SC-CO2 Jet Research Articles

Dynamical analysis of high-pressure supercritical carbon dioxide jet in well drilling

This paper presents the design of an experimental setup and mathematical and physical models to determine the dynamical characteristics of the high-pressure supercritical carbon dioxide (SC-CO2) jet with a highly potential applications in the well drilling. The effects of three major factors on the wellbore dynamical characteristics of the high-pressure SC-CO2 jet, i.e., the nozzle diameter, the standoff distance and the jet pressure are determined. It is indicated that the pressure of CO2 reduces severely in the SC-CO2 jet impact process. It is also found that the bottom-hole pressure and the temperature increase as the nozzle diameter increases but de- crease with the increase of the standoff distance. The higher the jet pressure at the wellbore inlet is, the higher the pressure and the lower the temperature at the bottom-hole will be.

Design and Test of Drilling and Completion Experimental System with Supercritical Carbon Dioxide

Supercritical Carbon dioxide (SC-CO2) has many excellent properties, such as high rock-breaking efficiency, strong dissolved performance and good displacement efficiency. It is a high-efficiency fluid to exploit coal-bed methane, shale gas, heavy oil, low permeability reservoirs and other unconventional oil and gas reservoirs. Using SC-CO2 jet to break formation rock assisted the drill bit can get several times the penetration rate of conventional drilling and effectively enhance the oil recovery while achieving an initiative reduction of greenhouse gas by storing the CO2 underground in the proper unconventional reservoirs. The functions and process of drilling and completion experimental system are designed based on the SC-CO2 fluid properties and the actual operation conditions. Tests find that the remote control of the system is reliable, pressurization process is steady, sealing and operating performances are excellent. The system can effectively simulate the actual drilling and completion process with SC-CO2. The rock-breaking performance of SC-CO 2 is much better than high pressure water jet which verifies the application superiority of SC-CO 2 in rock-breaking drilling. The research lays basis for the development of SC- CO2 drilling and completion technology.

Determination of rock-breaking performance of high-pressure supercritical carbon dioxide jet

In this study, a well-designed experimental setup is used to determine the rock-breaking performance of a high-pressure supercritical carbon dioxide (SC-CO2) jet. Its rock-breaking performance is first compared with that of a high-pressure water jet under the same operation conditions. The effects of five major factors that affect the rock-breaking performance of the high-pressure SC-CO2 jet, i.e., the nozzle diameter, the standoff distance, the jet pressure, the rock compressive strength and the jet temperature are experimentally determined. The experimental results indicate that the rock-breaking performance of the SC-CO2 jet is significantly improved over the high-pressure water jet. It is also found that the rock-breaking performance of the SC-CO2 jet is improved with the increase of the nozzle diameter or the standoff distance, until the nozzle diameter or the standoff distance reaches a certain critical value and after that it begins to deteriorate. The rock-breaking performance of the SC-CO2 jet improves monotonically with the increase of the jet pressure, while it shows a monotonic deterioration with the increase of the rock compressive strength. In addition, it is found that, under the same working conditions, the SC-CO2 jet can always provide a better rock-breaking performance than the subcritical liquid CO2 jet.