Exhibit
10.6





THE
SECURITIES REPRESENTED BY THIS INSTRUMENT HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED, OR THE SECURITIES LAWS OF ANY STATE AND MAY
NOT BE TRANSFERRED, SOLD OR OTHERWISE DISPOSED OF EXCEPT WHILE A REGISTRATION
STATEMENT RELATING THERETO IS IN EFFECT UNDER SUCH ACT AND APPLICABLE STATE
SECURITIES LAWS OR PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER SUCH ACT OR
SUCH LAWS.




WARRANT
No. W-2




to
purchase




Shares
of Common Stock




BRONCO
DRILLING COMPANY, INC.




a
Delaware Corporation




Issue
Date:  September 18, 2009




1.  Definitions. Unless
the context otherwise requires, when used herein the following terms shall have
the meanings indicated.




“Affiliate” means,
with respect to any specified Person, any other Person directly or indirectly
controlling, controlled by or under direct or indirect common control with, such
specified Person; as used in this definition, “control” shall mean, with respect
to any specified Person, the possession, directly or indirectly, of the power to
direct or cause the direction of the management and policies of such specified
Person, whether through ownership of voting securities, by contract or
otherwise.




“Appraisal Procedure”
means a procedure whereby two independent appraisers, one chosen by the
Corporation and one by the Warrantholder (or if there is more than one
Warrantholder involved in an Appraisal Procedure, a majority in interest of
Warrantholders based on the number of Shares issuable on the exercise of the
Warrants held by all such Warrantholders), shall mutually agree upon the
determinations then the subject of appraisal.  Each party shall
deliver a notice to the other appointing its appraiser within fifteen (15) days
after the Appraisal Procedure is invoked.  If within thirty (30) days
after appointment of the two appraisers they are unable to agree upon the amount
in question, a third independent appraiser shall be chosen within ten (10) days
thereafter by the mutual consent of such first two appraisers or, if such two
first appraisers fail to agree upon the appointment of a third appraiser, such
appointment shall be made by the American Arbitration Association, or any
organization successor thereto, from a panel of arbitrators having experience in
appraisal of the subject matter to be appraised.  The decision of the
third appraiser so appointed and chosen shall be given within thirty (30) days
after the selection of such third appraiser.  If three appraisers
shall be appointed and the determination of one appraiser is disparate from the
middle determination by more than twice the amount by which the other
determination is disparate from the middle determination, then the determination
of such appraiser shall be excluded, the remaining two determinations shall be
averaged and such average shall be binding and conclusive upon the Corporation
and the Warrantholder; otherwise, the average of all three determinations shall
be binding upon the Corporation and the Warrantholder.  One-half of
the costs of conducting anyAppraisal Procedure
shall be borne by the Corporation, and the other half shall be borne by the
Warrantholder (of, if more than one Warrantholder invokes an Appraisal
Procedure, by such Warrantholders in the same relative proportion as the number
of Shares issuable on the exercise of the Warrants held by each such
Warrantholder bear to the number of Shares issuable on the exercise of the
Warrants owned by all such Warrantholders).




“Board of Directors”
means the board of directors of the Corporation, including any duly authorized
committee thereof.




“Business Day” means a
day other than a Saturday, a Sunday or a day on which banks in Mexico City,
Mexico or in the state in which the office maintained by the Corporation
pursuant to Section 3 is located are required or permitted by law to be closed
(other than a general banking moratorium or holiday for a period exceeding four
(4) consecutive days).




“Business Combination”
means a merger, consolidation, statutory share exchange, sale of all or
substantially all of the Corporation’s assets or similar form of transaction
that requires the approval of the Corporation’s stockholders, or any tender
offer, exchange offer or similar offer that is commenced by any Person for
shares of Common Stock.




“Business Combination Payment
Amount” means, with respect to any Business Combination, the positive
excess, if any, of (i) the sum of (A) the per share cash consideration payable
in such Business Combination in respect of each share of Common Stock, and (B)
the per share Fair Market Value of any shares of stock or other securities,
property or any other non-cash consideration payable in such Business
Combination in respect of each share of Common Stock, over (ii) the Exercise
Price in effect on the date of the execution by the Corporation (or, if
applicable, a subsidiary thereof) of the definitive agreement in respect of such
Business Combination (or, in the case of a tender offer, exchange offer or
similar offer in which no such definitive agreement is executed by the
Corporation, the date of the commencement thereof, determined in accordance with
the applicable rules and regulations set forth in the Exchange
Act).




“Common Stock” means
the Corporation’s common stock, par value of $0.01 per share.




