Shale Heterogeneity in Western Hunan and Hubei: A Case Study from the Lower Silurian Longmaxi Formation in Well Laidi 1 in the Laifeng-Xianfeng Block, Hubei Province

Shale heterogeneity directly determines the alteration ability and gas content of shale reservoirs, and its study is a core research topic in shale gas exploitation and development. In this study, the shale from the Longmaxi Formation from well Ld1 located in western Hunan and Hubei is investigated. The shale’s heterogeneity is analyzed based on shale mineral rocks, microslices, geochemistry, and low-temperature N2 adsorption-desorption. It is found that the shales of the Longmaxi Formation from well Ld1 are mainly composed of siliceous shale, mixed shale, and clayey shale. The three types of shale facies exhibit strong heterogeneity in terms of the occurrence state of organic matter, organic content, mineral composition, microstructure and structure, brittleness, and micropore type. Sedimentation, late diagenesis, and terrigenous input are the main factors influencing the shale’s heterogeneity. With a total organic carbon (TOC) of 0.41%-4.18% and an organic matter maturity ( R o ) of 3.09%-3.42%, the shales of the Longmaxi Formation from well Ld1 are in an overmature stage, and their mineral composition is mainly quartz (5%-66%) and clay minerals (17.8%-73.8%). The main pore types are intergranular pores, intragranular pores, microfractures, and organic pores. The results of the low-temperature N2 adsorption-desorption experiment show that the shale pores are mainly composed of micropores and mesopores with narrow throats and complex structures, and their main morphology is of a thin-necked and wide-body ink-bottle pore. Based on the Frenkel-Halsey-Hill (FHH) model, the pore fractal dimension is studied to obtain the fractal dimension D 1 (2.73-2.76, mean 2.74) under low relative pressure ( P / P 0 ≤ 0.5 ) and D 2 (2.80-2.89, mean 2.85) under high relative pressure ( P / P 0 > 0.5 ). The shales of the Longmaxi Formation in the study area have a strong adsorption and gas storage capacity; however, the pore structure is complex and the connectivity is poor, which, in turn, imposes high requirements on reservoir reformation measures during exploitation. Moreover, the fractal dimension has a positive correlation with organic matter abundance, TOC, clay mineral content, and pyrite content and a negative correlation with quartz content. Since the organic matter contained in the shales of the Longmaxi Formation in the study area is in the overmature stage, the adsorption capacity of the shales is reduced, and the controlling effect of organic matter abundance on the same is not apparent.

Research On the Fractal Dimensions of the Organic-Rich Shale Pores Via Different Models

Fractal dimension can be used to the pore surface characterize. For pore structures in different sizes, the calculation models of fractal theory should be distinguished due to the different principles of the gas adsorption experiments. To further study the adaptability of the fractal model for gas adsorption experimental data, the author collected shale samples of Longmaxi formation from Well JY1, then CO2 and N2 adsorption provided the PSD curves. In addition, the fractal dimensions of micropore and mesopore were calculated by the Jaroniec fractal model and Frenkel–Halsey–Hill (FHH) fractal model respectively. The research shows that the Jaroniec model may be suitable to calculate CO2 adsorption data and could characterize the fractal dimension of micropore, while the FHH model may be suitable to calculate N2 adsorption data in the high relative pressure region. It suggests that the micropore and mesopore could have different dimensions and the evaluation of the structure in shale pores should consider both of them.

Исследование гидродинамического сопротивления щелевого микроканала с текстурированной стенкой

The results of numerical investigation of the hydrodynamic drag of a slit microchannel with a textured wall surface, as well as the pressure drop in such a channel and the effective slip length on the wall for various Reynolds numbers, are presented. The channel height was 10 µm, and the length varied from 25 to 500 µm. It was found that the pressure drop in the textured microchannel was less than in a conventional channel for any of its lengths. The dependences of the relative pressure drop, the friction factor, and the effective slip length on the Reynolds number were obtained for various channel lengths. A correlation that describes the dependence of the relative pressure drop on the Reynolds number for small channel lengths was proposed. The friction factor is described by a correlation of form 20 / Re.

