Annular Shape Research Articles

SYMMETRIC LEAFLET EXPANSION WITH MILD PROGRESSIVE LEAFLET TETHERING IS A NORMAL DEVELOPMENTAL FEATURE OF TRICUSPID VALVE MATURATION DURING YOUTH: A QUANTITATIVE THREE-DIMENSIONAL ECHOCARDIOGRAPHY (3DE) STUDY

SYMMETRIC LEAFLET EXPANSION WITH MILD PROGRESSIVE LEAFLET TETHERING IS A NORMAL DEVELOPMENTAL FEATURE OF TRICUSPID VALVE MATURATION DURING YOUTH: A QUANTITATIVE THREE-DIMENSIONAL ECHOCARDIOGRAPHY (3DE) STUDY

Expansion of a quantum gas in a shell trap

We report the observation of the controlled expansion of a two-dimensional (2D) quantum gas confined onto a curved shell-shaped surface. We start from the ellipsoidal geometry of a dressed quadrupole trap and introduce a novel gravity compensation mechanism enabling to explore the full ellipsoid. The zero-point energy of the transverse confinement manifests itself by the spontaneous emergence of an annular shape in the atomic distribution. The experimental results are compared with the solution of the three-dimensional Gross–Pitaevskii equation and with a 2D semi-analytical model. This work evidences how a hidden dimension can affect dramatically the embedded low-dimensional system by inducing a change of topology.

Coaxial laser metal wire deposition of Ti6Al4V alloy: process, microstructure and mechanical properties

Wire-based additive manufacturing (AM) shows a promising prospect in fabricating large-scale titanium aerospace components at a high deposition rate and low cost. The currently used wire-based AM processes commonly utilize a lateral feeding method with an acute angle to form a deposit, which reduces the flexibility and increases the difficulty of control in making complex components. In this work, a novel coaxial laser metal wire deposition (LMWD) process was used to fabricate the most widely used titanium alloy, Ti6Al4V. The coaxial wire feeding was achieved by a coaxial laser head through a vertically fed wire surrounded by an annular shape beam at focal plane. The surface quality, microstructure and mechanical properties of the deposited Ti6Al4V were examined. To show the characteristic of the coaxial LMWD process, conventional lateral LMWD was also conducted for comparison. The deposited Ti6Al4V wall showed a high surface quality and a microstructure with a mix of equiaxed β grains and columnar prior-β grains rather than coarse prior-β grains. The refined microstructure resulted in a low anisotropy in mechanical properties. The mechanism of the equiaxed β grains formation was also discussed. The combined effect of the reduced thermal gradient and the heterogeneous nucleation from the coaxial wire feeding played an important role in determining the refined microstructures in coaxial LMWD.

Interdigital annular shape filter design

The design of a small-size band-pass filter of an annular shape on interdigital rods has been developed. The results of experimental studies, which have shown that the developed filter has an acceptable quality index and can be successfully used for frequency selection of signals in multichannel microwave receivers with parallel spectral analysis are presented.

Reduction effect of final-pass heavy reduction rolling on the texture development, tensile property and stretch formability of ZWK100 alloy plates

