Exhibit 99.1

Oasis Petroleum Inc. Announces Quarter Ending September 30, 2013 Earnings

Houston, Texas — November 6, 2013 — Oasis Petroleum Inc. (NYSE: OAS) (“Oasis” or the “Company”) today announced financial results for the quarter ended September 30, 2013.

Highlights for the third quarter of 2013 include:

Recent highlights include:

“Oasis grew production in line with our expectations during the third quarter of 2013, as we executed on our plan to complete additional wells on pads,” said Thomas B. Nusz, Oasis’ Chairman and Chief Executive Officer. “We completed 38 gross operated wells with an average working interest of 73%. Through pad drilling and continued operational efficiencies, we drove down operated well costs on the wells completed in the third quarter of 2013 to approximately $8.0 million, excluding the impact of OWS. OWS reduced capital expenditures for the Company by $13.2 million in the third quarter of 2013, which equates to approximately $0.5 million per net operated well completed. So overall, capital efficiency continues to improve.”

Mr. Nusz added, “Including production from our recent acquisitions, we expect production to range between 42,000 Boepd to 46,000 Boepd in the fourth quarter of 2013. Given our further confidence in the growing resource potential in the Williston Basin, we have increased our current rig count to 14, including the two rigs we picked up in our acquisition in West Williston. With the continued growth in our project inventory, we expect to add another two rigs during 2014 which will further accelerate production growth. With the growth in rig count and continuous improvements in drilling efficiency, we expect to spud approximately 210 gross operated wells in 2014. In order to support our additional activity, we have decided to add a second frac fleet to OWS. We expect to spend approximately $20 million for the equipment in 2014 and to begin work in the late second quarter of 2014. We intend to provide more specifics on our 2014 program in late January 2014.”

“We currently have 13 of our 22 planned infill spacing tests online, many of which are in early stages of production,” said Taylor L. Reid, Oasis’ Chief Operating Officer. “Initial results are encouraging, although we will continue to monitor future production to better assess the impact of communication between wells. We expect to have numerous blocks that will be drilled with four to six wells per horizon drilling into the Middle Bakken and first bench of the Three Forks in our 2014 development program. Additionally, our drilling program will be relatively balanced between the Middle Bakken and Three Forks wells in 2014, including numerous wells targeting the lower benches of the Three Forks.”

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Operational and Financial Update

Average daily production by project area is listed in the following table:

The following table describes the Company’s producing Bakken and Three Forks wells by project area in the Williston Basin as of September 30, 2013:

Additionally, the Company also has a backlog of gross operated wells waiting on completion (“WOC”) and wells that were drilling as of September 30, 2013, as shown below:

The Company’s average price per barrel of oil, without derivative settlements, was $100.75 in the third quarter of 2013, compared to $83.71 in the third quarter of 2012 and $91.15 in the second quarter of 2013. The Company’s average price differential compared to NYMEX West Texas Intermediate (“WTI”) crude oil index prices was 5% in the third quarter of 2013, compared to 9% in the third quarter of 2012 and 3% in the second quarter of 2013. As the premium at coastal markets contracted each month during the third quarter of 2013, the Company’s price differentials relative to WTI increased.

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The Company’s revenues are detailed in the following table:

The Company’s operating expenses are detailed in the following table:

The sequential quarter-over-quarter increase in lease operating expenses (“LOE”) per barrel of oil equivalent (“BOE”) was primarily due to additional workover costs, which includes costs to protect producing wells from wells that are being completed.

The increase in marketing, transportation and gathering expenses from the second quarter of 2013 to the third quarter of 2013 is due to higher operated volumes flowing through third party oil gathering pipelines in the third quarter of 2013. As of September 30, 2013, the Company was flowing approximately 85% of its gross operated oil production through these gathering systems. While transporting volumes through third party oil gathering pipelines increases marketing, transportation and gathering expenses, it improves oil price realizations by reducing transportation costs included in our oil price differential for sales at the wellhead.

Production taxes as a percentage of oil and gas revenues were 9.4% in the third quarter of 2013, 9.2% in the third quarter of 2012 and 9.1% in the second quarter of 2013. The Company’s production tax rate increased in the third quarter of 2013 compared to the third quarter of 2012, primarily as a result of adding less Montana wells, which are subject to the lower incentivized production tax rates.

