Wormhole Structure Research Articles

Traversable wormholes in Einsteinian cubic gravity

In this work, we investigate wormhole configurations described by a constant redshift function in Einstein-Cubic gravity ( ECG ). We derive analytical wormhole geometries by assuming a particular equation of state ( EoS ) and investigate the possibility that these solutions satisfy the standard energy conditions. We introduce exact asymptotically flat and anti-de Sitter (AdS) spacetimes that admit traversable wormholes. These solutions are obtained by imposing suitable values for the parameters of the theory so that the resulted geometries satisfy the weak energy condition ( WEC ) in the vicinity of the throat, due to the presence of higher-order curvature terms. Moreover, we find that AdS solutions satisfy the WEC throughout the spacetime. A description of the geodesic motion of time-like and null particles is presented for the obtained wormhole solutions. Also, using gravitational lensing effects, observational features of the wormhole structure are discussed.

INFLUENCE OF ACID SOLUTIONS THICKENERS ON FILTRATION IN THE MODEL OF THE CARBONATE LAYER OF THE SEBORUKO OIL FIELD (REPUBLIC OF CUBA)

Background In the process of extracting oil from carbonate reservoirs, the permeability of the bottomhole formation zone (BFZ) strata decreases. The deterioration is due to the hydromechanical contamination of the filtering surface of the BFZ by mechanical impurities and hydrocarbon compounds, insoluble deposits, the loss of inorganic salts, the quality of opening of the productive layer, the increase in the saturation of BFZ and the decrease in phase permeability for oil. In order to increase the permeability of BFZ strata, various methods are used: mechanical, chemical and thermal. For carbonate collectors, the treatment of the BFZ with hydrochloric acid is one of the main methods for the intensification of oil production. The priority for the treatment of watered carbonate reservoirs is the creation of highly permeable channels with a wormhole structure. A large number of theoretical and experimental studies are devoted to the determination of parameters of effective acid exposure and the creation of conditions for wormholes formation in the carbonate reservoir. In recent years, acid thickeners are used to increase the acid treatment efficiency of fractured reservoirs. Increasing acidic solution viscosity allows increasing the penetration depth of the acid in the strata in the active state, thus forming channels of filtration of different geometry, which improve the permeability coefficient of BFZ. Aims and Objectives To carry out a comparative analysis of the acid exposure effectiveness with the use of acidic solutions thickeners and without thickeners. Estimate of the thickened acid filtration capacity in the strata and its dissolving ability according to the increase in the permeability coefficient of the sample from the Seboruko carbonate formation (Republic of Cuba). Results According to the research results, the increase in the permeability coefficient of the strata sample was determined when exposed to a traditional acid solution and thickened. The geometry of the formed dissolution channels was determined. Under the action of a conventional acid, a conical shape channel with low branching was formed, and when a thickened acid was applied to the sample, a branched channel formed with a wormhole geometry. Thus, this study shows that the treatment efficiency of carbonate formations increases with the addition of thickeners to acidic solutions. Thickeners increase the viscosity of the acidic solution, reducing the rate of acid reaction with carbonate minerals.

Tungsten oxide modified AlTUD-1 mesoporous acid catalyst for synthesis of thiazole aryl imines and phenylhydrazones

A non-surfactant route synthesized mesoporous AlTUD-1 (Si/Al = 25) with interconnected porous networks effectively utilized as a support for 10 wt% tungsten oxide (WO3) dispersions. The synthesized WO3/AlTUD-1 catalyst was characterized by different techniques. N2 sorption and XRD studies were confirmed its amorphous mesoporous nature, which measured a pore diameter of 6.4 nm and a surface area of 510 m2 g−1. Presence of WO3 on the pores and silica TUD-1 wormhole structure were evaluated by techniques including DRUV Visible and FT-Raman. The catalyst possessed both Lewis (L) and Bronsted (B) acidity, as measured by pyridine adsorbed FT-IR, which is responsible for the catalyst activity. WO3/AlTUD-1 acid catalyst showed an excellent catalytic performance yield of about 80% at 80 °C in reflux condition, for different 1-substituted benzylidene 4-methylbenzo[d]thizole-2-amines (thiazole based aryl imines) and substituted phenylhydrazone compounds.

