017] ⑤ High-viscosity fracturing fluid with a high displacement is used to deliver temporary plugging agent for the first time to temporarily plug the seam end and create complex seams;

[0018] ⑥ Medium and low viscosity fracturing fluid with high displacement and sand fracturing;

[0019] ⑦ The medium and low viscosity fracturing fluid is used to change the displacement and deliver temporary plugging balls for the first time to divert between clusters and create new fractures;

[0020] ⑧ Medium and low viscosity fracturing fluid with high displacement and sand fracturing;

[0021] ⑨ High-viscosity fracturing fluid with high displacement is used to deliver temporary plugging agent for the second time to temporarily plug the seam end and divert to create complex seams;

[0022] ⑩ Medium and low viscosity fracturing fluid with high displacement and sand fracturing;

[0023] The medium-low viscosity fracturing fluid is pumped at a variable displacement for the second time to deliver temporary plugging balls to divert clusters and create new seams, thus achieving batch fracturing.

[0024] Finally Maximum displacement of medium and low viscosity fracturing fluid with sand fracturing and displacement.

[0025] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably,

[0026] The viscosity of the fracturing fluid used in the fracturing method is 1 to 130 mPa·s;

[0027] Preferably,

[0028] High viscosity fracturing fluid refers to 170s -1 A fracturing fluid having a viscosity greater than 30 mPa·s after 120 min of shearing, preferably a fracturing fluid of 30 to 130 mPa·s; more preferably a fracturing fluid of 40 to 60 mPa·s; and / or,

[0029] Medium and low viscosity fracturing fluid refers to 170s -1 Fracturing fluid with a viscosity of 6 to 15 mPa·s after 120 min of shearing;

[0030] The displacement used in the fracturing method is,

[0031] Low displacement is 2~5m 3 / min; and / or,

[0032] Medium and high displacement is 6~9m 3 / min; and / or,

[0033] The highest displacement is 10~16m 3 / min; and / or,

[0034] High displacement: 18~20m 3 / min; and / or,

[0035] The maximum displacement is the maximum displacement of the fracturing equipment required by the construction design, preferably 21 to 25 m 3 / min; and / or,

[0036] The displacement range of variable displacement is limited to 2~25m 3 / min;

[0037] Preferably, the displacement in the fracturing process sections ①-④ is gradually increased in 5 displacement steps.

[0038] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably,

[0039] In the fracturing method,

[0040] The temporary plugging balls and temporary plugging agents are independently low-density water-soluble or degradable materials; and / or,

[0041] Add proppant to sand fracturing construction;

[0042] Preferably,

[0043] The density of the temporary plugging ball and the temporary plugging agent is independently (1.0-1.3)×10 3 kg / m 3 and / or,

[0044] The outer diameter of the temporary plugging ball is 16 to 44 mm; and / or,

[0045] The specification of the temporary plugging agent is selected from at least one of 8 / 40 mesh, 10 / 40 mesh, 20 / 80 mesh, 20 / 100 mesh and 40 / 140 mesh.

[0046] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably,

[0047] In the fracturing method,

[0048] In the fracturing process section ①, hydrochloric acid is injected at a low rate; the preferred injection rate of hydrochloric acid is 10-20m 3 ; The concentration of the hydrochloric acid solution is 15wt%; and / or,

[0049] In the fracturing process section ②, the injection volume of fracturing fluid is 40 to 80 m 3 ; The construction pumping time is preferably 10 to 20 minutes; the viscosity of the fracturing fluid used is further preferably less than 100 mPa·s; the viscosity of the fracturing fluid used is further preferably 40 to 60 mPa·s, and the damage rate to the reservoir permeability is less than 10%; and / or,

[0050] In the fracturing process section ③, the injection volume of fracturing fluid is 60-100m 3 and / or,

[0051] In the fracturing process section ④, the injection volume of fracturing fluid is 320~360m 3 The injection volume of the high viscosity fracturing fluid used in the fracturing process section is preferably 130 to 150 m 3 ;

[0052] In the fracturing process section ⑤, the injection volume of fracturing fluid is 20-30m 3 and / or,

[0053] In the fracturing process section ⑥, the injection volume of fracturing fluid is 200-240m 3 .

[0054] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably,

[0055] In the fracturing process section ⑦, the injection volume of fracturing fluid is 60-100m 3 and / or,

[0056] In the fracturing process section ⑧, the injection volume of fracturing fluid is 220~260m 3and / or,

[0057] In the fracturing process section ⑨, the injection volume of fracturing fluid is 30-40m 3 and / or,

[0058] In the fracturing process section ⑩, the injection volume of fracturing fluid is 240~280m 3 and / or,

[0059] Fracturing process section The injection volume of fracturing fluid is 60-120m 3 and / or,

[0060] Fracturing process section The injection volume of fracturing fluid is 300-400m 3 .

