1

                                                                     EXHIBIT 3.1

                                    RESTATED
                          CERTIFICATE OF INCORPORATION
                                       OF
                           PATTERSON-UTI ENERGY, INC.
           (Originally incorporated on October 14, 1993 under the name
                            Patterson Energy, Inc.)


         FIRST: The name of the Corporation is Patterson-UTI Energy, Inc.

         SECOND: The address of the Corporation's registered office in the State
of Delaware is Corporation Trust Center, 1209 Orange Street, in the City of
Wilmington, County of New Castle. The name of its registered agent at such
address is The Corporation Trust Company.

         THIRD: The nature of the business or purposes to be conducted or
promoted are to engage in any lawful act or activity for which corporations may
be organized under the General Corporation Law of the State of Delaware.

         FOURTH: The total number of shares of stock that the Corporation shall
have authority to issue is two hundred one million (201,000,000) shares, of
which two hundred million (200,000,000) shares shall be Common Stock, having a
par value of $0.01 per share, and one million (1,000,000) shares shall be
Preferred Stock, having a par value of $0.01 per share. The shares of such
classes of stock shall have the following express terms:

Section 1. PREFERRED STOCK

         1.1 Authority of the Board of Directors to Create Series. The Board of
Directors is hereby expressly granted authority, to the full extent now or
hereafter permitted herein and by the General Corporation Law of the State of
Delaware, at any time or from time to time, by resolution or resolutions, to
create one or more series of Preferred Stock, to fix the authorized number of
shares of any series (which number of shares may vary as between series and be
changed from time to time by like action), and to fix the terms of such series,
including, but not limited to, the following:

                  (a) the designation of such series, which may be by
                  distinguishing number, letter, or title;

                  (b) the rate or rates at which shares of such series shall be
                  entitled to receive dividends; the periods in respect of which
                  dividends are payable; the conditions upon, and times of
                  payment of, such dividends; the relationship and preference,
                  if any, of such


- --------------------------------------------------------------------------------
                               Exhibit 3.1 page 1
   2

                  dividends to dividends payable on any other class or classes
                  or any other series of stock; whether such dividends shall be
                  cumulative and, if cumulative, the date or dates from which
                  such dividends shall accumulate; and the other terms and
                  conditions applicable to dividends upon shares of such series;

                  (c) the rights of the holders of the shares of such series in
                  case the Corporation be liquidated, dissolved or wound up
                  (which may vary depending upon the time, manner, or voluntary
                  or involuntary nature or other circumstances of such
                  liquidation, dissolution, or winding up) and the relationship
                  and preference, if any, of such rights to rights of holders of
                  shares of stock of any other class or classes or any other
                  series of stock;

                  (d) the right, if any, of the Corporation to redeem shares of
                  such series at its option, including any limitation of such
                  right, and the amount or amounts to be payable in respect of
                  the shares of such series in case of such redemption (which
                  may vary depending on the time, manner, or other circumstances
                  of such redemption), and the manner, effect, and other terms
                  and conditions of any such redemption;

                  (e) the obligation, if any, of the Corporation to purchase,
                  redeem, or retire shares of such series and/or to maintain a
                  fund for such purpose, and the amount or amounts to be payable
                  from time to time for such purpose or into such fund, or the
                  number of shares to be purchased, redeemed, or retired, the
                  per share purchase price or prices, and the other terms and
                  conditions of any such obligation or obligations;

                  (f) the voting rights, if any, which, if granted, may be full,
                  special, or limited, to be given the shares of such series,
                  including, without limiting the generality of the foregoing,
                  the right, if any, as a series or in conjunction with other
                  series or classes, to elect one or more members of the Board
                  of Directors either generally or at certain times or under
                  certain circumstances, and restrictions, if any, on particular
                  corporate acts without a specified vote or consent of holders
                  of such shares (such as, among others, restrictions on
                  modifying the terms of such series or of the Preferred Stock,
                  restricting the permissible terms of other series or the
                  permissible variations between series of the Preferred Stock,
                  authorizing or issuing additional shares of the Preferred
                  Stock, creating debt, or creating any class of stock ranking
                  prior to or on a parity with the Preferred Stock or any series
                  thereof as to dividends, or assets remaining for distribution
                  to the stockholders in the event of the liquidation,
                  dissolution, or winding up of the Corporation);


- --------------------------------------------------------------------------------
                               Exhibit 3.1 page 2
   3

                  (g) the right, if any, to exchange or convert the shares into
                  shares of any other series of the Preferred Stock or into
                  shares of any other class of stock of the Corporation or the
                  securities of any other corporation, and the rate or basis,
                  time, manner, terms, and conditions of exchange or conversion
                  or the method by which the same shall be determined; and

                  (h) the other special powers, preferences, or rights, if any,
                  and the qualifications, limitations, or restrictions thereof,
                  of the shares of such series.

         The Board of Directors shall fix the terms of each such series by
resolution or resolutions adopted at any time prior to the issuance of the
shares thereof, and the terms of each such series may, subject only to
restrictions, if any, imposed by this Certificate of Incorporation or by
applicable law, vary from the terms of other series to the extent determined by
the Board of Directors from time to time and provided in the resolution or
resolutions fixing the terms of the respective series of the Preferred Stock.

