Experimental Development and Optimization of a Particle-Fiber-Powder Composite Temporary Plugging System for Diversion Fracturing

1 Introduction

Efficient development of unconventional tight oil and gas resources relies heavily on multistage and multi-cluster hydraulic fracturing in horizontal wells, which is widely used to create complex fracture networks and increase the stimulated reservoir volume [1]. However, owing to reservoir heterogeneity, natural-fracture development, stress interference, and local stress redistribution during staged stimulation, fracture initiation and propagation are often highly nonuniform. Previous studies have shown that fracture spacing, in-situ stress, rock mechanical parameters, horizontal stress difference, natural-fracture characteristics, and stress-shadow effects can significantly influence breakdown pressure, fracture morphology, and stimulated reservoir area in shale and tight reservoirs [2,3,4]. During the depletion and refracturing of fractured shale reservoirs, pressure depletion and vertical heterogeneity may further induce local stress redistribution and uneven fracture propagation, increasing the uncertainty of subsequent fracture propagation and infill-well stimulation design [5,6]. As a result, fracturing fluid and proppant tend to preferentially enter a few dominant low-resistance channels, leaving some perforation clusters or reservoir intervals insufficiently stimulated and limiting the productivity improvement of individual wells. Therefore, improving the uniformity of fluid distribution and fracture propagation has become a key issue in horizontal-well volume fracturing.

Temporary plugging and diversion fracturing has been developed to address this problem. By forming a temporary high-resistance zone in dominant fractures or preferential flow channels, subsequently injected fracturing fluid can be redirected toward under-stimulated intervals or newly initiated branch fractures, thereby improving fracture-propagation uniformity and enhancing reservoir stimulation efficiency [7,8,9]. Recent experimental studies on temporary plugging and diversion fracturing in multi-cluster horizontal wells have confirmed that temporary plugging can mitigate uneven multi-fracture propagation and promote more balanced fracture extension [10]. Visualized experiments have also shown that the migration behavior, retention position, and plugging efficiency of temporary plugging agents are closely related to particle size, material concentration, fracture morphology, and multi-fracture geometry [11]. Field-oriented studies on modern and far-field diversion technologies also indicate that solid particulate diverters should be designed according to transportability, bridging position, and temporary pressure-bearing requirements [12,13]. These findings indicate that temporary plugging performance is controlled not only by whether a plug can finally be formed, but also by where the plugging body forms, how rapidly it forms, and whether it remains stable under dynamic flow conditions.

An ideal temporary plugging material should be transported smoothly with the fracturing fluid, retained efficiently at the target position, rapidly form a plugging body under high-rate injection, and withstand strong fluid erosion and pressure differential. More broadly, temporary plugging and diversion performance is controlled by the coupling among fracture geometry, stress redistribution, leakage-channel development, and functional material placement. Previous studies have shown that fracture propagation and flow redistribution are strongly affected by in-situ stress, natural fractures, stress shadow effects, and pressure-depletion-induced stress changes. Severe fluid loss during workover and refracturing may also reduce the effectiveness of subsequent stimulation, further highlighting the need for rapid and reliable plugging intervention [14]. In addition, recent studies on injectable, degradable, and sealing-type materials have demonstrated that plugging agents should balance pumpability, retention capacity, plugging strength, and post-treatment cleanup [15,16,17,18]. Studies on artificial gel-barrier technology, bridging lost-circulation materials, leakage-control resins, and high-temperature fracturing-fluid polymers further emphasize that sealing materials should be evaluated together with transport, mechanical strength, and temperature/rheology adaptability [19,20,21,22]. Therefore, composite temporary plugging systems should be evaluated not only by their final pressure-bearing capacity, but also by their transport behavior, structural formation process, and stability under dynamic erosive-flow conditions.

