Preparation method and application of self-adaptive tail-chasing shell proppant for sand control of oil and gas well fracturing

Abstract

An adaptive tail-following nutshell proppant and its application in fracturing and sand control artificial wellbore are disclosed. The proppant uses nutshell particles as the matrix with an average particle size of 1-2.5 mm. By adjusting the nutshell particle size, optimizing the structural design, and enhancing the friction coefficient and strength, the proppant can adapt to the stress conditions at the fracture opening of different reservoir types. Compared with traditional tail-following proppants, the average particle size of the proppant in this invention is increased by more than 100%, the fracture breakage rate is reduced by 300%, and the sand barrier rate is less than 0.35%. This achieves a significant improvement in fracture opening sand control performance and oil production, with a single-well oil production increase of up to 10 tons, a single-well oil production increase rate of 86%, and an oil production efficiency of 100%. It effectively reduces near-wellbore blockage and sand production, and is suitable for fracturing and sand control operations in different reservoir types, including loose and tight reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to an adaptive tail-chasing shell proppant for fracturing and sand control in oil and gas wells, its preparation method, and its application. It is particularly suitable for fracturing and sand control in different types of reservoirs (loose sandstone, tight sandstone, etc.) and for the construction of artificial wellbore. Background Technology

[0002] In oil extraction, sand production in oil and gas wells is a significant issue affecting well output. Sand production can lead to decreased well production, damage to production equipment, burying of oil-bearing formations, and even formation depletion and collapse. It can also cause casing stress instability, resulting in casing deformation and breakage, and in severe cases, the well may become unusable. Hydraulic fracturing is an essential technique for developing unconventional oil and gas resources. However, as the scale of fracturing and proppant injection increases, the problem of proppant backflow becomes increasingly prominent. Proppant backflow often leads to reduced fracture conductivity or even fracture failure, erosion of surface pipelines, increased costs for well washing and sand flushing, and frequent pump inspections.

[0003] Currently, to address the issues of proppant backflow and sand control in fracturing, technicians have primarily adopted the following technical solutions: (a) Tail-following fiber method. Fibers with a certain degree of flexibility are mixed into the proppant-carrying fluid and simultaneously injected into the formation. The fibers and proppant particles interact through contact pressure and friction to form a spatial network structure, enhancing the cohesion of the proppant. However, this method is difficult to form a stable network structure in depleted areas without closure pressure or in wide fracture areas, resulting in poor prevention of proppant backflow.

[0004] (ii) Resin-coated proppant method. During the later stages of fracturing and sand filling, a curable resin-coated proppant is added as a tail filler, allowing the proppant to solidify and form a moderately strong, permeable artificial wellbore. However, this method requires a long shut-in time, high formation temperature, and high closure pressure to ensure good consolidation strength, limiting its application range and posing a construction risk of wellbore consolidation.

[0005] (iii) Surface-modified proppant method. An adhesive, non-hardened shell is formed on the surface of the proppant to increase the internal friction between particles. However, this method requires additional on-site spraying equipment, increasing operating costs, and is prone to agglomeration and clumping during construction, posing a risk of sand blockage.

[0006] (iv) Resin-based sand-fixing agent injection method. After fracturing and sand filling are completed, a resin-based sand-fixing agent is injected to bond and solidify the proppant in the near-wellbore formation. However, this method severely damages the conductivity of the proppant-filled layer.

[0007] Furthermore, existing proppants mainly use inorganic materials such as quartz sand and ceramsite, which have a high density. When used, they must be used in conjunction with gelling agents such as guar gum, which can damage the formation and is costly. While nutshell-based granules have advantages such as low density and easy sand carrying, traditional nutshell proppants suffer from problems such as a narrow particle size range, insufficient strength, and weak interlocking ability, making them unable to effectively solve the fracturing and sand control problems of different reservoir types, such as loose and dense formations, under different fracture stress conditions.

[0008] In summary, existing technologies still suffer from problems such as poor proppant backflow control, inability to adapt to different reservoir types, complex construction, and severe damage to conductivity. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, the purpose of this invention is to provide an adaptive tail-chasing nutshell proppant and its application in artificial wellbore for sand control in fracturing. By adjusting the nutshell particle size, optimizing the structural design, and enhancing the friction coefficient and strength, the proppant can adapt to the stress conditions at the fracture openings of different types of reservoirs, achieving efficient sand control at the fracture openings, reducing near-wellbore blockage and sand production, and significantly improving oil production.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An adaptive tail-chasing nut shell proppant for sand control in oil and gas well fracturing is characterized in that the proppant uses nut shell particles as the matrix, with an average particle size of 1-2.5 mm. The particle surface is structured to enhance the friction coefficient and interlocking ability. The fracture breakage rate is reduced by 300% compared with traditional proppants, and the sand barrier rate is less than 0.35%.