• ZWK100 alloy sheets with initial casting structures was fabricated by final-pass heavy reduction rolling (FHRR) up to 70% single reduction after single-pass rough rolling, and subsequent annealing causes a symmetrical ‘oblique-line split’ texture instead of the traditional ‘TD split’ texture. • The high rollability for 70% reduction was ascribed to the significant activity of the prismatic 〈 a〉 slip facilitated by the off-basal textures formed after rough rolling • The ‘oblique-line split’ texture was correlated with the preferred growth of grains with [ 1 ¯ 2 1 ¯ 1 ] - [ 1 ¯ 2 1 ¯ 2 ] //RD during annealing. • The FHRR-annealed ZWK100 sheets reveal quasi-planar isotropy in mechanical properties ( Δr 2 ∼0.1), large uniform-elongation of ∼35% and excellent stretch formability of 8.1. Obviously planar anisotropy due to ‘TD split’ orthotropic texture (TD indicates Transverse direction) always exist in the Rare-earth (RE) or Ca containing Mg alloy sheets, which is likely caused by the low-reduction rolling (and annealing) as revealed in our previous research. In this work, the as-cast billets of a ZWK100 alloy were subjected to final-pass heavy reduction rolling (FHRR) at 500 °C with different reductions (30%-70%) after rough rolling, aiming to investigate the reduction effect on the microstructure and texture formation. The results show that FHRR with higher reductions above 50% is in favor of shear banding formation but has little effect on the as-deformed texture components, and the excellent formability with single-pass reduction up to 70% is mainly ascribed to the activation of prismatic 〈 a〉 slip. FHRR with reduction above 50% and annealing can generate uniform grain structures of ∼10 μm and symmetrical ‘oblique-line split’ texture in (0001) pole figures, with basal poles tilting by about 50° from ND (Normal direction) towards some oblique-line of TD and RD (Rolling direction) as well as uniform distribution of counter lines as an annular shape, resulting in excellent elongation to failure of ∼50% and ultra-low planar anisotropy Δ r 2 of ∼0.1 and high stretch formability (Erichsen value: 8.1). The formation ‘oblique-line split’ texture in (0001) pole figures is mainly correlated with the preferred growth tendency of grains with [ 21 1 ¯ 1 ] - [ 12 1 ¯ 2 ] //RD, which was suggested to relate to the high mobility of some special boundaries such as 40°-45° [ 10 1 ¯ 0 ] (∑14). The influences of starting textures on the mechanical properties, planar anisotropy and related deformation modes, as well as their correlations with the stretch formability were comparatively investigated with the ‘TD split’ orthotropic texture as a counterpoint.

C14 A PROMISING SURGICAL TECHNIQUE IN PATIENTS WITH ATRIAL FUNCTIONAL MITRAL REGURGITATION: HYPER–DOWN–SIZING ANNULOPLASTY

Abstract Objective Atrial functional mitral valve regurgitation is a less common form of functional mitral regurgitation with normal leaflet motion and morphology, preserved dimension and function of left ventricle, associated with atrial fibrillation ad/or left atrial dilatation. Several factors are involved into the etiology, such as mitral annular dilation and insufficient leaflet remodeling, atriogenic leaflet tethering, loss of annular saddle shape and contractility, changes in heart rate. Methods Eleven consecutive patients with atrial functional mitral regurgitation, mean age 65 ± 12 years, normal left ventricle dimension and ejection fraction greater than 50% underwent mitral valve repair via right mini–thoracotomy in case of isolated mitral and tricuspid valve surgery or via median sternotomy in case of combined procedures. Concomitant procedures include tricuspid valve repair in 1 patient and coronary artery bypass in 5 patients. All patients presented an increased dimension of left atrium (mean left atrial volume: 90 ± 23 ml); mitral annular dimension was investigated with trans–esophageal echocardiography before operation. In all patients was implanted a downsized complete rigid annuloplasty ring with asymmetrical design of two sizes smaller respect to measured intercommissural distance. Clinical outcomes of patients and echocardiographic findings related to mitral regurgitation recurrence and left ventricle function were followed in the time. Results At discharge, any patient present a residual mitral regurgitation greater than mild, mean trans–mitral gradient was 2.5 ±2.1 mmHg. During the follow–up period of 24 ± 5 months, the New York Heart Association functional class significantly improved from 2.5 ± 0.4 to 1.5 ± 2.1. In three patients occurred cardiac rhythm disturbances requiring hospital stay, only one patient developed a greater than mild mitral regurgitation, reoperation was not becessary in any case. Left atrial volume decreased from 90 ± 23 ml to 58 ± 30 ml. Conclusions Mitral annuloplasty with downsized ring is a safe and effective procedure in patient with atrial functional mitral regurgitation in the same way of patient with functional mitral regurgitation due to ventricular dilation and tethering. The comforting clinical and echocardiographic outcome in our small group of patient encourage future studies in this particular group of patients.

