AMENDMENT NO. 6 TO AGREEMENT AND PLAN OF MERGER

THIS AMENDMENT NO. 6 to Agreement and Plan of Merger (this “Amendment”), dated as of July 20, 2015, is made by and among HEYCO Energy Group, Inc., a Delaware corporation (the “Sole Shareholder”), Matador Resources Company, a Texas corporation (“Parent”), and MRC Delaware Resources, LLC, a Texas limited liability company and wholly owned subsidiary of Parent (“MRC Delaware”).

WHEREAS, the Sole Shareholder, Harvey E. Yates Company, a New Mexico corporation (the “Company”), MRC Delaware and Parent entered into that certain Agreement and Plan of Merger, dated as of January 19, 2015, as amended by that certain Amendment No. 1 to the Agreement and Plan of Merger dated as of January 26, 2015, as amended by that certain Amendment No. 2 to the Agreement and Plan of Merger dated as of February 2, 2015, as amended by that certain Amendment No. 3 to the Agreement and Plan of Merger dated as of February 6, 2015, as amended by that certain Amendment No. 4 to the Agreement and Plan of Merger dated as of February 27, 2015 and as amended by that certain Amendment No. 5 to the Agreement and Plan of Merger dated as of April 15, 2015 (as amended, the “Merger Agreement”);

WHEREAS, on February 27, 2015, the transactions contemplated by the Merger Agreement were consummated and the Company merged with and into MRC Delaware;

WHEREAS, pursuant to Section 4.3(a) of the Merger Agreement, Parent delivered to the Sole Shareholder a (i) Pre-Closing Title Defect Notice on or before the Pre-Closing Title Claim Date and (ii) Post-Closing Title Defect Notice on or before the Post-Closing Title Claim Date;

WHEREAS, pursuant to Section 4.3(b)(i) of the Merger Agreement, the Sole Shareholder shall have the right, but not the obligation, to attempt to cure or remove to the reasonable satisfaction of Parent, on or before ninety (90) days after the Post-Closing Title Claim Date (the “Title Cure Date”), any Title Defects of which it has received a Pre-Closing Title Defect Notice or a Post-Closing Title Defect Notice;

WHEREAS, pursuant to Section 13.1 of the Merger Agreement, the parties desire to amend the Merger Agreement in the manner set forth below to extend the Title Cure Date; and

WHEREAS, all capitalized terms used herein without definition shall have the respective meanings given to them in the Merger Agreement;

NOW THEREFORE, in consideration of the premises and mutual covenants and agreements contained herein and in the Merger Agreement, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree as follows:

1.Section 4.3(b)(i) of the Merger Agreement is hereby amended by deleting the words “ninety (90) days” from the first sentence thereto and replacing such words with “one hundred and twenty (120) days.”

2.The parties acknowledge and agree that (i) as of the date hereof, the Sole Shareholder hereby revokes its intent to cure or remediate any Pre-Closing Environmental Conditions or Post-Closing Environmental Conditions as set forth in that certain Notice Letter, dated April 29, 2015 from Sole Shareholder to Parent and (ii) the sum of all Remediation Amounts with respect to all Environmental Conditions that exceed the Individual Environmental Threshold is equal to the aggregate of such amount referenced on Exhibit A of the Pre-Closing Environmental Defect Notice plus such amount referenced on Exhibit A of the Post-Closing Environmental Defect Notice and that such aggregate amount shall be applied to the Aggregate Deductible pursuant to Section 4.3(c)(iii) of the Merger Agreement.

3.The parties further acknowledge that, except as specifically amended hereby, all terms and conditions of the Merger Agreement remain unchanged and that the Merger Agreement, as amended hereby, is in full force and effect and confirmed in all respects.

Section 13.1    Amendment and Modification

Section 13.2    Severability

Section 13.6    Counterparts

Section 13.11    Governing Law

IN WITNESS WHEREOF, the undersigned have caused this Amendment to be signed, all as of the date first written above.