Alternating pulse injection method to promote proppant clustering

Abstract

The present application relates to the technical field of hydraulic fracturing method, and is an alternating pulse injection method for promoting proppant grouping, which comprises uniformly stirring A agent with proppant and injecting into the formation, and B agent is a slow-release promoter which is injected into the formation together with fracturing fluid in the preflush and mid-top fluid stage. The alternating pulse injection method for promoting proppant grouping can improve single well production by 20% to 90%, eliminates the loss of flow conductivity caused by residue blockage and proppant embedding, thereby reducing the pressure drop funnel effect near the wellbore and improving the fracturing reconstruction effect; and a centimeter-level high-flow channel is established, which greatly improves the flowback rate and flowback speed and reduces the risk of sand plugging during construction.

Description

Technical Field

[0001] This invention relates to the field of hydraulic fracturing methods, specifically an alternating pulse injection method that promotes proppant agglomeration. Background Technology

[0002] Currently, hydraulic fracturing technology is widely used in oil and gas field development as an important production enhancement measure, especially in low-permeability, ultra-low-permeability, and tight oil and gas fields, where it plays a crucial role. Hydraulic fracturing can be understood as using water as a medium to break up formation rocks under high pressure, creating three-dimensional fractures with length, width, and height. Propane is then filled into these fractures using proppant-carrying fluid, thus forming oil and gas channels and enhancing production. Without fracturing, oil and gas must migrate through the existing pores of the rock. The small pore size and high resistance of the rock make oil and gas extraction extremely difficult. By filling fractures with proppant, oil and gas migrate within the proppant-filled fractures, increasing the migration distance by several orders of magnitude compared to the rock's natural pore size.

[0003] During hydraulic fracturing, when the pressure exceeds the formation stress, a horizontal or vertical fracture is formed. The fracture length can reach hundreds of meters, the height tens of meters, and the thickness several millimeters. After the fracture opens, the fracturing fluid carries proppant to fill it. When fracturing ends, the fracture cannot completely close due to the proppant filling. However, because the proppant in artificial fractures formed by conventional fracturing is continuously laid, proppant breakage and embedding result in the actual conductivity and production cycle of the fracture being far lower than the design values. This is especially true for shale oil and gas fracturing.

[0004] (1) High-level stress makes it difficult for deep shale reservoirs to form complex fracture networks;

[0005] (2) High fracturing and closure stresses make it difficult for cracks to initiate and propagate;

[0006] (3) It is difficult to add sand under high closure stress and high elastic modulus, the main crack and micro crack are not fully supported, and the crack has little effective support;

[0007] (4) Using slickwater with sand has poor sand carrying capacity. Even with a large discharge, the proppant in the vertical crack is easy to settle to the bottom, making it difficult to obtain high conductivity.

[0008] (5) Under high closure stress and low strength sand addition conditions, the proppant is severely embedded, which greatly reduces the conductivity of the crack;

[0009] (6) Most shale rocks are quite sensitive to water, and conventional inorganic anti-swelling agents cannot effectively reduce water sensitivity. Clay swelling will reduce production.

[0010] How to create a complex fracture network: Main fractures, secondary fractures, and microfractures are interconnected. This prevents the artificial fractures generated during fracturing from closing. The proppant is arranged in clusters within the fractures, exhibiting a discrete distribution and high compressive strength to support the fractures and maintain high oil and gas conductivity.

[0011] The biggest difference between high-conductivity channel fracturing (HCC) and conventional fracturing is that the artificial water fractures created by HCC are filled and supported by discontinuous proppant. The proppant acts like a pillar supporting the fracture, and the channels within it form a well-connected seepage network to provide flow pathways for oil and gas. Therefore, the conductivity of the supported fractures can be increased by 10 to 100 times compared to conventional fractures, forming centimeter-scale flow channels. HCC can create longer fractures with higher conductivity and higher proppant utilization under the same proppant loading conditions. At the same time, the flow network is more conducive to fracturing fluid backflow. How to make the proppant particles aggregate from small particles into clusters with sufficient strength in the formation is a problem that urgently needs to be solved. Summary of the Invention

[0012] This invention provides an alternating pulse injection method to promote proppant agglomeration, overcoming the shortcomings of the prior art. It enables proppant particles to agglomerate from small particles in the formation and have a certain strength, thereby improving the oil and gas conductivity of the fracturing fracture.

[0013] The technical solution of the present invention is achieved through the following measures: an alternating pulse injection method for promoting proppant agglomeration, comprising the following steps:

[0014] Step (1): A portion of Agent B is injected into the formation along with the pre-fluid. Agent B is a slow-release promoter.

[0015] Step (2): Agent A is mixed evenly with proppant and injected into the formation. The proppant is natural sand and Agent A is a viscous polymer compound.

[0016] Step (3): During the top-flush stage, another portion of Agent B is injected into the formation along with the fracturing fluid;

[0017] Step (4): Repeat steps (2) and (3) until the sand addition is complete.

