UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 2)

Approach Resources Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

03834A103

(CUSIP Number)

Morgan D Neff

Wilks Brothers, LLC

17010 IH 20

Cisco, Texas 76437

(817) 850-3600

Matt Wilks

Wilks Brothers, LLC

17010 IH 20

Cisco, Texas 76437

817-850-3600

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

May 25, 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(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).

SCHEDULE 13D

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This Amendment No. 2 (“Amendment No. 2”) amends and supplements the statements on Schedule 13D filed by the Reporting Persons with the Commission on February 3, 2017, as amended by Amendment No. 1 thereto filed by the Reporting Persons with the Commission on March 28, 2017 (as amended, the “Original Schedule 13D”), relating to the Common Stock, $0.01 par value per share (the “Common Stock”) of Approach Resources, Inc. (the “Issuer”). All capitalized terms used but not defined herein shall have the meanings given to them in the Original 13D. The Original 13D is hereby amended as follows:

Item 3 of the Original 13D is hereby amended as follows:

As of the date hereof, the Reporting Persons have acquired an additional 1,025,000 shares of Common Stock for an aggregate purchase price of $2,955,000, including brokerage commissions, pursuant to a Rule 10b5-1 trading plan adopted by Wilks Brothers, LLC on May 5, 2017.

The Reporting Persons intend to review their respective investment in the Issuer on a continuing basis and may from time to time and at any time in the future, depending on various factors, including, without limitation, the outcome of any discussions referenced above, the Issuer’s financial position and strategic direction, actions taken by the Board of Directors of the Issuer, price levels of the shares of Common Stock, other investment opportunities available to the Reporting Persons, conditions in the securities market and general economic and industry conditions, take such actions with respect to the investment in the Issuer as they deem appropriate (subject to applicable contractual restrictions, including the Equity Cap under the Stockholders Agreement), including: (i) acquiring additional shares of Common Stock and/or other equity, debt, notes, other securities, or derivative or other instruments that are based upon or relate to the value of the shares of Common Stock or the Issuer (collectively, “Securities”) in the open market or otherwise (including pursuant to Rule 10b5-1 trading plans or otherwise); (ii) disposing of any or all of their Securities in the open market or otherwise; (iii) engaging in any hedging or similar transactions with respect to the Securities; (iv) advocating a sale or transfer of a material amount of assets of the Issuer or its subsidiaries or (v) proposing or considering one or more of the actions described in subsections (a) through (j) of Item 4 of Schedule 13D.

Items 5 (a) and (b) of the Original 13D are hereby amended by replacing them in their entirety with the following:

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Item 5(c) of the Original 13D is hereby amended by adding the following:

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After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

The original statement shall be signed by each person on whose behalf the statement is filed or his authorized representative. If the statement is signed on behalf of a person by his authorized representative (other than an executive officer or general partner of this filing person), evidence of the representative’s authority to sign on behalf of such person shall be filed with the statement, provided, however, that a power of attorney for this purpose which is already on file with the Commission may be incorporated by reference. The name and any title of each person who signs the statement shall be typed or printed beneath his signature.

Attention: Intentional misstatements or omissions of fact constitute Federal criminal violations (See 18 U.S.C. 1001).