SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)

Emerald Oil, Inc.

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

29101U100

(CUSIP Number)

White Deer Energy L.P.

667 Madison Avenue, 4th Floor

New York, New York 10065

Attention: Thomas J. Edelman

212-371-1117

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

May 22, 2013

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box.  ¨

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7(b) for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

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Explanatory Note: This Amendment No. 1 amends and supplements the Statement on Schedule 13D (the “Initial Statement”) filed by the reporting persons named in Item 2 thereof (the “Reporting Persons”) on March 1, 2013, relating to the shares of Common Stock, par value $0.001 (the “Common Shares”), of Emerald Oil, Inc. a Montana corporation (the “Issuer”).

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Item 1 of the Initial Statement is hereby amended and replaced with the following:

The principal executive offices of the Issuer are located at 1600 Broadway, Suite 1040, Denver, CO 80202. The total number of Common Shares reported as beneficially owned in this Schedule 13D is 7,900,233 which constitutes approximately 19.9% of the total number of Common Shares outstanding on a pro forma basis as follows. The beneficial ownership reported in this Schedule 13D reflects that at May 22, 2013 there would have been 39,699,658 Common Shares outstanding after giving pro forma effect to the issuance to the Reporting Persons of Common Shares as described herein. The Reporting Persons beneficially own 7,900,233 Common Shares, consisting of (i) 2,785,600 Common Shares which the Reporting Persons will become the record owner of on the Closing Date (as defined below) pursuant to that certain Securities Purchase Agreement, by and among the WDE Emerald Holdings LLC, a Delaware limited liability company (“WD Investor I”), and White Deer Energy FI L.P., a Cayman Islands exempted limited partnership (“WD Investor II” and, together with WD Investor I, the “Investors” and each, an “Investor”) and the Issuer, dated May 13, 2013 (the “May Securities Purchase Agreement”), and (ii) 5,114,633 Common Shares, which are issuable upon exercise of warrants (the “Warrants”) that the Reporting Persons acquired on February 19, 2013.

Each Warrant is coupled, and traded as a unit, with a number of Series B Shares (as defined below) equal to the number of Common Shares purchasable upon exercise of the Warrant. The Warrants and the Series B Shares (as such term is defined below) may not be transferred separately. If and when the Warrant is exercised, the holder of the Warrant will be required to deliver to the Issuer, as part of the payment of the exercise price, a number of Series B Shares equal to the number of shares of Common Shares purchased upon such exercise. The holders of Series B Shares will be entitled to vote in the election of directors and on all other matters submitted to a vote of the holders of Common Shares, with the holders of Series B Shares and the holders of Common Shares voting together as a single class. Each share of Series B Shares will have one vote.

Item 3 of the Initial Statement is hereby amended and replaced with the following:

Pursuant to the Securities Purchase Agreement, by and among the Investors and the Issuer, dated February 1, 2013, the Investors agreed to buy, and the Issuer agreed to sell, (i) an initial aggregate amount of 500,000 shares of Preferred Stock designated as Series A Perpetual Preferred Stock (the “Series A Shares”), (ii) an initial aggregate amount of 5,114,633 shares of Preferred Stock designated as Series B Voting Preferred Stock (the “Series B Shares”) and (iii) the Warrants.

On February 19, 2013, the Investors acquired the Series A Shares, the Series B Shares and the Warrants (collectively, the “February Purchased Securities”).

The Investors paid the Issuer an aggregate purchase price of $50,000,000 for the February Purchased Securities. The source of the purchase price was capital contributions by the partners of the White Deer Funds (as defined below). When exercised, the source of funds to purchase the Warrants will be from capital contributions by the partners of the White Deer Funds (as defined below).

Pursuant the May Securities Purchase Agreement, the Investors agreed to buy, and the Issuer agreed to sell, an aggregate amount of 2,785,600 Common Shares (collectively, the “May Purchased Securities”) on a date not later than June 6, 2013 (the “Closing Date”).

On May 22, 2013, the Investors are deemed to have acquired beneficial ownership of the May Purchased Securities. The actual purchase will be consummated on the Closing Date.

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The Investors agreed to pay the Issuer an aggregate purchase price of $16,346,458 for the May Purchased Securities on the Closing Date. The source of the purchase price will be capital contributions by the partners of the White Deer Funds (as defined below).

Item 4 of the Initial Statement is hereby supplemented to include the following:

The Investors will purchase the May Purchased Securities for investment purposes. The description of the Investors plans or proposals in connection with the May Purchased Securities is included in the Initial Statement.

Item 5 of the Initial Statement is hereby amended and replaced with the following:

(c) Other than as described in Item 3, none.

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(d) None.

(e) Not applicable.

Item 6 of the Initial Statement is hereby supplemented to include the following:

May Securities Purchase Agreement. Pursuant to the May Securities Purchase Agreement, the Investors acquired the right to purchase the May Purchased Securities on the Closing Date.

Amendment No. 1 to the Registration Rights Agreement. Pursuant to Amendment No. 1 to the Registration Rights Agreement by and among the Investors and the Issuer, the Investors have been granted registration rights with respect to the May Purchased Securities.

Item 7 of the Initial Statement is hereby amended and replaced with the following:

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SIGNATURES

After reasonable inquiry and to the best of each of the undersigned’s knowledge and belief, each of the undersigned certifies that the information set forth in this Schedule 13D is true, complete and correct.

Date: May 23, 2013

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