Exhibit 99.1

RELIMINARY CO Y SUBJECT TO COM LETION 1250 N.E. LOO 410, SUITE 1000 SAN ANTONIO, TX 78209 VOTE BY INTERNET Before The Meeting – www. roxyvote.com Use the Internet to transmit your voting instructions and for electronic delivery of information u until 11:59 .m., Eastern Time on Se tember 27, 2021. Have your roxy card in hand when you access the web site and follow the instructions to obtain your records and to create an electronic voting instruction form. During The Meeting – Go to www.virtualshareholdermeeting.com/ ES2021SM You may attend the meeting via the Internet and vote during the meeting. Have the information that is rinted in the box marked by the arrow available and follow the instructions. VOTE BY HONE 1-800-690-6903 Use any touch-tone tele hone to transmit your voting instructions u until 11:59 .m. Eastern Time on Se tember 27, 2021. Have your roxy card in hand when you call and then follow the instructions. VOTE BY MAIL Mark, sign and date your roxy card and return it in the ostage- aid envelo e we have rovided or return it to Vote rocessing, c/o Broadridge, 51 Mercedes Way, Edgewood, NY 11717. TO VOTE, MARK BLOCKS BELOW IN BLUE OR BLACK INK AS FOLLOWS: D59289-TBD KEE THIS ORTION FOR YOUR RECORDS DETACH AND RETURN THIS ORTION ONLY THIS ROXY CARD IS VALID ONLY WHEN SIGNED AND DATED. IONEER ENERGY SERVICES COR . THE BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR” THE FOLLOWING RO OSALS: For AgainstAbstain 1. The ro osal to a rove and ado t the terms of the Agreement and lan of Merger, dated as of July 5, 2021 (as amended from time to time, the “merger agreement”), by and among ioneer Energy Services Cor . (“ ioneer”), atterson-UTI Energy, Inc., Crescent Merger Sub Inc. and Crescent Ranch Second Merger Sub LLC and the transactions contem lated thereby. ☐ ☐ ☐ 2.The ro osal to a rove, on a non-binding advisory basis, the com ensation that may be aid or become ayable to ioneer’s named executive officers that is based on or otherwise relates to the mergers contem lated by the merger agreement. ☐ ☐ ☐ NOTE: Such other business as may ro erly come before the meeting or any adjournment thereof. lease sign exactly as your name(s) a ear(s) hereon. When signing as attorney, executor, administrator, or other fiduciary, lease give full title as such. Joint owners should each sign ersonally. All holders must sign. If a cor oration or artnershi , lease sign in full cor orate or artnershi name by authorized officer. Signature ( LEASE SIGN WITHIN BOX) Date Signature (Joint Owners) Date

RELIMINARY CO Y SUBJECT TO COM LETION Im ortant Notice Regarding the Availability of roxy Materials for the S ecial Meeting: The Notice of S ecial Meeting and roxy Statement is available at: www. roxyvote.com. FOLD AND DETACH HERE D59290-TBD IONEER ENERGY SERVICES COR . SPECIAL MEETING OF STOCKHOLDERS SE TEMBER 28, 2021, 9:00 AM CENTRAL TIME This roxy is solicited by the Board of Directors The undersigned stockholder(s) or convertible noteholder(s) of IONEER ENERGY SERVICES COR . hereby a oint(s) Matthew S. orter and Bryce T. Seki, or either of them, as roxies, each with the ower to a oint his substitute, and hereby authorize(s) them to re resent and to vote, as designated on the reverse side of this ballot, all of the shares of common stock of IONEER ENERGY SERVICES COR . that the stockholder(s) or convertible noteholder(s) are entitled to vote at the S ecial Meeting of Stockholders to be held at 9:00 AM Central Time, on Se tember 28, 2021 at www.virtualshareholdermeeting.com/ ES2021SM, and any adjournment or ost onement thereof. THIS ROXY, WHEN RO ERLY EXECUTED, WILL BE VOTED IN THE MANNER DIRECTED HEREIN. IF NO SUCH DIRECTION IS MADE, THIS ROXY WILL BE VOTED IN ACCORDANCE WITH THE BOARD OF DIRECTORS’ RECOMMENDATIONS. (CONTINUED AND TO BE SIGNED ON THE REVERSE SIDE)