Characteristics Of Plug Research Articles

Liquid plug characteristics and heat transfer performance of a silicon-based ultra-thin flat heat pipe at different incline angles

Silicon-based ultra-thin flat heat pipes (UFHPs) that can be integrated with semiconductor devices provide an opportunity for electronic thermal management. To meet the requirements of various operation states, the impacts of gravity on the liquid plug characteristics and heat transfer performance of an UFHP are investigated by a visualization experiment conducted at different incline angles. Condensate flows back through microgrooves under the capillary pressure and gravity under a low heating power (capillary flow stage), and then excess condensate flows back along the edges of the UFHP under a higher heating power (gravitational flow stage). Over a certain heating power (Q ≥ 14 W), liquid plug fluctuations caused by vapor entrainment are observed with periodic dry-out at the evaporator under large incline angles (α ≥ 60°), corresponding to temperature fluctuations. Intense fluctuations of the liquid plug enhance sensible heat transfer, although the liquid plug occupies the condenser area and impedes the vapor flow. Meanwhile, evaporation at the evaporator benefits from corner-film evaporation until a large area of dry-out occurs. Due to the increased gravity and buoyancy, a larger incline angle is conducive to thermal performance enhancement, but this effect becomes restricted as the heating power rises. At a cooling-water temperature of 20 ℃ and an incline angle of 90°, the lowest thermal resistances of the UFHP yield a value of 1.14 ℃/W at 4 W in the steady stage and a value of 1.22 ℃/W at 18 W in the fluctuation stage, respectively. The heat transfer limit of UFHP with overfilling reaches 24 W, compared with the theoretical heat transfer capacity of 8.9 W at an incline angle of 90°. Additionally, a higher cooling-water temperature is beneficial for the thermal performance in the capillary flow stage, but not in the gravitational flow stage and fluctuation stage. This study provides guidance for the operational design of silicon-based UFHP for electronic thermal management.

Parameters affecting plug characteristics in dense phase pneumatic conveying of ellipsoidal particles

Even though particle shape tends to have a major influence on the bulk behaviour of a granular system, perfectly spherical particles are often used in numerical simulations. In this study, we examine the plug flow of ellipsoidal particles in dense phase horizontal pneumatic conveying within a rigid and cylindrical pipe with periodic boundaries in the axial direction. We use coupled Computational Fluid Dynamics (CFD) – Discrete Element Method (DEM) simulations to investigate the effect of particle shape on four plug characteristics: velocity, length, porosity, and particle exchange rate with the stationary bed. Both ellipsoidal and spherical particles are used, and the parameters varied are the particle size, aspect ratio, pressure gradient, particle–particle and particle–wall sliding and rolling friction coefficients, and coefficients of restitution. The steady state characteristics of plugs composed of spherical particles are distinctly different from those composed of ellipsoidal particles. Certain parameters, including the particle–wall rolling friction and restitution coefficients, have minimal impact on the steady state plug characteristics. The present study also suggests that introducing interparticle rolling friction for perfectly spherical particles can achieve the velocity and length appropriate for plugs composed of ellipsoidal particles, although differences in dynamics may persist. Overall, this comprehensive analysis offers valuable insights into plug flow behaviour with non-spherical particles, aiding in the efficient modelling and design of pneumatic conveying systems.

Migration characteristics and plugging rules of self-aggregating nanoparticles in the porous media

Nanoparticle profile control agents have been widely used for water shut-off treatment due to their excellent properties. However, the contradiction between the injectability and the plugging characteristics of profile control agents seriously affects their sealing effect. Self-aggregating nanoparticles can effectively alleviate this contradiction by forming particle clusters in the formation to block water channels. In this study, the injection and plugging properties of self-aggregating nanoparticle profile control agents in porous media were investigated using visual porous media etching model and core model. Injectivity experiments showed that the flow of nanoparticles in porous media was divided into three phases: flow dispersion phase, self-aggregation migration phase, and aggregation plugging state. They could aggregate to form clusters similar to the pore throat size after 60 min. Core displacement experiments showed that the plugging performance of nanoparticles was influenced by solution concentration, injection volume, injection rate, and core permeability. When injecting a 3000 mg/L nanoparticle solution into the core at 60 °C, the residual resistance coefficient was larger than 1.83. The retention rate in pore throats was superior to 60%.

