Experimental investigation on rock fragmentation charactersitics of pressurized pulsed water jet.

As a novel type of pulsed water jet (PWJ), the pressurized pulsed water jet (PPWJ) shows great potential in the field of rock fragmentation engineering. In this study, the macro and micro morphologies of erosion craters on different targets (sandstone and granite) were measured to investigate the rock fragmentation characteristics of PPWJ. The results show that the fragmentation processes of granite and sandstone are significantly different from each other.

Development of a hydraulically controlled piston-pressurized pulsed water jet device and its application potential for hard rock breaking.

To improve the efficiency of hard rock breaking by a pulsed water jet (PWJ), a hydraulically controlled piston-pressurized PWJ (HCPPPWJ) device has been developed, by which the large amplitude pressurization of the jet could be realized through the motion coupling of the piston and the valve core inside the device without requiring additional control or ultra-high-pressure components. Under the continuous injection of low-pressure hydraulic oil, the device has a stable pressurization effect and controllable pulse pressure and pulse frequency. The jet pressure varies periodically with the alternation of high and low pressures; in the rising stage of the pulse pressure, the jet morphology presents an umbrella-like thin-layer structure, which ensures an effective initial impact force of the jet in contact with the target.

Different Effect Mechanisms of Supercritical CO on the Shale Microscopic Structure.

To better understand how supercritical carbon dioxide (CO) enhances shale gas production, it is necessary to study the interaction of supercritical CO with shale and its impact on shale microstructure. The different mechanisms by which supercritical CO changes the shale pore structure were studied by X-ray diffraction analyses, scanning electron microscopy (SEM), nuclear magnetic resonance spectroscopy, and low-pressure nitrogen gas adsorption tests on shale samples before and after treatment with different pressures and gases (CO and Ar). The results showed that after treatment with CO, the mineral content of shale changed significantly, and in particular, the proportions of calcite and dolomite decreased.