Network architecture determines vein fate during spontaneous reorganization, with a time delay

Vascular networks continuously reorganize their morphology by growing new or shrinking existing veins to optimize function. Flow shear stress on vein walls has been set forth as the local driver for this continuous adaptation. Yet, shear feedback alone cannot account for the observed diversity of network dynamics -- a puzzle made harder by scarce spatio-temporal data. Here, we resolve network-wide vein dynamics and shear during spontaneous reorganization in the prototypical vascular networks of Physarum polycephalum. Our experiments reveal a plethora of vein dynamics (stable, growing, shrinking) that are not directly proportional to local shear. We observe (a) that shear rate sensing on vein walls occurs with a time delay of 1 to 3 min and (b) that network architecture dependent parameters -- such as relative pressure or relative vein resistance -- are key to determine vein fate. We derive a model for vascular adaptation, based on force balance at the vein walls. Together with the time delay, our model reproduces the diversity of experimentally observed vein dynamics, and confirms the role of network architecture. Finally, we observe avalanches of network reorganization events which cause entire clusters of veins to vanish. Such avalanches are consistent with architectural feedback as the vein connections perpetually change with reorganization. As these network architecture dependent parameters are intrinsically connected with the laminar fluid flow in the veins, we expect our findings to play a role across flow-based vascular networks.

Role of Zn And Polyaniline In Magnetic Nanocomposites And Enhanced Arsenic Adsorption Capacity In Wastewater

Polyaniline/Fe0.90Zn0.10Fe2O4 (PANI/Zn0.10Fe2.90O4) nanocomposites were synthesized by a chemical method and an onsite polymerization method. XRD patterns showed that the Zn0.10Fe2.90O4 grain size about 12 nm, while TEM image showed grain size from 10 to 20 nm. The results of Raman spectra and DTA analyses showed that PANI participated in part of the PANI/Zn0.10Fe2.90O4 nanocomposite samples. The grain size of PANI/Zn0.10Fe2.90O4 samples measured by SEM was about 35–50 nm. These results demonstrated the shell–core structures of the nanocomposite material. The magnetization measurements at room temperature showed that in 1250 Oe magnetic field, the saturation magnetic moment of PANI/Zn0.10Fe2.90O4 samples decreased from 71.2 to 42.3 emu/g when the PANI concentration increased from 0 % to 15 %. The surface area and porous structure of nanoparticles were investigated by the BET method at 77 K and a relative pressure P/P0 of about 1. The arsenic adsorption capacity of the PANI/Zn0.10Fe2.90O4 sample with the PANI concentration of 5 % was better than that of Fe3O4 and Zn0.10Fe2.90O4 in a solution of pH 7. In the solution with pH P14, the arsenic adsorption of magnetic nanoparticles was insignificant. Due to substitution of Fe ions by Zn transition metal and coating polyaniline, these materials could be reabsorbed and reused.

Altered Aortic Hemodynamics and Relative Pressure in Patients with Dilated Cardiomyopathy

Ventricular-vascular interaction is central in the adaptation to cardiovascular disease. However, cardiomyopathy patients are predominantly monitored using cardiac biomarkers. The aim of this study is therefore to explore aortic function in dilated cardiomyopathy (DCM). Fourteen idiopathic DCM patients and 16 controls underwent cardiac magnetic resonance imaging, with aortic relative pressure derived using physics-based image processing and a virtual cohort utilized to assess the impact of cardiovascular properties on aortic behaviour. Subjects with reduced left ventricular systolic function had significantly reduced aortic relative pressure, increased aortic stiffness, and significantly delayed time-to-pressure peak duration. From the virtual cohort, aortic stiffness and aortic volumetric size were identified as key determinants of aortic relative pressure. As such, this study shows how advanced flow imaging and aortic hemodynamic evaluation could provide novel insights into the manifestation of DCM, with signs of both altered aortic structure and function derived in DCM using our proposed imaging protocol. Graphic Abstractr

