Low Injection Rates Research Articles

Optimization of the delivery of molecules into lymph nodes using a lymphatic drug delivery system with ultrasound

Conventional treatment for lymph node (LN) metastasis such as systemic chemotherapy have notable disadvantages that lead to the development of unwanted effects. Previously, we have reported the lymphatic administration of drugs into metastatic LNs using a lymphatic drug delivery system (LDDS). However, prior studies of the LDDS have not attempted to optimize the conditions for efficient drug delivery. Here, we investigated the influence of several factors on the efficiency of drug delivery by a LDDS in conjunction with ultrasound (US). First, the effect of the injection rate on delivery efficiency was evaluated. Fluorescent molecules injected into an upstream LN were delivered more effectively into a downstream LN when a lower injection rate was used. Second, the influence of molecular weight on drug delivery efficiency was determined. We found that molecules with a molecular weight >10,000 were poorly delivered into the LN. Finally, we assessed whether the administration route affected the delivery efficiency. We found that the delivery efficiency was higher when molecules were administered into an upstream LN that was close to the target LN. These findings revealed the importance of a drug’s physical properties if it is to be administered by LDDS to treat LN metastasis.

Simulation study of wormhole formation and propagation during matrix acidizing of carbonate reservoirs using a novel in-situ generated hydrochloric acid

Optimum acid selection based on reservoir condition is one of the key elements in achieving a successful treatment in carbonate matrix acidizing. High reaction and corrosion rate of regular hydrochloric acid especially in tight reservoirs with high temperatures is considered as a limitation of this acid. One alternative in a high-temperature reservoir is to use in-situ generated hydrochloric. The objective of this study is to simulate acidizing treatment using both regular hydrochloric and in-situ generated hydrochloric acid. A continuum two-scale model for linear and radial flow geometry was used to simulate dissolution pattern. A finite-volume method with an implicit backward Euler scheme was used to solve the governing equations. The results of the simulation in a linear system showed that, due to low face dissolution, the in-situ generated hydrochloric at low injection rates could create longer wormholes with less pore volume to breakthrough. The results also proved that using the in-situ generated hydrochloric acid could lead to less face dissolution and deeper penetration of acid into the reservoir. This acidizing system is very suitable in situations where a low injection rate is needed and regular hydrochloric cannot be used due to higher pore volume to breakthrough and high corrosion rate. Cited as : Kiani, S., Jafari, S., Apourvari, S. N., Mehrjoo, H. Simulation study of wormhole formation and propagation during matrix acidizing of carbonate reservoirs using a novel in-situ generated hydrochloric acid. Advances in Geo-Energy Research, 2021, 5(1): 64-74, doi: 10.46690/ager.2021.01.07

Numerical study on the effect of injection pressure on high-pressure diesel spray

This paper analyses the effect of injection pressures on spray and flame structures under high-pressure diesel spray conditions using a three-dimensional Reynolds-Average Navier-Stokes (RANS) model. The simulations are conducted using three kinetic mechanisms known as Luo (106 species), Cai (57 species) and Yao (54 species). Tabulation and Dynamic Adaptive Chemistry (TDAC) solver is adopted to reduce the computational cost. The reacting results obtained using the Luo kinetic mechanism demonstrate the best agreement with the experiment. The Cai and Yao chemistry models overpredict and underpredict the ignition delay time respectively, whereas both mechanisms overpredict the flame lift-off length, particularly at higher injection pressures. It is found that the error for the ignition delay time is larger at higher injection pressures while the opposite is true for the flame lift-off length. The results reveal that at lower injection rates, the cool flame, represented by the CH2O, occurs at richer mixture closer to the nozzle. On the other hand, the heat release rate is lower while the CO emission is higher. Detailed analysis on scalar fields shows that the Cai and Yao mechanisms lead to more consistent results in capturing the temperature field in terms of high-temperature reaction zone while Yao and Luo mechanisms result in a more consistent trend in producing the C2H2 species.

