Mechanical Characteristics and Permeability Characteristics of Dry-Hot Rock Mass.

As a rock mass with shallow burial, high temperature, and large-scale development, the study of its mechanical and seepage characteristics plays an important role in the efficient development of geothermal energy. With the development of geothermal energy in China, a breakthrough has been made in the exploration of dry-hot rocks, and the realization of efficient development of dry-hot rocks has become the focus of attention. Systematic research on rock mechanics and seepage characteristics of dry-hot rocks has become a key research topic. Granite is the most typical dry-hot rock. In this paper, granite in the Qinghai area is selected as the research object, and experiments on physical characteristics, mechanical parameters, and seepage characteristics of granite are carried out to study the effects of different depths and temperatures on mechanical parameters and seepage characteristics of granite. The results show that the physical parameters of granite in Qinghai do not change obviously with the increase of depth, and granite has the characteristics of low water absorption and low porosity. At the same time, the parameters of water absorption and porosity at different depths are close, and the dispersion is small, so the rocks are very dense. The rocks have relatively high P-wave velocity and low S-wave velocity, and the elastic wave velocity changes little at different depths. With the increase of confining pressure, the strength of granite rock increases. Under different confining pressures, the rock shows brittle failure characteristics after the peak stress. According to Hoek-Brown and Mohr-Coulomb strength curves, the strength value is 173.52 MPa. After high temperature treatment, a complex fracture network is formed in the granite. With the increase of temperature, the permeability and porosity of the granite increase continuously, and 500°C is the temperature threshold. When the temperature is lower than 300°C and the stress is less than 30 MPa, the granite has negative Poisson's ratio, and the permeability and effective stress of dry-hot rocks are piecewise linear functions. The research results provide theoretical guidance for fracturing of dry-hot rocks and exploitation of geothermal energy.

Dynamic Evaluation of Intensive Land Use Based on Objective Empowerment by Entropy Method and Neural Network Algorithm.

In the past, the extreme value standardization of indicators, the traditional weighting method, and the multifactor comprehensive model of land intensive use inevitably linearly correlate the evaluation indicators with the evaluation objects, ignoring the direction differences of different indicators in different intervals. At the same time, these methods are also difficult to meet the change of evaluation index weight value with land use type, and cannot adapt to the actual situation of land use environment level and dynamic change. Considering the objectivity of nonlinear correlation moderate index and weight assignment, based on the standardization of quadratic function index and entropy assignment, this paper studies the intensive and dynamic use of land in development zones by different regions to improve the realistic fit of the evaluation model. The results show that the overall level of land intensive use in Chongqing center district and western Chongqing is better than that in northeast Chongqing and southeast Chongqing, roughly showing the state of "high in west and low in east."

High-Temperature-Resistant, Clean, and Environmental-Friendly Fracturing Fluid System and Performance Evaluation of Tight Sandstone.

Hydraulic fracturing, as an oil-water well stimulation and injection technology, is particularly important in the production and stimulation of low-permeability oil and gas fields, and the performance of the fracturing fluid directly affects the success of the fracturing operation. Compared with traditional water-based fracturing fluids, clean fracturing fluids have the advantages of strong sand-carrying ability and easy gel breaking with no residue. Aiming at the problem of poor temperature resistance and shear resistance of the clean fracturing fluid, based on previous research, this paper selects a high-temperature-resistant clean fracturing fluid system and evaluates the performance of the system. The research results show that the system has better rheological properties, better sand-carrying performance, shorter gel-breaking time, and less damage to the reservoir.