Exhibit 2.1

Execution Version

FIRST AMENDMENT TO AGREEMENT AND PLAN OF MERGER

THIS FIRST AMENDMENT TO AGREEMENT AND PLAN OF MERGER (this “Amendment”), dated as of July 27, 2023, is made and entered into by and between Patterson-UTI Energy, Inc., a Delaware corporation (“Parent”), and NexTier Oilfield Solutions Inc., a Delaware corporation (the “Company”). Each of Parent and the Company are referred to herein individually as a “Party” and collectively as the “Parties.” Capitalized terms used herein but not otherwise defined shall have the meanings ascribed to such terms in the Merger Agreement (as defined below).

RECITALS

WHEREAS, Parent, Pecos Merger Sub Inc., a Delaware corporation and direct, wholly owned subsidiary of Parent, Pecos Second Merger Sub LLC, a Delaware limited liability company and direct, wholly owned subsidiary of Parent, and the Company entered into that certain Agreement and Plan of Merger, dated as of June 14, 2023 (the “Merger Agreement”); and

WHEREAS, in accordance with Section 10.2 of the Merger Agreement, the Parties desire to amend the Merger Agreement as specified herein.

NOW, THEREFORE, in consideration of the mutual covenants contained herein and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties hereby agree to the following:

1.    AMENDMENT TO THE MERGER AGREEMENT. The Merger Agreement is hereby amended by replacing Section 5.3 of the Merger Agreement with the following:

“5.3 Corporate Authority; Approval. Such Party has all requisite corporate power and authority and has taken all corporate action necessary in order to execute, deliver and perform its obligations under this Agreement and to consummate the Transactions, and the execution and delivery of this Agreement and the consummation of the Transactions by such Party have been duly authorized by all necessary corporate action on the part of such Party, in each case subject only to, in the case of Parent, approval of (a) the issuance of shares of Parent Common Stock pursuant to this Agreement (the “Share Issuance”) by the holders of shares of Parent Common Stock representing a majority of votes properly cast on the Share Issuance and (b) an amendment to the Parent Charter to increase the authorized number of shares of Parent Common Stock to 800,000,000 shares (the “Parent Charter Amendment”) by the votes of holders of the requisite number of shares of Parent Common Stock entitled to vote thereon, in accordance with Parent’s Organizational Documents and the DGCL (as in effect at the time of such meeting of the Parent stockholders or any adjournment or postponement thereof), in each case, at a meeting of the Parent stockholders duly called and held for such purpose (clauses (a) and (b), collectively, the “Requisite Parent Vote”), and in the case of the Company, adoption of this Agreement by the holders of a majority of the outstanding shares of Company Common Stock entitled to vote on such matter at a meeting of the Company stockholders duly called and held for such purpose (the “Requisite Company Vote”). Assuming the due execution and delivery by the other Party, this Agreement constitutes a valid and binding agreement of such Party enforceable against such Party in accordance with its terms, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar Laws of general applicability relating to or affecting creditors’ rights and to general equity principles (the “Bankruptcy and Equity Exception”).”

2.    EFFECT ON THE MERGER AGREEMENT. Except as expressly amended by this Amendment, the Merger Agreement shall continue in full force and effect in accordance with its terms, and the Merger Agreement, as amended hereby, is hereby confirmed and ratified in all respects. After giving effect to this Amendment, any references in the Merger Agreement to “this Agreement” or to the words “hereof” or “hereunder” or words of similar import, and all references to the Merger Agreement in any and all agreements, instruments, documents, notes, certificates and other writings of every kind or nature (other than in this Amendment or as otherwise expressly provided), shall mean the Merger Agreement as amended by this Amendment, whether or not this Amendment is expressly referenced. All references in the Merger Agreement to “the date hereof” or “the date of this Agreement” shall refer to June 14, 2023.

3.    MISCELLANEOUS. The provisions of the Merger Agreement set forth in Section 10.3 (Counterparts), Section 10.4 (Governing Law and Venue; Submission to Jurisdiction; Selection of Forum; Waiver of Trial by Jury) and Section 10.12 (Severability) are incorporated by reference herein, mutatis mutandis.

Remainder of page intentionally left blank; signature pages follow.

2

IN WITNESS WHEREOF, the Parties have executed this Amendment as of the date first above written.