In multiscale temporary plugging systems, different components usually play complementary roles. Fibers can anchor, entangle, and form a flexible network on rough or acid-etched fracture surfaces, thereby improving the integrity and erosion resistance of the plugging body. Particles can bridge and accumulate within fractures to construct the main load-bearing skeleton, whereas fine powders or gels can fill residual pores, reduce the permeability of the plugging layer, and accelerate pressure build-up [23,24,25]. Preformed particle-gel placement, degradable particle-gel systems, and near-wellbore particulate selection studies further demonstrate that multiscale material combinations can improve retention and sealing stability in fractures [26,27,28]. True-triaxial and 3D-printed fracture-model experiments have further indicated that the microstructural evolution of fiber attachment, particle capture, and pore densification is an important reason why multiscale composite systems can outperform single-component materials [29]. Therefore, a particle–fiber–powder ternary system is expected to be more effective than single-component or binary systems because it can integrate skeleton construction, network locking, and pore-space densification within one plugging body.

However, the stability of composite temporary plugging structures still faces significant challenges under dynamic high-erosion conditions. As fracture width, pumping rate, temperature, or fracture-wall complexity increases, the plugging body may experience repeated bridging, erosion, reconstruction, slippage, and re-channeling during continuous fluid injection [30,31]. Near-wellbore or complex-fracture conditions may also induce more complex bridging and redirection behavior, making designs based solely on average fracture width or final pressure-bearing capacity potentially insufficient [32]. Moreover, conventional static pressure-bearing tests mainly reflect the final plugging strength, but they cannot fully capture the dynamic processes of transport, retention, bridging, compaction, erosion resistance, and pressure build-up. Carrier-fluid rheology, temperature-sensitive fracture/microcrack behavior, and dynamic particle bridging can further affect particle suspension, deposition time, and plugging stability under field-scale pumping conditions [33,34,35,36]. Dynamic pressure response and fracture-geometry evolution during temporary plugging and diversion fracturing have been shown to be closely related to material placement and plugging behavior [37,38]. Therefore, dynamic evaluation methods are needed to reveal how different components cooperate during plug formation and how material composition controls both pressure-bearing capacity and plug-formation kinetics.

Based on the above understanding, this study investigates a particle–fiber–powder ternary composite temporary plugging system under dynamic erosive-flow conditions. A laboratory dynamic evaluation framework is established to compare the plugging behavior of single-component, binary, and ternary systems. Pressure evolution, maximum plugging pressure, time to maximum pressure, pressure growth rate, and plugging morphology are analyzed to evaluate both plugging strength and plug-formation kinetics. Within the proposed system, particles construct the primary load-bearing skeleton, fibers lock and stabilize the skeleton against erosion, and powder fills residual pores and accelerates pressure build-up. Through this design, this study systematically clarifies the synergistic mechanism among material composition, dynamic plug formation, and pressure-bearing performance, and proposes an optimized formulation window for temporary plugging and diversion fracturing.

2 Materials and Methods

2.1 Materials

The temporary plugging materials used in this study included particles, powder, and fibers. The particles were made of polylactic acid (PLA); the fibers had a diameter of 20 μm and a length of 3–4 mm; and the powder had a median particle size of 50–100 μm. The PLA particles and fibers both had a density of 1.25 g/cm3, and their degradation performance met industry standards for temporary plugging operations. To ensure controllable suspension and transport, guar gum was used as the carrier-fluid base. Specifically, 16 g of guar gum powder was added to 2000 mL of tap water with thorough stirring to prepare an 8 g/L guar-gum solution. Temporary plugging materials were then added to the base fluid at the designed mass fractions, mixed uniformly, and held in an intermediate container for subsequent use. For particle-size optimization, eight representative particle grades from 100–150 mesh to 6–8 mesh were examined. In subsequent formulation screening, 10–14 mesh was selected as the preferred particle grade. Powder concentration was evaluated over the range of 1%–5% in all relevant systems. In the single-component fiber tests, fiber concentration ranged from 1% to 5%, whereas in the binary and ternary systems the investigated range was 0.2%–5%, based on the observed performance response.

