Formation Permeability Research Articles

Hydraulic injection tests in the pilot EGS borehole PVGT-LT1 in Litoměřice, Czechia

Successful utilization of geothermal energy is conditioned by sufficient permeability of the rock formation as a heat exchanger. We present results of hydraulic injection tests carried out in 2020 in the pilot geothermal borehole PVGT-LT1 in Litoměřice, Czech Republic, which samples 800 m of Paleozoic and Mesozoic sediments on the top of a crystalline basement. The low hydraulic conductivity on the order of 10−11 m/s obtained by recovery tests was verified by large-scale injection tests monitored by DTS temperature logging. During the first test, 24 m3 of water were injected and a permeable fracture was created at 880 m depth, breaking through the ignimbrite layer. The opening pressure of 12.55 MPa corresponds to the lower estimate of the minimum stress at this depth. The second injection was performed 7 months later and 202 m3 were injected at flow rates reaching 50 l/min. It showed that the fracture had been preserved since the first injection, which was documented by a non-zero flow rate at the smallest injection pressures and also by a stabilized water level in the borehole, which dropped immediately after the fracture formation. No induced seismicity accompanied the injection, which indicates a possibly low seismogenic potential of this area of the Bohemian Massif. The model of finite conductive fracture fitted to the pressure decay curve during shut-in intervals gives an estimate of a fracture half-length exceeding 100 m.

Reactive flow of microemulsion-based EDTA fluid for carbonate stimulation

Traditional methods for stimulating carbonate formations primarily rely on the use of highly reactive acids, such as hydrochloric acid (HCl), to create wormholes. However, the limitations of this approach in certain scenarios have prompted the exploration of alternative strategies. In this study, we investigate the synergistic potential between microemulsion and ethylenediaminetetraacetic acid (EDTA) for stimulating carbonate formations. Microemulsion systems were formulated using a nonionic surfactant, sec-butanol as a cosurfactant, xylene as the oily phase, and an aqueous solution of EDTA as the water phase. The microemulsions were characterized by phase equilibrium and rheological behavior. Coreflooding and static dissolution experiments were performed. We employ microCT imaging to evaluate the change in porosity in static dissolution experiments. The results reveal that microemulsions containing EDTA presented remarkable stability and were able to significantly enhance carbonate rock permeability up to 85%, indicating that dissolution occurred and the rock was stimulated. Analyses of microCT images on static dissolution experiments of Indiana limestones in reactive microemulsions indicate an increase in porosity, confirming the dissolution process. These findings highlight the synergistic effect of EDTA in microemulsion media for enhancing the rock permeability of carbonate formation as an alternative as low reactive system.

Reactive Transport Modeling of Chemical Stimulation Processes for an Enhanced Geothermal System (EGS)

An enhanced geothermal system is a kind of artificial geothermal system, which can economically exploit geothermal energy from deep thermal rock mass with low permeability by artificially created geothermal reservoirs. Chemical stimulation refers to a reservoir permeability enhancement method that injects a chemical stimulant into the fractured geothermal reservoir to improve the formation permeability by dissolving minerals. In this study, a reactive solute transport model was established based on TOUGHREACT to find out the effect of chemical stimulation on the reconstruction of a granite-hosted enhanced geothermal system reservoir. The results show that chemical stimulation with mud acid as a stimulant can effectively improve the permeability of fractures near the injection well, the effective penetration distance can reach more than 20 m after 5 days. The improvement of porosity and permeability was mainly caused by the dissolution of feldspar and chlorite. The permeability enhancement increased with the injection flow rate and HF concentration in the stimulant, which was weakly affected by the change in injection temperature. The method of chemical enhancement processes can provide a reference for subsequent enhanced geothermal system engineering designs.