[0061] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably,

[0062] In the fracturing method,

[0063] In the fracturing process section ④, the sand-to-liquid ratio in the sand fracturing construction is 3% to 15%; and / or,

[0064] In the fracturing process stage ⑤, the amount of temporary plugging agent delivered for the first time is 150-200 kg; and / or,

[0065] In the fracturing process section ⑥, the sand-to-liquid ratio in the sand fracturing construction is 8% to 13%; and / or,

[0066] In the fracturing process section ⑦, the number of temporary plugging balls delivered for the first time is 30% to 40% of the total number of perforations, preferably 16 to 20. When the displacement is changed, the displacement is continuously increased, and the displacement increase range is 3 to 4 m 3 / min; and / or, in the fracturing process section ⑧, the sand-to-liquid ratio in the sand fracturing construction is 10% to 15%; and / or,

[0067] In the fracturing process section ⑨, the amount of temporary plugging agent delivered for the second time is 150-200 kg; and / or,

[0068] In the fracturing process section ⑩, the sand-to-liquid ratio in the sand fracturing construction is 12% to 18%; and / or,

[0069] Fracturing process section The number of temporary plugging balls delivered for the second time is 30% to 40% of the total number of perforations, preferably 16 to 20. When the displacement is changed, the displacement increases continuously, and the displacement increase range is 3 to 4 m 3 / min; and / or,

[0070] Fracturing process section In the sand-added fracturing construction, the sand-to-liquid ratio is 10% to 22%.

[0071] In the fracturing method of the present invention, the fracturing process section ② of low displacement and long time high viscosity fracturing fluid pre-placement is innovative. The existing technical method is to quickly increase the displacement to the maximum design displacement of the construction in a short time, or to increase the displacement to the maximum design displacement in a staged or stepped manner. 3 / min) The pumping construction time is short, generally less than 2 minutes; in addition, the viscosity of the fracturing fluid is generally too large, 100-300mPa·s, and the regulation is unreasonable, which can easily cause the cracks to be out of control and over-expanded. At the same time, in pursuit of high-viscosity fracturing fluid, guar gum fracturing fluid with higher damage is generally selected, which has great damage to the reservoir and fracture conductivity, reducing the fracturing effect. The low-displacement fracturing construction pumping time requirement in stage ② of the present invention is generally 10-20 minutes, accounting for 40% to 70% of the total time of the pre-fracturing stage (the total time of fracturing process sections ①-④). At the same time, the fracturing fluid uses low damage (the damage rate to the reservoir permeability is less than 10%), and the viscosity is less than 100mPa·s, generally 40-60mPa·s of the existing fracturing fluid.

[0072] Fracturing process section ③ Medium-high displacement high viscosity fracturing fluid stably expands the horizontal section to penetrate the small layer cracks, ④ High displacement high viscosity fracturing fluid all target small layers through layer fracturing, medium-low viscosity fracturing fluid high displacement plus sand fracturing. The medium-high displacement required by the present invention is 6-9m 3 / min, the highest displacement is 10~16m 3 / min are 25% to 40% and 45% to 70% of the maximum designed displacement of the fracturing pumping construction respectively. The displacement increase range is 1 to 2m / min in stage ②. 3 / min increased to 3-4m 3 / min, the pumping time is 20% to 40% and 20% to 30% of the total time of the pre-fracturing stage (the total time of the fracturing process sections ① to ④), respectively, and the displacement increase is increased and accelerated to ensure the stable, orderly and controllable expansion of the cracks. This pre-fracturing method of slow first and fast later has not been reported in the prior art.

[0073] Fracturing process section ⑤ High viscosity fracturing fluid with high displacement for the first time to deliver temporary plugging agent to temporarily plug the seam end and divert to create complex seams, ⑥ Medium and low viscosity fracturing fluid with high displacement and sand fracturing, ⑨ High viscosity fracturing fluid with high displacement for the second time to deliver temporary plugging agent to temporarily plug the seam end and divert to create complex seams. Medium and low viscosity fracturing fluid requires a viscosity of 6-15mPa·s, and a high displacement of 10-16m 3 / min is 45% to 70% of the maximum displacement designed for fracturing pumping construction. The high displacement required in step ⑨ is generally 18 to 20m 3 / min, which is 70% to 90% of the maximum displacement designed for fracturing pumping construction. This method is different from the existing technology that uses low-viscosity fracturing fluid to deliver temporary plugging agents at the maximum displacement designed for fracturing.

[0074] Fracturing process section ⑦ The low-viscosity fracturing fluid is used to change the displacement for the first time to deliver temporary plugging balls for cluster diversion and new fracture creation. The medium and low viscosity fracturing fluid is used to change the displacement and deliver temporary plugging balls for the second time to make new fractures between clusters again. The batch fracturing is different from the existing process. The existing method generally uses a constant displacement to deliver temporary plugging balls, which has a poor temporary plugging pressure effect and low temporary plugging efficiency. The method of the present invention is to use a ball delivery displacement of 8 to 10 m 3 / min, when the ball reaches the temporarily blocked perforation, keep the displacement unchanged first, and wait until the construction pressure is obviously increased and the blocking is effective, do not rush to increase the displacement, first increase the displacement to 12m 3 / min, maintain for 2-3min, after the ball is completely seated, increase the displacement to the same displacement before temporary plugging to avoid temporary plugging failure and judge the temporary plugging effect. The highest displacement for the first temporary plugging recovery in step ⑦ is generally 14m 3 / min, steps Medium and high displacement is generally 18 to 20m 3 / min.

