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Multiple hydraulic fractures in naturally fractured unconventional shale reservoirs have often induced complicated fracture network expansion, as revealed by micro-seismic fracture mapping. As productivity of conventional energy resources decreases and the proportion of reserves in unconventional oil/gas increases, the theoretical method about the modeling and simulation of complex fracture network propagation needs to be improved to innovate stimulated reservoir volume (SRV) fracturing technology. To simulate the fracture network growth, a new model based on the modified displacement discontinuity method (MDDM) coupling pseudo-3D fracture propagation model is proposed introducing the propagation pattern and criterion. The numerical result of this model is solved and the process of fracture network propagation is simulated in different natural fracture (NF) distribution and fracturing parameters. The effects of NF distribution, hydraulic fracture (HF) spacing, bottomhole pressure and segmented and multi-cluster fracturing mode on the fracture network propagation are discussed. The simulation results of complex fracture network are characterized by four parameters as well. The results show that there are reasonable fracturing parameters technically during the SRV fracturing in unconventional shale reservoirs. It is significant to reasonably and efficiently develop the unconventional shale resources by researching the fracture network propagation rules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two lanthanide − titanium oxo clusters EuTi 9 and TbTi 9 protected by four kinds of ligands were prepared. • The EuTi 9 and TbTi 9 cluster core containing ten metal ions shows pyramid-like structure. • EuTi 9 and TbTi 9 display the temperature-dependent luminescence properties. Two pyramid-like lanthanide − titanium − oxo clusters formulated as LnTi 9 (µ 2 -O) 5 (µ 3 -O) 7 (µ 3 -OH) 2 (O i Pr)(acac) 2 (TCA) 10 (THF) (LnTi 9 , Ln = Eu / Tb, HTCA = 2-thiophenecarboxylic acid) were prepared through the reaction of Ln(acac) 3 , 2-thiophenecarboxylic acid (HTCA), Ti(O i Pr) 4 and THF. The 10-nuclearity-metal-core [LnTi 9 (µ 2 -O) 5 (µ 3 -O) 7 (µ 3 -OH) 2 ]13+ is protected by four kinds of ligands. EuTi 9 and TbTi 9 exhibit characteristic emissions of Eu3+ / Tb3+ under ultraviolet excitation. The temperature-dependent luminescence results show EuTi 9 shows a good linear relationship between the luminescence intensity and temperature range of 80–320 K, while TbTi 9 has high temperature-sensitivity in different temperature ranges. [ABSTRACT FROM AUTHOR]

This paper proposes a semi-analytical model to evaluate the production performance for slanted wells in a multilayer commingled carbonate gas reservoir, in which the porous medium types and penetrated angles for each layer may be distinct. The triple-porosity/single-permeability and single porosity/permeability models are utilized to describe the fluids flow in natural fractured vuggy and tight formations, respectively. In addition, the stress sensitivity for different formations is considered in pseudo-time and pseudo-pressure. Laplace transformation, Fourier transform and inverse, Duhamel convolution, Stehfest inversion, and point source function are used to calculate the well bottom-hole pressure and production rate for each layer. After proper simplification on the proposed model, the calculated results match very well with the classical solutions in published papers. Furthermore, the accuracy of this model is validated by comparing the well bottom-hole pressure with the monitored data of a well in the Gaoshiti-Moxi carbonate gas reservoir. A synthetic case, which contains two layers that the upper one is naturally fractured vuggy formation and lower one is tight formation, is constructed to analyze the variation of horizontal-vertical permeability ratio and penetrated angles on production performance. The results show that the horizontal-vertical permeability ratio and the penetrated angle in naturally fractured vuggy formation determine the level of well bottom-hole pressure, while these two parameters have significant influences on production rate for tight formation. In practice, to enhance the gas recovery of tight formation, and to keep the well bottom-hole pressure a relatively high level, for tight and naturally fractured vuggy layers, the penetrated angles should be larger than 50° and 45°, respectively, and be increased as large as possible. • A semi-analytical model for slanted well in multilayer commingled carbonate gas reservoir is presented. • The geology characteristics and penetrated angles for individual layer can be various. • The effects of formation anisotropy and penetrated angles on production behaviors are evaluated. • The critical values of penetrated angle for different types of formations are determined. [ABSTRACT FROM AUTHOR]

The efficient removal of oil droplets and particles from volumes of a stable emulsified oil-contaminated polymer-flooding wastewater has been an interesting yet challenging research topic within the oilfield. In this work, a highly efficient composite flocculant (PAC-PSi-PDMDAAC) was prepared by modifying activated silicic acid onto polyaluminium chloride (PAC) through Si-O-Al bond firstly and then combined with polydimethyldiallyl ammonium chloride (PDMDAAC) by physical blending, the preparation conditions and the flocculation parameters that influence of the turbidity removal and oil removal were experimentally investigated. The optimal conditions are shown as follows: pH= 3.04, PAC/PSi = 5:1, PAC/PDMDAAC = 1:0.3. The characterization of composites were analyzed by Fourier infrared (FTIR), Thermogravimetry (Tg) and Static light scattering (SLS). The results revealed that PAC underwent the addition of PSi and PDMDAAC to form high-polymeric species. In addition, the formation of more denser flocs in wastewater treatment was affirmed with scanning electron microscope (SEM) analysis. The flocculation experiments results showed that the maximum turbidity removal rate and oil removal efficiency for polymer-flooding wastewater could reached 98.3% and 91.3% at dosage of 120 mg/L, respectively, and its flocculation efficiency was much better than that of flocculants (PAC, PAC-PSi and PAC-PDMDAAC), which confirmed the synergistic enhancement of performance of PAC by PSi and PDMDAAC. However, the Zeta potential results indicated that the maximum Zeta potential value of PAC-PDMDAAC treatment was not beneficial for oil and particles removal, which indicated the adsorption bridging effect of lager aggregates played a most significant role in the flocculation process. And this newly synthesized PAC-PSi-PDMDAAC would be a promising flocculant for polymer-flooding oily wastewater treatment to reduce oil and particulate matters. [Display omitted] [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare acoustic structure quantification (ASQ) with transient elastography for staging liver fibrosis. One hundred eighty-two patients with chronic hepatitis B and without moderate to severe hepatic steatosis scheduled for liver biopsy underwent ASQ and transient elastography examinations. All ASQ parameters, including total mode, total average, red mode, red average, red standard deviation, blue mode, blue average, blue standard deviation and focal disturbance (FD) ratio and liver stiffness obtained via transient elastography were found to correlate with fibrosis stage (Spearman's r = 0.783, 0.791, 0.750, 0.771, 0.544, 0.718, 0.691, 0.439, 0.815 and 0.814, respectively; all p values < 0.001). Among the ASQ parameters, the FD ratio had the highest correlation with the stage of fibrosis. The areas under the receiver operating characteristic curves (AUCs) of FD ratio and liver stiffness were 0.911 and 0.906 for F ≥ F1, 0.918 and 0.882 for F ≥ F2, 0.911 and 0.914 for F ≥ F3 and 0.926 and 0.978 for F = F4, respectively. There was no significant difference in AUCs between FD ratio and liver stiffness in predicting different stages of fibrosis (p = 0.062-0.912). ASQ is a promising technique for assessing liver fibrosis in the absence of moderate to severe hepatic steatosis. [ABSTRACT FROM AUTHOR]