Depreciation, depletion and amortization expenses (“DD&A”) totaled $72.7 million in the third quarter of 2013, $57.7 million in the third quarter of 2012 and $66.8 million in the second quarter of 2013. DD&A was $23.91 per Boe in the third quarter of 2013, $25.85 per Boe in the third quarter of 2012 and $24.33 per Boe in the second quarter of 2013.

General and administrative (“G&A”) expenses totaled $16.7 million in the third quarter of 2013, $13.9 million in the third quarter of 2012 and $16.7 million in the second quarter of 2013. G&A expenses were $5.50 per Boe in the third quarter of 2013, $6.22 per Boe in the third quarter of 2012 and $6.07 per Boe in the second quarter of 2013. Amortization of stock-based compensation, which is included in the aggregate G&A expenses, was $3.0 million, or $1.00 per Boe, in the third quarter of 2013 as compared to $2.7 million, or $1.22 per Boe, in the third quarter of 2012 and $3.1 million, or $1.12 per Boe, in the second quarter of 2013.

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The Company’s derivative activities are detailed in the following table:

The Company recorded non-cash charges for the impairment of oil and natural gas properties of $56,000 in the third quarter of 2013 related to unproved property leases that expired or have been forecasted to expire under current drilling plans, as compared to $36,000 in the third quarter of 2012 and $0.2 million in the second quarter of 2013.

Interest expense increased $1.9 million to $22.9 million for the third quarter of 2013 compared to the third quarter of 2012 and increased $1.5 million compared to the second quarter of 2013. The $1.9 million increase from the third quarter of 2012 was the result of additional interest expense from the Company’s issuance of 6.875% senior unsecured notes in September 2013. Capitalized interest totaled $1.4 million for the third quarter of 2013 and $0.9 million for the third quarter of 2012 and $1.1 million in the second quarter of 2013.

Income tax expense was $33.7 million for the three months ended September 30, 2013, resulting in an effective tax rate of 38.2%. The Company’s income tax expense for the three months ended September 30, 2012 was recorded at 38.5% of pre-tax net income. The Company’s effective tax rate is expected to continue to closely approximate the statutory rate applicable to the U.S. and the blended rate for each of the states in which the Company conducts business.

Adjusted EBITDA for the third quarter of 2013 was $219.6 million, an increase of $80.4 million, or 58%, over the third quarter of 2012 of $139.2 million, and an 18% increase from the second quarter of 2013 of $185.5 million. For a definition of Adjusted EBITDA and a reconciliation of Adjusted EBITDA to net income and net cash provided by operating activities, see “Non-GAAP Financial Measures” below.

For the third quarter of 2013, the Company reported net income of $54.5 million, or $0.59 per diluted share, as compared to net income of $18.3 million, or $0.20 per diluted share, for the third quarter of 2012. The Company’s third quarter 2013 results were impacted by several non-cash items, including a $31.8 million mark-to-market loss on derivative instruments. Excluding these items and their tax effect, the third quarter 2013 Adjusted Net Income (non-GAAP) was $74.5 million, or $0.80 per diluted share. Excluding similar non-cash items and their tax effect, Adjusted Net Income (non-GAAP) for the third quarter of 2012 was $35.4 million, or $0.38 per diluted share. For a definition of Adjusted Net Income and a reconciliation of net income to Adjusted Net Income, see “Non-GAAP Financial Measures” below.

Capital Expenditures

The following table depicts the Company’s exploration and production (“E&P”) capital expenditures (“CapEx”) by project area and total CapEx by category:

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Liquidity

On September 30, 2013, Oasis had total cash and cash equivalents of $125.4 million and restricted cash of $986.2 million. The restricted cash resulted from the net aggregate proceeds of the 6.875% senior unsecured notes issued in September 2013, which was held in escrow as of September 30, 2013 pending the closing of the West Williston acquisition. On September 3, 2013, the Company entered into an amendment to its revolving credit facility agreement (the “Amendment”) and completed its semi-annual redetermination of the Company’s borrowing base. Pursuant to the Amendment, the Company’s borrowing base increased from $1,250 million to $1,500 million. As of September 30, 2013, the Company had $160.0 million drawn on the revolver and $5.2 million of outstanding letters of credit issued under its revolving credit facility, resulting in an unused borrowing base capacity of $1,334.8 million. Following the close of the West Williston acquisition, the Company had $600.0 million drawn under the revolver. Pro forma cash and cash equivalents as of September 30, 2013, after giving effect to the West Williston acquisition and borrowing under the revolver, was $145.2 million.

