Experimental Study on the Impingement Characteristics of Self-Excited Oscillation Supercritical CO2 Jets Produced by Organ-Pipe Nozzles

Mengda Zhang,Zhenlong Fang,Yi’Nan Qian

doi:10.3390/en14227637

Mengda Zhang, Zhenlong Fang + Show 1 more

Open Access

https://doi.org/10.3390/en14227637

Copy DOI

Abstract

Supercritical carbon dioxide (SCO2) jets are a promising method to assist drilling, enhance oil–gas production, and reduce greenhouse gas emissions. To further improve the drilling efficiency of SCO2 jet-assisted drilling, organ-pipe nozzles were applied to generate a self-excited oscillation SCO2 jet (SEOSJ). The impact pressure oscillation and rock erosion capability of SEOSJs under both supercritical and gaseous CO2 (GCO2) ambient conditions were experimentally investigated. It was found that the impact pressure oscillation characteristics of SEOSJs produced by organ-pipe nozzles are dramatically affected by the oscillation chamber length. The optimum range of the dimensionless chamber length to generate the highest impact pressure peak and the strongest pressure oscillation is within 7–9. The dimensionless pressure peak and the pressure ratio decreases gradually with increasing pressure difference, whereas the pressure oscillation intensity increases with increasing pressure difference and the increasing rate decreases gradually. The dominant frequency was observed to decrease monotonically with increasing chamber length but increases with the increase of pressure difference. Moreover, the comparison of impingement characteristics of SEOSJs under different ambient conditions showed that the values of dimensionless peak impact pressure are similar under the two ambient conditions, and the SEOSJ achieves higher pressure oscillation intensity and dominant frequency in SCO2 at the same pressure difference. The rock breaking ability of the SEOSJ is closely related to its axial impact pressure. The erosion depth and mass loss of sandstone caused by the organ-pipe nozzle with the best impact pressure performance is higher than those produced by other nozzles. The SEOSJ results in a deeper and narrower crater in SCO2 than in GCO2 under the same pressure difference. The reported results provide guidance for SEOSJ applications and the design of an organ-pipe nozzle used for jet-assisted drilling.

Highlights

SCO2 jets have been widely applied in the fields of deep hole drilling, rock breaking, metal surface processing, and cooling of electronic equipment, owing to their superior physical properties such as low viscosity, high diffusivity, and high heat transfer capacity [1,2].With the sharp increase in world energy consumption in recent decades, economical exploitation of unconventional energy resources, represented by shale gas and coalbed methane, is gaining increasing importance [3]
There are optimal nozzle diameters and standoffs that lead to the largest rock erosion depth and volume, and the rock-breaking performance improves with increasing jet pressure or decreasing rock compressive strength
Rock erosion experiments performed by Wang et al [12] showed that the erosion depth increases with the increase of jetting time while the erosion rate decreases with the increase of jetting time

Summary

Introduction

SCO2 jets have been widely applied in the fields of deep hole drilling, rock breaking, metal surface processing, and cooling of electronic equipment, owing to their superior physical properties such as low viscosity, high diffusivity, and high heat transfer capacity [1,2].With the sharp increase in world energy consumption in recent decades, economical exploitation of unconventional energy resources, represented by shale gas and coalbed methane, is gaining increasing importance [3]. Many experimental investigations have been performed to study the rock-breaking characteristics and mechanisms, impingement pressure features, and flow behaviors of SCO2 jets [9,10]. Du et al [11] experimentally determined the effects of five major factors affecting the rock-breaking performance of SCO2 jets. They found that the erosion depth of rock by SCO2 jets is larger than that by water jets under the same experimental conditions. There are optimal nozzle diameters and standoffs that lead to the largest rock erosion depth and volume, and the rock-breaking performance improves with increasing jet pressure or decreasing rock compressive strength. Tian et al [14] found that for the same jet pressure both the jet impinging pressure and the erosion depth notably decrease with the increase of ambient pressure

Methods

Results

Conclusion