Experimental Study on Shut-in-Time Optimization for Multi-Fractured Horizontal Wells in Shale Reservoirs

The optimization of shut-in-time in shale gas well is an important factor affecting the production of single well after volume fracturing. In this study, a new method for determining the optimal shut-in-time considering clay mineral content and ion diffusion concentration was proposed. First, a novel water spontaneous imbibition apparatus under the conditions of formation temperature and confining pressure was designed. Then, the water imbibition satuation of 15 shale samples from the Longmaxi Formation (LF) of the Sichuan Basin were measured to quantitatively evaluate the water imbibition ability and classify reservoir types. Finally, the salt ion concentration diffusion experiment was carried out to optimize the shut-in-time of different types of shale reservoirs. The experimental results shown that the clay mineral content was the key factor affecting water wettability of shale, the shale reservoirs can be divided into two types and the critical value of clay mineral content was about 40%. Based on the law of salt ion diffusion in shale, the initiation time of micro-fractures induced by shale hydration was about 10-15 days. Under the experimental conditions, the optimal shut-in time of type I shale reservoir and type II shale reservoir were about 20 days and 15 days respectively. The average daily gas production has increased from 15.6×104 m3/day to 25.1×104 m3/day. The study results can provide scientific basis for the optimization of flowback regime of shale gas resrvoirs.

CO2 Mass Transfer and Oil Replacement Capacity in Fractured Shale Oil Reservoirs: From Laboratory to Field

CO2-based fracturing is widely introduced to stimulate shale oil reservoirs for its multiple advantages. However, the range of CO2 entering the matrix around fractures and CO2-oil replacement capacity between matrix and fractures cannot be fully explained. To address this issue, a radial constant volume diffusion experiment on shale cores was designed in this study, and the pressure drop curve history was matched through numerical model to determine the composition effective diffusion coefficient. A field-scale numerical model was established, in which a series of certain grids were used to explicitly characterize fracture and quantify the prosess of CO2 mass transfer and oil replacement. Based on the field-scale numerical model, the process of shut-in, flow back, and oil production was simulated. The distribution of CO2 in fractured shale oil formation and its impact on crude oil during shut-in stage and flow back stage were investigated. This study concludes that CO2 gradually exchanges the oil in matrix into fractures and improve the fluidity of oil in matrix until the component concentrations of the whole reservoir reaches equilibrium during the shut-in process. Finally, about 30∼35 mole % of CO2 in fractures exchanges for oil in matrix. The range of CO2 entering the matrix around fractures is only 1.5 m, and oil in matrix beyond this distance will not be affected by CO2. During the process of flow back and production, the CO2 in fracture flows back quickly, but the CO2 in matrix is keeping dissolved in oil and will not be quickly produced. It is conclued that the longest possible shut-in time is conducive to making full use of the CO2-EOR mechanism in fractured shale oil reservoirs. However, due to the pursuit of economic value, a shut-in time of 10 days is the more suitable choice. This work can provide a better understanding of CO2 mass transfer mechanism in fractured shale oil reservoirs. It also provides a reference for the evaluation of the shut-in time and production management after CO2 fracturing.

Establishment of the three-dimensional model of the nonwoven structure with fiber scale based on the GAN algorithm

The structure of nonwovens gives special functions, and the establishment of the structure model has important reference significance for the realization of functions. In this work, the two-dimensional configuration of polyester fibers in a spunlaced nonwoven fabric was extracted, and the configurational feature points of 2500 fibers were obtained. Combined with the generative adversarial nets algorithm, the generation model of the two-dimensional configuration of fibers was proposed after learning the configuration feature of 2500 fibers. Based on the assumption that the fibers are randomly distributed in the nonwoven fabric, we established a three-dimensional model of the spunlaced nonwoven fabric on the fiber scale using ABAQUS software. In addition, the water diffusion experiment and simulation were carried out to visualize the diffusion process of a water droplet in the nonwoven fabric, verifying the accuracy of the model. This method provides a novel idea for the modeling of textile structure on the fiber scale, which can be regarded as a model basis for the subsequent simulation analysis and function research.

Crosswind integrated concentration for various dispersion parameter systems

LFkkuh; Lrj izdh.kZu ds fy, xkSlh;u fiPNd ekWMy ¼Gaussian Plume Model½ dk O;kid :i ls iz;ksx fd;k tkrk gSA vuqizLFk iou dh dqy lkanzrk Kkr djus ds fy, xkSlh;u lw= ¼QkWewyk½ dks laxfBr fd;k gSA vuqizLFk iou dh dqy lkanzrk dh x.kuk djus ds fy, izdh.kZu izkpyksa dh fHkUu&fHkUu iz.kkfy;ksa dk mi;ksx fd;k x;k gSA lrg Lrj esa Å¡pkbZ ds vuqlkj iou xfr dh fHkUurk dk o.kZu djus ds fy, ykxfjFehd foaM izksQkby dk mi;ksx fd;k x;k gSA blesa NksM+h tkus okyh izHkkoh Å¡pkbZ dks /;ku esa j[kk x;k gSA fHkUu fHkUu izdh.kZu izkpy iz.kkfy;ksa ds fy, iwokZuqekfur lkanzrkvksa vkSj dksisugsxu ds folj.k iz;ksx ls izkIr fd, x, izsf{kr vk¡dM+ksa dh rqyuk djus ds fy, lkaf[;dh; ifjekiksa dk mi;ksx fd;k x;k gSA The Gaussian plume model is the most widely used model for local scale dispersion. The Gaussian formula has been integrated to obtain the crosswind-integrated concentration. Different systems of dispersion parameters are used to calculate the crosswind integrated concentration. A logarithmic wind profile is used to describe the variation of wind speed with height in the surface layer. The effective release height was taken into consideration. Statistical measures are utilized in the comparison between the predicted concentrations for different dispersion parameter systems and the observed concentrations data obtained from Copenhagen diffusion experiment.

