Rapid and Slow Unlocking-Induced Startup Mechanisms of Locked Segment-Dominated LandslidesRead the full article
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Experimental Research on Heating Transfer Improvement of Materials that Change Phase in Tunnels in Cold Regions
In tunnel heating systems, phase change materials may minimize the consumption of conventional electric energy, which is very considerate in the field of tunnel heating in cold regions. Because of the phase change material’s poor heat conductivity, its annual growth rate heat absorption and release is slower; thus, the majority of phase change heat storage systems must improve heat transmission. In this study, a spiral metal ring is implanted in the paraffin to improve heat transmission to achieve this objective using a concentric sleeve-type paraffin heat storage device as a medium. Experiments were performed out in order to determine the effects of heating rate, hot fluid flow rate, and the use of a spiral metal ring on the heat storage and release process of a thermal storage device. In comparison to the paraffin thermal storage device, the embedding of the spiral metal ring accelerates the internal thermal performance of the composite heat storage device, resulting in a more uniform temperature distribution. When the thermal radiation heating rate is 60°C, 65°C, or 70°C during the heat storage process, the heat storage time of the composite heating storage device is reduced by 59.2 percent, 44.4 percent, and 40.7 percent, respectively. When the ambient temperature is 26°C and the heat storage device’s starting temperature is 65°C, the exothermic time is reduced by 22.6 percent.
Research and Construction of a Global Hexagonal Marine Gravity Gradient Reference Map for Navigation
A high-precision marine gravity gradient reference map is key to enabling underwater gravity gradient matching navigation. At present, the construction of the reference maps is based on quadrilateral geographic grids. However, quadrilateral grids lead to detriangulation at high latitudes, which limits the global applicability of such maps to underwater gravity navigation. To circumvent the limitations of quadrilateral grids, a hexagonal grid is introduced for constructing the reference map. This paper analyzes the characteristics of the icosahedral Snyder equal area aperture 4 hexagon (ISEA4H) and H3 grid systems and selects an appropriate grid system. In addition, we calculate and analyze the grid model errors and matching positioning errors of hexagonal and quadrilateral grids at the same resolution. The experimental results show that the grid model and matching positioning errors of a hexagonal grid system are more than 14% and 15% less than those of a quadrilateral grid system, respectively, indicating the feasibility and effectiveness of applying hexagonal grids to gravity gradient matching navigation. Given the low construction efficiency of a marine hexagonal grid gravity gradient reference map, we propose an efficient CPU+GPU hybrid parallel scheme. A global total tensor marine hexagonal grid gravity gradient reference map model is then constructed.
Study on Compatibility between Complex Mode Micropore Structure and Polymer Solution of Different Formulation for Conglomerate Reservoir
In this paper, the conglomerate reservoir is selected as the object to investigate the micropore structure and the compatibility of polymer solutions. Firstly, the characteristics of complex mode pore structure are analyzed based on casting thin sections, scanning electron microscope, and capillary pressure curve. Then the conglomerate reservoir is divided into five types by use of the K-means clustering algorithm, and the differences in micropore structure among the different reservoir types are also clarified. Secondly, the dynamic light scattering technology is used to directly determine the hydrodynamic diameter of different polymer formulations. As the polymer molecular weight increases, the average hydrodynamic diameter becomes larger, and with the same polymer molecular weight, the average hydrodynamic diameter becomes gradually larger as the solution concentration increases. Based on the above research results, the matching relationship between five reservoir types and polymer solutions is determined through laboratory experiments. The experimental results show that when the polymer molecular weight is determined, the volume of pore volume that can be effectively swept by polymer hydration molecules gradually decreases as the concentration of the solution increases. When the polymer molecular weight and its concentration are both determined, the pore volume of effective displacement of polymer-hydrated molecules also gradually reduces with becoming worse reservoir pore structure. The scope of application of different polymer formulations becomes progressively smaller as the microscopic pore structure of type I to type V reservoirs becomes deteriorated. The compatibility between the micropore structure of different conglomerate reservoir types and polymer solution is determined to provide the geological basis for the reasonable formulation of the polymer flooding scheme.
