Exhibit 99.4

Dear Team,

This morning we announced that SemGroup has entered into a definitive merger agreement with Energy Transfer. This strategic transaction will further strengthen and accelerate growth for our assets, while creating significant value for our shareholders. A link to the press release we issued this morning can be found here: [LINK].

The merger will result in SemGroup combining with one of the largest diversified midstream energy companies in North America, with a strategic footprint in all major U.S. production basins. The combined entity’s size, scale and financial capacity will strengthen and accelerate the growth opportunities for our U.S. businesses and our SemCAMS Midstream JV in Canada well into the future.

The decision to enter into this merger came following an in-depth assessment of numerous strategic options. After significant review and contemplation, we concluded that it was in the best interests of our shareholders to accept this proposal. The last several years have been difficult for the energy industry, but together we have persevered through the ups and downs while building a highly valued company with desired assets. Because of those efforts, Energy Transfer identified SemGroup as a company that they wanted as part of their organization and was willing to pay a premium to secure the merger.

I know that you will have many questions about the merger and what it will mean to you personally. We will be holding an all-employee meeting this morning at 10:00 AM CT to discuss the transaction further. Our commitment to you is to keep you informed throughout this process and to do our best to answer your questions as quickly as possible.

We expect this transaction to close in the first quarter of 2020, subject to SemGroup shareholder approval and obtaining certain other customary regulatory approvals. Until it closes it will be business as usual at SemGroup. We will continue to operate as separate companies, and it is critical that we all stay focused on our day-to-day responsibilities and continue to deliver the safe and reliable service our customers have come to expect.

I would encourage you to review the press release we posted on semgroup.com and Inside SemGroup, as well as the Employee FAQ on Inside SemGroup. For any other questions, please reach out to your team leader and, as always, you can submit questions anonymously on Inside SemGroup.

Today’s announcement wouldn’t be possible without your continued dedication, hard work and focus on providing safe, efficient and reliable service to our customers. Thank you. I look forward to speaking with you later this morning and in the coming weeks.

Carlin

Forward-Looking Statements

This employee communication contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. These statements generally can be identified by the fact that they do not relate strictly to historical or current facts. Statements preceded by, followed by or that otherwise include the words “believes,” “expects,” “anticipates,” “intends,” “projects,” “estimates,” “plans,” “may increase,” “may fluctuate,” “will,” “should,” “would,” “may” and “could” or similar words or expressions are generally intended to identify forward-looking statements. Specific forward-looking statements include statements regarding the Company’s plans and expectations with respect to the proposed transaction and the anticipated impact of the proposed transaction on the Company’s results of operations, financial position, growth opportunities and competitive position. These statements reflect the Company’s current views with respect to future events based on management’s experience and perception of historical trends, current conditions, anticipated future developments and other factors believed to be appropriate. No assurances can be given, however, as of this date that these events will occur or that these projections will be achieved. Forward-looking statements involve known and unknown risks, uncertainties and other factors that are difficult to predict and could cause actual results to be materially different from those expressed in or implied by such forward-looking statements. Some of these factors include the Company’s ability to consummate the proposed transaction on the expected timeframe or at all, including due to the inability to obtain all approvals necessary or the failure of other closing conditions; the volatility of oil and natural gas prices; any sustained reduction in demand for, or supply of, the petroleum products we gather, transport, process, market and store; the overall forward markets for crude oil, natural gas and natural gas liquids; operational, regulatory and environment risks; cost and availability of equipment and labor; the Company’s ability to finance its activities; and other risks more fully discussed in the Company’s filings with the Securities and Exchange Commission (the “SEC”), including its Annual Reports on Form 10-K and Quarterly Reports on Form 10-Q, available on the Company’s website or the SEC’s website at www.sec.gov. Any forward-looking statement speaks only as of the date of which such statement is made and the Company undertakes no obligation to correct or update any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by applicable law.

Important Additional Information Regarding the Transaction Will Be Filed With the SEC

In connection with the proposed transaction, Energy Transfer will file a registration on Form S-4 that will include a proxy statement of the Company. The definitive proxy statement will be sent to the stockholders of the Company. The Company and Energy Transfer may also file other documents with the SEC regarding the proposed transaction. INVESTORS AND SECURITY HOLDERS OF THE COMPANY ARE ADVISED TO CAREFULLY READ THE PROXY STATEMENT AND ANY REGISTRATION STATEMENT/PROSPECTUS (INCLUDING ALL AMENDMENTS AND SUPPLEMENTS THERETO) WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE TRANSACTION, THE PARTIES TO THE TRANSACTION AND THE RISKS ASSOCIATED WITH THE TRANSACTION. A definitive proxy statement and any registration statement/prospectus, as applicable, will be sent to security holders of the Company in connection with the Company’s shareholder meetings. Investors and security holders may obtain a free copy of the proxy statement (when available), any registration statement/prospectus and other relevant documents filed by the Company with the SEC from the SEC’s website at www.sec.gov. Security holders and other interested parties will also be able to obtain, without charge, a copy of the proxy statement (when available), any registration statement/prospectus and other relevant documents by directing a request by mail or telephone to Investor Relations, SemGroup Corporation, 6120 S. Yale Ave, Suite 1500, Tulsa, OK 74136-4231. Copies of the documents filed by the Company with the SEC will be available free of charge on the Company’s website at ir.semgroup.com.

Participants in the Solicitation

The Company and its directors, executive officers and certain other members of management may be deemed to be participants in the solicitation of proxies from its security holders with respect to the transaction. Information about these persons is set forth in the Company’s definitive proxy statement relating to its 2019 Annual Meeting of Stockholders, as filed with the SEC on April 12, 2019, and subsequent statements of changes in beneficial ownership on file with the SEC. Security holders and investors may obtain additional information regarding the interests of such persons, which may be different than those of the Company’s security holders generally, by reading the proxy statement, any registration statement and other relevant documents regarding the transaction, which will be filed with the SEC.

No Offer or Solicitation

This document is not intended to and does not constitute an offer to sell or the solicitation of an offer to subscribe for or buy or an invitation to purchase or subscribe for any securities or the solicitation of any vote in any jurisdiction pursuant to the proposed transaction or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, the public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including, without limitation, facsimile transmission, telephone and the internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction.