A fine powder material and a construction method for microcrack support

Abstract

The present invention provides a micro-powder material and a micro-crack support construction method. The raw materials of the micro-powder material include aluminum oxide powder, bauxite, silicon micro-powder, calcium oxide micro-powder, magnesium oxide powder, and manganese ore powder in a mass ratio of 60-75:25-35:10-20:30-50:15-25:2-10. The construction method is carried out using the above-mentioned micro-powder material; the construction method includes support construction for micro-cracks with a size of less than 200μm. The micro-powder material provided by the present invention can effectively enter the micro-crack channel and provide efficient support, which can solve the problem of multi-scale complex fracture networks formed by the current unconventional reservoir fracturing. The existing proppant cannot enter the small and micro-scale fractures due to its large particle size, resulting in the micro-cracks being unable to be effectively supported and closing quickly after fracturing.

Description

Technical Field

[0001] The invention relates to a micro-powder material and a micro-crack support construction method, and belongs to the field of petroleum engineering rock mechanics. Background Art

[0002] Hydraulic fracturing has become an effective means of achieving economic development in unconventional oil and gas reservoirs. Its core principle is to continuously pump proppant-laden fracturing fluid into the reservoir, forcing the formation of effectively supported hydraulic fractures / fracture networks, thereby creating long-term oil and gas migration pathways and increasing oil and gas production. Therefore, how to effectively support hydraulic fractures is crucial to ensuring efficient reservoir development.

[0003] By implementing large-scale hydraulic fracturing operations, a complex multi-scale fracture network system can be formed in the reservoir, which can be mainly divided into primary fractures and secondary microfractures. Compared with artificial primary fractures, secondary microfractures are characterized by large number, small fracture width, and complex orientation. Their size is much smaller than that of primary fractures. Most microfractures are less than 200μm in size, of which about two-thirds are less than 100μm. As a result, conventional proppants (mesh size less than 140) are difficult to enter the microfractures, and the microfractures cannot be effectively filled. After production is put into operation, the closure of microfractures leads to a rapid decrease in production. Therefore, how to improve the support efficiency of microfractures is the key to further improving the production capacity of unconventional reservoirs.

[0004] Currently, the minimum mainstream proppant sizes attempted to be pumped into major shale oil and gas fields during fracturing are 100 mesh (particle size 149μm) and 140 mesh (particle size 102μm). Quartz sand is the primary proppant type, and while this has achieved some success, due to its low strength, it is not suitable for deep, highly closed stress reservoirs. Furthermore, it cannot effectively support microcracks smaller than 100μm. Therefore, a high-strength, fine proppant that can penetrate smaller microcracks is urgently needed. Furthermore, employing appropriate construction methods to maximize the migration of fine proppants into microcracks is a key issue that needs to be addressed. Currently, the conventional construction method of "creating the main fracture with high-viscosity fracturing fluid and continuously pumping or slugging quartz sand and ceramsite at high flow rates" can only effectively fill the main fractures, but cannot effectively transport the fine proppant into the microcracks, resulting in insufficient complexity in the fracture network required for effective support. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a micro-powder material and a micro-crack support construction method. The micro-powder material can effectively enter the micro-crack channel and provide efficient support. While increasing the complexity of hydraulic fractures, it can effectively fill multi-scale micro-cracks, so that the reservoir fracture network system can be connected as a whole, truly achieving volume fracturing transformation of the reservoir and greatly improving the single-well production capacity of the reservoir.

[0006] To achieve the above purpose, the present invention first provides a micropowder material, whose raw materials include aluminum oxide powder, bauxite, silicon powder, calcium oxide powder, magnesium oxide powder and manganese ore powder in a mass ratio of 60-75:25-35:10-20:30-50:15-25:2-10.

[0007] According to a specific embodiment of the present invention, preferably, the micropowder material is prepared by the following steps:

[0008] mixing and grinding the raw materials to obtain a mixed powder;

[0009] Granulating the mixed powder to obtain semi-finished pellets;

[0010] The semi-finished pellets are sintered at 1600-1800° C., and the sintering time is preferably 10-15 hours to obtain a finished product, namely the micropowder material.

[0011] According to a specific embodiment of the present invention, preferably, the particle size distribution of the mixed powder satisfies the following condition: the proportion of powder with a particle size of 1500-2000 mesh is ≥95%.

[0012] According to a specific embodiment of the present invention, preferably, the pellet semi-finished product meets the following requirements: the strength is greater than 2 MPa.