2.2 Apparatus and Test Conditions

Experiments were carried out using the multistage in-fracture temporary plugging and diversion dynamic evaluation apparatus shown in Fig. 1, and its main technical parameters are listed in Table 1. The device was equipped with wedge-shaped rough fracture plates with an inlet width of 5 mm and an outlet width of 3 mm. The average surface roughness (Ra) was approximately 0.05 mm, simulating a converging flow channel in a heterogeneous fracture. Standard dynamic test conditions were room temperature (25°C), a confining pressure of 10 MPa, and a pumping rate of 100 mL/min. Each test was terminated when the system pressure reached the safety limit of 15 MPa or when no significant pressure rise was observed after 1000 s of continuous pumping.

Figure 1: Multistage in-fracture dynamic evaluation apparatus for temporary plugging and diversion.

2.3 Experimental Design

To clarify the role of each material in the temporary plugging process and optimize the formulation, the experiments were arranged as a progressive matrix from single-factor to multi-factor combinations, as summarized in Table 2. Based on the concentration gradients and particle-size combinations listed in Table 2, a total of 60 dynamic erosive-flow experiments were performed. To keep the discussion focused, only representative concentration points and optimized formulations are presented and compared in detail in the main text and figures. The remaining data were used primarily to verify the overall trends. The maximum pressure and time values reported here are representative values from single tests; statistical error analysis and confidence intervals for key formulations will be examined in future work.

2.4 Evaluation Metrics

To quantify plugging capacity and plug-formation efficiency under dynamic erosive-flow conditions, the following parameters were used as the core evaluation metrics:

• (1)Criterion for effective plug formation. During dynamic pumping, system pressure typically rises in a serrated oscillatory manner, reflecting repeated bridging, destabilization, and reconstruction of the plugging body. Effective plug formation was identified when the terminal segment of the pressure curve showed a sustained sharp increase and reached the system safety threshold, triggering automatic unloading. It was also identified when pressure remained above 10 MPa, indicating that the plugging layer had reached an approximately mechanical equilibrium state. For experiments that did not meet either criterion within the 1000 s test window, tmax was recorded as “—”.
• (2)Maximum plugging pressure (Pmax). This is the instantaneous peak pressure immediately before system unloading, expressed in MPa. It reflects the maximum fluid shear the temporary plugging structure can withstand after repeated erosion and restructuring, and thus represents the upper limit of system pressure resistance. Under non-plugging conditions, it corresponds to the maximum fluctuating pressure differential observed.
• (3)Time to maximum pressure (tmax). This is the elapsed time, in seconds, from the moment the temporary plugging fluid enters the rough-fracture model to the moment the pressure reaches Pmax. This period includes the early stages of skeleton oscillation and structural rearrangement. At the macroscopic level, it represents the overall rate at which the materials are retained in the fracture and build a dense flow barrier.
• (4)Pressure growth rate (dP/dt). This parameter is defined as the slope of the quasi-linear pressurization stage near the end of the pressure curve, expressed in MPa/s. It is mainly used to quantify the densification rate of the filter cake during the critical plug-formation stage. For systems that failed to achieve effective plug formation, this value represents the average intensity of pressure increase within the test window and is listed in Table 3 as a reference.

After each experiment, the rough fracture plates were disassembled to examine the macroscopic morphology, bridging position, and compactness of the plugging body, allowing the macroscopic pressure response to be cross-checked against the inferred microscopic mechanism.

3 Results and Discussion

3.1 Plugging Performance of Single- and Binary-Component Systems

3.1.1 Particle-Size Optimization

Because particle size is the primary factor governing the stability of the temporary plugging skeleton, particle-size optimization was conducted first to determine the most suitable mesh range. The concentration-response behavior of the single-component, binary, and ternary systems was then systematically evaluated using the selected particle grade.