Visualization and Quantification of the Unrepaired Complete Atrioventricular Canal Valve Using Open-Source Software

Repair of complete atrioventricular canal (CAVC) is often complicated by residual left atrioventricular valve regurgitation. The structure of the mitral and tricuspid valves in biventricular hearts has previously been shown to be associated with valve dysfunction. However, the three-dimensional (3D) structure of the entire unrepaired CAVC valve has not been quantified. Understanding the 3D structure of the CAVC may inform optimized repair. Novel open-source work flows were created in SlicerHeart for the modeling and quantification of CAVC valves on the basis of 3D echocardiographic images. These methods were applied to model the annulus, leaflets, and papillary muscle (PM) structure of 35 patients (29 with trisomy 21) with CAVC using transthoracic 3D echocardiography. The mean leaflet and annular shapes were calculated and visualized using shape analysis. Metrics of the complete native CAVC valve structure were compared with those of normal mitral valves using the Mann-Whitney U test. Associations between CAVC structure and atrioventricular valve regurgitation were analyzed. CAVC leaflet metrics varied throughout systole. Compared with normal mitral valves, the left CAVC PMs were more acutely angled in relation to the annular plane (P<.001). In addition, the anterolateral PM was laterally and inferiorly rotated in CAVC, while the posteromedial PM was more superiorly and laterally rotated, relative to normal mitral valves (P<.001). Lower native CAVC atrioventricular valve annular height and annular height-to-valve width ratio before repair were both associated with moderate or greater left atrioventricular valve regurgitation after repair (P<.01). It is feasible to model and quantify 3D CAVC structure using 3D echocardiographic images. The results demonstrate significant variation in CAVC structure across the cohort and differences in annular, leaflet, and PM structure compared with the mitral valve. These tools may be used in future studies to catalyze future research intended to identify structural associations of valve dysfunction and to optimize repair in this vulnerable and complex population.

A new concept for a gas proportional scintillation counter: the annular anode

A new design of a Gas Proportional Scintillation Counter (GPSC) for X-ray spectrometry is presented and a proof of concept is demonstrated. The proposed design is much simpler, having only one electrode, the anode. In addition, this electrode has an annular shape with its axis aligned with the photosensor axis. Since the scintillation region is limited to a small region near the anode, the solid angle subtended by the photocathode is similar relative to any position in the scintillation region and the amount of scintillation reaching the photosensor is independent from the position where the radiation interaction occurs. Standard GPSCs with uniform electric field design have the scintillation region parallel to the photosensor active area resulting in a dependence of the amount of light collected by the photosensor on the axial distance of the radiation interaction due to solid angle effects. These effects impose limitations on the size of the detector radiation window relative to the photosensor active area. Therefore, the annular anode allows to obtain a GPSC design with a larger radiation window relative to the photosensor area. A first GPSC prototype with a 10-cm diameter annular anode placed at a distance of 4.4 cm from the photosensor has an energy resolution of 14% for anode voltages of 8 kV and, according to simulations, it can reach 11% for anode voltages of 12 kV. This is worse than the values of 8–9% obtained with a standard GPSC which, on the other hand, have a window-to-photosensor diameter ratio lower than 0.8. Simulations have shown that the main factor degrading the energy resolution in this new design is the low number of photons impinging the photosensor due to the low solid angle subtended by the photosensor relative to the electroluminescence region of the detector. A compromise has to be made between the anode-to-photosensor diameter ratio as well as between the anode-to-photosensor distance and the energy resolution that can be achieved with the annular anode design.