Identification and characterization of a proper gel system for large-volume conformance control treatments in a fractured tight reservoir: From lab to field

The existence of fractures in petroleum reservoirs can greatly reduce the sweep efficiency and subsequently limit the oil recovery during water flooding. Gel treatment is widely known as a cost-effective method for conformance control and water shutoff during water flooding in fractured reservoirs. In this study, we discuss the feasibility of three types of gel systems for conformance control in fractured reservoirs, aiming to select a proper one for field pilot applications in Huabei oilfield (China). Based on the gelation time and the gel strength, the water-soluble phenolic resin (WSPR) gel was chosen for field applications. This silica nanoparticle strengthened WSPR gel demonstrated high gel strength and long-term thermal stability in the lab. Furthermore, its plugging capability was studied by determining the rupture pressure of the gel-filled tubes. The results indicate that the plugging ability of WSPR gel is enhanced with increasing the polymer concentrations and decreasing the size of apertures. Besides, the WSPR gel exhibits high rupture pressure under low brine injection rate. For field applications, the pressure transient tests, tracer tests and the injection-production data were used collaboratively to determine the volume of the fractures in the reservoir. A large volume of gelant was designed for well treatment, and multiple gel slugs with different polymer concentrations were tailored to meet the operational conditions. After the gel treatments, the bottom hole pressure for each injector was significantly increased, indicating that the fractures were effectively plugged. Moreover, the oil production rates were notably increased, accompanied by a prominent decrease in water cut after the gel treatment. To date, the oil production rates of two well-connected production wells, HH55P56 and HH55P58, have been increased from 0.36 t/d to 0.9 t/d and from 0.19 t/d to 0.48 t/d, respectively. The oil production rate of well HH55P24 has been increased by 0.5 t/d.

Effect of miscibility and injection rate on water-saturated CO2 Injection

Water-saturated CO2 (wsCO2) injection into oil reservoirs has recently been proposed to provide better oil recovery and CO2 storage than can be obtained by pure CO2 injection. However, the interaction of wsCO2 with oil under different miscibility conditions and injection rates has not been investigated. We inject wsCO2 and pure CO2 at a "low rate" of 0.5 cc/min (to simulate gravity dominance) into Bentheimer sandstone cores at 70°C and at three pressures:14.5 MPa (2100 psia), 11.7 MPa (1700 psia), and 9.0 MPa (1300 psia) to represent miscibility, near-miscibility, and immiscibility, respectively. At near-miscibility, we also inject these fluids at a "high rate" of 2.5 cc/min in order to simulate gravity-viscous transition. The oil phase consists of a mixture of 0.65 hexane and 0.35 decane by molar fraction.For the low injection rate, at miscibility, the mobility ratio of wsCO2 injection is found to be 99% less than that of CO2 injection; at near-miscibility, 85% less; and at immiscibility, nearly the same. The greatly reduced mobility ratio at miscibility and near-miscibility yields higher oil recovery (4–11%), and higher net CO2 stored (4–9%) than that obtained by CO2 injection. However, at immiscibility, wsCO2 injection is found to yield 3% less oil recovery than does CO2 injection and to yield the same net CO2 storage as does CO2 injection. The high injection rate at near-miscibility also finds wsCO2 to be superior, although by a smaller margin. In summary, wsCO2 injection is found superior to CO2 injection only under miscible and near-miscible conditions.

Experimental study on fracture propagation of hydraulic fracturing for tight sandstone outcrop

The tight sandstone oil reservoirs characterized by the low porosity and permeability must be hydraulically fractured to obtain the commercial production. Nevertheless, the post-fracturing production of tight oil reservoirs is not always satisfactory. The influence mechanism of various factors on the fracture propagation in the tight oil reservoirs needs further investigation to provide an optimized fracturing plan, obtain an expected fracture morphology and increase the oil productivity. Thus, the horizontal well fracturing simulations were carried out in a large-scale true tri-axial test system with the samples from the Upper Triassic Yanchang Fm tight sandstone outcrops in Yanchang County, Shaanxi, China, and the results were compared with those of fracturing simulations of the shale outcrop in the 5th member of Xujiahe Fm (abbreviated as the Xu 5th Member) in the Sichuan Basin. The effects of the natural fracture (NF) development degree, horizontal in-situ stress conditions, fracturing treatment parameters, etc. on the hydraulic fracture (HF) propagation morphology were investigated. The results show that conventional hydraulic fracturing of the tight sandstone without NFs only produces a single double-wing primary fracture. The fracture propagation path in the shale or the tight sandstone with developed NFs is controlled by the high horizontal differential stress. The higher stress difference (<12MPa) facilitates forming the complex fracture network. It is recommended to fracture the reservoir with developed NFs by injecting the high-viscosity guar gum firstly and the low-viscosity slick water then to increase the SRV. The low-to-high variable rate fracturing method is recommended as the low injection rate facilitates the fracturing fluid filtration into the NF system, and the high injection rate increases the net pressure within the fracture. The dual-horizontal well simultaneous fracturing increases the HF density and enhances the HF complexity in the reservoir, and significantly increases the possibility of forming the complex fracture network. The fracturing pressure curves reflect the fracture propagation status. According to statistical analysis, the fracturing curves are divided into types corresponding to multi-bedding plane (BP) opening, single fracture generation, multi-fracture propagation under variable rate fracturing, and forming of the fracture network through communicating the HF with NFs. The results provide a reference for the study of the HF propagation mechanism and the fracturing design in the tight sandstone reservoirs.

