Impact of key parameters on far-field temporary plugging and diverting fracturing in fractured reservoirs: A 2D finite element study

Temporary plugging and diverting fracturing technology is of utmost importance in stimulating fractured reservoirs. However, studies investigating the mechanisms of new fracture initiation and propagation during far-field temporary plugging and diverting fracturing have been scarce, and the optimal technique parameters are still unknown. To address this issue, a two-dimensional fracturing model is developed via the finite element method in this work, which simulates the temporary plugging effect using the equivalent viscosity temporary blockage method and the unrestrained growth of hydraulic fractures by globally embedding the cohesive element of zero-thickness. Then, some key parameters for far-field temporary plugging and diverting fracturing in fractured reservoirs are discussed and some interesting insights are given. Firstly, a lower-permeability plugging zone expedites the pressure increase within the fracture, thereby boosting the probability of achieving temporary plugging and diverting fracturing. The size of the plugging zone significantly impacts the pressure increase within the fracture. Secondly, the plugging position should be determined considering the density and arrangement of natural fractures in the layer, and the temporary plugging construction should be performed after maximizing the elongation of initial hydraulic fracture. Thirdly, an increase in fluid viscosity and injection displacement promotes the pressure rise inside the fracture. Nonetheless, the impact of injection displacement on temporary plugging and diverting fracturing surpasses that of fluid viscosity. Overall, the established model can inform the design of temporary plugging and diverting fracturing in fractured reservoirs.Document Type: Original articleCited as: Liu, P., Lou, F., Du, J., Chen, X., Liu, J., Wang, M. Impact of key parameters on far-field temporary plugging and diverting fracturing in fractured reservoirs: A 2D finite element study. Advances in Geo-Energy Research, 2023, 10(2): 104-116. https://doi.org/10.46690/ager.2023.11.0

Assessing the Effectiveness of Direct Data Merging Strategy in Long-Term and Large-Scale Pharmacometabonomics

Because of the extended period of clinic data collection and huge size of analyzed samples, the long-term and large-scale pharmacometabonomics profiling is frequently encountered in the discovery of drug/target and the guidance of personalized medicine. So far, integration of the results (ReIn) from multiple experiments in a large-scale metabolomic profiling has become a widely used strategy for enhancing the reliability and robustness of analytical results, and the strategy of direct data merging (DiMe) among experiments is also proposed to increase statistical power, reduce experimental bias, enhance reproducibility and improve overall biological understanding. However, compared with the ReIn, the DiMe has not yet been widely adopted in current metabolomics studies, due to the difficulty in removing unwanted variations and the inexistence of prior knowledges on the performance of the available merging methods. It is therefore urgently needed to clarify whether DiMe can enhance the performance of metabolic profiling or not. Herein, the performance of DiMe on 4 pairs of benchmark datasets was comprehensively assessed by multiple criteria (classification capacity, robustness and false discovery rate). As a result, integration/merging-based strategies (ReIn and DiMe) were found to perform better under all criteria than those strategies based on single experiment. Moreover, DiMe was discovered to outperform ReIn in classification capacity and robustness, while the ReIn showed superior capacity in controlling false discovery rate. In conclusion, these findings provided valuable guidance to the selection of suitable analytical strategy for current metabolomics

Harmonics and Interharmonics Detection Based on Synchrosqueezing Adaptive S-Transform

The integration of renewable energy generation and nonlinear power electronic equipment into the grid brings about complex harmonics and interharmonics problems. The amplitude and frequency of harmonics and interharmonics should be detected by high time-frequency (T-F) resolution methods owing to their time-varying transient features. In this paper, a synchrosqueezing adaptive S-transform (SAST) method is proposed to detect the parameters of harmonics. Firstly, the time-frequency spectrum (TFS) of the harmonic signals is acquired by an adaptive S-transform (AST) algorithm. The TFS results are then subjected to synchronous compression, so as to achieve higher time-frequency representation precision. The detection results of the simulation signals show that SAST can achieve a better time-frequency resolution than the S-transform (ST) and synchrosqueezing short-time Fourier transform (SSTFT). In addition, the application of SAST to the analysis of experimental signals also suggests its superiority in the parameter detection of harmonics, especially for the time-varying interharmonics

Harmonics and Interharmonics Detection Based on Synchrosqueezing Adaptive S-Transform

The integration of renewable energy generation and nonlinear power electronic equipment into the grid brings about complex harmonics and interharmonics problems. The amplitude and frequency of harmonics and interharmonics should be detected by high time-frequency (T-F) resolution methods owing to their time-varying transient features. In this paper, a synchrosqueezing adaptive S-transform (SAST) method is proposed to detect the parameters of harmonics. Firstly, the time-frequency spectrum (TFS) of the harmonic signals is acquired by an adaptive S-transform (AST) algorithm. The TFS results are then subjected to synchronous compression, so as to achieve higher time-frequency representation precision. The detection results of the simulation signals show that SAST can achieve a better time-frequency resolution than the S-transform (ST) and synchrosqueezing short-time Fourier transform (SSTFT). In addition, the application of SAST to the analysis of experimental signals also suggests its superiority in the parameter detection of harmonics, especially for the time-varying interharmonics