Exhibit 5.1

600 Travis, Suite 4200 Houston, Texas 77002 713.220.4200 Phone 713.220.4285 Fax andrewskurth.com

May 24, 2012

Basic Energy Services, Inc.

500 W. Illinois, Suite 100

Midland, Texas 79701

Ladies and Gentlemen:

We have acted as counsel to Basic Energy Services, Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing of the Registration Statement on Form S-8 (the “Registration Statement”), under the Securities Act of 1933, as amended (the “Securities Act”), relating to the issuance by the Company under the Fourth Amended and Restated Basic Energy Services, Inc. 2003 Incentive Plan (the “Plan”), of up to 3,350,000 shares (the “Shares”) of the Company’s common stock, par value $0.01 per share (the “Common Stock”) and the resale of up to 1,581,721 Shares by certain selling stockholders named in the Registration Statement.

As the basis for the opinions hereinafter expressed, we have examined: (i) originals, or copies certified or otherwise identified, of (a) the Registration Statement; (b) the Plan (c) the Amended and Restated Certificate of Incorporation of the Company, as amended to date; (d) the Amended and Restated Bylaws of the Company, as amended to date; (e) certain resolutions of the Board of Directors of the Company; and (f) such other instruments and documents as we have deemed necessary or advisable for the purposes of this opinion; and (ii) such statutes, including the Delaware General Corporation Law, and regulations as we have deemed necessary or advisable for the purposes of this opinion. We have not independently verified any factual matter relating to this opinion.

In making our examination, we have assumed and have not verified (i) that all signatures on documents examined by us are genuine, (ii) the legal capacity of all natural persons, (iii) the authenticity of all documents submitted to us as originals and (iv) the conformity to the original documents of all documents submitted to us as certified, conformed or photostatic copies.

Based upon the foregoing, and subject to the limitations and assumptions set forth herein, and having due regard for such legal considerations as we deem relevant, we are of the opinion that (i) the Shares offered pursuant to the Plan and the Registration Statement have been duly authorized for issuance by the Company and (ii) the Shares, when issued against payment therefore as required under the Plan and any applicable award agreements, will be validly issued, fully paid and non-assessable.

Basic Energy Services, Inc.

May 24, 2012

Page 2

We express no opinion other than as to the federal laws of the United States of America and the Delaware General Corporation Law (including the statutory provisions, the applicable provisions of the Delaware Constitution and reported judicial decisions interpreting the foregoing). For purposes of this opinion, we assume that the Shares were issued in compliance with all applicable state securities or blue sky laws.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to this firm under the caption “Legal Matters” in the prospectus included in the Registration Statement. In giving this consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the SEC issued thereunder.

Our opinion is rendered as of the date hereof, and we assume no obligation to update or supplement our opinion to reflect any change of fact, circumstance or law after such time.

Very truly yours,

/s/ Andrews Kurth LLP