[0011] The shells are selected from one or more of the following: walnut shells, apricot kernels, peach kernels, macadamia nut shells, hickory shells, and jujube kernels.

[0012] The particle size distribution of the nutshell particles is controlled by grading and sieving to form a graded structure.

[0013] A method for preparing an adaptive tail-chasing shell proppant for sand control in oil and gas well fracturing, characterized by comprising the following steps: (1) The fruit shell raw material is washed, dried and crushed to obtain coarse fruit shell particles; (2) Pass the coarse nutshell particles through multi-stage sieving to obtain nutshell particles with an average particle size of 1-2.5 mm; (3) Surface structuring treatment is performed on the sieved fruit shell particles to enhance the surface roughness and friction coefficient of the particles; (4) Impregnate the surface-treated nutshell particles in reinforcing material to improve the compressive strength of the particles; (5) The enhanced shell particles are dried and solidified to obtain an adaptive tail-chasing shell proppant.

[0014] The surface structuring treatment in step (3) includes one or more combinations of mechanical polishing, chemical etching, or coating treatment.

[0015] The reinforcing material in step (4) includes thermosetting resin, thermoplastic resin, or a combination thereof.

[0016] As described above, in the later stage of fracturing and sand addition, the adaptive tail-following shell proppant is injected into the fracture seal along with the sand liquid. The proppant fills and accumulates at the fracture seal to form an artificial well wall, thereby achieving sand control and increased production.

[0017] The target reservoirs include loose sandstone reservoirs, tight sandstone reservoirs, medium-to-high permeability reservoirs, and low-permeability reservoirs.

[0018] The present invention has the following beneficial effects: 1. Significantly improves sand control performance. This invention optimizes particle structure, enhances friction coefficient and strength, and strengthens the interlocking ability between proppant particles by adjusting the fruit shell particle size to 1-2.5mm (average particle size increase of over 100%). This results in a 300% reduction in fracture breakage rate and a sand barrier rate below 0.35%, effectively solving the problems of proppant flowback and sand migration in fracturing fractures of different types of reservoirs.

[0019] 2. Adaptable to various reservoir types. Traditional tail-end proppant cannot solve the fracturing and sand control problems of different reservoir types, such as loose and dense reservoirs, under different fracture stress conditions. This invention, by adjusting the kernel size and structure, enables the proppant to adapt to different types of reservoir conditions, thus having a wide range of applications.

[0020] 3. Significant oil production increase. This invention achieves efficient sand control while maintaining excellent fracture conductivity, with a single well oil production increase of up to 10 tons, a single well oil production increase rate of 86%, and an oil production increase efficiency of 100%, realizing a synergistic effect of sand control and production increase.

[0021] 4. Low density and easy to carry. Compared with traditional fracturing proppants (quartz sand, ceramsite), granular materials made from nutshells have a low density, making them easy to carry sand. This can greatly reduce the cost of preparing proppant-carrying fluid and the risk of sand blockage during construction, effectively improving the success rate of construction.

[0022] 5. Reduce near-wellbore blockage. This invention effectively blocks formation sand from entering the wellbore by constructing a high-strength, high-permeability artificial wellbore, reducing near-wellbore blockage and sand production, and extending the oil well production cycle.

[0023] 6. Simple construction and low cost. This invention does not require complex on-site mixing equipment and operations, the preparation method is simple, the raw materials are widely available, and the cost is low, making it suitable for large-scale promotion and application. Attached Figure Description

[0024] Figure 1 This is a schematic diagram comparing the structure of the adaptive tail-chasing shell proppant of the present invention with that of a traditional tail-chasing proppant.

[0025] Figure 2 This is a flowchart illustrating the preparation process of the adaptive tail-chasing nutshell support agent of the present invention.

[0026] Figure 3 This is a schematic diagram of the structure of the adaptive tail-chasing nutshell proppant of the present invention forming an artificial well wall at the crack opening.

[0027] Figure 4 This is a performance comparison diagram between the proppant of the present invention and a traditional proppant. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. Example 1

[0029] Walnut shells were collected, washed, dried, and crushed. The resulting particles were then subjected to multi-stage sieving to obtain shell granules with an average particle size of 1.5 mm. The sieved shell granules underwent surface mechanical polishing to enhance surface roughness. The surface-treated granules were then impregnated in thermosetting phenolic resin at -30°C and cured at 120°C for 2 hours to obtain an adaptive tail-chasing shell proppant. Testing showed that this proppant exhibited a 200% increase in compressive strength and a 150% increase in the coefficient of friction compared to traditional shell proppants. Example 2

[0030] A mixture of walnut shells and apricot kernel shells (mass ratio 1:1) was washed, dried, and crushed. The mixture was then subjected to multi-stage sieving to obtain shell particles with an average particle size of 2.0 mm. The sieved shell particles were chemically etched, then impregnated in furan resin at -5°C and cured at 150°C for 1.5 hours to obtain an adaptive tail-chase shell proppant. This proppant is suitable for fracturing and sand control operations in loose sandstone reservoirs. Example 3

[0031] Peach kernel shells are collected as raw material, washed, dried, and crushed. The resulting particles are then subjected to multi-stage sieving to obtain shell particles with an average diameter of 1.0 mm. The sieved shell particles are then subjected to surface coating and strength enhancement treatments to obtain an adaptive tail-chase shell proppant. This proppant is suitable for fracturing and sand control operations in tight sandstone reservoirs.

[0032] Application examples In a loose sandstone reservoir, fracturing and sand control operations were conducted using the adaptive tail-following nutshell proppant prepared according to Example 1 of this invention for tail-following sand addition. The construction parameters were: sand ratio 25%, construction flow rate 3.5 m³ / min, and tail-following proppant dosage 15 t. After construction, the artificial wellbore permeability remained good, and the sand barrier rate was below 0.35%. Production data showed that a single well produced an additional 10 tons of oil, with a single-well oil increase rate of 86% and an oil increase efficiency of 100%, significantly improving the sand control effect compared to traditional tail-following proppant methods.

[0033] Summary of key technical indicators .

Claims

1. A method for preparing an adaptive tail-chasing shell proppant for sand control in oil and gas well fracturing, characterized in that, Includes the following steps: Step 1: Using nutshell particles as the base, wash, dry, and crush the nutshell raw material to obtain coarse nutshell particles. Step 2: Pass the coarse fruit shell particles through multi-stage sieving to obtain fruit shell particles with an average particle size of 1-2.5 mm, forming a graded structure; Step 3: Perform surface structuring treatment on the sieved fruit shell particles to enhance the surface roughness and friction coefficient of the particles, achieving interlocking structure, reducing the breakage rate at the joints by 300% compared to traditional proppant, and reducing the sand barrier rate to less than 0.35%; Step 4: Impregnate the surface-treated nutshell particles in reinforcing material to improve the compressive strength of the particles; Step 5: Dry and solidify the enhanced shell particles to obtain the adaptive tail-chasing shell proppant.

2. The preparation method of an adaptive tail-chasing shell proppant for sand control in oil and gas well fracturing according to claim 1, characterized in that, The shells are selected from one or more of the following: walnut shells, apricot kernels, peach kernels, macadamia nut shells, hickory shells, and jujube kernels.

3. The preparation method of an adaptive tail-chasing shell proppant for sand control in oil and gas well fracturing according to claim 1, characterized in that, The surface structuring treatment in step (3) includes one or more combinations of mechanical polishing, chemical etching, or coating treatment.

4. The preparation method of an adaptive tail-chasing shell proppant for sand control in oil and gas well fracturing according to claim 1, characterized in that, The reinforcing material in step (4) includes thermosetting resin, thermoplastic resin, or a combination thereof.

5. The preparation method of an adaptive tail-chasing shell proppant for sand control in oil and gas well fracturing according to claim 1, characterized in that, In the later stage of fracturing and sand addition, the adaptive tail-following nutshell proppant is injected into the fracture seal along with the sand liquid. The proppant fills and accumulates at the fracture seal to form an artificial well wall, thereby achieving sand control and increased production.

6. The adaptive tail-chasing shell proppant according to claim 1 is applied to target reservoirs including loose sandstone reservoirs, tight sandstone reservoirs, medium-to-high permeability reservoirs, and low permeability reservoirs.

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