[0018] The following are further optimizations and / or improvements to the above-mentioned technical solution:

[0019] The mass ratio of the above-mentioned agent A to agent B is 1:1.

[0020] Agent A is one or more of polyethylene glycol, hydroxypropyl cellulose, and polyacrylamide.

[0021] The above-mentioned agent B is one or more of solid-phase T4-RNA ligase, stearic acid, octadecanol, liquid paraffin, castor oil, and glycerol.

[0022] When injecting agent A and agent B as described above, the injection method is pulse injection.

[0023] The alternating pulse injection method for promoting proppant agglomeration described in this invention can increase single-well production by 20% to 90%, eliminate the loss of conductivity caused by residue blockage and proppant embedding, thereby reducing the pressure drop funnel effect near the wellbore and improving the fracturing effect; and establishes a centimeter-level high conductivity channel, which greatly improves the flowback rate and flowback speed and reduces the risk of sand blockage during construction. Attached Figure Description

[0024] Appendix Figure 1 This describes the placement method and scale of proppant of the same volume in the formation during conventional hydraulic fracturing.

[0025] Appendix Figure 2 This describes the placement status and scale of proppant of the same volume in the formation after using the alternating pulse injection method for proppant agglomeration described in this invention.

[0026] Appendix Figure 3 This is a diagram showing the equipment layout and connection for the alternating pulse injection method for proppant agglomeration described in this invention.

[0027] Appendix Figure 4 This is a parameter control chart for the fracturing process.

[0028] In the attached diagram, 1 is a storage tank, 2 is a ton container for agent B, 3 is a liquid injection pipeline for the agent A mixing device, 4 is an agent A mixing pump, 5 is a liquid output pipeline for the agent A mixing device, 6 is a pump pipeline for agent B connection, 7 is a pressure pump for agent B, 8 is an output pipeline for agent B, and 9 is a sand mixing truck. Detailed Implementation

[0029] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are preparation solutions commonly used in fracturing operations in the art.

[0030] The present invention will be further described below with reference to embodiments:

[0031] Example 1: The alternating pulse injection method for promoting proppant aggregation is performed according to the following steps:

[0032] Step (1): A portion of Agent B is injected into the formation along with the pre-fluid. Agent B is a slow-release promoter.

[0033] Step (2): Agent A is mixed evenly with proppant and injected into the formation. The proppant is natural sand and Agent A is a viscous polymer compound.

[0034] Step (3): During the top-flush stage, another portion of Agent B is injected into the formation along with the fracturing fluid;

[0035] Step (4): Repeat steps (2) and (3) until the sand addition is complete.

[0036] Agent A has a certain viscosity, which can encapsulate the proppant and has good sand-carrying performance; Agent B is a slow-release accelerator that reacts with Agent A in the formation to form a network structure that causes the proppant to clump together. As the temperature rises and time goes by, the strength of the proppant will gradually increase.

[0037] Example 2: As an optimization of the above example, the mass ratio of agent A to agent B is 1:1.

[0038] Example 3: As an optimization of the above examples, agent A is one or more of polyethylene glycol, hydroxypropyl cellulose, and polyacrylamide.

[0039] Example 4: As an optimization of the above example, agent B is one or more of solid-phase T4-RNA ligase, stearic acid, octadecanol, liquid paraffin, castor oil, and glycerol.

[0040] Example 5: As an optimization of the above example, when injecting agent A and agent B, the injection method for both is pulse injection.

[0041] This invention uses alternating pulsed injection of agent A and agent B to form proppant (natural sand) in fractures into relatively regular spherical clusters with discrete distribution and high compressive strength, thereby increasing fracture volume and oil and gas connectivity, preventing proppant clusters from embedding into the formation, and achieving the goal of increasing production and extending the production cycle.

[0042] To address the issue of low conductivity in traditional fracturing techniques caused by factors such as proppant embedding, fragmentation, calcification, minimal migration, fracturing fluid damage, multiphase flow, and non-Darcy effect, this invention involves uniformly mixing Agent A with the proppant and injecting it into the formation. Agent B, a slow-release promoter, is injected into the formation along with the fracturing fluid during the pre-fracturing and mid-top-fracturing stages. Agents A and B are injected alternately in two pulsed stages. After fracturing, Agent B is slowly released into the formation, forming a network structure with Agent A to encapsulate the proppant into clumps, thus gradually increasing its strength. The resulting clumps of proppant effectively prevent fracture closure and proppant embedding into the formation, and create centimeter-level high-speed channels between clumps that are 10 to 100 times larger than those in traditional hydraulic fracturing, increasing the oil and gas flow area and production lifespan, thereby achieving stable and increased production.

[0043] Through field application, the alternating pulse injection method for promoting proppant agglomeration described in this invention can increase single-well production by 20% to 90%, eliminate the loss of conductivity caused by residual blockage and proppant embedding, thereby reducing the pressure drop funnel effect near the wellbore and improving the fracturing effect. It establishes centimeter-level high-conductivity channels, significantly improving the flowback rate and speed, and reducing the risk of sand blockage during construction.