The prerequisite for particle-based plugging is the formation of a load-bearing skeleton through bridging, accumulation, and compaction. For a given fracture width, the particle-size distribution must satisfy an appropriate size-matching relationship; otherwise, two failure modes may occur. If the particles are too small, they pass through the fracture and are carried out with the fluid, preventing stable bridging. If they are too large, premature blockage or agglomeration may occur in the pipeline or at the fracture inlet, increasing operational risk. Under the conditions of this study, particles ranging from 100–150 mesh to 6–8 mesh were compared. The results show that finer particles, such as 100–150 mesh, 80–100 mesh, and 60–80 mesh, were more likely to pass through the fracture with the fluid and therefore failed to build pressure effectively. Although the coarser 6–8 mesh particles could form relatively strong bridging near the inlet, they also posed a high blockage risk. Considering both pressure response and pumpability, 8–10 mesh and 10–14 mesh particles both showed favorable bridging performance. Although Fig. 2a indicates a relatively high peak pressure for the 6–8 mesh particles, repeated instantaneous blockage at the inlet and an associated slippage risk were observed during testing, indicating a narrow operational safety window. By contrast, 10–14 mesh particles maintained high pressure-bearing performance while allowing more stable restructuring and transport of the particle skeleton, which was more favorable for subsequent powder filling and densification. Accordingly, 10–14 mesh was selected as the base skeleton grade for the ternary system.

Figure 2: Pressure-response curves of single-component systems.

3.1.2 Single-Component Plugging Behavior

For the particle-only system, the optimized 10–14 mesh particles showed an extremely weak pressure response across the concentration range of 1%–5%, with all Pmax values below 0.3 MPa; Table 3 therefore lists only the representative value at 5% concentration. This result indicates that under continuous erosive flow, particle accumulation alone is insufficient to form a stable, low-permeability plugging layer capable of bearing pressure. As shown in Fig. 2b, the powder-only system exhibited an extremely weak pressure response across all tested concentrations. Similarly, the fiber-only system showed only negligible pressure variation, as shown in Fig. 2c. Powder lacks anchoring points in the skeleton and is therefore easily carried out by the fluid, whereas fibers can form a network structure but cannot be compacted densely without support from a particle skeleton, leaving the plugging layer relatively permeable. Under the present experimental conditions, single-component systems therefore could not simultaneously deliver high pressure-bearing capacity and rapid pressure build-up.

3.1.3 Particle-Powder Binary System

In principle, particles provide the skeleton and powder fills the pores, so the combined system should produce a denser plugging layer. As shown in Fig. 3, however, the particle-powder binary system still failed to achieve effective plugging under the present conditions. For the formulation containing 1% particles and 5% powder, for example, both the peak pressure and the stabilized pressure remained low. This indicates that skeleton support and pore filling alone are insufficient to withstand continuous erosive flow. During dynamic flow, powder is readily removed by fluid shear before the particle skeleton is fully compacted, preventing the permeability of the plugging layer from dropping to the level needed to establish a significant pressure differential. At the same time, the particle skeleton lacks effective interparticle connection and restraint, making it prone to local loosening, rearrangement, and even overall erosion-induced failure. An additional component capable of structural locking and toughening is therefore required to improve the overall stability of the skeleton.

Figure 3: Plugging performance of the particle-powder binary system.

3.1.4 Fiber-Powder Binary System

In addition to the particle-powder combination, a fiber-powder binary system consisting of 1% fibers and 1%–5% powder was tested according to the experimental matrix. As shown in Fig. 4, fibers and powder alone could not establish high-strength plugging, with all Pmax values below 0.5 MPa. Although fibers possess a certain capacity for network entanglement, a purely fibrous network readily undergoes flexible deformation and compressive detachment in a relatively wide fracture when coarse particles are absent as a rigid supporting skeleton. Under strong dynamic erosion at 100 mL/min, powder cannot be effectively retained or deposited as a filter cake within the unstable fiber network, resulting in fluid breakthrough and through-flow. This further demonstrates the irreplaceable role of a coarse-particle skeleton in composite temporary plugging.

Figure 4: Plugging performance of the fiber-powder binary system.

