X0206 3 2017-09-20 0 0001652133 Oasis Midstream Partners LP OMP 0001486159 Oasis Petroleum Inc. 1001 FANNIN STREET, SUITE 1500 HOUSTON TX 77002 0 0 1 0 0001494070 Oasis Petroleum LLC 1001 FANNIN STREET, SUITE 1500 HOUSTON TX 77002 0 0 1 0 0001717320 OMS Holdings LLC 1001 FANNIN STREET, SUITE 1500 HOUSTON TX 77002 0 0 1 0 Common units representing limited partner interests 0 I See footnotes This Form 3 is being filed in connection with the effectiveness of the Issuer's Registration Statement on Form S-1 (Registration No. 333-217976). As of September 20, 2017, OMS Holdings LLC ("OMS Holdings") owns all of the issued and outstanding limited partner interests in Oasis Midstream Partners LP ("Issuer"), Oasis Petroleum LLC ("Oasis Petroleum") directly owns 100% of the outstanding membership interests in OMS Holdings and Oasis Petroleum Inc. ("OAS") directly owns 100% of the outstanding membership interests in Oasis Petroleum. Accordingly, OAS and Oasis Petroleum may be deemed to be indirect beneficial owners of any securities held by OMS Holdings. In connection with the closing of the Issuer's initial public offering, all of the previously issued and outstanding limited partner interests of the Issuer held by OMS Holdings will be redeemed and the Issuer will issue to OMS Holdings new common units representing limited partner interests and subordinated units representing limited partner interests. /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of Oasis Petroleum Inc. 2017-09-20 /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of Oasis Petroleum LLC 2017-09-20 /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of OMS Holdings LLC 2017-09-20