Gravitational Description and Graphics of a Wormhole Structure—A Galactic Megamaximon

Using the new exact solution of Einstein and Maxwell equations in the general relativity theory, they studied the internal structure of a geometric object with a nontrivial topology, the wormhole. They showed that the galactic black hole recently discovered by astronomers and astrophysicists as the part of the Event Horizon Telescope project with the radius about 1016 cm and the mass of about 1043 g can be a wormhole almost neutralized in charge with parameters close to critical—megamaximon, the radius of its neck curvature is equal to the so-called critical radius coinciding with half of the gravitational radius.

Superabsorbing metamaterial wormhole: Physical modeling and wave interaction effects

Conjugate-impedance matched superabsorbers are metamaterial bodies whose effective absorption cross section greatly exceeds their physical dimension. Such objects are able to receive radiation when it is not directly incident on their surface. Here, we develop methods of physical modeling of such structures and investigate interactions of the superabsorbers with passing electromagnetic radiation. The particular superabsorbing structure under study is a wormhole comprised of meshes of loaded transmission lines. A theory of electromagnetic wave propagation and absorption in such metamaterial structures is developed. At the frequency of operation, the structure exhibits greatly enhanced absorption as compared to the black body-type absorber of the same size. Peculiar wave absorption effects such as trapping of nearby passing beams of electromagnetic radiation are demonstrated by numerical simulations. Possible modifications of the wormhole structure under the goal of optimizing absorption while minimizing complexity of the involved metamaterials are discussed. Conjugate-impedance matched superabsorbers may find applications as efficient harvesters of electromagnetic radiation, novel antennas, and sensors.

Magnetic Mesocellular Foam Functionalized by Curcumin for Potential Multifunctional Therapeutics

The study investigates curcumin/SPIONs hybridized mesocellular foam type silica for potential dual purpose of drug delivery (curcumin) and magnetic resonance imaging. Magnetization capability and curcumin release was assessed for different structured silica such as spherical silica (Q-10), Si-MCM-41, Si-SBA-16, mesocellular foam (MSU-Foam), Si-KIT-6, ULPFDU-12, and silicalite. The phase, textural, and morphological variation was systematically scrutinized using various physico-chemical techniques. Ten weight percent SPIONs loading was found to generate magnetically active SPIONs in the following order: Q-10 (1.44 emu/g) > SBA-16 (0.80 emu/g) > MSU-Foam (0.24 emu/g) > Si-MCM-41 (0.07 emu/g) > Si-KIT-6 (0.07 emu/g) > silicalite (0.08 emu/g), respectively. The iron oxide dispersion, specific surface area, and porosity play a major role in various structured silicas. MSU-Foam with wormhole structure showed highest specific surface area occupation of SPIONs (73%). The presence of interconnected porosity of foam tends to generate external agglomeration of SPIONs (7–18 nm) at the pore surface contributing to expansion of pore sizes from 16.4 to 40.2 nm. The SPIONs over spherical micron-sized silica Q-10 showed the formation of large nanoclusters (10–25 nm). Thirty to 390 μg/ml of curcumin was loaded over silica and SPIONs/silica structured hybrid, and drug release was studied at pH 5.6 for 72 h. SPIONs/MSU-Foam with less magnetization showed the highest cumulative curcumin release (53.2%), while Q-10 spherical silica with high magnetization property showed less cumulative release of curcumin (12%).