The reliability assessment of the method for calculating the strength of oblique sections in reinforced concrete elements with various cross-sectional shape

Introduction. The current standards for the design of concrete and reinforced concrete structures provide no methods for calculating the strength of the oblique sections in bending elements of various cross-sectional shape under the action of transverse forces. This prompts the designers to use simplifications in calculation of such elements, which, in some cases, may lead to excessive consumption of transverse reinforcement or the strength underestimation.Aim. The performed study was aimed at assessing the reliability of a new method for calculating the strength of oblique sections in bending reinforced concrete structures with a non-rectangular cross-sectional shape.Materials and methods. The reliability assessment of a new procedure for calculating oblique sections of a various cross-sectional shape was performed by the comparison between the calculated and experimental values of the transverse force received by the oblique section of reinforced concrete elements with various cross-sectional shape. The study considers the oblique bending tests of the samples with an annular, circular, and square cross-sectional shape, as well as T-shaped samples with a crossbar both in a stretched and compressed zone. The reliability assessment was performed using generally accepted methods of statistical analysis.Results. The distributions of ratios of the experimental and calculated values of the destructive transverse force for various-section test samples were obtained to be close to normal ones. According to the results of the reliability assessment, the proposed procedure of calculating the strength of oblique sections in elements with various cross-sectional shape was established to be comparable with the procedure accepted in the SP 63.13330.2018 Rules and Regulations for calculating rectangular cross-section elements in terms of the accuracy and reliability indices.Conclusions. The proposed procedure of calculating the strength of oblique sections in elements with various cross-sectional shape was determined to be comparable with the procedure accepted in the SP 63.13330.2018 Rules and Regulations for calculating rectangular cross-section elements in terms of the accuracy and reliability indices.

Ferrofluid annulus in crossed magnetic fields.

We study the dynamics and pattern formation of a ferrofluid annulus enveloped by two nonmagnetic fluids in a Hele-Shaw cell, subjected to an in-plane crossed magnetic field configuration involving the combination of radial and azimuthal magnetic fields. A perturbative, second-order mode-coupling analysis is employed to investigate how the ferrofluid annulus responds to variations in the relative strength of the radial and azimuthal magnetic field components, as well as in the thickness of magnetic fluid ring. By tuning the magnetic field components and the annulus' thickness, we have found the development of several stationary annular shapes, presenting polygon-shaped structures typically having skewed, peaked fingers. Such fingered structures may vary their skewness, sharpness, and number and arise on the inner, outer, or even both boundaries of the annulus. In addition to controlling the morphologies of the ferrofluid annuli, the external field can be used to put the annulus into a rotational motion, with an angular velocity having prescribed magnitude, and direction. Our second-order theory is utilized to obtain a correction to the linear stability analysis prediction of such angular velocity, usually resulting in a decreased weakly nonlinear value as compared with the magnitude predicted by purely linear theory. These theoretical results suggest the use of magnetic-field-controlled ferrofluid annuli in Hele-Shaw cells as a potential laboratory for microscale applications related to the manipulation of shape-programmable magnetic fluid objects and tunable fluidic-mixing devices in confined environments.

Twin Extreme Ultraviolet Waves in the Solar Corona

Abstract Solar extreme ultraviolet (EUV) waves are spectacular propagating disturbances with EUV enhancements in annular shapes in the solar corona. These EUV waves carry critical information about the coronal magnetized plasma that can shed light on the elusive physical parameters (e.g., the magnetic field strength) by global solar coronal magnetoseismology. EUV waves are closely associated with a wide range of solar atmospheric eruptions, from violent flares and coronal mass ejections to less energetic plasma jets or mini-filament eruptions. However, the physical nature and driving mechanism of EUV waves are still controversial. Here, we report the unique discovery of twin EUV waves (TEWs) that were formed in a single eruption with observations from two different perspectives. In all earlier studies, a single eruption was associated at most with a single EUV wave. The newly found TEWs urge us to revisit our theoretical understanding of the underlying formation mechanism(s) of coronal EUV waves. Two distinct scenarios of TEWs were found. In the first scenario, the two waves were separately associated with a filament eruption and a precursor jet, while in another scenario, the two waves were successively associated with a filament eruption. Hence, we label these distinguished scenarios as “fraternal TEWs” and “identical TEWs,” respectively. Further, we also suggest that impulsive lateral expansions of two distinct groups of coronal loops are critical to the formation of TEWs in a single eruption.