[0075] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably,

[0076] The construction parameters in the fracturing method are obtained by:

[0077] A fracturing numerical model is established by simulating the crack extension of simulated rock samples of a target layer section for fracturing transformation of a simulated horizontal well; and shale oil and gas horizontal well interlayer expansion fracturing is performed after simulating and optimizing the fracturing construction parameters based on the fracturing numerical model.

[0078] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably, the construction parameters in the fracturing method are obtained by the following method:

[0079] (1) Obtaining geological parameters and mechanical parameters of all sub-layers in the target layer section of horizontal well fracturing stimulation;

[0080] (2) preparing simulated rock samples;

[0081] (3) performing an indoor fracturing physical simulation experiment on the simulated rock sample to obtain crack propagation parameters;

[0082] (4) numerically simulating the fracturing process of the indoor fracturing physical simulation experiment and establishing a centimeter-scale fracturing numerical model;

[0083] (5) Enlarging the centimeter-scale fracturing numerical model to the actual scale of the mine field to form a fracturing numerical model consistent with the key parameters of the fracturing transformation formation area;

[0084] (6) simulating and optimizing the fracturing construction parameters based on the fracturing numerical model of step (5);

[0085] (7) Perform fracturing construction based on optimized fracturing construction parameters.

[0086] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably,

[0087] In step (1), the geological parameters and mechanical parameters obtained include parameters of the target horizontal well's traversal horizon, lithology, thickness, mineral composition, rock mechanical parameters, geostress, fracture development, and interface strength of each sub-layer and top and bottom plates; and / or,

[0088] In step (2), the simulated rock sample is a simulated rock sample that is triple similar to the real shale reservoir in terms of lithology, mineral composition and rock mechanical properties; preferably, the size of the simulated rock sample is 300mm×300mm×300mm or 300mm×300mm×600mm; and / or,

[0089] In step (3), a true triaxial fracture extension simulation is performed on the simulated rock sample using a layered in-situ stress loading system to obtain the dynamic fracture extension morphology under different fracturing fluid viscosities and displacement combinations; wherein the pressure of a single-layer pressurization test in the layered in-situ stress loading system can reach 50 MPa, and the maximum interlayer stress difference can reach more than 15 MPa.

[0090] In the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention, preferably,

[0091] In step (4), based on synthetic geotechnical technology and a three-dimensional discrete grid algorithm, a full three-dimensional stress-pressure coupling numerical simulation of the initiation and propagation process of the rock sample fracturing crack simulated in step (3) is achieved; preferably, the mechanical parameters used in the centimeter-scale fracturing numerical model include fracture toughness, elastic modulus, geostress, shear strength and tensile strength; and / or,

[0092] In step (5), based on step (4), the centimeter-scale fracturing numerical model is enlarged to the actual scale of the mine field to form a fracturing numerical model consistent with the key parameters of the target reservoir lithology combination, mechanical properties, interface properties, fracture properties and stress state; and / or,

[0093] In step (6), the model established in step (5) is used to simulate and optimize different combinations of fracturing fluid viscosity and displacement construction parameters.

[0094] More preferably, the method for shale oil and gas horizontal well cross-layer expansion fracturing of the present invention comprises the following steps:

[0095] Step 1: Review relevant information such as geological design, drilling design, horizontal section trajectory, adjacent well fracturing conditions and rock mechanics parameter test reports to obtain basic parameters such as the target horizontal well penetration layer, designed transformation layer, length, width and height of the transformation box, horizontal section length, well spacing, lithology, thickness, mineral composition, rock mechanics parameters, ground stress, fracture development, interface strength, etc. of each sub-layer and top and bottom plates;

[0096] Step 2: According to the lithology, thickness, mineral composition, rock mechanical parameters, ground stress, fracture development, interface strength and other parameters of each sub-layer and top and bottom plates in step 1, prepare a multi-layer mixed rock sample with different lithology, which has a triple high similarity with the real shale reservoir in terms of lithology combination, mineral composition and rock mechanical properties. The specific size is 300mm×300mm×300mm or 300mm×300mm×600mm, wherein the mineral components are mainly felsic brittle minerals, clay and carbonate minerals, and the mechanical properties are similar mainly in Young's elastic modulus, tensile strength, shear strength and fracture toughness. The interlayer is of centimeter thickness, and the shale is of decimeter thickness. The simulated wellbore position is consistent with the position of the sub-layer through which the horizontal section passes;

[0097] Step 3: Using a layered in-situ stress loading system, a true triaxial fracture propagation simulation is performed on the large-scale mixed rock sample obtained in step 2 to obtain the dynamic fracture propagation morphology under different fracturing fluid viscosities and displacement combinations;

[0098] Step 4: Based on synthetic geotechnical technology and three-dimensional discrete grid algorithm theory, a full three-dimensional stress-pressure coupling simulation of the initiation and expansion process of the mixed rock sample fracturing in step 3 is realized, and a centimeter-scale high-precision fracturing numerical model is established that can take into account the influence of interlayer lithology differences, modulus changes, and interlayer weak surfaces on the longitudinal expansion morphology of the cracks.