A general method for simulating reactive dissolution in carbonate rocks with arbitrary geometry

The two-scale continuum model is widely used in simulating the reactive dissolution process and predicting the optimum injection rate for carbonate reservoir acidizing treatment. The numerical methods of this model are currently based on structured grids, which are not applicable for complicated geometries. In this study, a general numerical scheme for simulating a reactive flow problem on both structured and unstructured grids is presented based on the finite volume method (FVM). The convection and diffusion terms involved in the reactive flow model are discretized by using the upwind scheme and two-point flux approximation (TPFA), respectively. The location of the centroid node inside each control volume is moved by using an optimization algorithm to make the connections with the surrounding elements as orthogonal as possible, which systematically improves the accuracy of the TPFA scheme. Additionally, in order to avoid the computational complexity resulting from the discretization of the non-linear term, the mass balance equation is only discretized in the spatial domain to get a set of ordinary differential equations (ODEs). These ODEs are coupled with the reaction equations and then solved using the numerical algorithm on ODEs. The accuracy and efficiency of the proposed method are studied by comparing the results obtained from the proposed numerical method with previous experimental and numerical results. This comparison indicates that, compared with the previous methods, the proposed method predicts the wormhole structure more accurately. Finally, the presented method is used to check the effect of the domain geometry, and it is found that the geometry of the flow domain has no effect on the optimum injection velocity, but the radial domain requires a larger breakthrough volume than the linear domain when other parameters are fixed.

Study of galactic halo F(T,TG) wormhole solutions

In this paper, we investigate static spherically symmetric wormhole solutions with galactic halo region in the background of [Formula: see text] gravity. Here, [Formula: see text] represents torsion scalar and [Formula: see text] is teleparallel equivalent Gauss–Bonnet term. For this purpose, we consider a diagonal tetrad and two specific [Formula: see text] models. We analyze the wormhole structure through shape function graphically for both models. We also investigate the behavior of null/weak energy conditions. Finally, we evaluate the equilibrium condition to check stability of the wormhole solutions. It is concluded that there exists physically viable wormhole solution only for the first model that turns out to be stable.

Scalar geons in Born-Infeld gravity

The existence of static, spherically symmetric, self-gravitating scalar field solutions in the context of Born-Infeld gravity is explored. Upon a combination of analytical approximations and numerical methods, the equations for a free scalar field (without a potential term) are solved, verifying that the solutions recover the predictions of General Relativity far from the center but finding important new effects in the central regions. We find two classes of objects depending on the ratio between the Schwarzschild radius and a length scale associated to the Born-Infeld theory: massive solutions have a wormhole structure, with their throat at r≈ 2M, while for the lighter configurations the topology is Euclidean. The total energy density of these solutions exhibits a solitonic profile with a maximum peaked away from the center, and located at the throat whenever a wormhole exists. The geodesic structure and curvature invariants are analyzed for the various configurations considered.

Acid Jetting in Carbonate Rocks: An Experimental Study

Summary Acid jetting, as a well-stimulation method for carbonate reservoirs, has shown optimistic results in the production enhancement of some extended-reach horizontal wells. It was used initially to promote damage removal along a wellbore by means of multiple strategically located injection nozzles. It has the potential to place the injecting fluid at the locations that need stimulation. Jetting may also enhance wormhole propagation compared with conventional matrix acidizing. The hypotheses for the design of more-efficient stimulation treatments are currently being investigated. We have conducted an experimental study to investigate the effect of jetting on wormhole efficiency. Each jetting experiment was conducted as a constant-pressure (equivalent to a desired initial flux through the core) linear coreflood test, in which a standoff distance is maintained between the injection nozzle tip and the core. At low-velocity acid injection, jetting effectively removes mud filter cake by mechanical actions. Jetting also creates wormholes in limestone cores. The combination of mechanical and chemical reaction stimulates limestone rocks better than matrix acidizing without the jetting nozzle. When the jetting velocity increased, the dissolution pattern changed. An isolated local compact dissolution results in a cavity at the entries of core samples by jetting, followed by a wormhole structure. With the known dissolution pattern, sensitivity studies are carried out to investigate the effect of various parameters on the experimental outcome. We used Indiana and Winterset limestone rocks in the experiments. A 15% hydrochloric acid (HCl) (by weight) at ambient temperature was used, and the core dimensions were 4 in. in diameter and 16 in. in length. Various combinations of acid jetting velocities and acid fluxes were considered. The Winterset limestone cores are more heterogeneous, with higher porosity and lower permeability than the Indiana limestone cores. The experimental results from the two different rock samples are compared. Overall, the experimental results indicate that acid jetting follows the same trend as matrix acidizing, regarding wormhole propagation after cavities are created. Jetting velocity and acid flux are the critical parameters in jetting design for optimal stimulation results. Acid jetting tends to create different dissolution patterns for the cores from Indiana limestone and Winterset limestone. The observations from this work highlight the importance of understanding the dynamic physical and chemical process of jetting in the design of successful acid-stimulation jobs.