3.2 Plugging Performance of the Particle-Fiber Binary System

3.2.1 Effect of Fiber Concentration on Plugging Pressure

Unlike the particle-powder system, the particle-fiber binary system exhibited a marked improvement in plugging performance under dynamic erosive-flow conditions. According to the results from the 60-test matrix (Table 4 and Fig. 5), Pmax increased with fiber concentration in a distinctly staged and nonlinear manner. In the threshold-jump regime (0.2%–0.4%), increasing the fiber mass fraction from 0.2% to 0.4% caused Pmax to rise by an order of magnitude, from 0.48 MPa to 10.16 MPa. This indicates a clear network-percolation threshold: when fiber content is too low, the fiber network cannot become continuous or effectively lock the particle skeleton, and the plugging layer is readily damaged under strong erosion. Once the concentration exceeds approximately 0.4%, fibers can form multipoint entanglement and bridging among particles, substantially improving skeleton integrity and shear resistance. In the saturation-plateau regime (0.6%–5.0%), the incremental gain in plugging pressure becomes much smaller. When fiber concentration increased from 0.6% (13.20 MPa) to 5.0% (14.42 MPa), the material dosage increased by more than eightfold, whereas the ultimate pressure-bearing capacity increased by only about 9.2%. This further confirms that once the fiber network achieves spatial percolation and locks the skeleton, the marginal contribution of additional fibers to the ultimate strength of the plugging layer becomes limited. From an engineering perspective, 0.4%–0.6% is therefore an effective fiber-concentration window that balances material cost, pumpability, and plugging strength.

Figure 5: Effect of fiber concentration on maximum plugging pressure in the particle-fiber binary system.

3.2.2 Fiber-Network Locking Mechanism

Taken together with the pressure-response characteristics and the post-test state of the plugging body, the results show that the plugging layer formed by particles and fibers exhibits a distinct network-supporting structure. Under the combined effects of flow shear and surface roughness, fibers become oriented, entangled, and agglomerated to form a flexible skeleton capable of capturing particles; the particles then accumulate and compact gradually under confinement by the fiber network. Mechanically, fibers provide two main benefits. First, their multipoint bridging increases the number of effective interparticle contacts and enhances internal friction, making the particle skeleton less susceptible to bulk slippage or structural rearrangement under fluid erosion. Second, fibers can adapt to the irregular morphology of the fracture walls, span peaks and valleys on the rough surface, and fill local voids, thereby strengthening the bond between the plugging layer and the fracture walls. It should also be noted that a particle-fiber system alone may still form a porous plug with residual leakage channels under continuous erosion, which provides the rationale for introducing powder to further densify the pore space.

3.3 Plugging Response of the Ternary System

3.3.1 Effect of Powder Concentration on Pressure Build-up Time

Once the particle-fiber binary system had established relatively high pressure-bearing performance, adding powder produced a pronounced acceleration in pressure build-up. Using 1% particles and 0.5% fibers as the base formulation, increasing the powder concentration from 1% to 5% markedly shortened the time required to reach the maximum pressure, indicating that powder rapidly reduces the permeability of the plugging layer and promotes the development of a pressure differential. As shown in Table 5, tmax dropped sharply from 737 s to 248 s as the powder mass fraction increased from 1% to 5%. This kinetic response suggests that powder migrates into deeper pore spaces under the pressure differential and forms a dense filter cake, causing the pressure-control mechanism to shift rapidly from skeleton-induced flow resistance to pore-plugging domination. Within a certain range, powder concentration is therefore the key variable controlling the response speed of temporary plugging, which is critical for achieving rapid diversion in the field.

3.3.2 Effect of Powder Concentration on Plugging Strength

Unlike the monotonic decrease in pressure-build-up time, the maximum plugging pressure of the ternary system showed a nonmonotonic trend with powder concentration, increasing first and then decreasing. Increasing the powder concentration within a certain range improved plugging pressure, but when the powder mass fraction reached 5%, Pmax declined from 13.97 MPa to 12.18 MPa. Combined with the pressure-response behavior, three possible mechanisms may explain this trend. First, excessive powder may cause premature plug formation and insufficient compaction. An overly high powder content may quickly form a low-permeability surface filter cake that restricts the further inward transport and dense packing of coarse particles, thereby limiting the ultimate strength of the skeleton. Second, excessive fines may introduce a lubrication effect by filling contact surfaces between coarse particles, reducing effective interparticle interlocking friction and weakening the skeleton under shear. Third, high powder concentration may shift the bridging position forward toward the fracture inlet, shortening the effective load-bearing section and aggravating local stress concentration, which likely leads to premature failure of the plugging body.