[0099] Step 5. Based on step 4, the scale is enlarged to the actual scale of the mine to form a stable, fast, centimeter-level high-precision fracturing numerical model that is consistent with key parameters such as the target reservoir lithology combination, mechanical properties, interface properties, fracture properties and stress state.

[0100] Step 6: Use the model established in step 5 to simulate and optimize different fracturing fluid viscosity and displacement construction parameter combinations, mainly including ① low displacement pump acid injection;

[0101] ② Low-volume, long-term, high-viscosity fracturing fluid pre-placement;

[0102] ③ Medium-to-high displacement and high-viscosity fracturing fluid stably expands the horizontal section and penetrates the small layer cracks;

[0103] ④ Use high-viscosity fracturing fluid with a relatively high displacement to perform fracturing through all target small layers; use medium- and low-viscosity fracturing fluid with a relatively high displacement and sand fracturing;

[0104] ⑤ High-viscosity fracturing fluid with a high displacement is used to deliver temporary plugging agent for the first time to temporarily plug the seam end and create complex seams;

[0105] ⑥ Medium and low viscosity fracturing fluid with high displacement and sand fracturing;

[0106] ⑦ The medium and low viscosity fracturing fluid is used to change the displacement and deliver temporary plugging balls for the first time to divert between clusters and create new fractures;

[0107] ⑧ Medium and low viscosity fracturing fluid with high displacement and sand fracturing;

[0108] ⑨ High-viscosity fracturing fluid with high displacement is used to deliver temporary plugging agent for the second time to temporarily plug the seam end and divert to create complex seams;

[0109] ⑩ Medium and low viscosity fracturing fluid with high displacement and sand fracturing;

[0110] The medium-low viscosity fracturing fluid is pumped at a variable displacement for the second time to deliver temporary plugging balls to divert clusters and create new seams, thus achieving batch fracturing.

[0111] Finally The medium and low viscosity fracturing fluid is discharged at the maximum rate to add sand for fracturing and displacement; finally, a fracturing construction curve with obvious three steps and a four-dimensional expansion shape of the length, width and height of a multi-scale fracture network is obtained.

[0112] Step 7. The fracturing fluid used in the present invention is a "two lows and five good" integrated variable viscosity fracturing fluid with the characteristics of low friction, low damage, good mixing, good seam formation, good sand carrying, good permeation and good recycling in the prior art. The main agent is a water-soluble supramolecular association aggregate type drag reducing agent, and the auxiliary agents are anti-swelling agent, surfactant, viscosity regulator, temperature stabilizer, permeation enhancer, nanoparticle synergist, oil displacement agent, wetting improver, waterproof lock agent and gel breaker. The above substances can be selected from existing commonly used substances. The main performance indicators of the system are temperature resistance of 160°C, salt resistance of 25×10 4 mg / L, drag reduction rate 75% to 85%, apparent viscosity 1 to 130 mPa·s, surface tension less than 28 mN / m, reservoir matrix damage rate less than 8%, no residue, sand carrying capacity greater than 500 kg / m 3 , the maximum permeation height of the degelling liquid is 25-82mm, and the return fluid reuse rate is 100%. According to the optimization results of step 6, the same drag reducing agent is used to change the viscosity and drag reducing rate of the online control system of its concentration, and according to the characteristics of shale and the requirements of fracturing process, one or more of the above-mentioned additives are selected for optimization combination, and finally a fracturing fluid system with different performance is formed to meet the requirements of different shale oil and gas horizontal wells through-layer expansion fracturing transformation. The high viscosity fracturing fluid refers to 170s at reservoir temperature. -1The viscosity is greater than 30mPa·s after 120min of shearing, and the medium-low viscosity fracturing fluid refers to the viscosity of 6-15mPa·s, which becomes viscous and slippery water.

[0113] The low displacement described in step 8 and step 6 is 2 to 5 m 3 / min, medium and high displacement is 6~9m 3 / min, the highest displacement is 10~16m 3 / min, high displacement is 18~20m 3 / min, the maximum displacement is the maximum displacement of the fracturing equipment required by the construction design, generally 21 ~ 25m 3 / min. According to the optimization results of step 6, determine the size of the graded displacement.

[0114] The temporary plugging balls and temporary plugging agents described in step 9 and step 6 are low-density water-soluble or degradable temporary plugging balls with a density of (1.0-1.3)×10 3 kg / m 3 The outer diameter of the temporary plugging ball is 16-44 mm, and the specification of the temporary plugging agent is selected from at least one of 8 / 40 mesh, 10 / 40 mesh, 20 / 80 mesh, 20 / 100 mesh and 40 / 140 mesh. According to the optimization result of step 6, the density and specification of the temporary plugging ball agent are determined.

[0115] The effective temporary plugging pressure threshold described in step 10 and step 6 is generally 3 MPa, which can be comprehensively determined based on multi-cluster temporary plugging simulation, construction pressure curve, microseismic monitoring and production profile test results. If a certain level of temporary plugging fails to achieve effective temporary plugging, the temporary plugging parameters can be adjusted for repeated temporary plugging.

[0116] Step 11, repeating steps 6 to 10, with the goal of maximizing reserve utilization, EUR and internal recovery efficiency, gradually achieving overall optimization from local optimization section by section, layer by layer and well by well, to form a new method of cross-layer expansion fracturing for shale oil and gas horizontal wells that can be promoted and replicated for a wide spectrum.

