Jingshou Liu

Quantitative multiparameter prediction of fault-related fractures: a case study of the second member of the Funing Formation in the Jinhu Sag, Subei Basin

In this paper, the analysis of faults with different scales and orientations reveals that the distribution of fractures always develops toward a higher degree of similarity with faults, and a method for calculating the multiscale areal fracture density is proposed using fault-fracture self-similarity theory. Based on the fracture parameters observed in cores and thin sections, the initial apertures of multiscale fractures are determined using the constraint method with a skewed distribution. Through calculations and statistical analyses of in situ stresses in combination with physical experiments on rocks, a numerical geomechanical model of the in situ stress field is established. The fracture opening ability under the in situ stress field is subsequently analyzed. Combining the fracture aperture data and areal fracture density at different scales, a calculation model is proposed for the prediction of multiscale and multiperiod fracture parameters, including the fracture porosity, the magnitude and direction of maximum permeability and the flow conductivity. Finally, based on the relationships among fracture aperture, density, and the relative values of fracture porosity and permeability, a fracture development pattern is determined.

Study on pressure sensitivity of tight sandstone and its influence on reservoir characteristics

ABSTRACT The rocks with low permeability have a strong sensitivity to pressure. By changing the size of confining pressure, we can realize the effective stress change of rocks and calculate the permeability change under different effective stress to evaluate the stress sensitivity of the reservoir. We analyzed the factors affecting the stress sensitivity of tight sandstone reservoir, including material composition, fracture development, and pore structure of rock. The results show that the stress sensitivity of microfractured core is very weak, and the permeability change rate is less than 20%. The sensitivity curve is divided into two stages: the permeability decline rate in the first stage is more than 30%, mainly due to the pseudoplastic deformation of the fracture under compression. In the second stage, the decrease of permeability is less than 30%. At this stage, the elastic deformation mainly depends on the compression of the rock skeleton particles, and the net stress of the actual reservoir is mostly at this stage. Therefore, the application of the second stage to evaluate the stress sensitivity of reservoirs is more practical, and the stress sensitivity of microfracture cores is higher than that of matrix cores. Through the analysis of pressure-sensitive mechanism and experimental data, it is concluded that the main controlling factors affecting rock stress sensitivity are fracture development and pore structure of rock, while rock material composition is a relatively minor factor.

The methane adsorption characteristics of marine shale

ABSTRACT The marine shale gas in South China has great exploration potential, and exploration in the Sichuan Basin has been successful, but the degree of exploration is low in Guizhou Province. We used organic geochemical analyses, X-ray diffraction (XRD) analysis, and CH4 adsorption experimental methods to study pore structures and their effects on the methane adsorption capacity of organic-rich shales. According to the measured isothermal adsorption data, and based on the theory of adsorption potential, the calculation model of shale adsorption gas under the influence of temperature and pressure is established, and the model is validated and applied by the measured isothermal adsorption data. The results show that the adsorption performance of shale samples is better, with the average adsorption capacity of 4.38 ml/g. The Langmuir model fits well with the adsorption curves. The adsorption capacity of shale samples increases as total organic carbon (TOC) increases and temperature decreases. The adsorption potential theory was used to explain the influence of shale adsorption factors.