Effects of fluid flow in triple porosity medium on fracture width and its propagation during lost circulation control

During oil and gas well construction, lost circulation is one of the major challenges, and to migrate the problem, lost circulation materials (LCMs) should be used to resist fracture reopening with the hypothesis of fracture tip isolation. A triple porosity medium Darcy flowing model was developed to capture pressure distribution along the fracture surface, coupled with a dislocation-based fracture mechanics model to calculate fracture width and assess its propagation. In the model, mud cake on wellbore and fracture surface was considered as the third type of pore medium. The rest dual pore medium models incorporate the fluid flow through LCMs within fracture and the fluid leakoff from fracture into matrix. Sensitivity analyses of the key parameters, such as triple pore medium permeability, viscosity, wellbore pressure, plugging location are implemented, and the results emphasize that fracturing resistance effect of LCMs was controlled not only by the fluid flow within fractures, but also by the flow through mud cake on wellbore into matrix. To inhibit fracture reopening, in high permeability formations, both reduction of mud cake permeability and LCMs permeability were required while in lower permeability formations, fluid flow within fractures dominates and should be minimized. Besides, tip isolation can be achieved by extending sealing fracture length. However, high wellbore pressure or long operation time will result in elevated distances and unallowable fluid loss. Then, wellbore pressure must be reduced to cure the lost circulation. More viscosity of the fluid and total integrity plugging of LCMs are another major factor extending the time for pressure transfer to fracture tip, resisting unexpected fracture propagation. The method proposed in this study clarifies that tip isolation can be realized by fracture plugging and reduction of fluid filtration from the wellbore to matrix. Moreover, operational insights on LCMs design can also be derived.

A phase‐field model for hydraulic fracture nucleation and propagation in porous media

AbstractMany geo‐engineering applications, for example, enhanced geothermal systems, rely on hydraulic fracturing to enhance the permeability of natural formations and allow for sufficient fluid circulation. Over the past few decades, the phase‐field method has grown in popularity as a valid approach to modeling hydraulic fracturing because of the ease of handling complex fracture propagation geometries. However, existing phase‐field methods cannot appropriately capture nucleation of hydraulic fractures because their formulations are solely energy‐based and do not explicitly take into account the strength of the material. Thus, in this work, we propose a novel phase‐field formulation for hydraulic fracturing with the main goal of modeling fracture nucleation in porous media, for example, rocks. Built on the variational formulation of previous phase‐field methods, the proposed model incorporates the material strength envelope for hydraulic fracture nucleation through two important steps: (i) an external driving force term, included in the damage evolution equation, that accounts for the material strength; (ii) a properly designed damage function that defines the fluid pressure contribution on the crack driving force. The comparison of numerical results for two‐dimensional test cases with existing analytical solutions demonstrates that the proposed phase‐field model can accurately model both nucleation and propagation of hydraulic fractures. Additionally, we present the simulation of hydraulic fracturing in a three‐dimensional domain with various stress conditions to demonstrate the applicability of the method to realistic scenarios.

Temperature-sensitive and amphiphilic silica nanoparticle-stabilized Pickering emulsion for water shutoff

Due to the shale matrix's low permeability and narrow pore throats, conventional Pickering emulsion plugging agents are unable to effectively seal the formation, making it challenging to create a reliable mud cake that prevents fluid penetration. To address this issue, SiO2 nanoparticles (PEG200-SiO2-OTES) with amphiphilic and temperature-sensitive properties were synthesized for this study. These modified particles were used to prepare temperature-sensitive Pickering emulsions. The aim was to use the emulsion as a carrier to transport the nanoparticles to the specified stratum to release and seal the pore throat. This temperature-sensitive smart Pickering emulsion-based plugging agent (POOP) is used to water shutoff. The produced material had a particle size of around 20 nm, according to structural studies, and had a sensitive temperature response (response temperature of 80 °C). Furthermore, laboratory tests and characterizations revealed that the average diameter of the POOP emulsion droplets was measured to be 1.62 µm, with the emulsion exhibiting a response temperature for breakage at approximately 80 °C.The plugging agent could release PEG200-SiO2-OTES particles at the response temperature of the formation. At this temperature, the plugging agent particles undergo a transition from hydrophilic to hydrophobic, effectively sealing the low permeability (100 mD) and high permeability (1000 mD) formations with sealing efficiencies of up to 83.56% and 75.07% respectively.