Experimental Study on Pore Structure and Gas Desorption Characteristics of a Low Rank Coal: Impact of Moisture

Coal and gas outburst is one of the most serious disasters for underground coal mining. The water adsorbed on coal can leads to that the pore structure of moist coal is different from that of dry coal, thereby affecting methane desorption characteristics of coal for the outburst risk prediction. In this paper, the impact of moisture on pore structure and methane desorption performance were investigated. The analysis on low-temperature nitrogen gas adsorption tests show that the micropores (pore diameter < 10 nm) are most affected by the adsorbed water. In particular, for water-equilibrated coal sample at 98% relatively humidity, the micropores less than 4 nm analyzed by DFT pore size distributions almost disappear probably due to the blocking effect of the formed water clusters and capillary water. In this case, the micropores can still contributes most sites for gas adsorption. Furthermore, the fractal dimension at relative pressure of 0–0.5 (D1) and 0.5–1 (D2) calculated by the Frenkel-Halsey-Hill model indicates that, when moisture content is less than 4.74%, D1 decreases rapidly while D2 shows a slight change; whereas, further increases in moisture content results in that D2 decreases significantly and D1 remains at about 2.32. Further investigation shows that, below the equilibrium moisture content, the ultimate desorption volume (A) and initial desorption rate (V0) are closely related to D1, while the desorption constant (Kt) mainly depends on D2. Therefore, the adsorbed moisture has significant negative impact on methane desorption performances by affecting characteristics of coal’s pores.

The investigation of the height effect of a slit microchannel with a textured wall on its hydrodynamic drag

The numerical investigation of the fluid flow in a slit microchannel with a textured wall was carried out. The effect of the channel height on the hydrodynamic drag coefficient, as well as on the pressure drop in such channel and the effective slip length on the wall for various Reynolds numbers, are presented in the paper. The channel length was 100 µm, and its height was varied from 25 µm to 500 µm. The Reynolds number was varied from 0.1 to 100. The main studied characteristics were compared to the similar ones obtained for a channel with normal walls (no-slip conditions). It was found that the pressure drop in such textured microchannel was lower as compared to a conventional channel for any of its heights and for any Reynolds numbers. The dependences of the relative pressure drop, effective slip length, and drag coefficient on the Reynolds number were obtained for different channel heights. The drag coefficient was described as 20/Re for the average values of the channel height. A correlation that describes the dependence of the friction factor on the Reynolds number for small and large heights of the channel was proposed. The accuracy of the proposed correlation was about 90%.

Numerical assessment of hydrodynamic and mixing characteristics for mixed electroosmotic and pressure-driven flow through a wavy microchannel with patchwise surface heterogeneity

The micromixing of two fluids plays a vital role in lab-on-a-chip devices. For obtaining better mixing efficiency, we propose a micromixer using patchwise surface potential heterogeneity and wavy wall. We numerically investigate the hydrodynamic and mixing characteristics for flow through a microchannel with a straight top wall and wavy bottom wall. The primary flow is actuated by an external pressure-gradient and patches are placed at the top wall with positive zeta potential, such that the reversed electroosmotic actuation forms the recirculation zones close to the top wall. The streamlines, flow velocity, recirculation zone velocity, species concentration, flow rate, and mixing efficiency are investigated by varying the relative pressure-gradient strength, Debye parameter, zeta potential and wavy surface amplitude. Two different configurations are considered by placing the patches at the top wall, opposite to the peaks and valleys of the bottom wavy surface, respectively. It reveals that the recirculation zone velocity increases with the increase in both Debye parameter and surface amplitude, whereas it decreases with relative pressure-gradient strength near the patch surfaces. The flow rate decreases with the increase in zeta potential and we also identify the values of zeta potential for chocking of flow in the microchannel. It reveals that the mixing efficiency monotonically increases with surface amplitude, and the variation with zeta potential is non-monotonic. We also identify the range of zeta potential for which the value of mixing efficiency is higher than 90% for different configurations of the channel.