Sudden collapse of a pressure profile generated by off-axis heating in a linear magnetized plasma

The features of an unexpected, large event that arises spontaneously during a basic heat transport experiment are presented. It consists of the sudden collapse of the radial plasma pressure profile, akin to disruption events observed in toroidal magnetic confinement devices. The experiment is performed on the Large Plasma Device at the University of California, Los Angeles (UCLA). It uses a LaB6 thermionic emitter of annular shape to induce off-axis heating of a cold, afterglow plasma, in a linear magnetic geometry. The temporal evolution consists of three regimes. During an early, quiescent period, classical heat transport along and across the magnetic field arises from Coulomb collisions. After significant pressure gradients develop, drift-Alfvén waves become unstable. Upon reaching large amplitude, they trigger avalanche events that flatten the outer part of the heated region, which, in turn, quenches the instability. Due to the sustained heating, the pressure profile rebuilds and the process repeats, leading to a relatively long, second regime that displays multiple avalanches, but suddenly, the annular pressure profile is observed to collapse. After this collapse, the system enters a third regime with large fluctuations. Before the collapse, a rapid, runaway heating environment arises whose time evolution exhibits a self-similar dependence on the applied voltage. The time evolution, morphology, and scaling of the collapse event are presented, and an examination is made of the underlying mechanisms.

Arrangement design for horizontally omnidirectional audible sound source using facing ultrasonic transducer arrays

We developed an audible sound source with horizontal omnidirectional patterns using facing ultrasonic transducer arrays. The arrays emitted sound with different ultrasonic frequencies from each side, and an audible sound with a differential frequency is generated between input ultrasonic signals. In particular, we designed and created a new array that can control the number of transducers driven in the array. We evaluated the frequency–amplitude characteristics and directivity when the transducers in the array were driven in an annular shape. There is an optimum array shape and number of transducers that can be driven for a specific distance between arrays.

Analysis of Heat Transfer Rate for Different Annulus Shape Properties-Enhanced Beeswax-Based Phase Change Material for Thermal Energy Storage

Thermal exploration of melting phenomena of four different annulus shapes’ (circular-circular, circular-rectangular, rectangular-circular, and rectangular-rectangular) beeswax-based phase change material for latent heat energy storage system is discussed here. To overcome the low efficiency in heat transfer because of low thermal conductivity of beeswax (the energy storage material in the current study), the composite-beeswax approach has been investigated numerically. Three metal oxides (Al2O3, MgO, and SiO2) with different volume concentrations (1%, 3%, and 5%) containing high thermal conductivity are dispersed into the pure beeswax. The 2-d continuity and momentum as well as energy transport mathematical model inside the composite-beeswax system have been adopted for the study, and we validated the model by available results in the literature. The obtained results revealed that both the melting rate and heat transfer are improved slightly in the case of rectangular-rectangular annulus shape. It was also shown from the result that the melting rate and heat transfer are improved significantly with the presence of metal oxide particles. Moreover, it was obtained that the types of particles have not affected noticeably the melting rate and heat transfer. For the three investigated nanoparticles, temperature of the system attained 346.4 K at 15000 s of process; at the same time, it is 341 K as noted for the beeswax, which shows an improvement of 1.4% in the case of circular-circular annulus and Al2O3. In the same conditions, melt fraction increases from 0.58 for beeswax to 0.91 for composite unit, thus showing 56.8% of improvement in the melting rate.

The impact of transcatheter edge-to-edge repair on mitral valve annular geometry.