Monitoring of Matrix Acidizing by Use of Resistivity Measurements

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 181414, “Monitoring of Matrix Acidizing by Use of Resistivity Measurements,” by Mehdi Ghommem, American University of Sharjah, and Xiangdong Qiu, Dominic Brady, Firas Al-Tajar, Steve Crary, and Alaa Mahjoub, Schlumberger, prepared for the 2016 SPE Annual Technical Conference and Exhibition, Dubai, 26–28 September. The paper has not been peer reviewed. This paper describes the testing of a novel concept based on resistivity measurements to monitor acid-stimulation operations. It is believed that the proposed concept for monitoring the wormholing process can be adopted in the field with the deployment of induction tools. The outcome of this novel monitoring concept is expected to provide an unprecedented level of understanding of the depth, number, and type of wormholes being created downhole. Introduction Induction-logging tools can be viewed as an attractive option for characterizing wormhole morphology resulting from the acidizing process and can be used to assess acid-stimulation operations. The authors propose to extend the use of resistivity-logging tools for evaluating acid-stimulation jobs after well cleanup. This concept relies on the significant variations in the electrical resistivity of the different fluids and chemicals involved in the acidizing process and the increase in the effective porosity in the near-wellbore region resulting from the acid reactive dissolution. In this work, the authors conducted resistivity measurements while acidizing carbonate core samples. To do so, an electrically sensitive coreflooding setup was designed to conduct acidizing tests of carbonate core samples while measuring the change in the electrical resistivity at multiple points along the core and in real time. The paper shows the potential use of such measurements to monitor wormhole penetration and branching in real time. A yard test was conducted to verify the response of a real induction tool to simulated wormholing features. Resistivity Measurements While Coreflooding Experimental Setup and Procedure. A three-phase methodology was followed: rock-sample characterization, coreflooding and resistivity measurements, and characterization of the core samples after acidizing to inspect the wormhole structure and invert through the model to close the experimental loop. Saturation of Cores and Porosity Measurement. The core samples were put under a vacuum for a few hours and weighed. Then, they were saturated with 50,000 ppm of sodium chloride (NaCl) at a pressure of 2,000 psi for a few hours. After saturation, the samples were weighed again; the difference in the weight of dry and saturated samples was simply converted to the pore volume of the rock. Permeability Measurement. The permeability of the rock samples was measured by the constant-flow-rate method. This was performed by flowing deionized water across the cores in the coreflooding system while recording the pressure drop. The permeability was computed from the pressure drop and corresponding flow rate using Darcy’s law.

Einstein-Cartan wormhole solutions

In the present work we investigate wormhole structures and the energy conditions supporting them, in Einstein-Cartan theory ({\sf ECT}). The matter content consists of a Weyssenhoff fluid along with an anisotropic matter which together generalize the anisotropic energy momentum tensor in general relativity ({\sf GR}) to include spin effects. Assuming that the radial pressure and energy density obey a linear equation of state, we introduce exact asymptotically flat and anti-de-Sitter spacetimes that admit traversable wormholes and respect energy conditions. Such wormhole solutions are studied in detail for two specific forms for the redshift function, namely a constant redshift function and the one with power law dependency.