[0013] According to a specific embodiment of the present invention, preferably, the semi-finished pellet product meets the following requirements: the sphericity is above 0.9.

[0014] According to a specific embodiment of the present invention, preferably, the semi-finished pellet product meets the following requirements: the particle size is between 20-100 μm.

[0015] According to a specific embodiment of the present invention, preferably, the binder used in the granulation process is polyvinyl chloride, and the addition amount is 3-5% of the mass of the mixed powder.

[0016] According to a specific embodiment of the present invention, preferably, after obtaining the finished product, it is washed with water until the pH value is 8-10, that is, the pH value of the water after washing reaches 8-10.

[0017] According to a specific embodiment of the present invention, preferably, the compressive strength of the micropowder material is ≥100 MPa (the crushing rate is less than 5% at 100 MPa).

[0018] According to a specific embodiment of the present invention, preferably, the true density of the micropowder material is 2.7-3.0 g / cm 3 .

[0019] According to a specific embodiment of the present invention, preferably, the bulk density of the micropowder material is ≤1.4 g / cm 3More preferably 1.21-1.40g / cm 3 The bulk density of the micropowder material is within the above range, which can ensure uniform migration in clear water and slippery water without generating sand settling.

[0020] According to a specific embodiment of the present invention, preferably, the moisture content of the micropowder material is ≤0.5%.

[0021] According to a specific embodiment of the present invention, preferably, in the micropowder material, the proportion of micropowder with a particle size of 200-800 mesh is ≥98%.

[0022] The micropowder material of the present invention is synthesized from high-strength special materials, has a particle size distribution range of 200-800 meshes, has good suspension performance and high compressive strength, can smoothly enter fine cracks of 20-100 μm in size and provide effective support.

[0023] The micropowder material provided by the present invention can effectively penetrate microfracture channels and provide efficient support. This can address the complex multi-scale fracture networks formed by hydraulic fracturing in unconventional reservoirs. Existing proppants, due to their large particle size, are unable to penetrate small, micro-scale fractures, resulting in a lack of effective support and rapid closure of microfractures after fracturing. The micropowder material provided by the present invention can improve the support efficiency of microfractures and construct long-lasting, highly conductive channels after fracturing in oil and gas wells.

[0024] The present invention also provides a micro-crack support construction method, wherein the construction method is carried out using the above-mentioned micro-powder material.

[0025] According to a specific embodiment of the present invention, preferably, the construction method includes supporting construction of micro cracks with a size of less than 200 μm; more preferably, the size of the micro cracks is 20-100 μm.

[0026] According to a specific embodiment of the present invention, preferably, the construction method comprises the following steps:

[0027] (1) Define the fracturing stage and construction parameters, and perform bridge plug placement and perforation operations;

[0028] (2) Use supercritical carbon dioxide as the pre-fluid for construction;

[0029] (3) Use slick water for large-volume, high-density injection of micro-powder materials;

[0030] (4) Medium viscosity fracturing fluid injection construction;

[0031] (5) Alternately pumping proppant and micropowder material at high displacement;

[0032] (6) Medium viscosity fracturing fluid injection construction;

[0033] (7) Performing temporary plugging operations, wherein the temporary plugging agent and the micropowder material are injected simultaneously;

[0034] (8) Repeat steps (5) to (6) until the requirements are met;

[0035] (9) Carry out replacement operations;

[0036] (10) Complete the construction of the current fracturing section and start the construction of subsequent fracturing sections.

[0037] The construction method provided by the present invention breaks the traditional construction method of using high-viscosity pre-fluid to create main fractures and then carrying sand in large quantities. First, supercritical carbon dioxide is used as the pre-fluid for fracturing, and then slick water is used to inject micropowder at a high density. Then, medium-viscosity fracturing fluid is used to displace all the micropowder in the wellbore into the formation; in the next step, conventional particle size proppant and micropowder are alternately pumped in large quantities. Multiple micropowder-temporary plugging agent composite temporary plugging operations can be carried out in the middle to achieve temporary plugging and induction of microcracks and real-time filling, thereby achieving the effect of improving the full filling of microcracks and enabling the micropowder material to fully enter the microcracks for effective support.

[0038] According to a specific embodiment of the present invention, preferably, step (1) includes the following specific contents: for the target fracturing section, combined with the data of adjacent wells, with the optimal production capacity as the goal, and taking into account the wellbore safety, perforation and fracturing parameter optimization simulation are carried out to obtain the optimal perforation parameters, as well as fracturing parameters such as sand addition amount and injection amount.