Mechanisms of emerging resistance associated with non-antibiotic antimicrobial agents: a state-of-the-art review.

Although the development of resistance by microorganisms to antimicrobial drugs has been recognized as a global public health concern, the contribution of various non-antibiotic antimicrobial agents to the development of antimicrobial resistance (AMR) remains largely neglected. The present review discusses various chemical substances and factors other than typical antibiotics, such as preservatives, disinfectants, biocides, heavy metals and improper chemical sterilization that contribute to the development of AMR. Furthermore, it encompasses the mechanisms like co-resistance and co-selection, horizontal gene transfer, changes in the composition and permeability of cell membrane, efflux pumps, transposons, biofilm formation and enzymatic degradation of antimicrobial chemicals which underlie the development of resistance to various non-antibiotic antimicrobial agents. In addition, the review addresses the resistance-associated changes that develops in microorganisms due to these agents, which ultimately contribute to the development of resistance to antibiotics. In order to prevent the indiscriminate use of chemical substances and create novel therapeutic agents to halt resistance development, a more holistic scientific approach might provide diversified views on crucial factors contributing to the persistence and spread of AMR. The review illustrates the common and less explored mechanisms contributing directly or indirectly to the development of AMR by non-antimicrobial agents that are commonly used.

Acid-Soluble Drilling Fluid in the Northern Carbonate Reservoir of the Yishan Slope in the Ordos Basin

The carbonate reservoir in the northern Yishan slope of the Ordos Basin presents significant challenges to gas field exploration and development. With its low pressure, limited porosity, low permeability, and abundance of micro-fractures, the reservoir is resistant to acid dissolution. Once solid particles block these fractures during drilling and completion, serious reservoir damage ensues. To address these obstacles, we engineered an acid-soluble, solid-free drilling fluid system in the lab. This involved incorporating sodium carboxymethyl cellulose, heat-resistant starch, fungicides, and lubricants. Contrasted with the commonly used potassium ammonium based drilling fluid system, our innovative solution showed notable improvements. Specifically, the density decreased by 0.04 to 0.06 g/cm3, and the solid content decreased by 4.0% to 6.50%, while the acid-soluble rate surged from 8.50% to 95.45%. In addition, the reservoir permeability recovery value saw an increase from 51.50% to 95.88%. In practical field application, we employed this novel drilling fluid system in ten horizontal wells. Following acid fracturing and reconstruction, these wells registered a 75.94% increase in gas production compared to nearby wells. Our findings demonstrate that the proposed system effectively mitigates the incursion of solid-phase particles into the reservoir while enhancing acidification during acid fracturing. This results in the swift removal of plugging, restoration of formation permeability, and improved well production. Our research thus introduces a drilling and completion fluid system of high efficiency with superior reservoir protection performance, potentially offering substantial benefits to the development of carbonate rock salt gas reservoirs.