[Signature Page to First Amendment to Agreement and Plan of Merger]

[Signature Page to First Amendment to Agreement and Plan of Merger]

Exhibit 99.1

Patterson-UTI and NexTier Oilfield Solutions Announce

Expiration of Hart-Scott Rodino Waiting Period for Pending Merger

HOUSTON, July 28, 2023 / — Patterson-UTI Energy, Inc. (NASDAQ: PTEN) (“Patterson-UTI”) and NexTier Oilfield Solutions Inc. (NYSE: NEX) (“NexTier”) today announced the expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (the “HSR Act”), in connection with the previously announced all-stock merger of equals transaction.

The expiration of the waiting period under the HSR Act satisfies one condition needed to close the merger, which remains on track to occur this year. The transaction remains subject to Patterson-UTI and NexTier shareholder approvals and satisfaction of other customary closing conditions.

About Patterson-UTI

Patterson-UTI is a leading provider of oilfield services and products to oil and natural gas exploration and production companies in the United States and other select countries, including contract drilling, pressure pumping and directional drilling services. For more information, visit www.patenergy.com.

About NexTier Oilfield Solutions

Headquartered in Houston, Texas, NexTier is an industry-leading U.S. land oilfield service company, with a diverse set of well completion and production services across the most active and demanding basins. Our integrated solutions approach delivers efficiency today, and our ongoing commitment to innovation helps our customers better address what is coming next. NexTier is differentiated through four points of distinction, including safety performance, efficiency, partnership and innovation. At NexTier, we believe in living our core values from the basin to the boardroom, and helping customers win by safely unlocking affordable, reliable and plentiful sources of energy.

Cautionary Statement Regarding Forward-Looking Statements

This press release contains forward-looking statements which are protected as forward-looking statements under the Private Securities Litigation Reform Act of 1995 that are not limited to historical facts, but reflect Patterson-UTI’s current beliefs, expectations or intentions regarding future events. Words such as “anticipate,” “believe,” “budgeted,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “predict,” “potential,” “project,” “pursue,” “should,” “strategy,” “target,” or “will,” and similar expressions are intended to identify such forward-looking statements. The statements in this press release that are not historical statements, including statements regarding Patterson-UTI’s future expectations, beliefs, plans, objectives, financial conditions, assumptions or future events or performance that are not historical facts, are forward-looking statements within the meaning of the federal securities laws. These statements are subject to numerous risks and uncertainties, many of which are beyond Patterson-UTI’s control, which could cause actual results to differ materially from the results expressed or implied by the statements. The statements include, without limitation, projections as to the anticipated benefits of the proposed transaction, the impact of the proposed transaction on Patterson-UTI’s and NexTier’s businesses and future financial and operating results, the amount and timing of synergies from the proposed transaction, the combined company’s projected revenues, adjusted EBITDA and cash flow, accretion, business and employee opportunities, capital return policy, and the closing date for the proposed transaction, are based on management’s estimates, assumptions and projections, and are subject to significant uncertainties and other factors, many of which are beyond Patterson-UTI’s control.

These factors and risks include, but are not limited to: adverse oil and natural gas industry conditions; global economic conditions, including inflationary pressures and risks of economic downturns or recessions in the United States and elsewhere; volatility in customer spending and in oil and natural gas prices that could adversely affect demand for Patterson-UTI’s services and their associated effect on rates; excess availability of land drilling rigs, pressure pumping and directional drilling equipment, including as a result of reactivation, improvement or construction; competition and demand for Patterson-UTI’s services; the impact of the ongoing conflict in Ukraine; strength and financial resources of competitors; utilization, margins and planned capital expenditures; liabilities from operational risks for which Patterson-UTI does not have and receive full indemnification or insurance; operating hazards attendant to the oil and natural gas business; failure by customers to pay or satisfy their contractual obligations (particularly with respect to fixed-term contracts); the ability to realize backlog; specialization of methods, equipment and services and new technologies, including the ability to develop and obtain satisfactory returns from new technology; the ability to retain management and field personnel; loss of key customers; shortages, delays in delivery, and interruptions in supply, of equipment and materials; cybersecurity events; synergies, costs and financial and operating impacts of acquisitions; difficulty in building and deploying new equipment; governmental regulation; climate legislation, regulation and other related risks; environmental, social and governance practices, including the perception thereof; environmental risks and ability to satisfy future environmental costs; technology-related disputes; legal proceedings and actions by governmental or other regulatory agencies; the ability to effectively identify and enter new markets; public health crises, pandemics and epidemics; weather; operating costs; expansion and development trends of the oil and natural gas industry; ability to obtain insurance coverage on commercially reasonable terms; financial flexibility; interest rate volatility; adverse credit and equity market conditions; availability of capital and the ability to repay indebtedness when due; our return of capital to stockholders; stock price volatility; and compliance with covenants under Patterson-UTI’s debt agreements. In addition, material risks that could cause actual results to differ from forward-looking statements include: the inherent uncertainty associated with financial or other projections; the prompt and effective integration of Patterson-UTI’s and NexTier’s businesses and the ability to achieve the anticipated synergies and value-creation contemplated by the proposed transaction; the risk associated with Patterson-UTI’s and NexTier’s ability to obtain the approval of the proposed transaction by their shareholders required to consummate the proposed transaction and the timing of the closing of the proposed transaction, including the risk that the conditions to the transaction are not satisfied on a timely basis or at all and the failure of the transaction to close for any other reason; the risk that a consent or authorization that may be required for the proposed transaction is not obtained or is obtained subject to conditions that are not anticipated; unanticipated difficulties or expenditures relating to the transaction, the response of business partners and retention as a result of the announcement and pendency of the transaction; and the diversion of management time on transaction-related issues.

