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What: Units of Emerge Energy Services (NYSE: EMES) bucked the broader market's Brexit-induced sell-off by rallying sharply on Friday, up more than 19% by 11 a.m. EDT.

So what: Fueling Emerge Energy Services' gains was the announcement that it agreed to sell its fuel business to Sunoco LP (SUN -0.46%) for $178.5 million. That sale will enable Emerge Energy Services to reduce its debt significantly, while simplifying its operating platform.

Emerge Energy Services' fuel business consists of Direct Fuels and Allied Energy Company, which engage in the processing of transmix and the distribution of refined fuels. While those segments provided the company with some diversification benefits, the benefits were not enough to offset the company's weighty debt load, which at nearly $300 million has been a burden during the energy market downturn. By offloading these businesses, the company will cut its net debt by more than half, enabling it to focus on getting its core frack sand operations back on track, and emerging from this transaction as a pure-play frack sand producer.

For Sunoco, these assets fit like a glove. The company, which is engaged in the wholesale distribution and retail sale of motor fuels, will benefit from having these two fuel-related businesses in its portfolio. The transaction also fits in well with its growth-by-acquisition strategy, which entails continuing to roll up what is a relatively fragmented sector.

Now what: This deal removes a huge weight that had been holding down Emerge Energy Services. With its balance sheet in much better shape, the company will be in a stronger position to capture opportunities that should emerge as the energy markets start to recover. While those markets might remain weak for a while, the company now has the financial fortitude to withstand what lies ahead.