Mass Transfer Analysis of CO2-Water-Rock Geochemical Reactions in Reservoirs

It is difficult to exploit low-permeability reservoirs, and CO2 flooding is an effective method to improve oil recovery from low permeability reservoirs. However, in the process of CO2 flooding, acidic fluids dissolved in formation water will react with rock to cause dissolution and precipitation, resulting in pores and precipitates, changing the evolution law of seepage channels, destroying formation integrity, and affecting the effect of CO2 oil displacement. The change in rock’s physical properties and the mass transfer law between CO2-water-rock are unclear. This paper considers the coupling effects of seepage, mechanics, and chemistry when CO2 is injected into the formation. The mass transfer model of CO2-water-rock in the geochemical reaction process is established on this basis. The physical properties of the reservoir after CO2 injection are quantitatively studied based on the microscopic mechanism of chemical reaction, and the migration law of solute in the reservoir rock during CO2 flooding under the coupling effects of multiple fields is clarified. The experimental results show that with the increase in reaction time, the initial dissolution reaction of formation rocks will be transformed into a precipitation reaction of calcite, magnesite, and clay minerals. The porosity and permeability of the rocks near the well first increase and then decrease. The far well end is still dominated by dissolution reactions, and the average values of formation porosity and permeability show an upward trend. Although the dissolution reaction of CO2-water-rock can improve the physical properties of reservoir rocks to a certain extent, the mutual transformation of the dissolution reaction and precipitation reaction further exacerbates the heterogeneity of formation pore structure, leading to the instability of CO2 migration, uneven displacement, and destruction of formation stability. The research results of this paper solve the problem of quantitative calculation of physical parameters under the coupling effect of multiple fields after CO2 injection into reservoirs and can predict the changes in formation physical properties, which can provide a certain theoretical basis for evaluating formation integrity and adjusting CO2 injection under the condition of CO2 flooding.

Research and performance optimization of carbon dioxide foam fracturing fluid suitable for shale reservoir

Compared to conventional fracturing techniques, foam fracturing has numerous advantages, including good shear resistance, strong sand carrying capacity, low fluid loss, low damage, and fast return rates. It is particularly suitable for stimulation in low pressure, low permeability, and water-sensitive formations. Specifically, CO2 foam fracturing is crucial in energy savings and emission reductions, controlling the expansion of reservoir clay minerals, reducing crude oil viscosity, and improving the production of water-locked reservoirs. In this paper, we investigate the foam fracturing fluid and evaluate its performance. We selected thickeners with good foaming stability and foaming agents with excellent performance at low dosage levels, based on experimental evaluation. We finally determined the formulation of the foam fracturing fluid by analyzing the experimental data, such as foam half-life, foam mass, and viscosity. We experimentally evaluated the viscosity, static sand settling properties, and rheological properties of the fluid. After being tested on the reservoir core, the foam fracturing fluid has a viscosity of 2 mPas. Moreover, the residue content is 1.1 mg/L, the surface tension is 24.5 mN/m, and the interfacial tension is 1.5 mN/m. The fluid-carrying sand experiment of 40–70 mesh ceramic particles, commonly used in shale gas fracking, was evaluated. The sand-to-liquid ratio was set at 40% for the static sand-carrying experiment. The flow of the fluid-carrying sand was good, and the settling property was satisfactory for 3 h. We used shale reservoir cores from well W-1 to assess the rate of foam fracture, which was less than 19%. Under the experimental conditions of a shear rate of 170 S−1 and a temperature of 90°C, the viscosity of fracturing fluid was measured to be greater than 50 mPas, 90 min after shear, demonstrating the excellent temperature and shear resistance of the foam fracturing fluid. Using CO2 foam fracturing fluid can significantly improve the reconstruction effect of low permeability hydrocarbon reservoirs (especially unconventional reservoirs) and solve problems related to water resources and environmental protection during the process of oil and gas reservoir development. It will be a major factor in improving construction impacts and addressing water and environmental concerns for low permeability hydrocarbon reservoirs, particularly unconventional ones that utilize CO2 foam fracturing fluids.

Synthesis of Short Peptides with Perfluoroalkyl Side Chains and Evaluation of Their Cellular Uptake Efficiency.

With an increasing demand for macromolecular biotherapeutics, the issue of their poor cell-penetrating abilities requires viable and relevant solutions. Herein, we report tripeptides bearing an amino acid with a perfluoroalkyl (RF ) group adjacent to the α-carbon. RF -containing tripeptides were synthesized and evaluated for their ability to transport a conjugated hydrophilic dye (Alexa Fluor 647) into the cells. RF -containing tripeptides with the fluorophore showed high cellular uptake efficiency and none of them were cytotoxic. Interestingly, we demonstrated that the absolute configuration of perfluoroalkylated amino acids (RF -AAs) affects not only nanoparticle formation but also the cell permeability of the tripeptides. These novel RF -containing tripeptides are potentially useful as short and noncationic cell-penetrating peptides (CPPs).

