X0306 4 2017-09-25 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 2017-09-25 4 J 0 5125000 A 5125000 I See Footnotes Subordinated units representing limited partner interests 2017-09-25 4 J 0 13750000 A Common units representing limited partner interests 13750000 13750000 I See Footnotes In connection with the initial public offering of Oasis Midstream Partners LP's (the "Issuer") common units representing limited partner interests ("Common Units"), pursuant to that certain Contribution Agreement, by and among the Issuer, OMS Holdings LLC ("OMS Holdings") and other parties thereto, dated September 25, 2017, OMS Holdings contributed certain assets to the Issuer and received in exchange 5,125,000 Common Units and 13,750,000 subordinated units representing limited partner interests in the Issuer ("Subordinated Units"). The Subordinated Units have no expiration date and will convert into Common Units on a one-for-one basis at the end of the "subordination period" described in the Issuer's Prospectus (File No. 333-217976) filed with the Securities and Exchange Commission on September 22, 2017. This Form 4 is being filed jointly by OMS Holdings, Oasis Petroleum LLC ("Oasis Petroleum") and Oasis Petroleum Inc. ("OAS"). As of September 27, 2017 OMS Holdings directly owns 5,125,000 Common Units and 13,750,000 Subordinated Units of the Issuer, Oasis Petroleum directly owns 100% of the outstanding membership interests in OMS Holdings and OAS directly owns 100% of the outstanding membership interests in Oasis Petroleum. Accordingly, OAS and Oasis Petroleum may be deemed to be an indirect beneficial owner of the securities of the Issuer held by OMS Holdings. /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of Oasis Petroleum Inc. 2017-09-27 /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of Oasis Petroleum LLC 2017-09-27 /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of OMS Holdings LLC 2017-09-27