Lattice-Boltzmann simulation of dissolution of carbonate rock during CO2-saturated brine injection

Geological carbon sequestration is one of the key effective technologies proposed to reduce the atmospheric CO2, which is essential to achieve the net zero-emission target. Injection of supercritical CO2 in saline aquifers can trigger geochemical reactions, which would lead to a change of pore morphology, porosity and permeability of the rock. Reservoir models – as the key tools to simulate and predict the behaviour of a saline aquifer – employ reaction rates that are obtained from the batch experiments. Here, there is a critical discrepancy in the physical scales of a grid cell in a reservoir model and the physical scale of a batch experiment. To address this shortcoming, pore-scale models are utilized to upscale the geochemical reactions in the CO2–brine–rock system. We have developed a pore-scale volumetric lattice-Boltzmann model coupled with the geochemical simulator, PhreeqcRM, to investigate the pore-scale reactive transport in carbonate rocks. The model was successfully validated against two sets of pore-scale experiments. Finally, the evolution of porosity and permeability with time was studied under various flow rates, pressures and temperatures of the injected CO2-dissolved brine. Results show that with increase of flow rate, dissolution occurs more homogeneously in the rock, while at low injection rates, dissolution is larger closer to the injection boundary. As a result, for a given porosity, the permeability increase at higher injection rates is much more compared to small injection rates. Upscaled reaction rates initially increase with time until they reach a plateau reaction rates but still are smaller than the batch reaction rates. Finally, the implication of the results for the time scale of dissolution to impede the caprock integrity was explored.

Temperature-dependent factors on hydraulic fracturing of hot dry rock (HDR): An experimental investigation

Hot dry rock (HDR) is rich in geothermal energy and renewable and does not cause pollution; therefore, it has attracted considerable research attention. Previous studies have extensively discussed the process of HDR hydraulic fracturing based on the crack initiation mechanism, initiation pressure, and crack propagation law. However, the temperature-dependent factors (thermal damage and thermal shock) affecting the HDR hydraulic fracturing process have not been specifically discussed. Therefore, HDR hydraulic fracturing tests with different sample temperatures and injection rates were designed in this study. Further, various factors affecting the hydraulic fracturing related to temperature, including the thermal damage, thermal shock, and injection rate, were analyzed. The test results indicate that under the condition of variable temperature parameters, thermal damage and thermal shock caused the initiation pressure of the reservoir to decrease with the increasing temperature. The degree of weakening increased with the increasing temperature. After fracturing, the initial fracture in HDR continued to expand under the action of thermal shock and residual pressure, and the fracture expansion scale increased with the increasing temperature. Under the condition of variable fracturing parameters, microfractures with large areas were more likely to form when fracturing occurred at a lower injection rate, which is beneficial to improve the heat exchange efficiency of the reservoir and avoid short circuits. These research results provide a scientific explanation for the influencing factors of HDR hydraulic fracturing and offer geological and engineering guidance for optimizing the hydraulic fracturing in an enhanced geothermal system.

Three‐dimensional complex fracture propagation simulation: Implications for rapid decline of production capacity

AbstractIn this study, a simulation model of fracture network geometry in fractured and porous elastic reservoirs is established based on the globally embedded three‐dimensional cohesive zone model (3D CZM). The effects of stress interference between natural fractures (NFs), horizontal stress difference (HSD), injection rate, and fluid viscosity on fracture geometry were studied and the phenomenon of rapid failure of unconventional reservoir productivity was explained from a coupling fluid flow/geomechanics perspective. The intersection behavior of hydraulic fracture (HF) and NF is simulated; the simulation results are in good agreement with Blanton's criterion, proving the reliability of the 3D CZM. The research results show that in the process of hydraulic fracturing, in addition to the strong stress interference between HFs, there is also strong stress interference between NFs. Stress interference has an important impact on the traction separation of cohesive elements (CEs) and a continuous dynamic impact on the NF opening. For reservoirs with a small HSD, higher injection rate and fluid viscosity produce smaller stimulated reservoir volume (SRV) length, but larger SRV width. Complex fracture networks tend to develop in the vicinity of horizontal wellbores, which leads to rapid failure of productivity. For this kind of reservoir, minimizing the impact of stress interference with a small injection rate is recommended instead of maximizing the injection rate and fluid viscosity. For reservoirs with a large HSD, lower injection rate and fluid viscosity produce larger SRV length and smaller SRV width. The fracture geometries tend to develop simple straight fractures, which leads to low initial productivity. Thus, adopting a relatively large injection rate and fluid viscosity is recommended to make full use of stress interference effects to increase the development of complex fractures near horizontal wellbores. The results of this study can serve as a guide in evaluating fracture complexity, SRV, proppant migration, drainage reservoir volume (DRV), and well completion design; they can also promote the in‐depth understanding of the coupling effect between fluid flow and geomechanics.