Formation characteristics and leakage termination effects of CO2 hydrate cap in case of geological sequestration leakage

Geological sequestration of carbon dioxide (CO2) has been considered one of the most effective strategies against global warming. The greatest concern on the stored CO2 in sub-seabed sediments is leakage risk and can be solved by the plugging effect of CO2 hydrate cap, which is derived from the capillary force change by hydrate crystal formation inside pores. This study experimentally simulated CO2 upward leakage process in water-containing sediments and investigated the plugging characteristics of formed hydrate cap via magnetic resonance imaging (MRI) and flow characteristic analysis. Different CO2 flow rates (0.3–4.0 ml/min) and initial pressures (1.8–3.0 MPa) were employed for experimental conditions, and the hydrate cap appeared with no CO2 efflux any longer after hydrate formation for several minutes. It is found that both slow flow of CO2 and high pressure are beneficial for the formation of hydrate cap, and the strength of hydrate caps formed in all cases is confirmed by 10.0 MPa pressure test without any CO2 leakage. In addition, the spatial water distribution and the hydrate cap location inside the sediments are analyzed by multi-level MRI images and pressure evolution calculation, respectively. Ultimately, this study conducted a CO2-water flow case and found that the strength of hydrate cap increases with the continuous formation of hydrates. Approximately 27.8% of hydrate saturation is a watershed of the plugging strength of CO2 hydrate cap. This study provides experimental evidences for the plugging effect of hydrate cap on terminating CO2 leakage and is of great significance for the scheme design and risk assessment of CO2 geological sequestration.

Humeral Head Reconstruction With Osteochondral Allograft: Bone Plug Optimization for Hill-Sachs Lesions Using CT-Based Computer Modeling Analysis.

Engaging Hill-Sachs lesions (HSLs) pose a significant risk for failure of surgical repair of recurrent anterior shoulder instability. Reconstruction with fresh osteochondral allograft (OCA) has been proposed as a treatment for large HSLs. To determine the optimal characteristics of talus OCA bone plugs in a computer-simulated HSL model. Descriptive laboratory study; Level of evidence, 6. Included were 132 patients with recurrent anterior instability with visible HSLs; patients who had multidirectional instability or previous shoulder surgery were excluded. Three-dimensional computed tomography models were constructed, and a custom computer optimization algorithm was generated to maximize bone plug surface area at the most superior apex (superiorization) and minimize its position relative to the most medial margin of the HSL defect (medialization). The optimal number, diameter, medialization, and superiorization of the bone plug(s) were reported. Percentages of restored glenoid track width and conversion from off- to on-track HSLs after bone plug optimization were calculated. A total of 86 patients were included in the final analysis. Off-track lesions made up 19.7% of HSLs and, of these, the mean bone plug size was 9.9 ± 1.4 mm, with 2.2 mm ± 1.7 mm of medialization and 3.3 mm ± 2.9 mm of superiorization. The optimization identified 21% of HSLs requiring 1 bone plug, 65% requiring 2 plugs, and 14% requiring 3 plugs, with a mean overall coverage of 60%. The mean width of the restored HSLs was 68%, and all off-track HSLs (n = 17) were restored to on-track. A Jenks natural-breaks analysis calculated 3 ideal bone plug diameters of 8 mm (small), 10.4 mm (medium), and 12 mm (large) in order to convert this group of HSLs to on-track. Using a custom computer algorithm, we have demonstrated the optimal talus OCA bone plug diameters for reconstructing HSLs to successfully restore the HSL track and, on average, 60% of the HSL surface area and 68% of the HSL width. Reconstructing HSLs with talus OCA is a promising treatment option with excellent fit and restoration of HSLs. This study will help guide surgeons to optimize OCA bone plugs from the humeral head, femoral head, and talus for varying sizes of HSLs.

