Effects of a Nano-Silica Additive on the Rock Erosion Characteristics of a SC-CO2 Jet under Various Operating Conditions

Abstract

Abstract:In order to improve the erosion capacity of a supercritical carbon dioxide (SC-CO 2 ) jet, the influence of a nano-silica additive on the rock erosion characteristics was experimentally investigated. By impinging the SC-CO 2 jets with nano-silica mass fractions of 0 wt % (pure SC-CO 2 jet), 3 wt %, 6 wt %, 9 wt %, 12 wt %, 15 wt %, and 18 wt % on specimens of red sandstone, the erosion volumes under various operating conditions were measured and analyzed. Results show that an appropriate amount of nano-silica additive can greatly enhance the erosion ability of a SC-CO 2 jet. The effect on the erosion ability largely depends on the operating conditions. For instance, when the other conditions are fixed, 6 wt %, 9 wt %, 12 wt %, and 15 wt % were the optimum mass fractions, successively, with the inlet pressure increasing from 30 MPa to 60 MPa. With the increase in ambient pressure, the optimum mass fraction is unchanged under the constant inlet pressure, while it increases under the constant pressure drop. Additionally, the optimum mass fraction decreases when the fluid temperature increases. In addition, the optimal standoff distances are about five times the nozzle diameter of the nano-silica SC-CO 2 jet, and three times for the pure jet. This research provides a new method for effectively enhancing the rock erosion performance of a SC-CO 2 jet.

Effects of Nozzle Configuration on Rock Erosion Under a Supercritical Carbon Dioxide Jet at Various Pressures and Temperatures

“…This is because, with the increase of standoff distance, the diameter of the jet beam increases while the energy of the jet declines [9]. Moreover, the macroscopic appearances of eroded specimens are in good agreement with the results of rock erosion by jets in previous related articles [15,39], indicating the reliability of this experiment. Appl…”

“…This is because, with the increase of standoff distance, the diameter of the jet beam increases while the energy of the jet declines [9]. Moreover, the macroscopic appearances of eroded specimens are in good agreement with the results of rock erosion by jets in previous related articles [15,39], indicating the reliability of this experiment. It can also be observed in Figure 5 that, for the Laval nozzles, the size of the pits on the surface of the specimens are larger than that of the pits eroded by the jet discharging from the convergent nozzle at the same standoff distance, indicating that the erosion capability of the SC-CO2 jet can be enhanced by the Laval nozzles.…”

“…The experiment was conducted with the use of a multifunctional SC-CO 2 jet test system developed by our research team independently, and had been used in some related research [13,15]. The red arrows illustrate the flow direction of CO 2 , while the blue ones show that of hot water.…”

“…To make better use of SC-CO 2 fluid in the field of oil and gas development, different kinds of technologies using SC-CO 2 fluid have been invented, like SC-CO 2 flooding, SC-CO 2 fracturing, SC-CO 2 coiled tubing drilling, SC-CO 2 jets, and so on. Among them, the SC-CO 2 jet, which can be more efficient in eroding rocks than the water jet under the same conditions, has been the subject of numerous studies [9][10][11][12][13][14][15][16][17][18]. The most attractive point of this novel jet technology is that by taking full advantage of the high diffusivity of SC-CO 2 , it can produce an effective jet with a strong ability to erode rock without using any devices for increasing the inlet pressure in the drilling systems.…”

“…Their experimental results illustrated that the rock erosion efficiency of the SC-CO 2 combined with swirling and round jets is 42.9% higher than that of the conventional water jet, and the combined jet can lead to the occurrence of rock mass breakaway. Simultaneously, to improve the erosion capacity of the SC-CO 2 jet, the influence of nano-silica additive on the rock erosion characteristics was experimentally investigated by Huang et al [15]. They found that an appropriated amount of nano-silica additive can greatly enhance the erosion ability of the jet, and the effect on the erosion capability largely depends on the operating conditions.…”