The Effect of Wettability and Flow Rate on Oil Displacement Using Polymer-Coated Silica Nanoparticles: A Microfluidic Study

Polymer-coated silica nanoparticles (PSiNPs) have been experimentally investigated in core- and micro-scale studies for enhanced oil recovery (EOR). Wettability and flow rate have a considerable effect on oil displacement in porous media. This work investigates the efficiency of PSiNPs for oil recovery on micro-scale at three wettability states (water-wet, intermediate-wet, and oil-wet). In addition, a cluster mobilization regime is considered in all experiments. A microfluidic approach was utilized to perform flooding experiments with constant experimental settings such as flowrate, pore-structure, initial oil topology, porosity, and permeability. In this study, the wettability of the microfluidic chips was altered to have three states of wettability. Firstly, a micro-scale study (brine-oil-glass system) of each wettability condition effect on flow behavior was conducted via monitoring dynamic changes in the oleic phase. Secondly, the obtained results were used as a basis to understand the changes induced by the PSiNPs while flooding at the same conditions. The experimental data were extracted by means of image processing and analysis at a high spatial and temporal resolution. Low injection rate experiments (corresponding to ~1.26 m/day in reservoir) in a brine-oil-glass system showed that the waterflood invaded with a more stable front with a slower displacement velocity in the water-wet state compared to the other states, which had water channeling through the big pores. As a result, a faster stop of the dynamic changes for the intermediate- and oil-wet state was observed, leading to lower oil recoveries compared to the water-wet state. In a cluster mobilization regime, dynamic changes were noticeable only for the oil-wet condition. For the aforementioned different conditions, PSiNPs improved oil displacement efficiency. The usage of PSiNPs showed a better clusterization efficiency, leading to a higher mobilization, smaller remaining oil clusters, and lower connectivity of the residual oil. The knowledge from this experimental work adds to the understanding of the behavior of polymer-coated silica nanoparticles as a recovery agent at different wettability states and a cluster mobilization regime.

Understanding bubble and void nucleation in dual ion irradiated T91 steel using single parameter experiments

Ferritic-martensitic steels are attractive candidates for structural materials in next generation nuclear reactor systems due to their resistance to radiation induced swelling. Cavity and dislocation loop evolution was characterized in dual ion irradiated T91 steel in three separate irradiation campaigns examining single parameter dependencies of temperature, helium co-injection rate, and damage rate. Irradiations resulted in bimodal cavity size distributions across nearly all ranges of experimental parameters. It was determined that irradiation temperature and helium co-injection rate are stronger influences on bubble stability and the transition from bubbles to voids than is the irradiation damage rate. At low helium injection rates all helium is in vacancy clusters that evolve into bubbles or voids. At high helium injection rates, bubbles become saturated with helium resulting in accumulation of helium at other traps such as dislocation loops. At intermediate levels of He that should aid in the nucleation of bubbles and enhance swelling, the high density of sinks in the F-M microstructure suppresses bubble nucleation and therefore, the onset of swelling. At high enough temperatures, helium is only in bubbles as other strong helium traps, such as dislocation loops, did not form. The mechanism of bubble to void transition was found to shift from being driven by the accumulation of helium to the critical bubble at low damage rates to being driven by spontaneous formation by stochastic vacancy fluctuation at high damage rates.