Plugging characteristics of self-degradable diverters within three-dimensional hydro-fractures: An experimental investigation

The dominant fracture can be effectively plugged by injecting self-degradable diverters during temporary plugging fracturing. The subsequent fracturing fluids can divert into the poor fractures. The fracture complexity can be enlarged and the well production can be enhanced. This study established a new diverter temporary plugging evaluation system and carried out 23 groups of temporary plugging experiments to investigate the plugging characteristics of diverters within three-dimensional (3D) hydro-fractures. Experimental results show that (1) the formation process of a temporary plugged zone is determined by the bridging capability of the most significant particulates; (2) the tight plugged zone can undergo diverter attachment, bridging, filling, and compaction or diverter bridging, filling, and compaction; (3) diverters are most likely to plug distorted fractures, followed by inclined-flat fractures, and then axial/transverse-flat fractures due to the varying widths of hydro-fractures; (4) pure fibers can plug hydro-fractures when the fracture width is less than 1.5 mm, and the difference in the diameter of bridging particulates and the fracture width should be less than 1.5 mm when the fracture width exceeds 2.5 mm. Meanwhile, this study investigates the optimal temporary plugging agent formulations for different fracture widths based on economic factors and operational conditions, providing on-site recommendations.

Investigation of the plugging capacity and enhanced oil recovery of flexible particle three-phase foam

In the later stage of water flooding in reservoirs, the oil production decreases. The stability of three-phase foam system is strong, enhancing oil displacement effects of ultrahigh water cut reservoirs. In this paper, the flow state of the foam system was studied by using a microscopic visualization model. Second, sandpack flooding experiments were performed to analyze the optimal plugging conditions of three-phase foam through resistance factors. Finally, single and parallel sandpack flooding experiments were carried out to analyze plugging effect and production conditions under different injection systems and permeability ratios. The research shows that three-phase foam is more stable and capable of plugging. The stable residual resistance factor after injection of the three-phase foam system is 172.75. When the foam and particles are injected simultaneously, the gas–liquid ratio is 1:1, the formation permeability is 5526.5 mD, and the plugging effect of three-phase foam is the best. The oil recovery increases by 24.9% after the injection of three-phase foam system. The three-phase foam system combines Jamin effect of foam and dynamic plugging characteristics of flexible particles. The highest oil recovery factor of 80.87% is achieved at a permeability ratio of 9.99. Three-phase foam flooding has broad application prospects.

Effect of film cooling structures on the cooling characteristics of plugs for two-dimensional (2-D) plug nozzle

Based on a turbulence model experimental validation, some numerical simulations were conducted to investigate the effect of plug film cooling on cooling and aerodynamic characteristics for a 2-D plug nozzle. In this study, two cooling schemes namely the half-covering and full-covering film cooling were designed and involved. For each cooling configuration, the effects of perforated percentage (ranged from 0.5% to 2.0%) and non-dimensional inlet total pressure (ranged from 1.02 to 1.20) of coolant on the cooling and aerodynamic performances are discussed separately. The results confirm that an obvious reduction of plug temperature is achieved under both cooling schemes. While the full-covering film cooling configuration performs better, especially at the plug trailing edge where shock waves occurred. Within the scope of the investigation, a small perforated percentage of 0.5% is favorable due to its superior ability to improve the pressure difference between mainstream and coolant; inversely, a big perforated percentage leads to the coolant flow resistance increasing, which may cause the mainstream to flow back at the plug trailing edge. Rising the inlet total pressure of coolant could enhance the cooling performance but also deteriorate the aerodynamic performance of nozzle. Specifically, compared with the case without cooling configuration, the non-dimensional inlet total pressure of coolant ranged from 1.02 to 1.20, the surface temperature of plug decreased by 20% ～ 45%; the total pressure recovery coefficient decreased by 0.22% ～ 1.26%.

Plugging Characteristics and Evaluation Predicting Models by Controllable Self-Aggregation Nanoparticles in Pore Throat Microcapillaries.