Evaluation of Antimicrobial Activity of A Fast-Setting Bioceramic Endodontic Material

Background: To evaluate the antimicrobial activity of the fast-setting bioceramic iRoot Fast Set Root Repair Material (iRoot FS) and two other calcium silicate cements. Methods: The antimicrobial activity of iRoot FS, ProRoot MTA and Biodentine against E. faecalis and P. gingivalis were evaluated in this study. The materials were freshly mixed or set for 1 and 7 days on 5mm diameter sterile filter papers. The agar diffusion test, direct contact test and carry-over effect test were conducted, and the pH values (using a digital pH meter) were also evaluated. The data were analyzed by an analysis of variance and two-way ANOVA (α=0.05).Results: In the agar diffusion experiment, no obvious inhibition zone was observed for iRoot FS, ProRootMTA or Biodentine at any time interval. In the direct contact test, all three materials showed good antibacterial activity after setting for 20 minutes. The antibacterial properties of the three materials decreased with the increase of setting time. None of the three materials showed carry-over antibacterial effect. The pH measurement showed that the suspension of all the three materials showed high pH values (11-12). With the extension of setting time, the pH of iRoot FS and Biodentine slightly decreased.Conclusions: Fresh iRoot FS, Biodentine, and MTA killed E. faecalis and P. gingivalis effectively, and the antimicrobial effect of all the three materials decreased over 1 and 7 days after mixing. All three materials showed a tendency of alkalinity which last for at least 7 days after setting.

The Grimsel Test Site – more than 35 years of underground research

Nagra and its international partners have been conducting underground research projects at the Grimsel Test Site (GTS, https://www.grimsel.com, last access: 8 November 2021) for more than 35 years. The results have been incorporated directly into modelling, safety and engineering feasibility studies necessary for the siting and construction of deep geological repositories. Various types of experiments are carried out at the GTS, each involving field testing, laboratory studies, design and modelling tasks, thus integrating all scientific aspects. Projects are typically planned over a 5 year period with the option to extend depending on the latest findings from the experiment. In the current 5 year programme (2019–2023) new phases of running in situ experiments using radionuclides were started and include the Long-Term Diffusion experiment (LTD) and the Colloid Formation and Migration project (CFM). A completely new experiment studying the migration of C-14 and I-129 in aged cement (CIM) was also initiated. Other experiments focusing mostly on engineered barrier materials were continued such as the Material Corrosion Test (MaCoTe), which is studying anaerobic corrosion of candidate canister materials in bentonite (Fig. 1). Also, a 1:1 scale experiment studying the high-temperature (>175∘C) effects on bentonite materials (HotBENT project) was started last year. In this paper we provide an overview of the CIM, LTD and MaCoTe projects, including key findings so far. In addition to research, the GTS, as part of the Grimsel Training Centre (GTC), is also used as an education platform for knowledge transfer to the next generation of scientists and engineers in the area of radioactive waste disposal and geosciences.

Identification and assessment of the antibacterial activity of ZnO nanoparticles produced by Vigna mungo and Rhizobacteria.

ZnO nanoparticles have received a lot of interest in recent years due to their unusual features. Antimicrobial properties of ZnO NPs However, the qualities of nanoparticles are determined by their size and form, making them suitable for a variety of applications. The current work looks at the synthesis, characterization, and antibacterial activity of ZnO NPs produced by Vigna Mungo and Rhizobacteria. Rhizobacteria isolated from V. mungo root nodule were morphologically, biochemically, and molecularly examined and identified as Rhizobium sp. strain P4 and Bacillus flexus strain IFO15715. The GC-MS analysis of methanol leaf extract of V. mungo was performed to detect and identify bioactive chemicals, and this indicated phytol as an antibacterial agent, while Squalene and Alpha tocopherol had antioxidant and anti-tumour properties. Agar well diffusion experiment was used to determine the antibacterial properties of ZnO nanoparticles and Vigna Mungo leaf extract. This approach is widely documented, and standard zones of inhibition for sensitive and resistant values have been defined. The results demonstrated that both methanol extract and zinc oxide nanoparticles have strong antibacterial efficacy against the majority of the pathogens examined. he synthesized nanoparticles from Rhizobium sp. were characterized by analytical techniques like SEM, XRD, FTIR, and UV Vis.

Two crystallographic forms and the absolute structure of 5α,14α-androstane

5α,14α-Androstane (C19H32) crystallizes in two different polymorphic forms in the same vapor diffusion experiment. The major form (Form I) crystallizes as thin plates in the space group P21, with Z = 4. These plates are twinned along a long c axis of length 43 Å and readily suffer from radiation damage when diffracted. The minor form (Form II) crystallizes as fine needles in the space group P212121, Z = 3. In the minor form, 5α,14α-androstane cocrystallizes with 5α,14α-androstan-17-one, an oxidation product of 5α,14α-androstane. The presence of 5α,14α-androstan-17-one in the minor form of the crystals was confirmed by HR-MS. Form II can be crystallized as a pure form without the ketone impurity using a different solvent system. High level density functional theory (DFT) lattice free energy calculations were performed and show that both pure forms are isoergic within the estimated error of the calculations.