Sec Form 3 Filing - Oasis Investment Holdings LLC @ Oasis Midstream Partners LP - 2021-12-29

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Oasis Investment Holdings LLC 2. Issuer Name and Ticker or Trading Symbol Oasis Midstream Partners LP [ OMP] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 1001 FANNIN STREET, SUITE 1500 3. Date of Earliest Transaction (MM/DD/YY) 12/29/2021 (Street) HOUSTON, TX77002 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Units Representing Limited Partner Interests 12,000,000( 1 )( 2 ) D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Oasis Investment Holdings LL C 1001 FANNIN STREET SUITE 1500 HOUSTON, TX77002 X Oasis Petroleum North America LLC 1001 FANNIN STREET SUITE 1500 HOUSTON, TX77002 X Signatures /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of Oasis Investment Holdings LLC 01/07/2022 Signature of Reporting Person Date /s/ Nickolas J. Lorentzatos, Executive Vice President, General Counsel and Corporate Secretary of Oasis Petroleum North America LLC 01/07/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )This Form 3 is being jointly filed by Oasis Investment Holdings LLC ("OIH") and Oasis Petroleum North America LLC ("OPNA"). OPNA directly owns 12.7% of the outstanding membership interests in OIH and OMS Holdings LLC ("OMS Holdings") directly owns the remaining 87.3% of the outstanding membership interests in OIH and is the managing member of OIH. Oasis Petroleum LLC ("Oasis Petroleum") directly owns 100% of the outstanding membership interests in each of OMS Holdings and OPNA, and Oasis Petroleum Inc. ("OAS") directly owns 100% of the outstanding membership interests in Oasis Petroleum. Accordingly, OAS, Oasis Petroleum, OMS Holdings and OPNA may be deemed to be indirect beneficial owners of any securities held by OIH. ( 2 )On December 29, 2021, OMS Holdings contributed 12,000,000 common units representing limited partner interests in Oasis Midstream Partners LP to OIH pursuant to that certain Contribution Agreement, dated as of December 29, 2021, by and between OMS Holdings and OIH.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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