Injecting nanoparticle profile agents into low-permeability heterogeneous reservoirs to plugging water breakthrough channels is a widely used technical method to enhance oil recovery. However, insufficient research on the plugging characteristics and prediction models of nanoparticle profile agents in the pore throat has led to a poor profile control effect, short profile control action time, and poor injection performance in the actual reservoir. This study uses controllable self-aggregation nanoparticles with a diameter of 500 nm and different concentrations as profile control agents. Microcapillaries of different diameter sizes were used to simulate the pore throat structure and flow space of oil reservoirs. Based on a large number of cross-physical simulation experimental data, the plugging characteristics of controllable self-aggregation nanoparticles in the pore throat were analyzed. Gray correlation analysis (GRA) and gene expression programming algorithm (GEP) analysis were used to determine the key factors affecting the resistance coefficient and plugging rate of profile control agents. With the help of GeneXproTools, the evolutionary algebra 3000 was selected to obtain the calculation formula and prediction model of the resistance coefficient and plugging rate of the injected nanoparticles in the pore throat. The experimental results show that the controllable self-aggregation nanoparticles will achieve effective plugging when the pressure gradient is greater than 100 MPa/m in the pore throat, and when the injection pressure gradient is 20-100 MPa/m, the nanoparticle solution will be in the aggregation to breakthrough state in the pore throat. The main factors affecting the injectability of nanoparticles, from strong to weak, are as follows: injection speed > pore length > concentration > pore diameter. The main factors affecting the plugging rate of nanoparticles, from strong to weak, are as follows: pore length > injection speed > concentration > pore diameter. The prediction model can effectively predict the injection performance and plugging performance of controllable self-aggregating nanoparticles in the pore throat. The prediction accuracy of the injection resistance coefficient is 0.91, and the accuracy of the plugging rate is 0.93 in the prediction model.

Preparation and Performance Evaluation of a Temperature and Salt Resistant Hydrophobic Associative Weak Polymer Gel System.

We targeted high-temperature and highly saline old oil fields, whose environmental conditions could be attributed to the significantly high heterogeneity cause by long-term water flooding. The Huabei Oilfield was chosen as the research object. We developed a hydrophobic functional monomer-polymer with temperature and salt resistance by introducing the temperature-resistant and salt-resistant monomer NVP and a hydrophobic functional monomer into the main chain for copolymerization. We used a crosslinking agent with phenolic resin to prepare a weak gel system that showed temperature and salt resistance and investigated its temperature and salt resistance, infective property, plugging performance, liquid flow ability, micropore throat migration, and plugging characteristics. The results obtained using the infrared spectroscopy technique revealed the successful preparation of the phenolic resin crosslinker. The weak gel exhibited good temperature and salt resistance when the polymer concentration was 2000 mg/L, the cohesion ratio was 1:1.5, the additive concentration was 2000 mg/L, the reservoir temperature was 120 °C, and the injected water salinity was 40,300.86 mg/L. The average viscosity retention rate of the 90-day weak gel reached more than 80% and its microstructure was examined. The coreflow experiment results revealed that the weak gel system was characterized by good infectivity. After plugging the weak gel, the effect on the direction of the liquid flow was evident and the flow rate of the low permeability layer increased to a maximum of 48.63% under conditions of varying permeability levels. A significant improvement in the water absorption profile was achieved. The plugging was carried out through a sand-filling pipe under varying permeability conditions and the pressure measuring points in the sand-filling pipe were sucessfully pressurized. The migration ability of the weak gel was good and the blocking rate was >85%.

Synthesis of high strength agar and its water plugging application in enhanced oil recovery

The most popular oil displacement technique in oilfield development is water flooding, yet sustained water flooding makes it simple to create water channeling in the formation, lowering development efficiency. A high strength agar was synthesized by using raw agar and 3-chloro-2-hydroxy-propyl trimethyl ammonium chloride, and it was then combined with PAM to prepare a plugging system to address the issue of water channeling in old oilfields. The successful synthesis of a modified agar was demonstrated by FITR, EM, TG/DSC, and its temperature resistance and agar strength were improved. Gelation and flow experiments were used to test the gelation and plugging characteristics of the plugging system. The results show that the plugging system is a pseudoplastic fluid, the temperature resistance less than 120 °C, the salinity resistance less than 1 × 105 mg/L, the gelation time of is 1 ∼ 3d, the gelation strength reaches grade I, the resistance coefficient less than 10, the breakthrough pressure gradient greater than 20 MPa·m−1, the plugging ratio greater than 90%, and the oil recovery ratio increases 22.8%. This work’s study has a significant impact on enhancing oil recovery.

