SemGroup LP was engaged in diversified services for the North American crude oil and refined products industry.

SemCAMS offers midstream service options for wet or dry, sweet or sour gas gathering and processing, as well as dehydration, field compression and sulfur forming and handling.

Often referred to as 'HFOTCO,' the business unit operated one of the largest oil terminals in the U.S. HFOTCO is in the Houston Ship Channel on the U.S. Gulf Coast.

[9][10][11] New York billionaire John Catsimatidis then became engaged in efforts to take over SemGroup and gained control over a majority of the company's management committee.

[13] The company and its unsecured creditors committee sued former CEO Thomas L. Kivisto and former CFO Gregory C. Wallace, seeking return of $362 million that they claim the defendants used for their own transactions and benefits.

[14] In April 2009, former FBI director Louis Freeh released a report on the circumstances surrounding the SemGroup bankruptcy, claiming it was a result of lies by its top executives about its liquidity problems and a mismanaged speculative oil trading strategy.

[16][17] On December 1, 2009, SemGroup exited bankruptcy under a new corporate structure, eliminating its master limited partnership structure and becoming a publicly traded company focused on asphalt manufacture and marketing and on oil and natural gas storage and transport, with about 1,000 employees including 140 employees in Tulsa.

[31][32] In April 2018, it sold a petroleum products storage facility in the U.K.[33] In December 2019, the company was acquired by Energy Transfer LP.

In September 2009, SemGroup announced a new leadership team, to be led by a new president and CEO, Norm Szydlowski, an experienced oil industry executive who had previously served as president and CEO of Colonial Pipeline Co. A new board was also announced, chaired by John F. Chlebowski, a director of NRG Energy, Inc. and previously president/CEO of GATX Terminals.