Research and Application of Optimization Technology for High-Efficiency Fracturing and Packing Parameters of Unconsolidated Sandstone
The fracturing and filling technology is expected to meet the dual needs of production stimulation and sand control of unconsolidated sandstone reservoirs, but there is no clear guiding method for the optimization of construction parameters, which hinders its efficient development. In order to study the optimization technology of high-efficiency fracturing and packing parameters in loose sandstone, this paper takes a loose sandstone reservoir in Liaohe Oilfield as the research object and firstly studies the fracture initiation and extension laws of loose sandstone fracturing based on really well and formation data and takes this as a physical. The model explores the migration law of proppant under different working conditions. Research shows that (a) the layered fracturing is more likely to form a fracture shape that meets the dual needs of filling and production enhancement. (b) Increasing the viscosity of the sand-carrying fluid is conducive to the migration of proppant to the far end, and increasing the sand ratio will make the proppant more easily suspended in the fracture, but it is not conducive to remote migration. (c) Taking “increasing viscosity + increasing sand ratio in a small range” as the optimization idea, the ideal filling parameters are preferably 85 mPa∙s . The field application results show that the daily oil production of three wells after adopting this optimization method is 2.5-3.4 times higher than that of the adjacent wells at the initial stage of production and after stable production.
Evolution Mechanism and Control of Floor Heave in the Deep Roadway with Retained Bottom Coal
Roadways with retained bottom coal are common in thick coal seam mining, and floor heaving is a prominent problem. In this study, based on the interaction between the floor and two sides of the roadway-surrounding rock, a Winkler elastic foundation beam model is established to analyze the floor heave problem. A 3DEC model was used to analyze the failure range, failure mode, and migration law of the floor-surrounding rock with different bottom coal thicknesses and coal body strengths. The results show that (1) an increase in the thickness of the bottom coal results in a decrease in the stiffness of the roadway side coal body (the foundation of the supporting rock layer) and an increase in the bending deformation range, the amount of floor rock beam deformation, and the extrusion force. This leads to an expansion in the range of the sides of the coal body that are squeezed by the floor rock layer, resulting in additional failure and deformation of the coal body sides. Therefore, the damage to the floor rock layer is extended and increased. (2) The expansion of the floor pressure-bearing arch and surrounding rock in the arch are the causes of floor heave in the deep coal roadway with retained bottom coal. (3) Because of an increase in the thickness of the bottom coal and a decrease in the coal body strength, the floor pressure-bearing arch expands to the deeper part; thus, the range of surrounding rock in the arch with deformation and failure increases, resulting in an increase in floor heave. The field practice indicates that the support strategy of the “high prestressed strong rock bolt (cable) supporting two sides and bottom corners in time” can effectively control the floor heave of a roadway with retained bottom coal.
Differential Occurrence Characteristics and Influence Factors of Reservoir Movable Fluids in Tight Gas: A Case Study of Shan 1 Reservoir in Yanchang Area
The occurrence characteristic of movable fluid is a crucial index for tight sandstone reservoir evaluation, and the study of the differential occurrence of reservoir movable fluid is vitally important for the exploration and development of tight gas. Therefore, on the basis of casting thin section, scanning electron microscope, X-ray diffraction, high-pressure mercury injection, and nuclear magnetic resonance testing, the differential occurrence characteristics and influencing factors of reservoir movable fluid are analyzed based on the reservoir of Shan 1 reservoir. The results show that the main types of Shan 1 reservoir are lithic quartz sandstone and lithic sandstone, and intergranular solution pores and cutting solution pores are mainly developed in Shan 1 reservoir in Yanchang area. The movable fluid saturation of Shan 1 reservoir is 21.64%~69.62%, and the average of the movable fluid saturation is 35.32%. Most of the spectra are unimodal. According to the pore development, the reservoir is divided into four types, and fluid flow property in reservoir varies with the difference of reservoir pore development. Sandstone types, reservoir porosity, permeability, pore type, pore throat parameters, and cement content affect movable fluid saturation. The pores provide the main space for the movable fluid. The better the development of intergranular solution pores, the larger the average pore throat radius and the higher the movable fluid saturation of the reservoir. The higher the content of the calcite, the more obvious pore loss of the reservoir and the lower movable fluid saturation in the reservoir. The higher the content of illite, the worse the pore evolution and the lower fluid flow property in reservoir.