Study on Microstructure and Silting Characteristics of Soft Soil: A Case Study of Nansha District, Guangzhou

With the development of society and economy, land subsidence in soft soil areas has become a prominent geological disaster in our country’s coastal area. Land subsidence has the characteristics of irreversibility, wide influence range, long aging, etc., and these characteristics are closely related to the characteristics of soft soil, such as physical and mechanical parameters, microstructure characteristics, etc. The Nansha District of Guangzhou was taken as the study area in this paper. Through the collection of preliminary data, two-dimensional scanning electron microscopy, and three-dimensional Computed Tomography (CT), the micro-structure characteristics of soft soil are expounded and its plugging characteristics are further analyzed. The results show that the study area’s soft soil has a honeycomb, granular, and flocculent structure. From the perspective of pore scale distribution, the number of macropores and ultramicro pores is small, and the continuity is poor. In most small and medium pores, namely the aggregate and granular pores. The siltation of soft soil is closely related to the microstructure of soil and can be treated according to the effect of siltation characteristics on the consolidation settlement of soft soil. The research results of this paper can provide targeted prevention and control suggestions for the soft land subsidence disaster in the Nansha area, and also provide a reference for other similar research.

Developments and applications of the CFD-DEM method in particle–fluid numerical simulation in petroleum engineering: A review

Particle and fluid flow is a general problem existing in a series of engineering activities during oil and gas development. Many efforts have been made to investigate the migration, deposition, and plugging characteristics of particles carried by the fluid medium. The discrete element method (DEM) is used for the particle phase, the computational fluid dynamic (CFD) is applied for the fluid phase and many coupling schemes are introduced for interactions between phases. The CFD-DEM studies have been conducted to help mechanism explanation and flow prediction under various work conditions. This work reviews the progress in CFD-DEM coupling simulations about oil and gas development by summarizing the models and relevant applications. Different coupling schemes and their applicable petroleum engineering problems are reviewed. The needs for future research are also discussed. This will be helpful for researchers who are new to particle flow numerical simulation in the CFD-DEM method to shorten the learning cycle and improve the efficiency of problem solving.

Research on plugging characteristics of microorganism induced calcite precipitation in sandstone environment

Microorganism-induced calcite precipitation (MICP) has been proposed to increase crude oil recovery for more than two decades. It is only recently that mine trials have emerged. The present study was conducted to advance the application of MICP for enhanced crude oil recovery. The changes of core permeability and bacterial biomass on permeability reduction rate during MICP treatment were investigated by core blocking experiments and reverse unblocking experiments. The permeability conditions for biomass and calcite production blocking were explored. Based on this, the changes in mechanical properties of the cores by MICP were explored by unconfined pressure experiments. Finally, the mineral composition and mineral phases were analyzed by XRD and SEM. Our study shows that MICP is much less effective at permeabilities less than 66mD. The decrease in permeability presented in the experiment comes from the blocking effect of the injection end of the core on the bacteria. The compressive strength of the MICP-treated cores was increased by 10.05% and was more resistant to brittle damage. Also calcite is attached to the sandstone matrix. The characteristic peaks of calcite were observed in the cores treated with MICP by SEM and XRD. In addition, under the same culture conditions, the mineral morphology in the sandstone environment is quite different from that in the shake flask. In the sandstone environment, calcite is tightly adsorbed on the sandstone matrix, showing a typical rhombic hexahedral structure, and in the shake flask environment, it is more Spherical or spherical aggregates. Based on the above study, the blocking mode of MICP is proposed. The free agglomerated calcite particles form a physical seal in the pore throat and the biofilm mineralizes directly in the sandstone matrix together to seal the sandstone cores. The results of this study report a new mineral morphology difference in MICP. It is also a theoretical support for further improving the MICP for enhanced oil recovery.

