Lab-Supported Hypothesis and Mathematical Modeling of Crack Development in the Fluid-Soaking Process of Multi-Fractured Horizontal Wells in Shale Gas Reservoirs

The objective of this study is to develop a technique to identify the optimum water-soaking time for maximizing productivity of shale gas and oil wells. Based on the lab observation of cracks formed in shale core samples under simulated water-soaking conditions, shale cracking was found to dominate the water-soaking process in multi-fractured gas/oil wells. An analytical model was derived from the principle of capillary-viscous force balance to describe the dynamic process of crack propagation in shale gas formations during water-soaking. Result of model analysis shows that the formation of cracks contributes to improving well inflow performance, while the cracks also draw fracturing fluid from the hydraulic fractures and reduce fracture width, and consequently lower well inflow performance. The tradeoff between the crack development and fracture closure allows for an optimum water-soaking time, which will maximize well productivity. Reducing viscosity of fracturing fluid will speed up the optimum water-soaking time, while lowering the water-shale interfacial tension will delay the optimum water-soaking time. It is recommended that real-time shut-in pressure data are measured and shale core samples are tested to predict the density of cracks under fluid-soaking conditions before using the crack propagation model. This work provides a shut-in pressure data-driven method for water-soaking time optimization in shale gas wells for maximizing well productivity and gas recovery factor

Effect of alloying elements Ti, Zr on the property and microstructure of molybdenum

Mo-Zr and Mo-Ti alloy were fabricated by adding alloying element Zr, Ti in molybdenum via powder metallurgy process. The effect of Zr, Ti alloying elements on the tensile strength and microstructure of molybdenum are investigated. Two types of alloying additives are used: one is elemental powder of Zr or Ti; the other is their respective hydride powders, TiH(2) or ZrH(2). The experimental results show that the formed Mo-Zr, Mo-Ti alloy possess much higher mechanical properties than pure sintered molybdenum. The tensile strength of Mo-Zr alloy is more affected by adding elemental Zr powder than ZrH(2) powder, the optimal tensile strength is obtained with addition of 0.1 wt% Zr, most of Zr forms Zr-oxide existed both inside the grain and at the grain boundaries, while very little Zr diffuses into the Mo matrix. Meanwhile, for Mo-Ti alloy, the tensile strength is more influenced by addition of TiH(2) powder than elemental Ti powder, the tensile strength is optimized at the content of 0.8 wt% TiH2, some Ti diffuses into molybdenum and forms Mo-Ti solid solution and some forms as Mo(x)Ti(y)O(z) oxide particles uniformly distributed at the grain boundaries. (C) 2008 Elsevier Ltd. All rights reserved

Effect of alloyed elements Ti, Zr on the property and microstructure of Mo alloy

Mo-Zr and Mo-Ti alloy were fabricated by powder metallurgy process, the effect of the adding forms and addition amount of Zr, Ti on the tensile property and microstructure of the alloy were studied. The results indicate that the addition of the alloyed element Zr, Ti obliviously enhances the mechanical property of molybdenum. The tensile strength of Mo-Zr alloy added pure Zr is higher than that of Mo-Zr alloy added ZrH(2) powder. The highest value of tensile strength is achieved when the addition amount of Zr is 0.1wt%. The minority of Zr solves in to the Mo matrix while the majority forms ZrO(2) particles with oxygen in the alloy. Mo-Ti alloy possesses higher tensile strength when the alloyed element Ti is added in the form of TiH(2) powder, which is of highest tensile strength when the addition amount of TiH(2) is 0.8wt%. One part of Ti solves into the Mo matrix and the others forms Mo(x)Ti(y)O(z) composite oxide particles with Mo and oxygen in the alloy

Effect of microelement Zr on the property and microstructure of Mo alloy

Mo-Zr alloy were fabricated by powder metallurgy process, the effect of the adding forms of Zr and its content on the tensile property and microstructure of the alloy were studied. The results indicate that the addition of alloying element Zr obliviously enhance the mechanical property of Mo alloy. Mo-Zr alloy added with element Zr powder exhibits higher tensile strength than that with ZrH. The highest tensile strength value is achieved at 0.1wt% of Zr. The minority of Zr solve into the Mo matrix while most of Zr form ZrO particles due to reaction with oxygen in the Mo powder

Bioinspired leaves-on-branchlet hybrid carbon nanostructure for supercapacitors

Designing electrodes in a highly ordered structure simultaneously with appropriate orientation, outstanding mechanical robustness, and high electrical conductivity to achieve excellent electrochemical performance remains a daunting challenge. Inspired by the phenomenon in nature that leaves significantly increase exposed tree surface area to absorb carbon dioxide (like ions) from the environments (like electrolyte) for photosynthesis, we report a design of micro-conduits in a bioinspired leaves-on-branchlet structure consisting of carbon nanotube arrays serving as branchlets and graphene petals as leaves for such electrodes. The hierarchical all-carbon micro-conduit electrodes with hollow channels exhibit high areal capacitance of 2.35 F cm(-2) (-500 F g(-1) based on active material mass), high rate capability and outstanding cyclic stability (capacitance retention of similar to 95% over 10,000 cycles). Furthermore, Nernst-Planck-Poisson calculations elucidate the underlying mechanism of charge transfer and storage governed by sharp graphene petal edges, and thus provides insights into their outstanding electrochemical performance