The Ordos Basin is an important energy and chemical base in China, with a large number of low-cost, high-concentration coal chemical CO₂ sources and low-permeability reservoir storage space suitable for CO₂ storage, making it an ideal candidate for CCUS technology demonstration. However, there are still many challenges to achieve efficient CO₂-EOR and effective storage in low-permeability reservoirs. In this paper, we take the Haziping reservoir of the Yanchang Formation in the Ordos Basin as the target layer for geological storage, and find that the original porosity, permeability and initial mineral fraction have different levels of influence on the evolution of CO₂ transport and reservoir water chemistry changes through numerical simulations. As CO₂ is injected, the original minerals begin to undergo hydrogeochemical reactions and some of the minerals begin to dissolve, with the dissolved amounts of minerals ranked from largest to smallest: chlorite, feldspar-like, kaolinite. Mineral precipitation amounts were ranked as follows: iron dolomite, sodium montmorillonite, calcite, magnesite, illite, quartz. By analysing whether the precipitated minerals can be stabilised as carbon fixing minerals in the reservoir, the final determination of the carbon fixing mineral combination in the target reservoir is iron dolomite+magnesite. The presence of carbon fixing minerals in the target reservoir is indicative of geological storage, and it was found that iron dolomite could be used as a mineral tracer for the presence of CO₂ in the geological storage process.

In nature, fissures in rock mass are often distributed in the shape of X and V. In order to explore the influences of cross fissures on the mechanical failure characteristics of rock mass and crack propagation under load, rock specimens with dip angles of 30°, 60° and 90°, fracture lengths of 10 mm, 20 mm, 30 mm and 40 mm and shape of V and X were producted, respectively. The RYL-600 computer-controlled rock shear rheometer was adopted to conduct uniaxial compression tests, and the mechanical properties, crack propagation and evolution law of rock-like specimens with different crack lengths and angles were analyzed. The results show that the stress intensity of the rock mass test block with X-type and V-type fissures is obviously lower than that of the complete test block, and the stress-strain curve of the rock mass test block with cross frac fissures tures is obviously earlier entering failure state than complete test block. The angle and length of fissures can change the initiation, propagation direction and failure mode of rock mass. With the increase of fissure angle, the crack propagation of the test block with cross fissures becomes more obvious, and the area and number of surface peeling off gradually decrease.

Faults are an important factor inducing mine safety accidents, and it poses difficulties on the identification of faults within 5 m of drop.Taking the Liupanshui coalfield of Guizhou province as the study area, this paper investigated the coalfield strata and carried out an on-site survey.It proposed a seismic physical model and used the unique velocity ratio of 1∶1.74 to realize the construction and analysis of small faults with a burial depth of 800 m, 1 000 m and 1 200 m and a drop of 5 m, 3 m and 1 m.This paper extracted a variety of seismic properties by seismic dynamics method to analyze small faults, and obtained the sensitivity of seven seismic properties to the characteristic response of small faults, including amplitude envelope, amplitude first derivative, and amplitude second derivative, and the correlation between seismic properties and drop was established accordingly.The results show that when the small fault drop of the coal seam is less than or equal to 5 m, there is a linear relationship with the traditional amplitude attributes, and a linear relationship with the seismic properties related to phase and frequency.There is high correlation between the amplitude envelope and the amplitude imaginary part, and low correlation between the instantaneous frequency, the amplitude first derivative, the cosine instantaneous phase, the amplitude second derivative and the amplitude envelope.

Small faults are an important factor that affects the safe and efficient mining of coal mines.In recent years, although great progress has been made in seismic wave identification methods for faults including small faults, it is still a difficult problem to identify small faults with a drop of less than 5 m in coalfield.Southern coalfields generally have complex topography and well-developed fault.In order to promote the seismic exploration of small faults in southern coal fields, this paper selects a typical southern coalfield—the Liupanshui coalfield in Guizhou Province as the study area.The coal-measure stratigraphic seismic physical model is established for seismic data acquisition, processing and interpretation, from the seismic wave kinematics and dynamics.The angle identifies small faults with a drop of 5 m, 3 m, and 1 m at different depths.The research results show that it is difficult to identify small faults with a drop of 1 to 5 m by using seismic wave kinematics method because coal seam is in a low-velocity layer on the surface.However, the application of dynamic method to extract multiple seismic attributes for analysis can find that the amplitude attributes are more sensitive to the identification of small faults, and the resolution ability is strong.Through the seismic physical model test, under the condition of the seismic source frequency of 60 kHz, the small faults with a drop of less than 5 m were successfully explained, and the results are consistent with the actual small faults of the coal-measure strata seismic physical model.