Injectivity and plugging characteristics of CO2-responsive gel particles for enhanced oil recovery in fractured ultra-low permeability reservoirs

Although CO2-responsive gel particles (CRGP) injection appears to be a viable strategy for delaying CO2 breakthrough in fractured ultra-low permeability reservoirs, few studies have been conducted to thoroughly evaluate the injectivity and plugging characteristics of CRGP. In the present work, the swelling kinetics of the CRGP at various temperatures and salinities were first characterized through the change in CRGP volume. The rheology properties of CRGP dispersion solution were then evaluated. And then, taking the resistance coefficient, residual resistance coefficient and plugging rate as indexes, the effect of matching coefficient, injection rate, and injection concentration on CRGP injectivity and plugging characteristics was investigated using simulated artificial fractures. Finally, the empirical correlations of injectivity and plugging characteristics parameters were established. According to experimental result, the equilibrium swelling ratio of CRGP was greater than 40-fold at varied salinity conditions. The shear-thinning capabilities of the CRGP dispersion solution, as well as its favorable storage modulus, endowed CRGP with favorable in-depth migration and plugging properties. In addition, in terms of fracture plugging by CRGP, the plugging ratio of CRGP in fractures was higher than 90% when the matching coefficient ranged from 1.0 to 2.0, the injection rate was less than 0.5 mL/min, and CRGP concentration was larger than 3000 mg/L. The acquired empirical relationships were expected to guide the selection of CRGP size, injection concentration, and injection rate for fracture plugging.

Characteristics of CO2 foam plugging and migration: Implications for geological carbon storage and utilization in fractured reservoirs

Fractured reservoirs exhibit heterogeneity and high conductivity, posing challenges to the application of low-carbon and clean production technologies. In this study, the flow and plugging characteristics of CO2 foam in fractured cores were analyzed in physical fracture cores and visual slab fracture models. The influence of surface roughness and fracture openings on foam flow and plugging efficiency were studied. Results show that polymer-enhanced foam displays a higher-pressure drop in a single core with a small fracture opening. With increasing fracture opening, the plugging capacity of the polymer-enhanced foam gradually decreases to that of ordinary foam. In parallel fractures of different openings, ordinary foam is better able to regulate the flow, whereas the conformance control of polymer-enhanced is more robust. Prolonged foam flow in the fractures leads to foam collapse, especially for small fracture openings and high roughness. For such a core, the difference in distance lapsed by the upper and lower ends of the polymer-enhanced foam front is greater than that of the ordinary foam, and the bubble collapse during migration is less. For a given surface roughness, the smaller the fracture opening, the greater the resistance to foam flow. However, the resistance brought forth by surface roughness is greater, for a given fracture opening. Foam flow in the fracture is analyzed in terms of the forces acting on the foam. Understanding foam flow resistance is a key to preventing gas channeling, expanding sweep range and improving the oil washing efficiency.

Sand production behaviors during gas recovery from sandy and clayey‐silty hydrate‐bearing sediments: A comparative analysis

AbstractSand production is a crucial geotechnical issue for safe and efficient gas recovery from natural gas hydrate (NGH) reservoirs. Although the same gas production method of depressurization was chosen for the production trials in the Nankai Trough and the Northern South China Sea, their sand production behaviors differed greatly due to the skeleton diversity of sand in the Nankai Trough and clayey‐silt in the Northern South China Sea, which resulted in different sand control and sand production characteristics. In this study, we conducted experiments to compare sediment responses and sand production behaviors from these two typical gas hydrate‐bearing sediments (GHBSs) before, during, and after hydrate dissociation under depressurization. The results reveal the fluid and sand production rates in both GHBSs are relatively low before and after hydrate dissociation. However, the sand production rate in sandy GHBS keeps stable at a relatively high value during the whole hydrate dissociation period, accompanied by a high fluid production rate and continuous sample subsidence. In contrast, the fluid and sand production rates are proved to be high only at the early stages of hydrate dissociation in clayey‐silty GHBS with sand production decreasing obviously afterward, and the sample subsidence rate exponentially decay until the ultimate subsidence is reached. After experiments, two kinds of particle plugging phenomena, sand bridge and mud cake, are found to form outside sand screens in sandy and clayey‐silty GHBSs, respectively. Differences in permeability, particle migration, and plugging characteristics are thought to be the main inducement of the variability in sand production behaviors in different GHBS types. These findings indicate that sand‐production control strategies should obey geological engineering integration and differ according to the GHBS type. Specifically, we should concern sand production risk in sandy GHBS during and after hydrate dissociation, whereas more attention should be paid to the early stages of hydrate dissociation in clayey‐silty GHBS.