Geodesically complete BTZ-type solutions of 2 + 1 Born–Infeld gravity

We study Born–Infeld gravity coupled to a static, non-rotating electric field in 2 + 1 dimensions and find exact analytical solutions. Two families of such solutions represent geodesically complete, and hence nonsingular, spacetimes. Another family represents a point-like charge with a singularity at the center. Despite the absence of rotation, these solutions resemble the charged, rotating BTZ solution of general relativity but with a richer structure in terms of horizons. The nonsingular character of the first two families turn out to be attached to the emergence of a wormhole structure on their innermost region. This seems to be a generic prediction of extensions of general relativity formulated in metric-affine (or Palatini) spaces, where metric and connection are regarded as independent degrees of freedom.

Laboratory Measurements and Numerical Simulation of Cyclic Solvent Stimulation with a Thermally Aided Solvent Retrieval Phase in the Presence of Wormholes after Cold Heavy Oil Production with Sand

In this study, an experimental setup consisting of a sand pack with different configurations of complexity of wormhole patterns was designed. These different configurations have the same wormhole coverage index (WCI) determined by our earlier field-scale history match studies. After saturation of the model with heavy oil, three different solvents (CO2, heptane, and diluents) were introduced into the wormhole structure inside the sand pack (injection phase) and then left for a period of time (soaking phase). Next, the resulted mixture (solvent and oil) was allowed to be produced (production phase). The experiment was aimed to mimic cyclic solvent stimulation at reservoir conditions, and several cycles were run for each experiment. At each cycle, the amount of collected oil and solvent was determined, and the resulting mixture was analyzed through gas chromatography and refractometry. It was observed that some of the injected solvent was trapped inside the sand pack. Therefore, in the final step, a solvent retrieval attempt was made by injecting different low-temperature hot water based on the solvent type. The aim was to observe how much additional solvent could be retrieved from the sand pack at reservoir conditions. Next, the sand-pack experiments were numerically simulated, and effective diffusion coefficients were obtained through history matching. To generate accurate predictions in field-scale simulation, an upscaling procedure from laboratory results of the cyclic solvent injection process was suggested. In this study, we observed that the use of light solvents (CO2) could maintain the sand-pack pressure for a longer period (attributed to foamy oil phenomenon) compared to liquid solvent during the production phase. However, the oil recovery from sole application of light solvent was not as considerable as with the heavier solvents of heptane and diluents. These observations suggest that an improved heavy oil recovery could be achieved using a hybrid application of solvents and hot water in cold heavy oil production with sand (CHOPS) reservoirs. A post-flush hot water was found to play a positive role in solvent retrieval; however, the scale dependency of solvent retrieval behavior needs to be investigated. The findings of this paper can be used in a later study to optimize the field-scale solvent injection schemes considering the economics of the process tested.

Black hole solutions in functional extensions of Born-Infeld gravity

We consider electrovacuum black hole spacetimes in classical extensions of Eddington-inspired Born-Infeld gravity. By rewriting Born-Infeld action as the square root of the determinant of a matrix $\hat{\Omega}$, we consider the family of models $f (|\hat{\Omega}|)$, and study black hole solutions for a power-law family of models labelled by a simple parameter. We show how the innermost structure of the corresponding black holes is modified as compared to their General Relativity counterparts, discussing in which cases a wormhole structure replaces the point-like singularity. We go forward to argue that in such cases a geodesically complete and thus non-singular spacetime is present, despite the existence of curvature divergences at the wormhole throat.