[0039] According to a specific embodiment of the present invention, preferably, in step (2), the injection rate of supercritical carbon dioxide is 2-4m 3 The amount of supercritical carbon dioxide used can be controlled according to actual needs, for example, 150-200t.

[0040] According to a specific embodiment of the present invention, preferably, in step (3), the displacement of the large-volume high-density injection of micro-powder material is increased in a step-by-step manner to 16-20m within 2-3min. 3 / min, after reaching the target value, start injecting the micro powder material; wherein, the particle size of the micro powder material is 200-800 mesh, and the total injection volume of the micro powder material can be controlled according to actual needs, for example, 200-300m 3 The injection concentration of the micro powder material can be 200-240 kg / m 3 , measured by volume of slickwater.

[0041] According to a specific embodiment of the present invention, preferably, based on the prepad X, the fracture creation efficiency of the prepad is Y (about 25%-50%), and the transformation volume can be calculated as SRV=X·Y; considering the effective connectivity rate between the cracks is a (5%-20%), the effective transformation volume ESRV=SRV·a=X·Y·a can be calculated; based on the distributed filling (point support) of the micro-powder material in the micro-cracks, the volume proportion of the filled cracks is b (15%-30%), and the amount of micro-powder used in this stage is calculated as ESRV·b=X·Y·a·b, that is, the amount of the micro-powder material is calculated according to the following formula:

[0042] Amount of micro powder material = X·Y·a·b

[0043] Where X is the amount of pre-fluid, in m 3 ; Y is the crack-forming efficiency of the pre-fluid; a is the effective connectivity between cracks; b is the volume ratio of the filled cracks.

[0044] According to a specific embodiment of the present invention, preferably, in step (4), the viscosity of the medium-viscosity fracturing fluid is 30-60 mPa·s. The displacement of step (4) is the same as that of the previous step, and the injection volume is controlled to be 1-1.2 times the wellbore volume, in order to completely displace the fine powder material inside the wellbore into the formation.

[0045] According to a specific embodiment of the present invention, preferably, in step (5), the proppant and the micropowder material are respectively pumped with a low-viscosity fracturing fluid, and the low-viscosity fracturing fluid is a slick water fracturing fluid with a viscosity of 3-30 mPa·s, a drag reduction rate of ≥70%, and a salt tolerance of ≥20×10 4 mg / L. In this step, the displacement size is the same as in the previous step.

[0046] According to a specific embodiment of the present invention, preferably, in step (5), the proppant is 70-140 mesh quartz sand and / or 40-70 mesh ceramsite.

[0047] According to a specific embodiment of the present invention, preferably, in step (5), the proppant and the micropowder material are injected alternately, and one pumping of the proppant and the micropowder material is regarded as an injection cycle; within one cycle, the amount of the injection liquid containing the proppant is 2-3 times the volume of the wellbore, and the amount of the injection liquid containing the micropowder material is 0.5-1 times the volume of the wellbore.

[0048] According to a specific embodiment of the present invention, preferably, in step (5), the injection concentration of the proppant and the micropowder material is gradually increased for different injection cycles, and the injection concentration of the proppant is increased from 80 kg / m 3 Gradually increase to the target sand concentration of 160-180kg / m 3In the same cycle, the injection concentration of micro powder material is 20-40 kg / m lower than that of proppant. 3 , after the sand concentration is increased to the target, maintain the highest sand concentration for injection.

[0049] According to a specific embodiment of the present invention, before implementing the temporary plugging operation, it is necessary to completely displace the proppant and fine powder in the wellbore into the formation to reduce the risk of sand plugging. Preferably, in step (6), the viscosity of the medium-viscosity fracturing fluid is 30-60 mPa·s, and the injection volume is 1-1.2 times the wellbore volume. The displacement of this step is the same as that of the previous step.

