X0306 4 2021-03-30 0 0001652133 Oasis Midstream Partners LP OMP 0001486159 Oasis Petroleum Inc. 1001 FANNIN ST., SUITE 1500 HOUSTON TX 77002 0 0 1 0 0001494070 Oasis Petroleum LLC 1001 FANNIN ST., SUITE 1500 HOUSTON TX 77002 0 0 1 0 0001717320 OMS Holdings LLC 1001 FANNIN ST., SUITE 1500 HOUSTON TX 77002 0 0 1 0 Common units representing limited partner interests 2021-03-30 4 J 0 14644220 A 37469220 I See Footnote Pursuant to that certain Contribution and Simplification Agreement, dated as of March 22, 2021, by and among Oasis Midstream Partners LP (the "Issuer"), OMS Holdings LLC ("OMS Holdings"), Oasis Midstream Services LLC, OMP GP LLC (the "General Partner"), OMP Operating LLC, OMP DevCo Holdings Corp., Beartooth DevCo LLC, Bobcat DevCo LLC, OMS Holdings Merger Sub, LLC and, for certain limited purposes set forth therein, Oasis Petroleum Inc. ("OAS"), among other things, (a) OAS caused OMS to contribute certain assets to OMP Operating, as the Issuer's designee, in exchange for the distribution to OMS Holdings of consideration including 12,949,644 common units representing limited partner interests ("common units") and (b) the Issuer and the General Partner caused the Incentive Distribution Rights (as defined in the Contribution and Simplification Agreement) to be cancelled and converted into 1,850,356 common units, 1,694,576 of which were distributed to OMS Holdings, which is now is the (continued from footnote 1) sole member of the General Partner. This Form 4 is being jointly filed by OMS Holdings, Oasis Petroleum LLC ("Oasis Petroleum") and OAS. As of March 30, 2021, OMS Holdings directly owns 37,469,220 common units, 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. 2021-04-01 /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of Oasis Petroleum LLC 2021-04-01 /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of OMS Holdings LLC 2021-04-01