Hydraulic Fracturing Design Optimization Guidelines for Heterogeneous Reservoir

This paper describes the journey of hydraulic fracturing design solutions and implementation in Khazzan field. More than 100 wells have been stimulated with hydraulic fracturing in the field in the last decade. Most of these wells were treated with a single-stage massive propped hydraulic fracturing treatment aimed at stimulating the entire vertical productive zone in a single treatment. More recently, hydraulic fracturing has begun on the southern acreage from Khazzan, referred to as Ghazeer. Producing layers in this area are thicker and higher permeability and, as a result, more prolific. Based on the available data and experiences, the establishment of clear guidelines has become a requirement to help the understanding and adjust the hydraulic fracturing design for each well to be become a well-specific optimum design. During the stimulation journey, surveillance techniques have been utilized and implemented in the Khazzan and Ghazeer fields to provide and develop better understanding of the fracture propagation process. These data have proven essential to support stimulation design evolvement and determine if multiple fracturing stages are justified or whether a single stage would be sufficient. Based on a wide range of hydraulic fracture stimulation operations performed across the Khazzan and Ghazeer fields, a flowchart was developed to integrate all the lessons learned from the previous experience and help optimize future fracture design. Clear guidelines include the rationale between the selection of single or multiple fracturing stages, the selection of optimal pad fractions, and other associated details of the fracture design. This flowchart has been extensively validated with surveillance and has proven its inherent value in many stimulated wells, with either single or multiple proppant fracturing stages.

Identifying Multiple Influential Spreaders in Complex Networks by Considering the Dispersion of Nodes

Identifying multiple influential spreaders, which relates to finding k (k > 1) nodes with the most significant influence, is of great importance both in theoretical and practical applications. It is usually formulated as a node-ranking problem and addressed by sorting spreaders’ influence as measured based on the topological structure of interactions or propagation process of spreaders. However, ranking-based algorithms may not guarantee that the selected spreaders have the maximum influence, as these nodes may be adjacent, and thus play redundant roles in the propagation process. We propose three new algorithms to select multiple spreaders by taking into account the dispersion of nodes in the following ways: (1) improving a well-performed local index rank (LIR) algorithm by extending its key concept of the local index (an index measures how many of a node’s neighbors have a higher degree) from first-to second-order neighbors; (2) combining the LIR and independent set (IS) methods, which is a generalization of the coloring problem for complex networks and can ensure the selected nodes are non-adjacent if they have the same color; (3) combining the improved second-order LIR method and IS method so as to make the selected spreaders more disperse. We evaluate the proposed methods against six baseline methods on 10 synthetic networks and five real networks based on the classic susceptible-infected-recovered (SIR) model. The experimental results show that our proposed methods can identify nodes that are more influential. This suggests that taking into account the distances between nodes may aid in the identification of multiple influential spreaders.

Research on Multiscene Vehicle Dataset Based on Improved FCOS Detection Algorithms

Whether in intelligent transportation or autonomous driving, vehicle detection is an important part. Vehicle detection still faces many problems, such as inaccurate vehicle detection positioning and low detection accuracy in complex scenes. FCOS as a representative of anchor-free detection algorithms was once a sensation, but now it seems to be slightly insufficient. Based on this situation, we propose an improved FCOS algorithm. The improvements are as follows: (1) we introduce a deformable convolution into the backbone to solve the problem that the receptive field cannot cover the overall goal; (2) we add a bottom-up information path after the FPN of the neck module to reduce the loss of information in the propagation process; (3) we introduce the balance module according to the balance principle, which reduces inconsistent detection of the bbox head caused by the mismatch of variance of different feature maps. To enhance the comparative experiment, we have extracted some of the most recent datasets from UA-DETRAC, COCO, and Pascal VOC. The experimental results show that our method has achieved good results on its dataset.

Combustion Characteristics According to the Chemical Composition of Land Fill Gas

This study was conducted using the existing ignition device to verify the effectiveness of LFG, a renewable energy source. The experimental method used a constant volume combustion chamber to check the flame propagation process and combustion pressure. The experiment was carried out by changing the fuel composition ratio of LFG in the range of LFG70 to LFG40. From the result, it was found that the methane combustion occurred smoothly in LFG70 during the flame propagation process, and that combustion progressed gradually over time. In the LFG60 and LFG50 regions, which are fuels with a high CO2 ratio, it was confirmed that the combustion slowed down and the brightness of the light decreased at the same time. In LFG40 with 40% of CH4, a misfire phenomenon in which combustion does not occur was discovered. For combustion pressure, the CH4 chemical composition of the LFG was lowered, which led to the combustion delay and the reduction of combustion pressure

Numerical Study of Global ELF Electromagnetic Wave Propagation with Respect to Lithosphere–Atmosphere–Ionosphere Coupling

Before and after earthquakes, abnormal physical and chemical phenomena can be observed by gathering ground-based and satellite data and interpreted by the lithosphere–atmosphere–ionosphere coupling (LAIC) mechanism. In this study, we focused on the mechanism of LAIC electromagnetic radiation and investigated the seismic electromagnetic (EM) wave generated in the lithosphere by earthquakes and its global propagation process from the lithosphere through the atmosphere and into the bottom of ionosphere, in order to analyze the abnormal disturbance of ground-based and space-based observation results. First, analytic formulas of the electrokinetic effect were used to simulate the generation and propagation process of the seismic EM wave in the lithosphere, interpreted as the conversion process of the seismic wave and EM wave in porous media. Second, we constructed a three-dimensional Earth–ionosphere waveguide by applying the finite-difference time-domain (FDTD) algorithm to model the global propagation process of the seismic EM wave into the atmosphere and cavity between the bottom of the ionosphere and the surface of the Earth. By combining the model of the electrokinetic effect in the lithosphere with the numerical model of the Earth–ionosphere waveguide in the atmosphere and ionosphere, we numerically simulated the global transmission process of extremely low-frequency (ELF: 3 Hz–3000 Hz) EM waves which are related to earthquakes. The propagation parameters of coseismic ELF EM waves with different duration times and center frequencies were analyzed and summarized. The simulation results demonstrate that the distribution characteristics of an electric field along longitude, latitude and altitude with time are periodic and the time interval during which an EM wave travels around the whole Earth is approximately 0.155 s when adopting the conductivity of the knee profile. We also compared the observation data with the simulation results and found that the attenuating trends of the ELF electric field are consistent. This proposed ELF EM wave propagation model of lithosphere–atmosphere–ionosphere coupling is very promising for the explanation of abnormal disturbances of ground-based and space-based observation results of ELF EM fields which are associated with earthquakes.