13D Filing: Blue Mountain Capital and Ocean Rig UDW Inc.

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Ocean Rig UDW Inc.: Andrew Feldstein And Stephen Siderow’s Blue Mountain Capital filed an amended 13D.

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You can access the original SEC filing by clicking here.

Ownership Summary Table

Name Sole Voting Power Shared Voting Power Sole Dispositive Power Shared Dispositive Power Aggregate Amount Owned Power Percent of Class
BlueMountain Capital Management 0 9,846,060 0 9,846,060 9,846,060 10.9%
BlueMountain GP Holdings 0 7,272,878 0 7,272,878 7,272,878 8.0%
BlueMountain Credit GP 0 4,546,482 0 4,546,482 4,546,482 5.0%
Blue Mountain CA Master Fund GP, Ltd 0 4,546,482 0 4,546,482 4,546,482 5.0%
Blue Mountain Credit Alternatives Master Fund 0 4,546,482 0 4,546,482 4,546,482 5.0%
BlueMountain Foinaven GP 0 682,878 0 682,878 682,878 0.8%
BlueMountain Foinaven Master Fund 0 682,878 0 682,878 682,878 0.8%
BlueMountain Long Short Credit GP 0 338,370 0 338,370 338,370 0.4%
BlueMountain Guadalupe Peak Fund 0 338,370 0 338,370 338,370 0.4%
BlueMountain Montenvers GP S. r.l 0 1,090,501 0 1,090,501 1,090,501 1.2%
BlueMountain Montenvers Master Fund SCA SICAV-SIF 0 1,090,501 0 1,090,501 1,090,501 1.2%
BlueMountain Summit Opportunities GP II 0 1,449,360 0 1,449,360 1,449,360 1.6%
BlueMountain Summit Trading 0 1,449,360 0 1,449,360 1,449,360 1.6%
BlueMountain Kicking Horse Fund GP 0 255,788 0 255,788 255,788 0.3%
BlueMountain Kicking Horse Fund 0 255,788 0 255,788 255,788 0.3%
BlueMountain Timberline Ltd 0 630,047 0 630,047 630,047 0.7%

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Page 1 of 24 – SEC Filing

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13D

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. )*

OCEAN RIG UDW
INC.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

G66964118

(CUSIP Number)

Eric M. Albert

BlueMountain Capital Management, LLC

280 Park Avenue, 12th Floor

New York, New York 10017

212-905-5647

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

September 22, 2017

(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 §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-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 § 240.13d-7
for other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting persons initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information
which would alter disclosures provided in a prior cover page.

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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