3.3.3 Dynamic Response and Plug-Formation Evolution

As shown in Fig. 6a–c, the pressure response of the ternary system varied markedly with powder concentration. At low powder concentration, the overall pressure curve rose slowly and showed only small fluctuations, indicating that although a particle-fiber framework had formed, pore plugging remained limited and the system could not rapidly establish an effective pressure differential. As powder concentration increased, the pressure-rise rate accelerated substantially and the time required to reach the high-pressure stage shortened markedly, showing that powder can rapidly fill pores within the particle-fiber skeleton, reduce the permeability of the plugging layer, and promote the formation of a dense plug. A faster pressure rise, however, does not necessarily correspond to higher ultimate pressure-bearing performance. As shown by Table 3 and Table 5, the system containing 4% powder exhibited the best overall pressure-bearing performance, whereas the system containing 5% powder built pressure more rapidly but reached a slightly lower maximum plugging pressure. This indicates that ternary-system performance is governed not by plug-formation rate alone, but jointly by plug-formation kinetics, skeleton compaction, and overall structural stability.

Figure 6: Dynamic plugging responses and post-test morphology of the particle–fiber–powder ternary system.

The post-test morphology further supports this interpretation. As shown in Fig. 6d, the ternary system containing 1% particles, 0.5% fibers, and 5% powder formed a visible composite plugging body on the rough fracture surface after the dynamic erosive-flow test. The accumulated plugging mass indicates the combined effects of particle bridging, fiber entanglement, and powder filling. This morphology confirms the rapid plug formation of the 5% powder formulation. However, the relatively localized accumulation also suggests that excessive powder may promote premature deposition before sufficient skeleton compaction is achieved, which is consistent with its slightly lower maximum plugging pressure compared with the 4% powder system.

3.3.4 Synergistic Role of Fiber Concentration in the Ternary System

In the particle-fiber-powder ternary system, fiber content not only determines the ultimate strength of the plugging layer, but also plays a key role in regulating plug-formation kinetics. The results show that the synergistic effect of fiber concentration also follows a critical threshold near 0.4%, although its manifestation is strongly modulated by powder filling. When the fiber concentration is below 0.4%, plug-formation stability decreases markedly. As shown in Fig. 6c, even though the 0.3% fiber group exhibited some late-stage pressure rise at relatively high powder concentration, the curve fluctuated strongly and required much longer to reach the high-pressure stage, making it more difficult to stably exceed the threshold for effective plug formation. This indicates that fiber-network locking is a prerequisite for effective powder deposition and dense plugging. Once the fiber concentration reaches the percolation threshold of 0.4%, the spatially entangled network can firmly lock the particle skeleton and provide a stable load-bearing foundation, thereby improving powder accumulation within the pores and accelerating the transition from skeleton-induced flow resistance to dense filter-cake plugging. A comparison between the binary and ternary systems further shows that powder markedly accelerates plug formation at similar fiber concentrations. For the formulation containing 1% particles + 0.5% fibers + 4% powder, for example, tmax was only 265 s, which is 559 s shorter than that of the representative high-pressure-bearing binary formulation. This demonstrates a favorable spatiotemporal synergy between the fiber network and powder filling: the former constructs and stabilizes the spatial skeleton, whereas the latter seals pores and accelerates pressure build-up, allowing high pressure-bearing performance and rapid plug formation to be optimized simultaneously.

3.4 Synergistic Mechanism and Formulation Optimization

3.4.1 Three-Layer Model of Particle Skeleton Construction, Fiber-Network Locking, and Pore Densification

Based on the dynamic pressure-response patterns and the experimental observations discussed above, a conceptual model of the synergistic structural evolution of the particle-fiber-powder composite plugging body is proposed, as illustrated in Fig. 7. In the first stage, particles construct the skeleton: coarse particles preferentially bridge in geometrically convergent sections of the fracture and at wall asperities, thereby forming the basic load-bearing framework. In the second stage, fibers lock the network: under flow shear, fibers become oriented and entangled across interparticle gaps, providing multipoint flexible binding that substantially improves the erosion resistance of the skeleton. In the third stage, powder fills and densifies the pores: fine powder migrates and deposits deep within the internal pore space under the pressure differential, progressively sealing microscopic seepage channels so that overall permeability drops rapidly and a high pressure differential is established. Within this framework, the effectiveness of composite temporary plugging depends not on the extreme performance of any single material, but on the spatiotemporal synergy among all three material classes.

