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Abstract Plug and abandonment (P&A) of oil and gas wells is a promising technique for mitigating greenhouse gas emissions, groundwater contamination, and ecological damage caused by reservoir fluid leakages from wells at the end of their lifespan. In this operation, precise cement plug placement is crucial at specific intervals within the wellbore to achieve highest cement placement efficiency, while minimizing mixing between the wellbore fluid and cement. Several techniques are used for cement plug placement, among which the dump-bailing method stands out as a ringless, fast, and cost-effective approach widely used worldwide. This method involves the injection of cement slurry from a bailer and allowing it to settle on top of a permanent bridge plug. Fluid flow dynamics during this process is governed by several critical parameters, including the properties of the in-situ and injected fluids, geometric parameters, and operational conditions. In this study, we examine injection of heavy suspension fluid (representative of cement slurry) into a near-vertical closed-end pipe filled with a light Newtonian fluid (representative of wellbore fluid) through a scaled-down experimental setup. We focus on the impact of the suspension injection rate on placement efficiency. By utilizing high-speed camera imaging, detailed flow dynamics is captured. Our experimental results indicate that an increasing injection rate improves suspension placement within the pipe. The findings of this study can help us better understand the fluid dynamics involved in cementing processes using the dump-bailing method, as well as the importance of injection rate as a primary operational parameter when cement slurry is considered as a suspension.
Faramarzi et al. (Sun,) studied this question.