Additional information concerning factors that could cause actual results to differ materially from those in the forward-looking statements is contained from time to time in Patterson-UTI’s SEC filings. Patterson-UTI’s filings may be obtained by contacting Patterson-UTI or the SEC or through Patterson-UTI’s website at http://www.patenergy.com or through the SEC’s Electronic Data Gathering and Analysis Retrieval System (EDGAR) at http://www.sec.gov. Patterson-UTI undertakes no obligation to publicly update or revise any forward-looking statement.

Important Information for Stockholders

In connection with the proposed transaction, Patterson-UTI has filed with the SEC a registration statement on Form S-4 that includes a joint proxy statement of Patterson-UTI and NexTier that also constitutes a prospectus of Patterson-UTI. The information in such registration statement is not complete and may be changed. Each of Patterson-UTI and NexTier also plans to file other relevant documents with the SEC regarding the proposed transaction. No offering of securities shall be made, except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act of 1933, as amended. After the registration statement is declared effective, the definitive joint proxy statement/prospectus will be mailed to shareholders of Patterson-UTI and NexTier. INVESTORS AND STOCKHOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT, JOINT PROXY STATEMENT/PROSPECTUS AND OTHER DOCUMENTS THAT MAY BE FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY IF AND WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. Investors and shareholders will be able to obtain free copies of these documents (if and when available) and other documents containing important information about Patterson-UTI and NexTier once such documents are filed with the SEC through the website maintained by the SEC at http://www.sec.gov. Copies of the documents filed with the SEC by Patterson-UTI will be available free of charge on Patterson-UTI’s website at http://www.patenergy.com or by contacting Patterson-UTI’s Investor Relations Department by phone at (281) 765-7170. Copies of the documents filed with the SEC by NexTier will be available free of charge on NexTier’s website at https://nextierofs.com or by contacting NexTier’s Investor Relations Department by phone at (346) 242-0519.

Participants in the Solicitation

Patterson-UTI, NexTier and certain of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about the directors and executive officers of Patterson-UTI is set forth in its proxy statement for its 2023 annual meeting of shareholders, which was filed with the SEC on April 11, 2023, Patterson-UTI’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, which was filed with the SEC on February 13, 2023, and Patterson-UTI’s amendment to its Annual Report on Form 10-K/A, which was filed with the SEC on July 17, 2023. Information about the directors and executive officers of NexTier is set forth in its proxy statement for its 2023 annual meeting of shareholders, which was filed with the SEC on April 28, 2023, and NexTier’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, which was filed with the SEC on February 16, 2023. Other information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, are or will be contained in the joint proxy statement/prospectus and other relevant materials to be filed with the SEC regarding the proposed transaction when such materials become available. Investors should read the joint proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Patterson-UTI or NexTier using the sources indicated above.

No Offer or Solicitation

This communication is not intended to and does not constitute an offer to sell or the solicitation of an offer to subscribe for or buy or an invitation to purchase or subscribe for any securities or the solicitation of any vote in any jurisdiction pursuant to the proposed transaction or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, the public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone and the internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction.

Contact:

Mike Drickamer

Patterson-UTI Vice President, Investor Relations

(281) 765-7170

Michael Sabella

NexTier Vice President, Investor Relations and Business Development

(346) 242-0519

Media for Transaction:

Joele Frank, Wilkinson Brimmer Katcher

PTEN-NEXMedia@joelefrank.com

212-355-4449