[0117] Therefore, the present invention is based on the high-similarity mixed rock mass true triaxial fracture expansion layered simulation and centimeter-level high-precision full three-dimensional fracture dynamic expansion discrete lattice method efficient simulation coupling model of the shale oil and gas horizontal well penetration and expansion efficient fracturing method, the system optimizes the viscosity, scale, displacement step duration and lifting amplitude of the pre-fluid, and forms a "2543" fracturing mode with two viscosity integrated fracturing fluids, five pre-fluid displacement steps, four-level enhanced temporary plugging, three obvious construction pressure steps and batch fracturing as the main features, optimizes the net pressure in real time, and reasonably regulates the spatiotemporal morphology of fracture expansion, while achieving full penetration of the target small layer of the fracture height, avoiding excessive fracturing fluid viscosity causing serious damage to the fracture diversion and reservoir matrix, solving the problems of excessive expansion of fractures in non-target layers, concentrated transformation near the wellbore and repeated transformation, greatly increasing the fracture length, effective transformation volume and drainage area, achieving the fracturing goals of penetration and expansion to promote complex fractures and increase production and efficiency, providing technical support for high-quality exploration and development of shale oil and gas, and providing reference for other types of reservoir transformation.

[0118] The second object of the present invention is to provide the application of the method for shale oil and gas horizontal well cross-layer expansion fracturing described in any one of the objects of the present invention in shale oil and gas production.

[0119] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0120] Compared with the prior art, the present invention has the following advantages:

[0121] The present invention is rationally designed, highly targeted and adaptable. The present invention optimizes the viscosity, scale and displacement of the pre-fluid, the step duration, the lifting amplitude and the temporary plugging parameters, optimizes the net pressure in real time, and reasonably regulates the spatiotemporal morphology of fracture expansion, so as to achieve full penetration of the target small layer by the fracture height, avoid excessive expansion of the non-target layer of the fracture, and concentrated and repeated transformation near the horizontal wellbore, greatly increase the fracture length, effective transformation volume and drainage area, and achieve the fracturing goals of penetrating the layer to expand the body to promote the formation of complex fractures and increase production and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0122] Figure 1 It is a fracturing construction curve in the method for layer-penetrating and body-expanding fracturing of shale oil and gas horizontal wells of the present invention.

[0123] The construction curve includes 12 stages ( Figure 1 According to the direction indicated by the arrow, each divided process section is followed by steps ①-): ① low displacement pump injection of 15% concentration hydrochloric acid; ② low displacement long time high viscosity fracturing fluid pre-placement, ③ medium and high displacement high viscosity fracturing fluid stably expands the horizontal section to penetrate the small layer cracks, ④ high displacement high viscosity fracturing fluid all target small layers through layer fracturing, medium and low viscosity fracturing fluid high displacement plus sand fracturing, ⑤ high viscosity fracturing fluid high displacement first delivery of temporary plugging agent to temporarily plug the seam end to turn to create complex seams, ⑥ medium and low viscosity fracturing fluid high displacement plus sand fracturing, ⑦ medium and low viscosity fracturing fluid variable displacement first delivery of temporary plugging ball to turn between clusters to create new seams, ⑧ medium and low viscosity fracturing fluid high displacement plus sand fracturing, ⑨ high viscosity fracturing fluid high displacement second delivery of temporary plugging agent to temporarily plug the seam end to turn to create complex seams, ⑩ medium and low viscosity fracturing fluid high displacement plus sand fracturing, The medium and low viscosity fracturing fluid is pumped at a variable displacement for the second time to deliver temporary plugging balls to divert between clusters and create new fractures, thus achieving batch fracturing. Maximum displacement of medium and low viscosity fracturing fluid with sand fracturing and displacement. DETAILED DESCRIPTION

[0124] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0125] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0126] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0127] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0128] Comparative Example 1

[0129] Taking the fracturing transformation of Jurassic shale well A in Sichuan Basin as an example, the well has a vertical depth of 2438-2556m, a horizontal section length of 2006m, a target layer thickness of 30m, and 3 small layers developed, among which there are multiple centimeter-level limestone and argillaceous sandstone interlayers, relatively developed laminar fractures, and medium to weak interlayer interface strength. The horizontal well trajectory passes through the middle and lower part of the lower small layer, and the top and bottom plates are dense sandstone with poor gas content. The highly similar mixed rock mass true triaxial fracture extension layered simulation and centimeter-level high-precision full three-dimensional fracture dynamic extension discrete grid method are efficient simulation results. Under different construction parameter combinations, different fracture morphologies of inverted "T", "Tu", "Gong", "Wang", "Feng" and "Gui" are formed respectively. The geological design requires that the upper fracture height of the horizontal wellbore is 20m, the lower fracture height is 10m, the well spacing is 240m, the half fracture length is 120m, and the three small layers are fully penetrated to increase the transformation volume, form complex fractures, and maximize the fracture-controlled reserves and production. After optimization, 30 sections and 230 clusters of fracturing were carried out, using an integrated variable viscosity fracturing fluid composed of a resistance reducing agent + an anti-swelling agent + a drainage agent + a gel breaker, and supporting two balls and two agents to strengthen temporary plugging, microseismic fracture monitoring and tracer production profile monitoring. In the early stage, fracturing was carried out according to the conventional practice of fast-lifting displacement and pre-placement of high-viscosity fracturing fluid to create fractures. The fracture length was only 201m, the fracture network width was 91m, and the total fracture height was 39m. The main construction parameter indicators failed to meet the design requirements, and there were problems such as small transformation volume, low fracture complexity, and serious near-wellbore and repeated transformation.