Experimental Investigation of Mechanical Properties of Clay–Cement Slurry Containing Graphene Oxide

As a widely used material in underground engineering, clay–cement slurry grouting is known for its initial poor anti-seepage and filtration capacity, the low strength of the resulting stone body, and its tendency towards brittle failure. To explore efficient and environmentally friendly grouting materials, industrial-grade graphene oxide (GO) was incorporated into a clay–cement slurry to create a new type of slurry called a GO composite. These GO composites were then utilized to reinforce fractured formations. Uniaxial compression tests, shear strength tests, permeability tests, and electron microscopy scans were conducted to investigate the strength, permeability, and microscopic features of the GO composite-reinforced fractured formations. Furthermore, the optimization effect and application prospects of graphene oxide on clay–cement slurry materials were evaluated. The experimental results demonstrated that the modified slurry effectively improved the compressive strength (increased by 7.2% to 32.5%) and shear strength (increased by 28.6% to 105.3%) of consolidated fractured gravel. By conducting orthogonal experiments with range analysis, variance analysis, and multiple regression analysis, it was shown that there was a strong correlation between the consolidated body and three factors influencing the permeability coefficient. Among these factors, the OPC content had the most significant impact on the permeability coefficient, followed by the GO content. Graphene oxide was found to promote cement hydration reactions, guide the growth of hydration products on the surface of graphene oxide nanosheets, optimize the pore structure in grouting materials, and reduce microcracks between the slurry and the fractured gravel interface. Electron microscopy characterization and fractal analysis revealed that the addition of graphene oxide effectively reduced the degree of microdamage during the sample’s failure process. This ensured the integrity of the sample during the unstable failure process, enhanced the material’s toughness, and improved its ability to resist loads.

Hydraulic fracturing using high-boiling fraction of oil as a fracturing fluid

Background: In recent years, there has been a trend towards deterioration in the structure of residual reserves at the fields of Kazakhstan. A significant part of the reserves is located in low-permeability reservoirs and in the zones not covered by flooding. The main factor negatively affecting the productivity and efficiency of development is the heterogeneity of oil reservoirs.
 Oil-saturated formations are an alternation of permeable oil-saturated sand or limestone and impermeable clay or dolomite layers, lenses and interlayers. Up to 1020 interlayers can be distinguished within the reservoir, which indicates a strong compartmentalization of the reservoirs. Due to the complexity of the structure of oil deposits, it is very difficult or impossible to ensure complete drainage of the entire volume of the deposit and complete coverage of oil displacement by water into production wells through injection wells.
 Aim: Increasing oil recovery in a cost-effective way.
 Materials and methods: Experimental studies of the processes of impact on the bottomhole formation zone with high-boiling oil components were carried out using a laboratory machine for diamond drilling, an installation for determining the permeability of a rock in terms of liquid and gas, an installation for determining oil viscosity, and an installation for pumping fracturing fluid into the reservoir model.
 Results: As a result of applying the hydraulic fracturing method using high-boiling oil components, it is possible to increase the permeability of low-permeability formations and significantly increase oil recovery.
 Conclusion: Due to the geological structure of multi-layer oilfields, water-based gel fracturing fluids to increase oil flow to wells are considered ineffective due to the adsorption of gels with long molecules in the pores of the formation and swelling of the clay particles of the reservoir when they interact with the water-based fluid.