Mitral valve transcatheter edge-to-edge repair (TEER) is becoming increasingly common to treat severe mitral regurgitation. However, the lack of concomitant annuloplasty raises concerns regarding its durability. As a result, there is an emerging body of literature evaluating the impacts of TEER on mitral annular geometry. In this review, we summarize the most recent literature evaluating the impacts of TEER on annular geometry in the acute, intermediate and long-term. We also review the relationship between changes in annular geometry and clinical endpoints. Current evidence suggests that TEER acutely induces favourable changes in mitral annular size and shape, which may persist for at least up to 1 year. Few studies suggest that TEER-induced annular remodelling is associated with positive clinical outcomes. The current body of literature is sparse and limited to primarily small case series. Data from the surgical literature suggest that ringless edge-to-edge repair is associated with eventual failure. Unfortunately, few studies evaluate TEER-induced annular changes beyond the acute postprocedural phase. Future research needs to focus on and evaluate the significance of TEER-induced changes in annular dimensions in the long-term.

Experimental study of fire propagation and heat transfer of biomass straw fuel with different stacked diameters and thicknesses

The combustion of biomass straw that ignited by a fire point is an important latent danger form of wildfire. The investigation of development of the straw burning are essential for the efficient and safety utilization of biomass straw as a typical fuel. In this paper, the naturally stacked straws with diameters of 60 cm, 90 cm, and 120 cm and thicknesses from 2.0 cm to 12.2 cm were ignited from a point-source fire. The fire propagation and combustion characteristics including propagation stage, flame spreading rate, mass loss rate (MLR), and flame central temperature were measured and analyzed. The results showed that the straw combustion process was divided into four typical stages, namely the center combustion stage, merged annular stage, separated annular stage, and decay stage. The combustion area between the inside and outside flame front forms an annular shape, thus forming a hollow structure in the flame. The outside flame front spreads outward linearly with the spreading rate approximately rising with the increase of diameter and thickness. The peak of MLR is determined by diameter and thickness, hence an MLR quantitative model was constructed as m′/SL̇″h∝Deq2.391 . The exponential function between the dimensionless flame temperature Tf-T∞T∞ and the z-z0ṁ-2/5 was established. The inclined trend was becoming more obvious with a smaller negative slope in the three longitudinal regions.

Direction-independent temperature monitoring for Laser Metal Deposition with coaxial wire feeding

Among the Directed Energy Deposition (DED) processes, Laser Metal Deposition with wire (LMD-w) combines the advantages of a high precision and a high deposition rate. Recently, optical systems have been developed that allow to coaxially feed the wire through the center of a hollow laser beam into the induced melt pool. When a pyrometer is coupled to such an optical system, the measurement spot features the same annular shape as the laser spot. In this work, the temperature signal of such a setup was studied and the system was qualified for inline process monitoring. The size of the measurement spot was systematically varied, and the temperatures that resulted from the two modalities of a one-color as well as a two-color measurement were compared. It was shown that the size of the annular measurement spot significantly influences the temperature signal for both modalities. A better understanding of the measurement is essential to monitor the process reliably.

Development of Stochastic Voronoi Lattice Structures via Two-Photon Polymerization

ABSRACT Low-density polymer foams of varying sizes, shapes, and densities are of specific interest to the inertial confinement fusion (ICF) program and related high-energy density plasma physics research. Historically, these foams are comprised of polystyrene or other low atomic number materials and have densities in the 30 to 300 mg/cm3 range. However, at the lower end of this density range, these traditional polymer foams become fragile and difficult to cast and machine into the geometries needed. Recently, the need by experimentalists for materials with densities below 30 mg/cm3 has increased. To address these needs, we are developing three-dimensional (3-D) printing techniques to create high-precision, low-density, and repeatable complex lattice structures. Using two-photon polymerization 3-D printing, we recently developed the first 5 mg/cm3 low-density lattice structure having an annular hemispherical shape. These microscale to mesoscale structures were modeled and designed using the nTopology software, specifically utilizing the “Voronoi volume lattice” and “random points in body” option blocks. All printing operations were performed using the Nanoscribe Photonic Professional GT instrument. Characterization of these 3-D structures was conducted using various microscopic and X-ray tomographic imaging techniques. Overall printed part sizes ranged from 1 to 5 mm in diameter and were composed of lattice ligaments having thicknesses in the 3- to 5-µm range. These structures have been incorporated into ICF targets recently shot on both the University of Rochester’s Laboratory of Laser Energetics Omega laser and the National Ignition Facility.