[0050] According to a specific embodiment of the present invention, preferably, in step (7), in order to increase the complexity of the fracture network, a temporary plugging operation can be implemented to induce the fracture to turn and form more complex fractures. When performing the temporary plugging operation, micropowder and temporary plugging agent are added at the same time. This is because the particle size of the micropowder is small and will not induce sand plugging. Compared with step (3), the particle size of the micropowder in this step is smaller because the temporary plugging agent and micropowder are added at the same time, which will increase the construction pressure. Selecting micropowder with a smaller particle size can allow the micropowder to quickly enter the opened microcracks, thereby avoiding excessive increase in construction. Preferably, the particle size of the micropowder material is 600-1500 mesh. The amount of the micropowder material is preferably controlled to be 10%-20% of the amount of the temporary plugging agent. This method is different from the traditional fracturing method. The traditional fracturing method is to first add a temporary plugging agent for temporary plugging operation and then add a proppant operation. This practice is because the conventional proppant particle size is larger and is easily induced by the risk of sand plugging when added at the same time as the temporary plugging agent. The temporary plugging agent used in this step can be a conventional temporary plugging agent in the field.

[0051] According to a specific embodiment of the present invention, preferably, in step (8), according to design and construction requirements, step (7) can be repeated to implement temporary plugging multiple times to further increase the complexity of the fracture network and improve the fracturing effect.

[0052] According to a specific embodiment of the present invention, in step (9), after the construction of steps (2) to (8), the fracturing requirements of the injection fluid and sand volume are completed, and a displacement operation is performed; preferably, the displacement operation is first performed using a medium-viscosity fracturing fluid with a viscosity of 30-60 mPa·s, and the injection volume is 1.2-1.5 times the volume of the wellbore, the purpose of which is to displace all the proppant or micropowder in the wellbore into the formation to prevent the proppant from settling in the wellbore and clogging the blasthole; then, an appropriate amount of dilute hydrochloric acid is injected (the concentration of the dilute hydrochloric acid can be selected as needed, for example, about 10%), the purpose of which is to promote the rapid degradation of the bridge plug and prepare for the later gas production; finally, after the dilute hydrochloric acid is pumped, the dilute hydrochloric acid is displaced to the bottom of the wellbore using slick water to allow it to contact the bridge plug.

[0053] The construction method of the present invention can promote the formation of complex cracks and achieve the purpose of forming a large number of micro cracks to effectively support the structure. The reasons are:

[0054] First, using supercritical carbon dioxide as a fracturing fluid can take advantage of its low viscosity, good diffusivity, and good permeability. Compared with water-based fracturing fluids, it can more easily enter fine fractures, promote the opening of more fine fractures, and increase the complexity of near-wellbore fractures.

[0055] Secondly, for the complex fractures formed near the wellbore by supercritical carbon dioxide, slick water is used to inject micropowder at a high density and large flow rate. The micropowder material with small particle size can smoothly enter the fine fractures, and high-density injection will not cause pressure buildup or signs of rapid pressure rise similar to sand plugging. This not only achieves the purpose of fully filling the microfractures, but also effectively blocks small micro-scale fractures with micropowder. As a result, the main fractures can be fully extended in length under the action of large flow rate, facilitating smooth sand addition in the subsequent stage.

[0056] Third, by alternately injecting conventional particle proppant and micro-powder material, conventional proppant can support the main fracture and micro-powder material can support the micro-fracture in a timely manner. At the same time, this alternating injection method can achieve discontinuous filling support for the main fracture and increase the conductivity of the main fracture.

[0057] Fourthly, the use of temporary plugging and diversion in the middle combined with the injection of micro-powder materials can effectively fill a large number of micro-cracks activated by crack diversion.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) Micro-powder materials, with their small size, high strength, and low density, can smoothly enter micro-cracks such as bedding and effectively support them, thus achieving three-dimensional support for multi-level cracks, establishing a three-dimensional fully supported high-conductivity complex fracture network, and improving the fracturing effect.

[0060] (2) Supercritical carbon dioxide is used as a pre-fluid to open micro-cracks to form complex cracks, and then micro-powder materials are used for effective filling and support, thereby increasing the area of high conductivity areas near the wellbore, which is beneficial to the subsequent flow of oil and gas and increases the single well recovery rate.

[0061] (3) By alternately injecting conventional proppants and micro-powder materials, the micro-cracks activated during the fracturing process can be supported in a timely manner, effectively improving the stable production effect of fracturing.

[0062] (4) By using temporary plugging agents and micropowder materials simultaneously to implement temporary plugging operations, timely and effective support for the microcracks formed by temporary plugging can be achieved, and the complexity of the effective supported crack network can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 Schematic diagram of the construction method under a temporary blocking condition.

[0064] Figure 2 Schematic diagram of fracture morphology at different fracturing stages.