         1.2 Status of Certain Shares. Shares of any series of the Preferred
Stock, whether provided for herein or by resolution or resolutions of the Board
of Directors, which have been redeemed (whether through the operation of a
sinking fund or otherwise) or which, if convertible or exchangeable, have been
converted into or exchanged for shares of stock of any other class or classes,
or which have been purchased or otherwise acquired by the Corporation, shall
have the status of authorized and unissued shares of the Preferred Stock of the
same series and may be reissued as a part of the series of which they were
originally a part or may be reclassified and reissued as part of a new series of
the Preferred Stock to be created by resolution or resolutions of the Board of
Directors or as a part of any other series of the Preferred Stock, all subject
to the conditions or restrictions on issuance set forth herein or in the
resolution or resolutions adopted by the Board of Directors providing for the
issue of any series of the Preferred Stock.

Section 2. COMMON STOCK

         2.1 Issuance, Consideration, and Terms. Any unissued shares of the
Common Stock may be issued from time to time for such consideration, having a
value of not less than the par value thereof, as may be fixed from time to time
by the Board of Directors. Any treasury shares may be disposed of for such
consideration as may be determined from time to time by the Board of Directors.
The Common Stock shall be subject to the express terms of the Preferred Stock
and any series thereof. Each share of Common Stock shall be of equal rank and
shall be identical to every other share of Common Stock. Holders of Common Stock
shall have such rights as are provided herein and by law.

         2.2 Voting Rights. Except as expressly required by law or as provided
in or fixed and determined pursuant to Section 1 of this Article FOURTH, the
entire voting power and all voting rights shall be vested exclusively in the
Common Stock. Each holder of shares of Common Stock shall be entitled to one (1)
vote for each share standing in such holder's name on the books of the
Corporation.


- --------------------------------------------------------------------------------
                               Exhibit 3.1 page 3
   4

         2.3 Dividends. Subject to Section 1 of this Article FOURTH, the holders
of Common Stock shall be entitled to receive, and shall share equally share for
share, when and as declared by the Board of Directors, out of the assets of the
Corporation which are by law available therefor, dividends or distributions
payable in cash, in property, or in securities of the Corporation.

         FIFTH: The Board of Directors is authorized to make, alter, or repeal
the Bylaws of the Corporation.

         SIXTH: Meetings of stockholders shall be held at such place, within or
without the State of Delaware, as may be designated by or in the manner provided
in the Bylaws, or, if not so designated, at the registered office of the
Corporation in the State of Delaware. Elections of directors need not be by
written ballot unless and to the extent that the Bylaws so provide.

         SEVENTH: Special meetings of the stockholders of the Corporation for
any purpose or purposes may be called at any time by the Board of Directors (or
a majority of the members thereof) of the Corporation by action at a meeting, a
majority of the members of the Board of Directors of the Corporation acting
without a meeting, the Chief Executive Officer of the Corporation, the President
of the Corporation or the holders of a majority of the issued and outstanding
stock of the Corporation entitled to be voted at such special meeting. Such
special meetings may not be called by any other person or persons or in any
other manner.

         EIGHTH: The Corporation reserves the right to amend, alter, or repeal
any provision contained in this Certificate of Incorporation in the manner now
or hereafter prescribed by statute, and all rights of stockholders herein are
subject to this reservation.

         NINTH: To the fullest extent permitted by the General Corporation Law
of the State of Delaware, as the same exists or may hereafter be amended, a
director of the Corporation shall not be liable to the Corporation or its
stockholders for monetary damages for breach of fiduciary duty as a director.

         TENTH: Any action required or permitted to be taken by the holders of
the stock of the Corporation entitled to vote in the election of directors must
be effected at a duly called annual meeting or special meeting of such holders
and may not be effected by any consent in writing by such holders.

         ELEVENTH: Whenever a compromise or arrangement is proposed between the
Corporation and its creditors or any class of them and/or between the
Corporation and its stockholders or any class of them, any court of equitable
jurisdiction within the State of Delaware may, on the application in a summary
way of the Corporation or of any creditor or stockholder thereof or on the
application of any receiver or receivers appointed for the Corporation under the
provisions of Section 291 of Title 8 of the Delaware Code or on the application
of trustees in dissolution or of any receiver or receivers appointed for the
Corporation under the provisions of Section 279 of Title 8 of the Delaware Code
order a meeting of the creditors or class of creditors, and/or of the
stockholders or class of


- --------------------------------------------------------------------------------
                               Exhibit 3.1 page 4
   5

stockholders of the Corporation, as the case may be, to be summoned in such
manner as the said court directs. If a majority in number representing
three-fourths in value of the creditors or class of creditors, and/or of the
stockholders or class of stockholders of the Corporation, as the case may be,
agree to any compromise or arrangement and to any reorganization of the
Corporation as a consequence of such compromise or arrangement, the said
compromise or arrangement and the said reorganization shall, if sanctioned by
the court to which the said application has been made, be binding on all the
creditors or class of creditors, and/or on all the stockholders or class of
stockholders, of the Corporation, as the case may be, and also on the
Corporation.

         This Restated Certificate of Incorporation of Patterson-UTI Energy,
Inc. (i) was duly adopted by the Board of Directors of Patterson-UTI Energy,
Inc., without a vote of the stockholders, in accordance with Section 245 of the
Delaware General Corporation Law, (ii) only restates and integrates and does not
further amend the provisions of the Certificate of Incorporation of
Patterson-UTI Energy, Inc., as heretofore amended; and there is no discrepancy
between those provisions and the provisions of this Restated Certificate of
Incorporation.

         Dated this 8th day of May, 2001.


                                        ----------------------------------------

                                        A. Glenn Patterson, President






- --------------------------------------------------------------------------------
                               Exhibit 3.1 page 5