[0044] The placement method and scale of proppant of equal volume in the formation during conventional hydraulic fracturing are as follows: Figure 1 After employing the alternating pulse injection method for proppant agglomeration described in this invention, the placement and scale of the same volume of proppant in the formation are as follows: Figure 2 .

[0045] Field Application Example 1: Well 05 in an oilfield, the equipment layout and connection diagram for the alternating pulse injection method for proppant agglomeration described in this invention is shown below. Figure 3 During fracturing operations, parameters such as displacement, total fluid volume, and sand concentration are controlled as follows: Figure 4 As shown, inject agent A and agent B according to the following steps:

[0046] Step (1): A portion of Agent B is injected into the formation along with the pre-fluid. Agent B is a mixture of stearic acid and octadecyl alcohol.

[0047] Step (2): Agent A and proppant are mixed evenly in a sand mixing truck and injected into the formation. The proppant is natural sand, and Agent A is a mixture of polyethylene glycol and hydroxypropyl cellulose.

[0048] Step (3): During the top-flush stage, another portion of Agent B is injected into the formation along with the fracturing fluid;

[0049] In step (4), agent A and agent B are injected in a pulse manner. Repeat steps (2) and (3) until the sand addition is completed.

[0050] In the field application example 1, the well (05) was designed to produce 12 tons per day, and currently produces 20.4 tons of oil and gas equivalent per day, which exceeds the designed production capacity by 70% and the production capacity of adjacent wells by 51.2%.

[0051] Field Application Example 2: A well in an oil field, where the equipment layout and connection diagram for the alternating pulse injection method for proppant agglomeration described in this invention is shown below. Figure 3 During fracturing operations, parameters such as displacement, total fluid volume, and sand concentration should be controlled according to Example 1 of field application, and Agent A and Agent B should be injected according to the following steps:

[0052] Step (1): A portion of agent B is injected into the formation along with the pre-solvent. Agent B is a solid-phase T4-RNA ligase.

[0053] Step (2): Agent A is mixed evenly with the proppant and injected into the formation. The proppant is natural sand and Agent A is polyacrylamide.

[0054] Step (3): During the top-flush stage, another portion of Agent B is injected into the formation along with the fracturing fluid;

[0055] In step (4), agent A and agent B are injected in a pulse manner. Repeat steps (2) and (3) until the sand addition is completed.

[0056] In the field application example 1, the well was designed to produce 10 tons per day, and currently produces 18.5 tons of oil and gas equivalent per day, exceeding the designed production capacity by 85% and the production capacity of adjacent wells by 48.7%.

[0057] Field Application Example 3: A well in an oil field, where the equipment layout and connection diagram for the alternating pulse injection method for proppant agglomeration described in this invention is shown below. Figure 3 During fracturing operations, parameters such as displacement, total fluid volume, and sand concentration should be controlled according to Field Application Example 1, and Agent A and Agent B should be injected according to the following steps:

[0058] Step (1): A portion of Agent B is injected into the formation along with the pre-fluid. Agent B is a mixture of octadecanol, liquid paraffin, castor oil, and glycerin.

[0059] Step (2): Agent A is mixed evenly with the proppant and injected into the formation. The proppant is natural sand, and Agent A is a mixture of hydroxypropyl cellulose and polyacrylamide.

[0060] Step (3): During the top-flush stage, another portion of Agent B is injected into the formation along with the fracturing fluid;

[0061] In step (4), agent A and agent B are injected in a pulse manner. Repeat steps (2) and (3) until the sand addition is completed.

[0062] In the field application example 1, the well was designed to produce 10 tons per day, and currently produces 19.1 tons of oil and gas equivalent per day, exceeding the designed production capacity by 91% and the production capacity of adjacent wells by 52.6%.

[0063] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for promoting proppant aggregation using alternating pulse injection, characterized in that... Follow these steps: Step (1): A portion of Agent B is injected into the formation along with the pre-fluid. Agent B is a slow-release promoter. Step (2): Agent A is mixed evenly with proppant and injected into the formation. The proppant is natural sand and Agent A is a viscous polymer compound. Step (3): During the top-flush stage, another portion of Agent B is injected into the formation along with the fracturing fluid; Step (4): Repeat steps (2) and (3) until the sand addition is complete; Among them, agent A is one or more of polyethylene glycol, hydroxypropyl cellulose, and polyacrylamide; agent B is one or more of solid-phase T4-RNA ligase, stearic acid, octadecanol, liquid paraffin, castor oil, and glycerin.

2. The alternating pulse injection method for promoting proppant agglomeration according to claim 1, characterized in that... The mass ratio of agent A to agent B is 1:

1.

3. The alternating pulse injection method for promoting proppant agglomeration according to claim 1 or 2, characterized in that... When injecting agent A and agent B, the injection method is pulse injection.

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