Western Midstream Partners LP美股招股说明书(2025-09-12版)

Dear Stockholder of Aris Water Solutions, Inc.: Aris Water Solutions, Inc. (“Aris”) and Western Midstream Partners, LP (“WES”) have entered into an Agreement and Plan of Merger (the “Merger Agreement”)that provides for Aris and Aris Water Holdings, LLC (“Aris OpCo”) to become subsidiaries of WES through a series of mergers (the “Mergers”), upon the terms andsubject to the conditions set forth in the Merger Agreement. As a result of the Mergers, (i)each share of ClassA common stock, par value $0.01 per share, of Aris (“ArisClassA Common Stock”), and (ii)each Aris OpCo Stapled Unit (comprising one unit of Aris OpCo and one corresponding share of ClassB common stock, par value$0.01 per share, of Aris (“Aris ClassB Common Stock”)), held as of immediately prior to the Mergers, subject to certain exceptions as set forth in the MergerAgreement, will, in each case, be converted into the right to receive one of the following forms of consideration: (i)a combination of 0.450 common units representinglimited partner interests in WES (“WES Common Units”) and $7.00 in cash (without interest) (the “Mixed Election Consideration”), (ii) $25.00 in cash (without interest)(the “Cash Election Consideration”), provided that the Cash Election Consideration is subject to proration to ensure that the aggregate amount of cash paid in theMergers does not exceed $415.0million, or (iii) 0.625 WES Common Units (the “Common Unit Election Consideration” and, together with the Mixed ElectionConsideration and the Cash Election Consideration, the “Merger Consideration”). Aris stockholders and Aris OpCo unitholders (collectively, “Aris securityholders”) willhave an opportunity to elect which form of Merger Consideration they will receive in the Mergers, and Aris securityholders that do not timely make an election willreceive the Common Unit Election Consideration. The market value of thenon-cashportion of the Merger Consideration will fluctuate with the price of WES Common Units. Based on the closing price of WESCommon Units on August5, 2025, the last trading day before the public announcement of the signing of the Merger Agreement, the value of the per share MergerConsideration was approximately $24.90, assuming the Mixed Election Consideration, or approximately $24.86, assuming the Common Unit Election Consideration.Based on the closing price of WES Common Units on September9, 2025, the last practicable date before the date of the proxy statement/prospectus accompanying thisletter, the value of the per share Merger Consideration, was approximately $24.14, assuming the Mixed Election Consideration, or approximately $23.80, assuming theCommon Unit Election Consideration. We urge you to obtain current stock price quotations for Aris ClassA Common Stock and WES Common Units. Shares of ArisClassA Common Stock are currently traded on the New York Stock Exchange (the “NYSE”) under the symbol “ARIS,” and WES Common Units are currently traded onthe NYSE under the symbol “WES.” In connection with the Mergers, Aris will hold a special meeting of its stockholders to consider and vote on a proposal to adopt the Merger Agreement. Theaffirmative vote of the holders of a majority of all outstanding shares of Aris ClassA Common Stock and Aris ClassB Common Stock (collectively, “Aris CommonStock”), voting as a single class, entitled to vote on the merger proposal is required to adopt the Merger Agreement. Stockholders of record as of September 10, 2025, areentitled to vote on the adoption of the Merger Agreement. Certain Aris securityholders have entered into support agreements with Aris and WES, pursuant to which,among other things, they have agreed to vote all of their shares of Aris Common Stock in favor of the adoption of the Merger Agreement and approval of the transactionscontemplated thereby, including the Mergers. Collectively, these securityholders hold approximately 42% of the outstanding shares of Aris Common Stock as of the dateof the accompanying proxy statement/prospectus. Your vote is very important. Information about the special meeting, the Mergers and the other business to be considered by the Arisstockholders at the special meeting is contained in the accompanying proxy statement/prospectus, which we urge you to read. In particular, seethe section titled “Risk Factors” beginning on page24 of the accompanying document. The Aris board of directors (the “Aris board”) has unanimously determined that it is advisable and in the best interests of Aris and its stockholders forAris to enter into the Merger Agreement and has approved the Merger Agreement, the Mergers and the other transactions contemplated by the MergerAgreement. The Aris board unanimously recommends that the Aris stockholders vote “FOR” the proposal to adopt the Merger Agreement. Sincerely, William A. ZartlerFounder and Executive Chairman Amanda M. BrockPresident and Chief Executive Officer Neither the U.S. Securities and Exchange Commission nor any state securities commi