Publications

In recent years, shale gas development in Fengnan 4 well area of Xinjiang Oilfield is dominated by platform wells. In contrast to conventional fracturing development, the zipper fracturing is primarily used in this block. In this paper, the finite element model of platform well fracturing is established by establishing the mathematical model of multi-cluster fractures interacting with each other, considering the condition of multi-well and multi-fracture. The sequential fracturing of platform wells and the zipper fracturing (well alternating fracturing, fracturing stage alternating fracturing) are simulated in this paper, and the variation law of induced stress and horizontal principal s are established by establishing the mathematical model of multi-cluster fractures interacting with each other, taking into consideration the condition of multi-well and multi-fracture. Considered is the variance of in-situ stress in various fracturing techniques. The results show that: 1) In the fracturing of platform wells, due to the mutual interference of adjacent well fracturing, the non-uniformity of fracture propagation is high, which results in a non-uniform change of in-suit stress; 2) Under each fracturing process condition, the in-suit stress increases to some extent, with the minimum principal stress increasing the most, followed by the vertical principal stress and the maximum horizontal principal stress. 3) Zipper fracturing has a bigger impact than sequential fracturing on the platform intermediate well's peripheral stress value. The research results may be useful for optimizing the well fracturing mode on a shale gas platform.

Considering the critical role of uncertainties in structural damage detection, primarily arising from measurement errors and finite element model discrepancies, a nonprobabilistic approach based on interval analysis is proposed. This nonprobabilistic approach integrates phase space matrices with convolutional neural networks (CNNs) for damage identification. The compatibility of the phase space matrix data format with CNN allows for high sensitivity in detecting damage. Unlike probabilistic methods, this approach does not rely on specific probability distributions but considers the upper and lower bounds of uncertainties, making it highly applicable to real‐world applications. The proposed method employs the phase space matrix as the input for the CNN and the elemental stiffness parameter (ESP) as the output. When accounting for uncertainties, distinct networks are developed from the upper and lower bounds of the input phase space matrix. Both the undamaged state and the state under assessment are processed through these networks. The resulting outputs enable the computation of the possibility of damage existence (PoDE) and the damage measure index (DMI), which collectively provide a comprehensive assessment of the level and probability of damage. Validation using a numerical model and experimental data confirms the effectiveness of this method in accurately determining the location and level of damage while considering uncertainties.

This article presents experimental verification on damage identification of a substructure using a wavelet-domain response reconstruction technique. The response reconstruction is based on the unit impulse response function in the wavelet domain to form a transformation matrix between two different sets of time-domain response vectors. The initial finite element model updating is performed to achieve an accurate model in the intact stage as a baseline, and measured acceleration responses from the damaged substructure are used for the damage identification. Substructure damage identification is conducted by minimizing the discrepancy between a measured response vector and the reconstructed one. A dynamic response sensitivity-based model updating method is used for the identification of the target substructure. Local damage is identified as a change in the elemental stiffness factors. The adaptive Tikhonov regularization technique is adopted to improve the identification results with measured responses including measurement and environmental noises in laboratory. Experimental studies on a 7-storey plane frame structure are conducted to investigate the accuracy of the presented response reconstruction technique and the performance of substructure damage identification approach. Good response reconstruction accuracy is obtained with the baseline model, and the introduced damages in the substructure can be identified effectively. The damage locations are identified correctly with a close estimation of damage extents.

Abstract It is important to accurately estimate the impact of flow and geometric variations for engineering design and manufacture. In this paper, an efficient uncertainty quantification analysis framework based on the combination of Universal Kriging (UK) metamodels and sparse Polynomial Chaos Expansion (PCE) is proposed. A challenging analytical test function and an engineering test are considered to investigate the response performance of the UK-PCE method. Then, this method was applied to the uncertainty quantification on the aerodynamic and heat transfer performance of GE-E3 rotor blade squealer tip. Meanwhile, a global parameter sensitivity analysis using the Sobol Indice method is carried out to identify the key parameters for the aerothermal performance of the squealer tip. Wherein, the inlet total temperature is considered as flow condition uncertainty parameters and tip clearance and cavity depth are considered as geometrical uncertainty parameters. The results show that the UK-PCE method reduces the computational cost by more than 70% in comparison to the typical PCE method. Under the influence of the uncertain geometry and operating conditions, the heat flux of the squealer tip basically conforms to the normal distribution and the statistical mean value of it increased by 5.32% relative to the design value and the probability of it deviating from the design value by 5% is as high as 44.62%. The result of sensitivity analysis reveals that the uncertainty of the aerodynamic characteristics of the squealer tip is almost entirely caused by the tip clearance which accounts for 90.31% and 98.77% of the variance of the leakage flow rate and total pressure loss coefficient. And it is also a key variable for the uncertainty of the heat transfer performance considering that its variance indexes for tip heat flux and blade heat flux are 31.23% and 73.14%, respectively. Finally, the influence mechanisms of the uncertainty parameters on the aerothermal performance of the squealer tip are investigated by detailed flow and thermal field analysis.

Abstract The challenge of the alpha/beta waves gravel packing open hole in the Brazil offshore is how to successfully displace the proppant slurry in a large wellbore with a low fracture gradient formation, deep to ultra-deep water depths, and extended reach horizontal section. Since 2001, job data from more than 72 open hole horizontal gravel packings have been compiled into a database. This paper reviews the well information and the key gravel packing parameters: pump rate, fluid density, injection proppant concentration, inner/outer annulus area ratio, dune ratio, packing rate, packing time and packing efficiency during alpha/beta waves. The engineering implementations and challenges, the best practices and lessons learned for open hole horizontal gravel packing are also summarized. The data analysis yields a better understanding about the open hole horizontal gravel packing in the Brazil offshore and provides a good guideline for future practice. A historical review is also presented showing how the gravel packing methodology has improved packing efficiency and success rate. Case histories are provided demonstrating how to deploy the single trip system and pack the extended reach wellbore utilizing ultra-light-weight (ULW) proppant under extreme with improved packing efficiency and the success rate.

On the working principle of the high frequency oscillator for arc ignition ,the circuit model of the high frequency oscillator is set up in this paper. After the mathematic analysis of the model, the waveform functions in the instantaneous process of the current and voltage are obtained. Based on the real condition, these functions are analyzed deeply in the review. In order to improve the effect of arc ignition of high frequency oscillator ,the problems of relationship among the parameters and parameters definition in the circuit are discussed on the result of the mathematical analysis. Some significative conclusions and calculation functions of the circuit parameters are reached. Those supply theoretical foundation to a certain extent for the design and debugging of the high frequency oscillator.

A new effective algorithm of speckle noise reduction was presented in the paper, which took the characteristics of the multiplicative of speckle noise and the complexity of fringe pattern into account explicitly. The relationship expressions are deduced between intensity and speckle noise from the intensity distribution of speckle pattern, which indicates that the intensity ratio is equivalent to the speckle noise ratio in a neighborhood. Due to the complexity and correlativity of fringe pattern information, it leads to the problems of uncertainties during the information processed, the algorithm of speckle noise reduction was built based on exponent entropy, and the approximation precision based on rough set was considered in order to preserve the detail information very well. The presented method has a preferable performance based on the integrated visual and quantitative comparison. Because the filter parameters are adaptively determined by the speckle noise coefficient in the local window, the presented method was able to remove the noise in fringe pattern, and simultaneously preserve its edge effectively. The presented algorithm is effective for the laser speckle noise of fringe pattern particularly.

Climate change and limited primary energy resources make China to increase renewable electricity generation to change the coal-dominated situation. China has rich wind power resource and great potential for utilization, nowadays the healthy development of wind power becomes a predominant problem, which will affect the future energy framework of China. Though many factors relate to Chinese wind power, the cooperation between wind generation and power transmission system is a critical one, current situation of out-of-step is caused by the astonished rate that wind generation proceeds as well as relative lag of transmission system in some specific areas, the noncooperation will impedes the rapid growth of domestic wind power industries. Without a robust and well-planned transmission system, wind power can not be consumed on a larger scope. This paper first outlines the current status of wind power and power system of China, and then indicates that unified transmission planning and inter-province/region transmission grid with the help of ultra high voltage (UHV) technique will be beneficial for enlarging the consuming market space and help the rapid and healthy development of China's wind power.