Hedging Activity

The Company has not modified its commodity derivative contracts since its October 1, 2013 press release, which included its current hedging position.

Conference Call Information

Investors, analysts and other interested parties are invited to listen to the conference call:

A recording of the conference call will be available beginning at 3:00 p.m. Central Time on the day of the call and will be available until Thursday, November 14, 2013 by dialing:

The conference call will also be available for replay at www.oasispetroleum.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. All statements, other than statements of historical facts, included in this press release that address activities, events or developments that the Company expects, believes or anticipates will or may occur in the future are forward-looking statements. Without limiting the generality of the foregoing, forward-looking statements contained in this press release specifically include the expectations of plans, strategies, objectives and anticipated financial and operating results of the Company, including the Company’s drilling program, production, derivative instruments, capital expenditure levels and other guidance included in this press release. These statements are based on certain assumptions made by the Company based on management’s experience and perception of historical trends, current conditions, anticipated future developments and other factors believed to be appropriate. Such statements are subject to a number of assumptions, risks and uncertainties, many of which are beyond the control of the Company, which may cause actual results to differ materially from those implied or expressed by the forward-looking statements. These include, but are not limited to, changes in oil and natural gas prices, weather and environmental conditions, the timing of planned capital expenditures, availability of acquisitions, uncertainties in estimating proved reserves and forecasting production results, operational factors affecting the commencement or maintenance of producing wells, the condition of the capital markets generally, as well as the Company’s ability to access them, the proximity to and capacity of transportation facilities, and uncertainties regarding environmental regulations or litigation and other legal or regulatory developments affecting the Company’s business and other important factors that could cause actual results to differ materially from those projected as described in the Company’s reports filed with the SEC.

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Any forward-looking statement speaks only as of the date on which such statement is made and the Company undertakes no obligation to correct or update any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by applicable law.

About Oasis Petroleum Inc.

Oasis is an independent exploration and production company focused on the acquisition and development of unconventional oil and natural gas resources, primarily operating in the Williston Basin. For more information, please visit the Company’s website at www.oasispetroleum.com.

Contact:

Oasis Petroleum Inc.

Richard Robuck, (281) 404-9600

Director – Finance

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Oasis Petroleum Inc.

Condensed Consolidated Balance Sheet

(Unaudited)

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Oasis Petroleum Inc.

Condensed Consolidated Statement of Operations

(Unaudited)

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Oasis Petroleum Inc.

Selected Financial and Operational Statistics

(Unaudited)

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Oasis Petroleum Inc.

Condensed Consolidated Statement of Cash Flows

(Unaudited)

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Non-GAAP Financial Measures

Adjusted EBITDA is a supplemental non-GAAP financial measure that is used by management and external users of the Company’s consolidated financial statements, such as industry analysts, investors, lenders and rating agencies. The Company defines Adjusted EBITDA as earnings before interest expense, income taxes, depreciation, depletion, amortization, exploration expenses and other similar non-cash charges. Adjusted EBITDA is not a measure of net income or cash flows as determined by United States generally accepted accounting principles, or GAAP.

The following tables present a reconciliation of the non-GAAP financial measure of Adjusted EBITDA to the GAAP financial measures of net income and net cash provided by operating activities, respectively.

Adjusted EBITDA Reconciliations

Adjusted Net Income is a supplemental non-GAAP financial measure that is used by management and external users of the Company’s consolidated financial statements, such as industry analysts, investors, lenders and rating agencies. The Company defines Adjusted Net Income as net income after adjusting first for (1) the impact of certain non-cash items, including changes in unrealized gains and losses on derivative instruments, impairment of oil and gas properties, and other similar non-cash charges, and then (2) the non-cash items’ impact on taxes based on the Company’s effective tax rates in the same period. Adjusted Net Income is not a measure of net income as determined by GAAP.

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The following table provides a reconciliation of net income (GAAP) to Adjusted Net Income (non-GAAP):

Adjusted Net Income Reconciliation

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