No abstract

Due to the drill pipe in the Riserless Mud Recovery (RMR) system is exposed to seawater, so the characteristics of the temperature changing are very different from the conventional offshore drilling. Considering temperature is an important factor affecting the annulus pressure, it is necessary to study the variation law of the temperature field of the RMR. In this paper, according to the physical process of the heat transfer in RMR, the mathematical model of the temperature field is established. The Computational Fluid Dynamics (CFD) software is used to simulate the temperature distribution in the drill pipe and the annulus, so that the law of the temperature changing can be observed more intuitively. In order to be more aware of the influencing factors of the temperature field changing, this paper analyzes the influence mechanism of the different discharge capacity and the different injection temperature on temperature changing. Moreover, this paper also analyzes the influence of the annulus temperature on the annulus pressure, which provides a theoretical basis for the well control of RMR.

The storage spaces of carbonate reservoir are complicated, matrix pores, vugs, fractures and large caves are coexistence. Traditional numerical simulation methods have harsh requirement for geology model and computing method, these methods are not suitable for carbonate reservoir. A comparatively perfect equivalent permeability and porosity model for multi-media reservoir was developed based on the theory of equivalent continuum media and the law of equivalent seepage resistance. The equivalent parameters of a practical reservoir were calculated by this model, and a numerical simulation was carried out by using these parameters, the results showed that the equivalent numerical simulation of fractured-vuggy carbonate reservoir was reasonable.

No abstract

No abstract

In the large-scale underground explosion, the dynamic mechanical behavior of deep rock mass under the coupled loading of the high in situ stress and the explosive stress wave is difficult to study. And the coupled loading of the in situ stress and the stress waves of large-scale underground explosions are hard to simulate. Based on this problem, an experimental device was developed, and a nonexplosive method for simulating stress waves of large-scale underground explosions was presented by us. In the experimental device, the impact energy is provided by the high-pressure gas in the air chamber, the stress wave is generated by the impact of the piston, and the waveform of the stress wave is adjusted by the composite pulse shaper. The adjusted stress wave can be transmitted to the container, where the coupled loading of the stress wave and the confining stress can be realized. The stress wave that corresponded to the real explosion is obtained by the developed device, and the function of the composite pulse shaper for adjusting the waveform is verified in the experiments by using a variety of mediums for wave adjustment. The experimental and calculation results showed that the stress wave corresponding to underground explosion at kilotons of equivalent on rock mass at great depth can be simulated by the experimental device, and the simulated explosion equivalent and buried depth can be adjusted by controlling the experimental conditions.

To study the theoretical calculation method of the HEL for hard rock, the major factors determining the strength of rock under dynamic loadings are firstly discussed. Secondly, the calculation method of the HEL of hard rock is suggested based on the Lundborg strength criterion, and the parameters influencing the HEL are analyzed and discussed. Thirdly, the HEL obtained by theoretical calculation, numerical modeling, and experiments are compared. Fourthly, the abnormal decreasing or increasing of the HEL in plate impact experiments of hard rock is explained. This research shows that the HEL increases with Poisson’s ratio, the shear strength at zero pressure, the coefficient of internal friction and the plastic limit, and Poisson’s ratio and the plastic limit could be the most important factors. The simplified model of this work can give a rational and practical prediction of the HEL of hard rock in theory, and the complicated interaction between the “damage front” and the diffuse elastic precursor is assumed to explain two special effects of the HEL in plate impact experiments of hard rock, where Poisson’s ratio related to damage levels seems to be the dominant factor.

No abstract