“Corporation” means
Bronco Drilling Company, Inc., a Delaware corporation.




“Exchange Act” means
the Securities Exchange Act of 1934, as amended, or any successor federal
statute, and the rules and regulations of the SEC thereunder, all as the same
shall be in effect from time to time.  Reference to a particular
section of the Exchange Act shall include a reference to the comparable section,
if any, of any such successor federal statute.




“Exercise Price”
means, (i) from the Issue Date through the first anniversary of the Issue Date,
$6.50 per share; (ii) following the first anniversary of the Issue Date through
the second anniversary of the Issue Date, $7.00 per share; and (iii) following
the second anniversary of the Issue Date through the third anniversary of the
Issue Date, $7.50 per share.




“Expiration Time” has
the meaning set forth in Section 3.




“Fair Market Value”
means, with respect to any security or other property, the fair market value of
such security or other property as determined by the Board of Directors, acting
in good faith.  If the Warrantholder objects in writing to the Board
of Directors’ calculation of fair market value within ten (10) days of receipt
of written notice thereof and the Warrantholder and the Corporation are unable
to agree on fair market value during the 10-day period following the delivery of
the Warrantholder’s objection, the Appraisal Procedure may be invoked by either
party to determine Fair Market Value by delivering written notification thereof
to the other party not later than the 30th day after delivery of the
Warrantholder’s objection.




“Investor” has the
meaning set forth in the Warrant Agreement.




“Investor Group” means
the Investor, any Affiliate thereof, and any other Person whose beneficial
ownership of Common Stock would be aggregated with the Investor’s for purposes
of Section 13(d) of the Exchange Act.




“Issue Date” means
September 18, 2009.




“Market Price” means,
with respect to the Common Stock, on any given day, the last sale price, regular
way, or, in case no such sale takes place on such day, the average of the
closing bid and asked prices, regular way, of the shares of Common Stock on
NASDAQ on such day.  If the Common Stock is not traded on NASDAQ on
any date of determination, the Market Price of the Common Stock on such date of
determination means the closing sale price on such date as reported in the
composite transactions for the principal U.S. national or regional securities
exchange on which the Common Stock is so listed or quoted, or, if no closing
sale price is reported, the last reported sale price on the principal U.S.
national or regional securities exchange on which the Common Stock is so listed
or quoted, or if the Common Stock is not so listed or quoted on a U.S. national
or regional securities exchange, the last quoted bid price for the Common Stock
in the over-the-counter market on such date as reported by Pink Sheets LLC or
similar organization, or, if such bid price is not available, the Market Price
of the Common Stock on that date shall mean the Fair Market Value per share as
determined by the Board of Directors in reliance on an opinion of a nationally
recognized independent investment banking firm retained by the Corporation for
this purpose and certified in a resolution sent to the
Warrantholder.  For the purposes of determining the Market Price of
the Common Stock on the “trading day” preceding, on or following the occurrence
of an event, (i) that trading day shall be deemed to commence immediately after
the regular scheduled closing time of trading on NASDAQ or, if trading is closed
at an earlier time, such earlier time and (ii) that trading day shall end at the
next regular scheduled closing time, or if trading is closed at an earlier time,
such earlier time (for the avoidance of doubt, and as an example, if the Market
Price is to be determined as of the last trading day preceding a specified event
and the closing time of trading on a particular day is 4:00 p.m. and the
specified event occurs at 5:00 p.m. on that same day, the Market Price would be
determined by reference to such 4:00 p.m. closing price).




“NASDAQ” means The
NASDAQ Global Select Market.


-1-





“Net Per Share
Consideration” shall mean, with respect to any Transfer of all or a
portion of this Warrant by the Investor or any other member of the Investor
Group, the quotient obtained by dividing (i) the amount obtained by subtracting
(A) the aggregate amount of fees and expenses (including, without limitation,
brokerage commissions or similar fees or expenses) paid by the Investor or such
other member of the Investor Group in connection with such Transfer (other than
legal fees and disbursements in an amount not to exceed $25,000 with respect to
any such Transfer) from (B) the aggregate consideration paid to the Investor or
such other member of the Investor Group in connection with such Transfer, by
(ii) the aggregate number of shares of Common Stock issuable upon exercise of
the portion of the Warrant subject to such Transfer.




“Person” has the
meaning given to it in Section 3(a)(9) of the Exchange Act and as used in
Sections 13(d)(3) and 14(d)(2) of the Exchange Act.