[0065] Figure 3 Schematic diagram of micro-powder material entering micro-cracks.

[0066] Description of Figure Numbers:

[0067] 1. Supercritical carbon dioxide action stage; 2. High-density micropowder injection stage; 3. First medium-viscosity fracturing fluid displacement stage; 4. Conventional proppant and micropowder alternating injection stage; 5. Second medium-viscosity fracturing fluid displacement stage; 6. Temporary plugging agent and micropowder injection stage; 7. Conventional proppant and micropowder alternating injection stage after temporary plugging; 8. Third medium-viscosity fracturing fluid displacement stage; 9. Displacement curve; 10. Micropowder injection concentration; 11. Conventional proppant injection concentration; 12. Conventional proppant injection time within one cycle; 13. Micropowder injection time within one cycle; 14. Auxiliary line; 15. Wellbore; 16. Microcracks; 17. Primary secondary cracks; 18. Main cracks; 19. Secondary secondary cracks. DETAILED DESCRIPTION

[0068] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0069] Example 1

[0070] This embodiment provides a micropowder material, the raw materials of which include aluminum oxide powder, bauxite, silicon powder, calcium oxide powder, magnesium oxide powder, and manganese ore powder in a mass ratio of 62:26:11:42:17:3.

[0071] The micro powder material is prepared by the following steps:

[0072] The raw materials are mixed and ground to obtain a mixed powder, wherein the particle size distribution of the mixed powder meets the following conditions: the proportion of powder with a size of 1500-2000 mesh is ≥95%;

[0073] Granulating the mixed powder to obtain a semi-finished pellet product, which meets the following requirements: strength greater than 2 MPa, sphericity greater than 0.9, and particle size between 20-100 μm;

[0074] The semi-finished pellets are sintered at 1600-1800° C. for 14 hours to obtain the finished product, and then washed with water until the pH value is 8-10.

[0075] The compressive strength of the micropowder material prepared in this embodiment is ≥100 MPa and the true density is 2.8 g / cm 3 , the volume density is 1.3g / cm 3 , the moisture content is 0.3%, and the proportion of 200-800 mesh micropowder materials is 98%.

[0076] Example 2

[0077] This embodiment provides a construction method under temporary blocking conditions. The construction method is carried out using the micropowder material of Example 1. The process is as follows: Figure 1 shown.

[0078] The construction method includes:

[0079] (1) Define the fracturing section and construction parameters, and perform bridge plugging and perforation operations. Specifically, through fracturing parameter optimization, the optimal production parameters are obtained as follows: the fracturing section length is 60m, the number of perforation clusters is 6 clusters, the number of perforations is 48 holes, and the amount of sand added is 1800t;

[0080] (2) Supercritical carbon dioxide action stage 1: supercritical carbon dioxide is used as the pre-fluid for construction, wherein the injection rate of supercritical carbon dioxide is 2-4m 3 / min, injection volume is 180t;

[0081] (3) High-density micro-powder injection stage 2: Use slippery water to inject micro-powder materials in a large-volume and high-density manner, specifically including: Use slippery water to inject micro-powder materials in a large-volume and high-density manner, and increase the displacement to 18m in 2 minutes in a step-by-step manner. 3 / min, after reaching the target value, start injecting micro powder. The particle size of the micro powder material used in this step is 200-800 mesh, and the injection concentration of the micro powder is 220kg / m 3 The total injection volume is 300m 3 ;

[0082] (4) First medium-viscosity fracturing fluid displacement stage 3: medium-viscosity fracturing fluid injection construction, the viscosity of the medium-viscosity fracturing fluid is 60 mPa·s; the displacement of this step is the same as the displacement of the previous step, and the injection volume is controlled to be 1.2 times the wellbore volume;

[0083] (5) Alternating injection of conventional proppant and micropowder Stage 4: Low-viscosity fracturing fluid is used to alternately pump proppant and micropowder material at a large displacement. The proppant is 70-140 mesh quartz sand, and the particle size of the micropowder material is 200-800 mesh. The purpose is to achieve the support of the main fracture by the conventional proppant and the timely support of the microcrack by the micropowder material. At the same time, this alternating injection method can achieve discontinuous filling support for the main fracture and increase the conductivity of the main fracture. The low-viscosity fracturing fluid uses slick water fracturing fluid with a viscosity of 3 mPa·s, a drag reduction rate of 72%, and a salt tolerance of 20×10 4 mg / L; in this step, the displacement size is the same as the previous step; proppant and micro powder material are injected alternately, and completing one pump injection of proppant and micro powder material is considered as an injection cycle; in one cycle, the injection volume of proppant-containing injection liquid is 2 times the wellbore volume, and the injection volume of micro powder material is 0.5 times the wellbore volume; for different injection cycles, the injection concentration of proppant and micro powder material is gradually increased, and the injection concentration of proppant is 80kg / m 3 Gradually increase to the target sand concentration of 180kg / m 3 In the same cycle, the injection concentration of micro powder material is 20 kg / m lower than that of proppant. 3 , after the sand concentration is increased to the target, maintain the highest sand concentration for injection;