[0130] Example 1

[0131] In the later stage of construction of the comparative example 1, the new "2543" layer-penetrating and body-expanding fracturing method was used for optimization and adjustment, in which the viscosity of the pre-fluid was increased to 45 mPa·s, the total fracture creation time was increased from less than 10 min to 30 min, and the initial low displacement was 2-4 m 3 / min duration increased to 15min, 6, 8m 3 / min medium and high displacement for 10min, and then increase the displacement increase range, from 8m 3 / min quickly increased to 12, 16m 3 / min, and then carry out sand fracturing construction according to the above method. The medium-low viscosity fracturing fluid is 9mPa·s slick water, and the displacement of the three steps is 14-16, 18-19, and 20-23m 3 / min, the two temporary blocking balls are 20 and 15, the ball delivery and inter-cluster temporary blocking steering displacement are adjusted to 8, 10, 12, 16, 18m 3 / min, the two temporary plugging agents are 10 / 40 mesh 100kg + 20 / 80 mesh 100kg, and 20 / 80 mesh 160kg.

[0132] The specific construction steps are as follows: ①2m 3 / min pump to inject 15% hydrochloric acid 20m 3 ;②2~4m3 / min low-displacement high-viscosity fracturing fluid pre-pump injection for 15 minutes, fracturing fluid dosage 50m 3 , viscosity is 45mPa·s; ③6, 8m 3 / min medium-high displacement high viscosity fracturing fluid stably expands the horizontal section through the small layer cracks and pumps for 10 minutes. The amount of fracturing fluid is 70m 3 , viscosity is 45mPa·s; ④12, 16m 3 / minHigher displacement and high viscosity fracturing fluid are pumped into all target small layers for fracturing for 10 minutes. The amount of fracturing fluid is 140m 3 , viscosity is 45mPa·s; 9mPa·s medium and low viscosity fracturing fluid is 16m 3 / min higher displacement sand fracturing, fracturing fluid dosage is 220m 3 , the proppant is 70 / / 140 mesh quartz sand 35m 3 , sand-liquid ratio is 3% to 15%; ⑤45mPa·s high viscosity fracturing fluid 16m 3 / min, 200kg of temporary plugging agent was first delivered at a higher displacement to temporarily plug the seam end and turn to create complex seams, including 100kg of 10 / 40 mesh and 100kg of 20 / 80 mesh. The amount of fracturing fluid used was 25m 3 ⑥ 9mPa·s medium and low viscosity fracturing fluid with 16m 3 / min higher displacement sand fracturing, fracturing fluid dosage is 220m 3 , the proppant is 40 / / 70 mesh quartz sand 25m 3 , the sand-liquid ratio is 8% to 13%; ⑦9mPa·s medium-low viscosity fracturing fluid variable displacement for the first time to send 20 temporary plugging balls to divert between clusters to create new fractures, the outer diameter of the temporary plugging balls is 24 to 26mm, and the displacement is 8, 10, 12, and 16m 3 / min, the fracturing fluid dosage is 100m 3 ⑧9mPa·s medium and low viscosity fracturing fluid with 18m 3 / min high-displacement sand fracturing, the fracturing fluid dosage is 240m 3 , the proppant is 70 / / 140 mesh quartz sand 30m 3 , sand-liquid ratio is 10% to 15%; ⑨45mPa·s high viscosity fracturing fluid is 18m 3 / min high displacement for the second time to deliver 160kg of 20 / 80 mesh temporary plugging agent to temporarily plug the seam end and divert to create complex seams. The amount of fracturing fluid used is 35m 3 ; ⑩9mPa·s medium and low viscosity with 18m 3 / min fracturing fluid high displacement and sand fracturing, fracturing fluid dosage is 260m 3 , the proppant is 40 / / 70 mesh quartz sand 25m 3, the sand-liquid ratio is 12% to 18%; 9mPa·s medium-low viscosity fracturing fluid is delivered with variable displacement for the second time, and 15 temporary plugging balls are delivered to divert between clusters to create new seams, realizing batch fracturing. The outer diameter of the temporary plugging balls is 24 to 26mm, and the displacements are 8, 10, 12, 16, and 18m 3 / min, the fracturing fluid dosage is 120m 3 ; Finally, the maximum displacement of 9mPa·s medium-low viscosity fracturing fluid is 23m 3 / min sand fracturing and displacement, fracturing fluid dosage is 350m 3 , the proppant is 70 / / 140 mesh quartz sand 30m 3 , 40 / / 70 mesh quartz sand 35m 3 , the sand-to-liquid ratio is 10% to 22%, and the displacement fluid volume is 80m 3 .