“Regulatory Approvals”
with respect to the Warrantholder, means, to the extent applicable and required
to permit the Warrantholder to exercise this Warrant for shares of Common Stock
and to own such Common Stock without the Warrantholder being in violation of
applicable law, rule or regulation, the receipt of any necessary approvals and
authorizations of, filings and registrations with, notifications to, or
expiration or termination of any applicable waiting period under, the
Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and the rules
and regulations thereunder.




“SEC” means the United
States Securities and Exchange Commission or any successor agency
thereto.




“Securities Act” means
the Securities Act of 1933, as amended, or any successor federal statute, and
the rules and regulations of the SEC thereunder, all as the same shall be in
effect from time to time.  Reference to a particular section of the
Securities Act shall include a reference to the comparable section, if any, of
any such successor federal statute.




“Shares” has the
meaning set forth in Section 2.




“Spread Value” means,
with respect to any Transfer of the Warrant (or any portion thereof), the
positive excess, if any, of (i) the Market Price per share of the Common Stock
on the date of the execution of the definitive agreement in respect of such
Transfer over (ii) the Exercise Price in effect as of such date.




“Transaction
Documents” has the meaning set forth in the Warrant
Agreement.




“Transfer” or “Transferred” means,
with respect to this Warrant, the sale, assignment, transfer, exchange or other
disposition of such Warrant, in whole or in part, in any case whether pursuant
to a sale, merger, combination, consolidation, reclassification or otherwise,
and whether voluntarily or by operation of law.




“Warrantholder” has
the meaning set forth in Section 2.




“Warrant” means the
warrant to purchase shares of Common Stock issued pursuant to the Warrant
Agreement.




“Warrant Agreement”
means the Warrant Agreement, dated as of September 18, 2009, as may be amended
from time to time, among the Corporation and Banco Inbursa S.A., Institucion de
Banca Multiple, Grupo Financiero Inbursa, including all schedules and exhibits
thereto.




2.  Number of Shares; Exercise
Price. This certifies that, for value received, CARSO INFRAESTRUCTURA Y
CONSTRUCCIÓN, S.A.B. DE C.V., or its permitted transferees, successors and
assigns (the “Warrantholder”) is
entitled, upon the terms and subject to the conditions hereinafter set forth,
including, without limitation, the exercise limitations set forth in Section
13(H) hereof, to acquire from the Corporation, in whole or in part, after the
receipt of all applicable Regulatory Approvals, up to an aggregate of 5,440,770
(FIVE MILLION FOUR HUNDRED FORTY THOUSAND SEVEN HUNDRED AND SEVENTY) fully paid
and nonassessable shares of Common Stock, at a purchase price per share of
Common Stock equal to the Exercise Price.  The number of shares of
Common Stock (the “Shares”) and the
Exercise Price are subject to adjustment as provided herein, and all references
to “Common Stock,” “Shares” and “Exercise Price” herein shall be deemed to
include any such adjustment or series of adjustments.




3.  Exercise of Warrant;
Term.  Subject to Section 2 and Section 13(H), the right to
purchase the Shares represented by this Warrant is exercisable, in whole or in
part, by the Warrantholder, at any time or from time to time after the Issue
Date but in no event later than 5:00 p.m., New York City time, September 18,
2012 (the “Expiration
Time”), by (A) the surrender of this Warrant and Notice of Exercise
annexed hereto, duly completed and executed on behalf of the Warrantholder, at
the principal executive office of the Corporation located at 16217 North May
Avenue, Edmond, Oklahoma 73013 (or such other office or agency of the
Corporation in the United States as it may designate by notice in writing to the
Warrantholder at the address of the Warrantholder appearing on the books of the
Corporation), and (B) payment of the Exercise Price for the Shares thereby
purchased at the election of the Warrantholder in one of the following manners:
(i) by tendering in cash or, with the consent of the Corporation, a certified or
cashier’s check payable to the order of the Corporation, or by wire transfer of
immediately available funds to an account designated by the Corporation, or (ii)
by electing to make a cashless exercise of this Warrant (or a portion thereof),
in which case the Corporation shall issue to the Warrantholder a number of
Shares computed using the following formula:




X=
Y(A-B)A





For
      purposes of the foregoing formula:




X
      =
            the
      number of Shares to be issued to the
  Warrantholder;




Y
      =
            the
      number of Shares purchasable under this Warrant subject to the exercise
      election;




A
      =
            the
      Market Price of one Share as of the date of the exercise of this Warrant
      (or portion thereof); and




B
      =
            the
      Exercise Price in effect immediately prior to the exercise of this Warrant
      (or portion thereof).