Abstract 11938: Mechanisms of Significant Functional Tricuspid Regurgitation in Pulmonary Arterial Hypertension

Introduction: The relationship between pulmonary arterial hypertension (PAH) and secondary (or functional) tricuspid regurgitation (STR) is well-established, and the simultaneous presence of both conditions portends particularly poor outcomes. Yet not all patients with PAH develop significant STR, and the mechanisms underlying this phenomenon remain unclear. Methods: From the Cleveland Clinic Pulmonary Hypertension Registry, patients diagnosed with PAH between 2007-2013 were included. STR, defined by absent primary tricuspid valve disease on transthoracic echocardiogram (TTE), was considered significant if ≥moderate in severity (≥2+ grade) on TTE. Right-sided chambers, annular, and valvular anatomic and functional characteristics by cardiac computed tomography and TTE were compared between patients with significant vs. nonsignificant STR. Results: Among 88 included patients, 52 had significant STR. The median age was 57 years, and 78% were female. No differences were observed in all baseline clinical characteristics between groups. Relative to those with nonsignificant STR, patients with significant STR had worse right ventricular (RV) dysfunction as evidenced by lower tricuspid annular planar systolic excursion [1.5 (1.3,1.7) vs 2.1 (1.7,2.4); p=0.02] and fractional area change, and worse RV global longitudinal strain and RV free wall strain. Significant STR was further associated with increased RV sphericity as denoted by a smaller sphericity index [1.8 (1.6,2.1) vs. 2 (1.7,2.5); p=0.004], with similar annular dimensions and shape, mural and septal leaflets’ length and angle, and tenting height. Conclusion: Anatomic and functional alterations in the RV rather than in the tricuspid valve are implicated in the development of STR in patients with PAH. The underlying mechanism may be linked to RV dyfunction and remodeling, via increasing RV size and sphericity.

Pore Preservation and Failure Mechanism of Sinian Dengying Formation Carbonate Reservoirs: A Case Study of Two Ultradeep Wells in the Sichuan Basin, Western China

Despite being one of the most important factors in deep oil and gas exploration, the preservation mechanisms of ultradeep carbonate reservoirs remain poorly understood. This study performed thin-section, geochemistry, field emission scanning electron microscopy, fluid inclusion, and basin model analysis of samples from two boreholes over 8,000 m deep in the Sichuan Basin to determine the pore features and preservation mechanism of the Sinian (Ediacaran) Dengying Formation carbonate reservoirs. The reservoir of CS well #1 is characterised by pore diameters larger than a centimetre (average porosity 7.48%; permeability 0.8562 mD), and the pores are mainly filled with dolomite or bitumen. In contrast, the reservoir of MS well #1 is predominantly composed of micron-scale residual pores (average porosity 1.74%; permeability 0.0072 mD), and the pores are typically filled with dolomite, bitumen, and multistage quartz. The burial thermal histories suggest that both reservoirs were subjected to high pressure (i.e., pressure coefficient &gt; 1.5 ) before the Late Cretaceous. However, the pressure coefficient of the reservoir of MS well #1 has decreased to less than 1.0 owing to strong structural adjustment this well since the Late Cretaceous, which allowed other ore-forming fluids to enter and fill the pores, resulting in further compaction of the pores. In contrast, the pressure coefficient of CS well #1 is 1.1–1.2, which effectively prevented other ore-forming fluids from entering and filling the pores. The findings show that the dynamic adjustment of the Dengying Formation palaeo-gas reservoir indirectly affects the preservation or failure of the reservoir. The occurrence and geometry of bitumen in the Dengying reservoir exhibit good consistency with the pressure changes in both boreholes. In particular, bitumen with an annular shape and contraction joints in reservoir pores is widespread in CS well #1, which is attributed to the continuous preservation of palaeo-gas fields. Conversely, bitumen with a broken particle shape is located among the epigenetic minerals widespread in MS well #1, which is attributed to failure and depletion of the palaeo-gas fields.