Abstract
Supercritical carbon dioxide (SC-CO2) jet is capable of decreasing the threshold pressure of rock breakage and mitigating formation damage, owing to its low viscosity, high diffusivity, and extremely-low surface tension. The swirling-round jet holds the advantages of both a swirling jet and a round jet. Therefore, the comprehensive technique, swirling-round SC-CO2 (SR-SC-CO2) jet, is expected to substantially enhance rock-breaking efficiency. However, theoretical analysis of the flow field characteristics of SR-SC-CO2 has not been reported yet. This work aims to lay a theoretical foundation for employing SR-SC-CO2 in drilling and fracturing. The flow field is simulated using Naiver-Stokes equations and the RNG k-ε turbulence model. Sensitivity analysis, regarding pressure drop of the nozzle, confining pressure, fluid temperature, jetting distance, the diameter of the nozzle’s central hole, and grooving area, are performed. We show that the combined swirling-round SC-CO2 jet flow could maintain a relatively larger axial as well as tangential velocity compared to a single approach of swirling jet or round jet, enabling one to acquire a deeper oillet and expand the perforation area effectively. The simulation results substantiate the enormous potential of SR-SC-CO2 in improving rock-breaking efficiency and clarify the influence of relevant parameters on the impact pressure of the jet flow.
Highlights
With the development of petroleum exploration and exploitation toward a deeper formation, the quantity of deep and ultra-deep wells is ever-increasing [1,2,3]
The round jet and swirling jet are fully mixed in the mixing section, giving rise to a swirling-round SC-CO2 jet flow, which hits the wall after flowing through the nozzle outlet and lengthened section
When the SC-CO2 flow through the convergent section of the nozzle, fluid pressure decreases, and flow velocity sharply rises, resulting in the swirlinground SC-CO2 jet flow that hits the wall on the right side
Summary
With the development of petroleum exploration and exploitation toward a deeper formation, the quantity of deep and ultra-deep wells is ever-increasing [1,2,3]. High-pressure water (HPW) jet has played a crucial role in deep-well exploitation. Several problems of HPW, including high water consumption, clay swelling, groundwater contamination, treatment of flow-back fluid, and high threshold pressure of rock breaking, remain to be solved [5,6,7,8,9,10,11,12]. By improving the jet pressure, modifying nozzle structures, or introducing new fluid, a series of novel jet technologies have been proposed. Buckman et al [14] designed the swirling-round jet bit to effectively eliminate the central low-speed zone and the convex plate of the swirling jet. The rock-breaking effect and flow field characteristics of the swirling-round water (SRW) jet have been
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