[0084] (6) Second medium-viscosity fracturing fluid displacement stage 5: medium-viscosity fracturing fluid injection construction, the viscosity of the medium-viscosity fracturing fluid is 30mPa·s. The displacement of this step is the same as the displacement of the previous step, and the injection volume is controlled to be 1.2 times the wellbore volume;

[0085] (7) Temporary plugging agent and micropowder injection stage 6: temporary plugging operation is performed, wherein the temporary plugging agent and micropowder material are injected simultaneously, wherein the particle size of the micropowder material is 600-800 mesh, and the amount of the micropowder material is controlled to be 10% of the amount of the temporary plugging agent; the temporary plugging agent is a powder temporary plugging agent;

[0086] (8) After temporary plugging, conventional proppant and micro powder are alternately injected in stage 7, i.e., steps (5) to (6) are repeated until the requirements are met;

[0087] (9) The third medium-viscosity fracturing fluid displacement stage 8: After completing the fracturing requirements of the injected fluid volume and sand volume, the displacement operation is carried out; wherein, the displacement operation is first carried out using a medium-viscosity fracturing fluid with a viscosity of 60 mPa·s, and the injection volume is 1.5 times the wellbore volume; then an appropriate amount of dilute hydrochloric acid with a concentration of 10% is injected to promote the rapid degradation of the bridge plug and prepare for the later gas production; finally, after the dilute hydrochloric acid is pumped, the dilute hydrochloric acid is displaced to the bottom of the wellbore with slick water to allow it to contact the bridge plug.

[0088] (10) Complete the construction of the current fracturing section and start the construction of subsequent fracturing sections.

[0089] In the above construction process, the process parameters of each step are shown as the displacement curve 9, the fine powder injection concentration 10, the conventional proppant injection concentration 11, the conventional proppant injection time within a cycle 12, the fine powder injection time within a cycle 13 and the auxiliary line 14.

[0090] Figure 2 Schematic diagram of fracture morphology at different fracturing stages.

[0091] Depend on Figure 2 As can be seen in (a), in the first stage, supercritical carbon dioxide forms complex microfractures 16 near the wellbore 15;

[0092] Depend on Figure 2 As can be seen from (b) in the figure: in the second stage, proppant and micro powder are injected alternately to create main cracks 18 and a certain degree of micro cracks (first-level secondary cracks 17), and form effective support; the schematic diagram of micro powder material entering micro cracks is shown in Figure 3 As shown;

[0093] Depend on Figure 2 As can be seen from (c) in the figure: in the third stage, temporary blocking occurs in the middle, forming secondary cracks 19 and micro cracks 16, thereby forming a more complex crack network and forming effective support.

[0094] Before and after the construction of this embodiment, among the four wells on a certain platform in a shale gas field, under the same geological conditions, three wells did not use micropowder materials, and had an average daily gas production of 150,000 cubic meters three months after fracturing and production. One well used the method of Example 2 of the present invention, and had a daily gas production of 220,000 cubic meters three months after fracturing and production, an increase of 46.7%.