A coupling prediction model of annular pressure build-up for deepwater oil and gas wells during transient-state testing

To accurately predict annular pressure build-up of deepwater high pressure-high temperature oil and gas wells during the transient-state testing, a coupling prediction model of trapped & untrapped annular pressure build-up is proposed. For the short-term process of gas well transient testing, a wellbore transient heat transfer model has been established. Then the improved coupling model of trapped & untrapped annular pressure build-up is established, which is not only novelly considering fluid thermodynamic properties (isobaric expansion coefficient and isothermal compression coefficient) under high pressure-high temperature conditions and annulus fluid mass changes of untrapped annulus, but also considering annulus volume changes. For precise coupling calculating the annular pressure build-up, the annulus is divided into infinitesimal grid cells along well depth. The impact of different considering factors, testing times, testing production rates, formation permeability and cement sheath sealing positions on the annular pressure build-up in the model is investigated. The results show that conventional models (high pressure-high temperature properties and mass changes of the fluid are not considered) will greatly overestimate the annular pressure build-up; as the testing time increases, the impact of untrapped annulus fluid mass changes on the annular pressure build-up will gradually take the dominant role; reasonably optimizing the setting of untrapped annulus open hole section in high permeability formations and increasing the distance between cement sheath and the upper casing shoe can effectively relieve the increasing annular pressure build-up. These findings can achieve accurate prediction of trapped and untrapped annular pressure build-up, and play an important role in guaranteeing the wellbore integrity and safety of deepwater oil and gas wells during transient-state testing.

Endothelial Permeability and the Angiopoietin/Tie2 System Following Mild and Severe COVID-19

Endotheliopathy plays a role in the development of acute kidney and lung injury in COVID-19, probably due to inflammation, endothelial permeability, vascular leakage and edema formation. This study examined alterations in the circulation of patients with mild and severe COVID-19 on in vitro endothelial permeability and its relation to the endothelial angiopoietin/Tie2 system, which is involved in the regulation of endothelial permeability. Plasma was obtained from COVID-19 patients admitted to the ward (n = 14) or ICU (n = 20) at admission and after 1 and 2 weeks and healthy controls (n = 5). Human kidney and lung endothelial cells were exposed to patient plasma and treated with recombinant angiopoietin-1. In vitro endothelial barrier function was assessed using electric cell-substrate impedance sensing. Circulating markers of the angiopoietin/Tie2 system, endothelial dysfunction and glycocalyx degradation were measured by ELISA. Plasma from COVID-19 patients reduced endothelial resistance compared to healthy controls, but COVID-19 plasma-induced drop in endothelial resistance did not differ between ward and ICU patients. Circulating angiopoietin-2, soluble Tie2 and soluble Tie1 levels increased over time in ICU patients, whereas levels remained stable in ward patients. The increase in angiopoietin-2 was able to predict 90-day mortality (AUC = 0.914, p < 0.001). Treatment with recombinant angiopoietin-1 did not restore COVID-19 plasma-induced hyperpermeability. In conclusion, these results suggest that indirect effects of the virus represented in the circulation of COVID-19 patients induced endothelial hyperpermeability irrespective of disease severity and changes in the endothelial angiopoietin/Tie2 system. Nonetheless, angiopoietin-2 might be of interest in the context of organ injury and patient outcome in COVID-19.

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.

Sensitivity Analysis of Oil and Gas Production in the In Situ Pyrolysis of Oil Shale

The Maoming basin in south China is rich in oil shale resources, whereas the Youganwo formation is a potential area for large-scale in situ exploration because of its relatively large thickness, high oil content, and good continuity. Based on previous geologic studies on the Maoming basin and the laboratory experimental data, in situ pyrolysis models for shale oil are established using the CMG-STARS software to simulate the in situ heating and reactions. To analyze the major influencing factors, the CMOST module is employed to conduct the sensitivity analysis with accumulated oil and gas production as the target functions. The initial kerogen concentration, formation permeability, activation energy of pyrolysis reaction, frequency factor, heating rate, heating power, heat loss, heat conductivity, heat capacity, and bottom-hole pressure are chosen to be the controlling parameters. A total of 128 cases are calculated for each target function with the fractional factorial sampling method. The sensitivity analysis results demonstrate that the heating power, initial kerogen concentration, and reaction activation energy are the major influencing factors for oil and gas production. The simulation results also reveal that high non-uniformity of the temperature field will cause the light oil to convert to gas and char at the high-temperature zone near the heater well. It is suggested that proper control of formation temperature, such as increasing permeability to promote oil and gas flow and form a more uniform temperature field, will help to prevent oil production loss caused by secondary reactions.