Figure 7: Synergistic plugging mechanism of the particle–fiber–powder composite system, involving particle bridging, fiber-network locking, and powder filling.

3.4.2 Comprehensive Assessment of Plugging Performance

The experimental results show that Pmax and tmax are not simply positively correlated. Pmax represents the maximum mechanical strength and the upper limit of erosion resistance that the plugging layer can withstand in the fracture, whereas tmax reflects how quickly powder deposits within the skeleton and completes pore plugging. Considering these two parameters together makes it possible to evaluate not only the ultimate pressure-bearing capacity of a composite material, but also differences in pressure-build-up response time, which correspond to field requirements for different diversion rhythms. Formulation optimization should therefore not rely on peak pressure alone; instead, the most appropriate balance between pressure-bearing capacity and response speed should be selected according to specific engineering requirements.

3.4.3 Recommended Formulation Window under the Present Test Conditions

Based on the laboratory evaluation conditions used in this study—room temperature (25°C), a confining pressure of 10 MPa, and a target fracture width of 3–5 mm—the following formulation windows are recommended for practical use. When ultimate pressure-bearing performance is the primary objective, the recommended formulation is 1% particles + 0.5% fibers + 4% powder. When faster diversion response, that is, a shorter plug-formation time, is more important, the powder mass fraction should be increased to 5%.

These recommended formulations should be interpreted within the physical scale of the laboratory simulation. In field applications, geological and engineering factors such as high pumping rates, elevated reservoir temperature, and complex natural fracture networks can significantly alter the in-fracture transport and deposition behavior of temporary plugging materials. It is therefore recommended that coefficient correction and scaled pilot testing be performed on the basis of the synergistic patterns identified in this study, together with the parameters of the target field.

4 Conclusions

• (1)Under dynamic high-erosion conditions, single-component systems and particle-powder binary systems exhibit extremely low plugging pressure because they lack effective spatial structural locking and therefore cannot resist intense fluid shear. The experiments show that particle skeleton support and powder pore filling alone are insufficient; without the constraint of a fiber network, the plugging layer is highly prone to rearrangement and destabilization.
• (2)Fiber is the key structural-locking component required for high-strength plugging, and the system exhibits a pronounced critical concentration threshold near 0.4%. Once this threshold is exceeded, Pmax increases sharply. Beyond that point, the system enters a saturation plateau, and further increases in fiber concentration produce only limited pressure gains. This indicates that, once the fiber network becomes continuous, its primary role shifts from continuously increasing mechanical strength to maintaining the stability of the internal skeleton.
• (3)Powder is the key variable controlling plug-formation kinetics. Its concentration directly governs the pressure-build-up response, as reflected by tmax, whereas fiber is the prerequisite for effective powder deposition. Powder also has an optimal concentration range for maximizing ultimate pressure-bearing capacity. Excessive powder content (5%) causes premature plug formation and may induce insufficient internal compaction or a fines-lubrication effect, leading to a reduction in the upper limit of load-bearing capacity.
• (4)On the basis of the dynamic pressure-response patterns and experimental observations, this study proposes a conceptual three-layer synergistic model for composite plug formation, consisting of particle skeleton construction, fiber-network locking, and pore densification by powder. Guided by this model, two representative field-oriented formulations were identified: a high-pressure-bearing formulation (1% particles + 0.5% fibers + 4% powder) and a rapid plug-formation formulation (1% particles + 0.5% fibers + 5% powder). These results provide quantitative guidance for the precise design of temporary plugging and diversion operations in the field.
• (5)For more complex and extreme field conditions, future work should evaluate the dynamic adaptability of these systems under high-temperature, high-salinity, and proppant-coupled conditions, systematically assess formation damage after material degradation, and explore scale-up methods that link laboratory physical simulation with field pumping-schedule design.