Exhibit 10.1

FIRST AMENDMENT TO THE
PATTERSON-UTI ENERGY, INC. 2005 LONG-TERM INCENTIVE PLAN

THIS AGREEMENT is by Patterson-UTI Energy, Inc. (the “Sponsor”),

W I T N E S S E T H:

WHEREAS, the Sponsor maintains the Plan known as the “Patterson-UTI Energy, Inc.
2005 Long-Term Incentive Plan” (the “Plan”); and

WHEREAS, the Sponsor retained the right in Section 12.1 of the Plan to amend the
Plan from time to time; and

WHEREAS, the Board of Directors of the Sponsor approved resolutions on April 10,
2008 to amend the Plan subject to the approval of the Sponsor’s stockholders;

NOW, THEREFORE, the Sponsor agrees that, effective as of the approval of the
Company’s stockholders, Section 3.1(a) of the Plan is hereby amended and
restated in its entirety as follows:

3.1 Number of Shares. (a)  Subject to adjustment as provided in Section 12.2 and
this Section 3.1, the total number of Shares authorized for grant under the Plan
shall be 10,250,000, reduced by the total number of Shares subject to any
options or awards granted under the Prior Plans during the period commencing on
January 1, 2005 and ending on the effective date of this Plan (the
“Pre-Effective Period”). Any Shares that are subject to Awards of Options or
Stock Appreciation Rights, whether granted under this Plan or a Prior Plan
during the Pre-Effective Period, shall be counted against this limit as one
(1) Share for every one (1) Share granted. Any Shares that are subject to Awards
other than Options or Stock Appreciation Rights, whether awarded under this Plan
or a Prior Plan during the Pre-Effective Period, shall be counted against this
limit as one and six tenths (1.6) Shares for every one (1) Share awarded. In
connection with the granting of a Performance Unit denominated in dollars, the
number of Shares that shall be counted against this limit shall be an amount
equal to the quotient of (i) the dollar amount in which the Performance Unit is
denominated, divided by (ii) the Fair Market Value of a Share on the date the
Performance Unit is granted.

Approved and Adopted by the Board of Directors April 10, 2008

Effective June 5, 2008