Abstract Plug and abandonment (P&A) of oil and gas wells at the end of their operational life is one of the helpful techniques to reduce reservoir fluid leakage to upper geological formations and surface. This operation typically involves the placement of cement paste at targeted depths within the wellbore using various techniques to maximize cementing efficiency while limiting wellbore fluid-cement mixing. Among the different techniques, the dump-bailing method—a rapid, ringless, and economical approach—is extensively employed worldwide. In this process, cement slurry is injected from a bailer into the wellbore and settles on top of a permanent bridge plug. From a fluid mechanics perspective, many parameters, such as geometrical conditions, operational parameters, and fluid properties, may affect the efficiency of this process. In this work, we experimentally investigate the injection of heavy suspensions (representative of cement paste) under two different inclination angles into water, a common wellbore fluid in such processes. The experiments are performed within a closed-end pipe (simulating the wellbore and bridge plug) using a scaled-down setup. To examine the effects of injection rates and inclination angle, we employ advanced equipment to prepare and characterize the fluid, conduct experiments, and use non-intrusive techniques, such as a high-speed camera, to capture and analyze the flow dynamics. The results show that the dimensionless pipe filling time remains nearly constant across experiments, regardless of the injection rate or inclination angle. However, during the suspension placement, a higher injection rate increases mixing between the fluids, while a lower inclination angle reduces it. The outcome of this study is beneficial not only for cementing using the dump-bailing method but also for other cementing applications using different methods in oil and gas wells, including primary cementing, cementing during hydrocarbon production, and wellbore decommissioning.
Faramarzi et al. (Sun,) studied this question.