Differing responses of the quasi-biennial oscillation to artificial SO<sub>2</sub> injections in two global models

Abstract. Artificial injections of sulfur dioxide (SO2) into the stratosphere show in several model studies an impact on stratospheric dynamics. The quasi-biennial oscillation (QBO) has been shown to slow down or even vanish under higher SO2 injections in the equatorial region. But the impact is only qualitatively but not quantitatively consistent across the different studies using different numerical models. The aim of this study is to understand the reasons behind the differences in the QBO response to SO2 injections between two general circulation models, the Whole Atmosphere Community Climate Model (WACCM-110L) and MAECHAM5-HAM. We show that the response of the QBO to injections with the same SO2 injection rate is very different in the two models, but similar when a similar stratospheric heating rate is induced by SO2 injections of different amounts. The reason for the different response of the QBO corresponding to the same injection rate is very different vertical advection in the two models, even in the control simulation. The stronger vertical advection in WACCM results in a higher aerosol burden and stronger heating of the aerosols and, consequently, in a vanishing QBO at lower injection rate than in simulations with MAECHAM5-HAM. The vertical velocity increases slightly in MAECHAM5-HAM when increasing the horizontal resolution. This study highlights the crucial role of dynamical processes and helps to understand the large uncertainties in the response of different models to artificial SO2 injections in climate engineering studies.

Magma diversity reflects recharge regime and thermal structure of the crust

The chemistry of magmas erupted by volcanoes is a message from deep within the Earth’s crust, which if decrypted, can provide essential information on magmatic processes occurring at inaccessible depths. While some volcanoes are prone to erupt magmas of a wide compositional variety, others sample rather monotonous chemistries through time. Whether such differences are a consequence of physical filtering or reflect intrinsic properties of different magmatic systems remains unclear. Here we show, using thermal and petrological modelling, that magma flux and the thermal structure of the crust modulate diversity and temporal evolution of magma chemistry in mid to deep crustal reservoirs. Our analysis shows that constant rates of magma input leads to extractable magma compositions that tend to evolve from felsic to more mafic in time. Low magma injection rates into hot or deep crust produces less chemical variability of extractable magma compared to the injection of large batches in colder or shallower crust. Our calculations predict a correlation between magma fluxes and compositional diversity that resembles trends observed in volcanic deposits. Our approach allows retrieval of quantitative information about magma input and the thermal architecture of magmatic systems from the chemical diversity and temporal evolution of volcanic products.

Non-planar fracture propagation model for fluid-driven fracturing based on fluid-solid coupling

Non-planar fractures often occur in directional well fracturing and old well refracturing, which has great influence on fracture parameters and well production. To better understand the mechanism of non-planar fracture propagation, the mathematical model of non-plane fracture propagation is established based on the coupling of rock deformation and fluid flow in fracture. The coupled model is solved by a combination of the displacement discontinuity method and finite difference method, and the whole numerical calculations are carried out by MATLAB-developed program. The accuracy of the model is verified by comparing the calculated results with existing models and published experiment. The effect of perforation angles, horizontal stress differences and injection rates on fracture extension trajectory, fracture width, injection pressure and pressure distribution in fracture is investigated. The model is also employed to explore the influence of injection rate and perforation angles on fracture propagation path in the Mahu block, Xinjiang province, China. The results indicate that the coupled model has a good agreement with the published experiment data. Fracture turning distance increases with the increasing injection rate. Perforating in the direction of maximum principal stress and low injection rate is beneficial to reduce the injection pressure. Fracture width near wellbore decreases with the increasing perforation angle and differential stress, and increase with the increasing injection rate. Injection pressure increases with the increasing perforation angle, differential stress and injection rate. In the non-planar fracture propagation process, fracture width first increases and then decreases gradually. With the growing differential stress, perforation angle and injection rate has less influence on fracture turning. In the formation with high differential stress, it is difficult to achieve long fracture turning distance.

Simulation and Optimization of Venturi Injector by Machine Learning Algorithms

AbstractThis paper discusses the problem of low injection rates from Venturi injectors. The optimal combination of key structural parameters for Venturi injectors was investigated using a simulatio...

Enhancement of bitumen recovery from the oil sand in an alkaline solution using ultrasound irradiation and carbon dioxide

Herein, we demonstrated the enhancement of bitumen recovery from the oil sand in a concentrated alkaline solution using ultrasound irradiation and carbon dioxide. The alkaline solution allowed the separation of bitumen and sand; however, it was difficult to collect bitumen via aeration. CO2 exhibited a high contact angle for bitumen even at a high pH. Therefore, we attempted to use CO2 for bitumen recovery under ultrasound irradiation, increasing the number of collisions between bitumen and the CO2 bubbles; thus, the bitumen recovery ratio exhibited a high value of approximately 70% even at a low CO2 injection rate of 20 ml min−1.