Insights on the penetration and migration of chemically cross-linked systems in porous media

Using the sand-packed tubes with different lengths (0.2–20 m) and different long flat-sand-inclusion visualization models, the penetration and migration laws, in-depth dynamic gelation and plugging characteristics, and the related mechanism of chemically cross-linked systems (HPAM/Cr3+) in porous media are investigated. The results show that there is an optimal concentration ratio between the polymer and the crosslinking agent, and the system of 4000 mg/L HPAM and 3000 mg/L SD-307 can obtain the gel with maximum strength (grade G) and breakthrough pressure gradient (3.13 MPa/m). The relatively weak system of 1800 mg/L HPAM +1000 mg/L SD307 (grade C) can present a similar injection pressure with the strong system of 4000 mg/L HPAM + 3000 mg/L SD307. Moreover, the onset and equilibrium of cross-linking agent production respectively lags behind polymer by at least 1.38 PV and 20.5 PV, and the adsorption amount of the crosslinking agent is 5111 μg/g greater than that of the polymer. Compared strong system (grade G) with the weak one (grade C), the former only has slight difference with the latter in the production and equilibrium of polymer but has significant difference in cross-linking agent. The corresponding injected volumes of production and equilibrium of polymer present significantly increase before the length of 1 m. Furthermore, the effluent of strong cross-linked system in 8 m in front of 20 m-long sand-packed tube exhibits the effective gelation and can achieve efficient plugging. On the contrary, the gel strength is very low or even the gelation is difficult as the migration distance exceeds 8 m. Although a greater fractional flow more than 75% can be achieved at high permeability under heterogeneous condition, the sweep of subsequent water to the low permeability layer after injecting the system become worse and worse with increasing injected volume (0.1–0.9 PV) due to the damage to the low permeability layer.

Study on selective plugging characteristics and oil displacement mechanism of microsphere in porous media

Microspheres are widely used as profile control and water plugging products at present. However, the current research on microspheres is mainly focused on oil displacement experiments. In order to solve this problem, based on the Bohai sea in the BZ of inhomogeneous reservoir conditions, this article has done the matching study on particle size and hole roar and the seepage research in porous medium by means of particle size analysis, pressure tests, single-phase block experiments, and the double tube parallel oil displacement experiments, revealing the characteristics of oil & water selective plugging and the mechanism of oil displacement in porous media. The results show that the average particle size of the microspheres increases from 4.857μm to 24.53μm, and the maximum expansion factor reaches 5.03 times after 72h of swelling in BZ25 oilfield water at 75 C. In the two-pipe parallel oil flooding experiment with the permeability of 1000mD and 3000mD respectively, the comprehensive recovery rate after the first water flooding is 28.06%, and the two-pipe average recovery rate is increased by 1.58% after the injection of 2000ppm microsphere with 0.3PV, and there is no significant increase in oil displacement efficiency. The comprehensive recovery rate reached 38.6% and increased by 8.99% after 4PV of subsequent water flooding, indicating that microsphere flooding effectively improved the water sweep efficiency of subsequent injection.

Study on ammonium-promoted phenol-formaldehyde-based gel for enhanced oil recovery and its seepage characteristics in porous media

The phenol-formaldehyde crosslinker has low reactivity at low temperature, and is not easy to occur crosslinking reaction. In order to solve this problem, a kind of ammonium-promoted phenol-formaldehyde-based gel profile control agent was constructed which has the reactivity at low temperature. The basic formula is 0.30%~0.60%polymer, 0.01%resorcinol, 0.60% phenol-formaldehyde crosslinker and 0.10% ammonium salt. The results showed that the final gelling time was 6 days at 65°C, and the final gelling strength could reach G grade. In response to the problem that the plugging characteristics of ammonium-promoted phenol-formalde-hydebased gel are still unclear, the seepage characteristics of the phenol-formaldehyde-based gel in porous media are revealed by physical simulation of sand-pack. The research shows that the plugging rate of porous media with permeability of 2000 mD reaches 98%, the breakthrough pressure gradient is greater than 1.35 MPa/m.