[0133] The adjusted parameters such as liquid strength and sand addition strength are consistent with the previous ones, and finally a construction curve with three obvious pressure steps of 55-60, 60-65, and 65-70 MPa is formed (such as Figure 1 As shown, Figure 1 According to the direction indicated by the arrows, each separated process section is step ①-). The fracture length reaches 240m, the fractures on both sides expand evenly, the fracture height is controlled at 30m, the fracture network sweep width is 72m, the microseismic event points are evenly distributed, the fracture length increases by 32%, the transformation volume increases by 80%, the fracture complexity increases by 50%, and the test output increases by 80% year-on-year compared with the original method. The problems of difficult fracture height control, small transformation volume, high repeated transformation rate and low complexity have been solved, and the expected design goals have been achieved.

[0134] Example 2

[0135] On the basis of the above-mentioned Example 1, the same method was adopted in the whole well B in the same area and layer, and the drainage agent was replaced with an imbibition and permeability enhancing agent. The test production increased by 120% year-on-year, and the production increase effect of the through-layer expansion fracturing was obvious.

[0136] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0137] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0138] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0139] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A method for fracturing a shale oil and gas horizontal well through-layer expansion, characterized in that: The fracturing method comprises a pre-fracturing step and a fracture creation step; The displacement of the fracturing fluid used in the pre-fracturing step is gradually increased, and the displacement increase amplitude is gradually increased; the fracture making step includes 4 levels of enhanced temporary plugging construction steps, and when temporary plugging balls are delivered for temporary plugging construction, variable displacement temporary plugging construction is adopted.

2. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 1, characterized in that: The following steps are involved: Pre-fracturing steps: ① Low-displacement pump to inject acid; ② Low-volume, long-term, high-viscosity fracturing fluid pre-placement; ③ Medium-to-high displacement and high-viscosity fracturing fluid stably expands the horizontal section and penetrates the small layer cracks; ④ Use high-viscosity fracturing fluid with a relatively high displacement to perform fracturing through all target small layers; use medium- and low-viscosity fracturing fluid with a relatively high displacement and sand fracturing; Seam making steps: ⑤ High-viscosity fracturing fluid with a high displacement is used to deliver temporary plugging agent for the first time to temporarily plug the seam end and create complex seams; ⑥ Medium and low viscosity fracturing fluid with high displacement and sand fracturing; ⑦ The medium and low viscosity fracturing fluid is used to change the displacement and deliver temporary plugging balls for the first time to divert between clusters and create new fractures; ⑧ Medium and low viscosity fracturing fluid with high displacement and sand fracturing; ⑨ High-viscosity fracturing fluid with high displacement is used to deliver temporary plugging agent for the second time to temporarily plug the seam end and divert to create complex seams; ⑩ Medium and low viscosity fracturing fluid with high displacement and sand fracturing; The medium-low viscosity fracturing fluid is pumped at a variable displacement for the second time to deliver temporary plugging balls to divert clusters and create new seams, thus achieving batch fracturing. Finally Maximum displacement of medium and low viscosity fracturing fluid with sand fracturing and displacement.

3. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 2, characterized in that: High viscosity fracturing fluid refers to 170s -1 A fracturing fluid having a viscosity greater than 30 mPa·s after 120 min of shearing, preferably a fracturing fluid of 30 to 130 mPa·s; more preferably a fracturing fluid of 40 to 60 mPa·s; and / or, Medium and low viscosity fracturing fluid refers to 170s -1 Fracturing fluid with a viscosity of 6 to 15 mPa·s after 120 min of shearing; The displacement used in the fracturing method is, Low displacement is 2~5m 3 / min; and / or, Medium and high displacement is 6~9m 3 / min; and / or, The highest displacement is 10~16m 3 / min; and / or, High displacement: 18~20m 3 / min; and / or, The maximum displacement is the maximum displacement of the fracturing equipment required by the construction design, preferably 21 to 25 m 3 / min; and / or, The displacement range of variable displacement is limited to 2~25m 3 / min.

4. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 2, characterized in that: In the fracturing method, The temporary plugging balls and temporary plugging agents are independently low-density water-soluble or degradable materials; and / or, Add proppant to sand fracturing construction; Preferably, The density of the temporary plugging ball and the temporary plugging agent is independently (1.0-1.3)×10 3 kg / m 3 and / or, The outer diameter of the temporary plugging ball is 16 to 44 mm; and / or, The specification of the temporary plugging agent is selected from at least one of 8 / 40 mesh, 10 / 40 mesh, 20 / 80 mesh, 20 / 100 mesh and 40 / 140 mesh.

5. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 2, characterized in that: In the fracturing method, In the fracturing process section ①, hydrochloric acid is injected at a low rate; the preferred injection rate of hydrochloric acid is 10-20m 3 and / or, In the fracturing process section ②, the injection volume of fracturing fluid is 40 to 80 m 3 and / or, In the fracturing process section ③, the injection volume of fracturing fluid is 60-100m 3 and / or, In the fracturing process section ④, the injection volume of fracturing fluid is 320~360m 3 The injection volume of the high viscosity fracturing fluid used in the fracturing process section is preferably 130 to 150 m 3 ; In the fracturing process section ⑤, the injection volume of fracturing fluid is 20-30m 3 and / or, In the fracturing process section ⑥, the injection volume of fracturing fluid is 200-240m 3 .

6. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 2, characterized in that: In the fracturing process section ⑦, the injection volume of fracturing fluid is 60-100m 3 and / or, In the fracturing process section ⑧, the injection volume of fracturing fluid is 220~260m 3 and / or, In the fracturing process section ⑨, the injection volume of fracturing fluid is 30-40m 3 and / or, In the fracturing process section ⑩, the injection volume of fracturing fluid is 240~280m 3 and / or, Fracturing process section The injection volume of fracturing fluid is 60-120m 3 and / or, Fracturing process section The injection volume of fracturing fluid is 300-400m 3 .

7. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 2, characterized in that: In the fracturing method, In the fracturing process section ④, the sand-to-liquid ratio in the sand fracturing construction is 3% to 15%; and / or, In the fracturing process stage ⑤, the amount of temporary plugging agent delivered for the first time is 150-200 kg; and / or, In the fracturing process section ⑥, the sand-to-liquid ratio in the sand fracturing construction is 8% to 13%; and / or, In the fracturing process section ⑦, the number of temporary plugging balls delivered for the first time is 30% to 40% of the total number of perforations, preferably 16 to 20. When the displacement is changed, the displacement is continuously increased, and the displacement increase range is 3 to 4 m 3 / min; and / or, In the fracturing process section ⑧, the sand-to-liquid ratio in the sand fracturing construction is 10% to 15%; and / or, In the fracturing process section ⑨, the amount of temporary plugging agent delivered for the second time is 150-200 kg; and / or, In the fracturing process section ⑩, the sand-to-liquid ratio in the sand fracturing construction is 12% to 18%; and / or, Fracturing process section The number of temporary plugging balls delivered for the second time is 30% to 40% of the total number of perforations, preferably 16 to 20. When the displacement is changed, the displacement is continuously increased, and the displacement increase range is 3 to 4 m 3 / min; and / or, Fracturing process section In the sand-added fracturing construction, the sand-to-liquid ratio is 10% to 22%.

8. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 1, characterized in that: The construction parameters in the fracturing method are obtained by: A fracturing numerical model is established by simulating the crack extension of simulated rock samples of a target layer section for fracturing transformation of a simulated horizontal well; and shale oil and gas horizontal well interlayer expansion fracturing is performed after simulating and optimizing the fracturing construction parameters based on the fracturing numerical model.

9. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 8, characterized in that: The construction parameters in the fracturing method are obtained by: (1) Obtaining geological parameters and mechanical parameters of all sub-layers in the target layer section of horizontal well fracturing stimulation; (2) preparing simulated rock samples; (3) performing an indoor fracturing physical simulation experiment on the simulated rock sample to obtain crack propagation parameters; (4) numerically simulating the fracturing process of the indoor fracturing physical simulation experiment and establishing a centimeter-scale fracturing numerical model; (5) Enlarging the centimeter-scale fracturing numerical model to the actual scale of the mine field to form a fracturing numerical model consistent with the key parameters of the fracturing transformation formation area; (6) simulating and optimizing the fracturing construction parameters based on the fracturing numerical model of step (5); (7) Perform fracturing construction based on optimized fracturing construction parameters.

10. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 9, characterized in that: In step (1), the geological parameters and mechanical parameters obtained include parameters of the target horizontal well's traversal horizon, lithology, thickness, mineral composition, rock mechanical parameters, geostress, fracture development, and interface strength of each sub-layer and top and bottom plates; and / or, In step (2), the simulated rock sample is a simulated rock sample that is triple similar to the real shale reservoir in terms of lithology, mineral composition and rock mechanical properties; preferably, the size of the simulated rock sample is 300mm×300mm×300mm or 300mm×300mm×600mm; and / or, In step (3), a true triaxial fracture extension simulation is performed on the simulated rock sample using a layered in-situ stress loading system to obtain the dynamic fracture extension morphology under different fracturing fluid viscosities and displacement combinations; wherein the pressure of a single-layer pressurization test in the layered in-situ stress loading system is above 50 MPa, and the maximum interlayer stress difference is above 15 MPa.

11. The method for shale oil and gas horizontal well cross-layer expansion fracturing according to claim 9, characterized in that: In step (4), based on synthetic geotechnical technology and a three-dimensional discrete grid algorithm, a full three-dimensional stress-pressure coupling numerical simulation of the initiation and propagation process of the rock sample fracturing crack simulated in step (3) is achieved; preferably, the mechanical parameters used in the centimeter-scale fracturing numerical model include fracture toughness, elastic modulus, geostress, shear strength and tensile strength; and / or, In step (5), based on step (4), the centimeter-scale fracturing numerical model is enlarged to the actual scale of the mine field to form a fracturing numerical model consistent with the key parameters of the target reservoir lithology combination, mechanical properties, interface properties, fracture properties and stress state; and / or, In step (6), the model established in step (5) is used to simulate and optimize different combinations of fracturing fluid viscosity and displacement construction parameters.

12. Use of the method for cross-layer expansion fracturing of shale oil and gas horizontal wells according to any one of claims 1 to 11 in shale oil and gas production.

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