Simulation of sandstone formation damage caused by solid particle invasion

During the drilling and completion process, the invasion of solid particles can have a serious impact on reservoir permeability, but there is a lack of effective prediction models for its impact. We developed a prediction model of solid particle invasion damage in response to the issue of reservoir damage induced by solid particle invasion during the exploitation of sandstone reservoirs. By considering the changes in pore permeability characteristics, particle migration and rock stress-strain state are coupled. The findings reveal that as filtration duration increases, the concentration of suspended particles and sediment particles increases, resulting in a progressive reduction in formation permeability around the wellbore. The greater the filtration coefficient, the greater the quantity of particle deposition, however, this also leads to a slowdown in the growth in deposition quantity. As the diffusion rate increases, particles are more likely to deposit. The concentration of suspended particles decreases progressively as tortuosity increases, as does the concentration of sediment particles. Large saturation sedimentation in the pore throat may cause more suspended particles to deposit, lower the effective seepage channel of the pore throat, and drastically impair formation permeability. The results of the impact factor comparison showed that filtration coefficient and medium tortuosity are the key factors. Improving the temporary plugging effect of solid particles in formations with large tortuosity of pore throats can effectively reduce reservoir damage. The findings of this study can help for optimization design of solid particles in drilling fluid for reservoir protection.

UTILIZATION OF MODIFIED PLASTIC WASTE ON THE POROUS CONCRETE BLOCK CONTAINING FINE AGGREGATE

Modification of plastic waste to be use as a replacement of coarse aggregate on the manufacturing of porous concrete block is presented in this paper. Different proportions of sand content were used with percentage of 1%, 5% and 10% by total weight of the sample to investigate its effects on the performance of porous concrete blocks based on some conducted tests i.e., compression and flexural load resistance, porosity, and infiltration rate tests. The results show that the porous concrete block with 5% of sand addition showed better strength properties compared to other mixtures. With 5% modified PET coarse aggregate, the compressive strength decreased for about 26%. Similar trends can be also observed when using PP and HDPE plastic aggregate. However, the inclusion of PET aggregate in porous concrete blocks with 5% of sand inclusion does not significantly show better strength indicating the weak bonding between plastic and cement mortar was performed in porous concrete block matrix as evident through the Scanning Electron Microscopy analysis. The formation of pores and higher permeability can be also expected after adding PET plastic waste as seen in porosity and infiltration rate results. Furthermore, the utilization of coarse aggregate made from plastic waste in porous concrete blocks containing fine aggregate is a potential solution on plastic waste management for permeable pavement including foot traffic and light load application.

The tigecycline resistance gene tetX has an expensive fitness cost based on increased outer membrane permeability and metabolic burden in Escherichia coli

Livestock-derived tetX-positive Escherichia coli with tigecycline resistance poses a serious risk to public health. Fitness costs, antibiotic residues, and other tetracycline resistance genes (TRGs) are fundamental in determining the spread of tetX in the environment, but there is a lack of relevant studies. The results of this study showed that both tetO and tetX resulted in reduction in growth and an increased in the metabolic burden of E. coli, but the presence of doxycycline reversed this phenomenon. Moreover, the protection of E. coli growth and metabolism by tetO was superior to that of tetX in the presence of doxycycline, resulting in a much lower competitiveness of tetX-carrying E. coli than tetO-carrying E. coli. The results of RNA-seq showed that the increase in outer membrane proteins (ompC, ompF and ompT) of tetX-carrying E. coli resulted in increased membrane permeability and biofilm formation, which is an important reason for fitness costs. Overall, the increased membrane permeability and metabolic burden of E. coli is the mechanistic basis for the high fitness cost of tetX, and the spread of tetO may limit the spread of tetX. This study provides new insights into the rational use of tetracycline antibiotics to control the spread of tetX.