An experimental study of proppant transport mechanisms to the pump intake in low-flow oil wells

The exploitation of low-flow oil wells following hydraulic fracturing is often hindered by residual proppant and proppant production during early production phases, which can infiltrate pumps and drastically shorten their service life. Managing proppant reliably and cost-effectively in these wells remains challenging due to the limited understanding of proppant transport mechanisms from the well bottom to the pump intake. This manuscript addresses this critical knowledge gap by presenting novel experimental insights into proppant transport in low-flow oil wells, marking the first elucidation of the underlying mechanism. Through innovative laboratory experiments simulating post-fracturing well conditions, we demonstrate that proppant invariably ascends to the pump intake, driven by a previously unrecognized process: droplets of immiscible hydrocarbon fluids capture and transport proppant particles upward. Comparative analyses using fluids of varying viscosities reveal, for the first time, that the viscosity of the immiscible phase has negligible impact on droplet transport capacity. Additionally, our studies establish that proppant concentration during transport is independent of well flow rate, challenging conventional assumptions. A key novel finding is the pivotal role of free gas bubbles in enhancing proppant transport probability, as they facilitate capture by oil and kerosene droplets; higher gas content correlates directly with elevated proppant concentrations in the flow. These experimental discoveries are validated by field trial data from wells with high free gas content under bottomhole conditions, where reduced pump operational times were observed, confirming the mechanism's real-world relevance. By unveiling this transport mechanism, the manuscript provides a foundational basis for developing targeted proppant management strategies, offering new pathways to enhance pump longevity and operational efficiency in low-flow oil wells.