| Cover Page | Mar. 26, 2021 | Feb. 25, 2020 |
| Cover [Abstract] | ||
| Document Type | 8-K | |
| Document Period End Date | Mar. 26, 2021 | |
| Entity Registrant Name | OASIS MIDSTREAM PARTNERS LP | |
| Entity Incorporation, State or Country Code | DE | |
| Entity File Number | 001-38212 | |
| Entity Tax Identification Number | 47-1208855 | |
| Entity Address, Address Line One | 1001 Fannin Street | |
| Entity Address, Address Line Two | Suite 1500 | |
| Entity Address, City or Town | Houston | |
| Entity Address, State or Province | TX | |
| Entity Address, Postal Zip Code | 77002 | |
| City Area Code | 281 | |
| Local Phone Number | 404-9500 | |
| Title of 12(b) Security | Common units, representing limited partner interests | |
| Trading Symbol | OMP | |
| Security Exchange Name | NASDAQ | |
| Written Communications | false | |
| Soliciting Material | false | |
| Pre-commencement Tender Offer | false | |
| Pre-commencement Issuer Tender Offer | false | |
| Entity Emerging Growth Company | true | |
| Entity Ex Transition Period | true | |
| Entity Central Index Key | 0001652133 | |
| Amendment Flag | false | |
| Current Fiscal Year End Date | --12-31 |