Nonclassicality of the two-photon laser with Kerr nonlinearity

We have studied the photon statistics of the non-degenerate two-photon laser composed of many noninteracting atoms with Kerr nonlinearity. Nonlinearity of the gain is accounted for by the Lamb–Scully approach. Under certain conditions, we obtain an approximate photon distribution function. In the region above lasing threshold, the first few moments of the photon numbers are calculated analytically, and the threshold condition for stable lasing that depends on the Kerr parameter and detuning are obtained. We analyze the properties of the cavity field through the Mandel Q parameter, second-order correlation functions, Cauchy–Schwarz inequality for a range of Kerr parameters, atomic injection rate, and cavity detuning. Nonclassicality of the field is found through sub-Poissonian statistics, particularly at a low injection rate and high Kerr coupling with negative detuning. These nonclassicality conditions correspond to low photon numbers and depend on the sign of the detuning. The violation of the Cauchy–Schwarz inequality also occurs at low photon numbers but over a wide range of parameters, especially at short transient times. Our results show that the two-photon laser with Kerr nonlinearity is a promising quantum nonlinear optical system for developing controllable nonclassical light sources.

Development and validation of a numeric tool for partially degraded core quenching under low injection rates

Quenching of reactor core has been studied numerically with the help of several numeric tools reported in literature. These tools have been developed to simulate core quenching under design basis conditions. Hence, most of these tools make use of classical homogeneous equilibrium model of two phase flow which are reported to perform better under high pressure conditions with relatively small temperature gradients. System codes such as RELAP5 make use of two fluid model. Such system codes can simulate core quenching under design basis injection rates (1 g/s per unit length of single fuel pin) prescribed under Emergency Operating Procedures (EOPs). However, because of possibilities of flow path breakage under Severe Accident conditions, the injection rate reaching the core is expected to be lesser than the typical injection rate used for Severe Accident Management Guidelines (SAMG). A numeric tool ‘Program for Degraded Reactor Core Reflood’ (PDRCR) has been developed to simulate quenching of partially degraded reactor core under low injection flow rates. PDRCR has specific modules to tackle issues such as water packing, high temperature gradients in the fuel and simulation of parallel flow paths to account for flow re-distribution in partially ballooned fuel pin condition. This paper presents validation results for PDRCR. The predictions of PDRCR for SEFLEX and DRCRE test facilities and comparison with the experimental results are presented. The predictions of PDRCR are found to be better than RELAP5 for low injection flow conditions.

Mirror saturation in amplified reflection Distributed Denial of Service: A case of study using SNMP, SSDP, NTP and DNS protocols

Over the last six years, there have been two major game changers in Distributed Deny of Service (DDoS) attacks: amplified reflection and the Internet of Things (IoT). Together, they motivated well-founded security concerns relating to IoT’s offered attack surface, and how it could potentialize DDoS. In order to assess those concerns, the feasibility of IoT device abuse as reflectors were evaluated in this paper. Attacks abusing four protocols were tested showing a pattern that indicates that reflector saturates without sustaining maximum amplification rates, for very low injection rates (between 10 and 100 probe/sec). Hence, if on the one hand IoT devices, in general, would not be considered good reflectors, they would be good injectors. Any prepared attacker could thus use more injectors while maintaining low injection rates. This would certainly require greater coordination from the attacker but tends to hamper detection. It is expected to new levels of higher sophistication in DDoS attack execution, as in carpet bombing and pulse attacks, with the evolution of Command and Control (C2) incorporating orchestration and attack coordination.

Feasibility of limestone reservoirs as a carbon dioxide storage site: An experimental study

Carbon capture and storage technology is a means to permanently store carbon dioxide (CO2) in suitable geologic formations, such as depleted oil and gas reservoirs and saline aquifers. The potential of depleted carbonates reservoirs for being a secure storage site has been assessed in several studies based on the key storage aspects. However, minor attention has been given to rock type and the potential compaction of carbonates at different injection rates when geochemical interactions posed by supercritical CO2 reduces their elastic properties and strength. In this study, limestone samples were tested to investigate changes in their physical and mechanical characteristics once flooded by CO2 at a very low injection rate. The results obtained indicate that an excessive pressure drop might be experienced even under a very low injection rate because of continuous dissolution of carbonates in the presence of CO2 and brine. Creation of wormholes and the dissolution of the matrix were also observed through scanning electron microscope, computerized tomography scan, and nuclear magnetic resonance tests. It was also observed that the elastic parameters and the strength of the limestone samples may significantly decrease after CO2 flooding, which might be linked to calcite dissolution and weakening of the solid skeleton.