Claims

1. A micro-crack support construction method, wherein: The raw materials of the micropowder material used in this construction method include alumina powder, bauxite, silicon powder, calcium oxide powder, magnesium oxide powder, and manganese ore powder in a mass ratio of 60-75:25-35:10-20:30-50:15-25:2-10; among the micropowder materials, the proportion of 200-800 mesh micropowder is ≥98%, and the bulk density is 1.21-1.40 g / cm 3 ; The construction method includes support construction of micro cracks with a size of 20-100 μm; The construction method comprises: (1) Define the fracturing stage and construction parameters, and perform bridge plug placement and perforation operations; (2) Use supercritical carbon dioxide as the pre-fluid for construction; the injection rate of supercritical carbon dioxide is 2-4m 3 / min; (3) Use slick water for large-volume, high-density injection of micro-powder materials; the displacement of the large-volume, high-density injection of micro-powder materials is increased in a step-by-step manner to 16-20m within 2-3 minutes. 3 / min, after reaching the target value, start injecting the micro powder material; (4) Medium viscosity fracturing fluid injection construction; (5) Alternately pumping proppant and micropowder material at high displacement; (6) Medium viscosity fracturing fluid injection construction; (7) performing a temporary plugging operation, wherein the temporary plugging agent and the micropowder material are injected simultaneously; wherein the particle size of the micropowder material is 600-1500 mesh; (8) Repeat steps (5) to (6) until the requirements are met; (9) performing a displacement operation; the displacement operation is first performed using a medium-viscosity fracturing fluid with a viscosity of 30-60 mPa·s, with an injection volume of 1.2-1.5 times the wellbore volume, followed by injection of dilute hydrochloric acid, and finally using slick water to displace the dilute hydrochloric acid to the bottom of the wellbore; (10) Complete the construction of the current fracturing section and start the construction of subsequent fracturing sections.

2. The construction method according to claim 1, wherein: In step (3), the injection concentration of the micro powder material is 200-240 kg / m 3 , measured by volume of slickwater.

3. The construction method according to claim 2, wherein: The amount of the micropowder material is calculated according to the following formula: Amount of micro powder material = X·Y·a·b Where X is the amount of pre-fluid, in m 3 ; Y is the gap-making efficiency of the prepad fluid; a is the effective connectivity rate between cracks; b is the volume ratio of the filled cracks.

4. The construction method according to claim 1, wherein: In step (4), the viscosity of the medium-viscosity fracturing fluid is 30-60 mPa·s, and the injection amount is 1-1.2 times the wellbore volume.

5. The construction method according to claim 1, wherein: In step (5), the proppant and the powder material are respectively pumped with a low-viscosity fracturing fluid, wherein the low-viscosity fracturing fluid is a slick water fracturing fluid with a viscosity of 3-30 mPa·s, a drag reduction rate of ≥70%, and a salt tolerance of ≥20×10 4 mg / L.

6. The construction method according to claim 5, wherein: The proppant is 70-140 mesh quartz sand and / or 40-70 mesh ceramsite.

7. The construction method according to claim 5, wherein: The proppant and the micropowder material are injected alternately, and one pumping of the proppant and the micropowder material is regarded as an injection cycle; in one cycle, the injection liquid containing the proppant is 2-3 times of the wellbore volume, and the injection liquid containing the micropowder material is 0.5-1 times of the wellbore volume.

8. The construction method according to claim 5, wherein: For different injection cycles, the injection concentration of the proppant and micro powder material is gradually increased. The injection concentration of the proppant is increased from 80kg / m 3 Gradually increase to the target sand concentration of 160-180kg / m 3 In the same cycle, the injection concentration of micro powder material is 20-40 kg / m lower than that of proppant. 3 , after the sand concentration is increased to the target, maintain the highest sand concentration for injection.

9. The construction method according to claim 1, wherein: In step (6), the viscosity of the medium-viscosity fracturing fluid is 30-60 mPa·s, and the injection amount is 1-1.2 times the wellbore volume.

10. The construction method according to claim 1, wherein: The amount of the micropowder material is 10%-20% of the amount of the temporary blocking agent.

11. The construction method according to claim 1, wherein: The micro powder material is prepared by the following steps: mixing and grinding the raw materials to obtain a mixed powder; Granulating the mixed powder to obtain semi-finished pellets; The semi-finished pellets are sintered at 1600-1800° C. to obtain the finished product, namely the micropowder material.

12. The construction method according to claim 11, wherein: The sintering time is 10-15 hours.

13. The construction method according to claim 11, wherein: The particle size distribution of the mixed powder satisfies the following condition: the proportion of powder with a particle size of 1500-2000 mesh is ≥95%.

14. The construction method according to claim 11, wherein: The semi-finished pellets meet the following requirements: strength greater than 2 MPa, sphericity greater than 0.9, and particle size between 20-100 μm.

15. The construction method according to claim 11, wherein: After obtaining the finished product, it is washed with water until the pH is 8-10.

16. The construction method according to claim 1, wherein: The compressive strength of the micropowder material is ≥100MPa and the true density is 2.7-3.0g / cm 3 , moisture content ≤0.5%.

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