Worm-hole structured mesoporous carbon monoliths synthesized with amphiphilic triblock copolymer

In the present work, mesoporous carbon monoliths with worm-hole structure had been synthesized through hydrothermal reaction by using amphiphilic triblock copolymer F127 and P123 as templates and resole as carbon precursor. Synthesis conditions, carbonization temperature and pore structure were studied by Fourier transform infrared, thermogravimetric analysis, transmission electron microscopy and N2 adsorption–desorption. The results indicated that the ideal pyrolysis temperature of the template is 450 °C. The organic ingredients were almost removed after further carbonized at 600 °C and the mesoporous carbon monoliths with worm-hole structure were obtained. The mesoporous carbon synthesized with P123 as single template exhibited larger pore size (6.6 nm), higher specific surface area (747 m2 g−1), lower pore ratio (45.9 %) in comparison with the mesoporous carbon synthesized with F127 as single template (with the corresponding value of 4.9 nm, 681 m2 g−1, 49.6 %, respectively), and also exhibited wider pore size distribution and lower structure regularity. Moreover, the higher mass ratio of template P123/resole induced similar pore size, larger specific surface area and lower pore ratio at the same synthesizing condition. It was also found that the textural structure of mesoporous carbon was affect by calcination atmosphere.

Wormholes and nonsingular spacetimes in Palatinif(R)gravity

We reconsider the problem of $f(R)$ theories of gravity coupled to Born-Infeld theory of electrodynamics formulated in a Palatini approach, where metric and connection are independent fields. By studying electrovacuum configurations in a static and spherically symmetric space-time, we find solutions which reduce to their Reissner-Nordstr\"om counterparts at large distances but undergo important non-perturbative modifications close to the center. Our new analysis reveals that the point-like singularity is replaced by a finite-size wormhole structure, which provides a geodesically complete and thus nonsingular space-time, despite the existence of curvature divergences at the wormhole throat. Implications of these results, in particular for the cosmic censorship conjecture, are discussed.

Global monopoles in f(R) gravity

In this study, we investigate whether global monopoles cause black holes or wormholes to form. Field equations for static spherically symmetric spacetimes with global monopoles are obtained in [Formula: see text] gravity. We found exact solutions for the field equations without using any perturbation or approximation methods. It is shown that the obtained [Formula: see text] function is in accordance with the [Formula: see text]-cold dark matter ([Formula: see text]-CDM) model. Also, it is shown that the static spherically symmetric spacetimes associated with global monopoles form black holes or wormhole structures under some restrictions. Finally, geometrical and physical results of the solutions are discussed.

Wormhole on DGP brane

We analyze a spacetime structure on a new brane configuration constructed recently in the Dvali-Gabadadze-Porrati braneworld context. The brane, embedded on a five-dimensional bubble of nothing, has a wormhole structure. It is an exact solution without any matter fields, and thus the energy conditions for matter fields are trivially satisfied. We see that, under the traversability condition, the size of the bubble should be larger than 10^{10}cm or so.

Dynamical generation of wormholes with charged fluids in quadratic Palatini gravity

The dynamical generation of wormholes within an extension of General Relativity (GR) containing (Planck's scale-suppressed) Ricci-squared terms is considered. The theory is formulated assuming the metric and connection to be independent (Palatini formalism) and is probed using a charged null fluid as a matter source. This has the following effect: starting from Minkowski space, when the flux is active the metric becomes a charged Vaidya-type one, and once the flux is switched off the metric settles down into a static configuration such that far from the Planck scale the geometry is virtually indistinguishable from that of the standard Reissner-Nordstr\"om solution of GR. However, the innermost region undergoes significant changes, as the GR singularity is generically replaced by a wormhole structure. Such a structure becomes completely regular for a certain charge-to-mass ratio. Moreover, the nontrivial topology of the wormhole allows to define a charge in terms of lines of force trapped in the topology such that the density of lines flowing across the wormhole throat becomes a universal constant. To the light of our results we comment on the physical significance of curvature divergences in this theory and the topology change issue, which support the view that space-time could have a foam-like microstructure pervaded by wormholes generated by quantum gravitational effects.