If the
Warrantholder does not exercise this Warrant in its entirety, the Warrantholder
will be entitled to receive from the Corporation within a reasonable time, and
in any event not exceeding three (3) Business Days, a new warrant in
substantially identical form for the purchase of that number of Shares equal to
the difference between the number of Shares subject to this Warrant and the
number of Shares as to which this Warrant is so exercised.




4.  Issuance of Shares;
Authorization; Listing.  Subject to Section 8, certificates for
Shares issued upon exercise of this Warrant will be issued in such name or names
as the Warrantholder may designate and will be delivered to such named Person or
Persons within a reasonable time, not to exceed three (3) Business Days after
the date on which this Warrant has been duly exercised in accordance with the
terms of this Warrant. The Corporation hereby represents and warrants that any
Shares issued upon the exercise of this Warrant in accordance with the
provisions of Section 3 will be duly and validly authorized and issued, fully
paid and nonassessable and free from all taxes, liens and charges (other than
liens or charges created by the Warrantholder, income and franchise taxes
incurred by the Warrantholder in connection with the exercise of the Warrant, or
any transfer taxes that become payable by the Warrantholder as a result of the
issuance of shares of Common Stock upon exercise of this Warrant to a Person
other than the Warrantholder).  The Corporation agrees that the Shares
so issued will be deemed to have been issued to the Warrantholder as of the
close of business on the date on which this Warrant and payment of the Exercise
Price are delivered to the Corporation in accordance with the terms of this
Warrant, notwithstanding that the stock transfer books of the Corporation may
then be closed or certificates representing such Shares may not be actually
delivered on such date. The Corporation will at all times reserve and keep
available, out of its authorized but unissued Common Stock, solely for the
purpose of providing for the exercise of this Warrant, and irrespective of the
exercise limitations set forth in Section 13(H) hereof, the aggregate number of
shares of Common Stock issuable upon exercise of this Warrant.  The
Corporation (A) will procure, at its sole expense, the listing of the Shares
issuable upon exercise of this Warrant, subject to issuance or notice of
issuance, on all principal stock exchanges on which the Common Stock is then
listed or traded and (B) will use commercially reasonable efforts to maintain
the listing of such Shares after the issuance thereof.  The
Corporation will use commercially reasonable efforts to ensure that the Shares
may be issued without violation of any law or regulation applicable to the
Corporation or of any requirement of any securities exchange on which the Shares
are listed or traded.  The Corporation will cooperate with the
reasonable requests of the Warrantholder in taking such other actions as are
necessary to obtain (i) any Regulatory Approvals applicable to Warrantholder’s
exercise of its rights hereunder, including with respect to the issuance of the
Shares and (ii) any regulatory approvals applicable to the Corporation solely as
a result of the issuance of the Shares.  Before taking any action
which would cause an adjustment pursuant to Section 13 to reduce the Exercise
Price below the then par value of the Common Stock, the Corporation shall take
any and all corporate action which may, in the opinion of its counsel, be
necessary in order that the Corporation may validly and legally issue fully paid
and non-assessable shares of Common Stock at the Exercise Price as so
adjusted.




5.  No Fractional Shares or
Scrip.  No fractional Shares or scrip representing fractional
Shares shall be issued upon any exercise of this Warrant.  In lieu of
any fractional Share to which the Warrantholder would otherwise be entitled, the
Warrantholder shall be entitled to receive a cash payment equal to the Market
Price of the Common Stock on the last trading day preceding the date of exercise
less the Exercise Price for such fractional share.




6.  No Rights as Stockholders;
Transfer Books.  This Warrant does not entitle the
Warrantholder to any voting rights or other rights as a stockholder of the
Corporation prior to the date of exercise hereof, provided that any voting
rights that the Warrantholder may have in respect of any shares of Common Stock
or other capital stock of the Corporation owned thereby shall not be limited in
any respect.  The Corporation will at no time close its transfer books
against exercise or transfer of this Warrant in any manner which interferes with
the timely exercise or transfer of this Warrant.


-2-





7.  Charges, Taxes and
Expenses.  Issuance of certificates for Shares to the
Warrantholder upon the exercise of this Warrant shall be made without charge to
the Warrantholder for any issue or transfer tax or other incidental expense in
respect of the issuance of such certificates imposed under any law, rule or
regulation applicable to the Corporation, all of which taxes and expenses shall
be paid by the Corporation; provided, however, that any
transfer taxes that become payable by the Warrantholder as a result of the
issuance of shares of Common Stock upon exercise of this Warrant to a Person
other than the Warrantholder shall be paid by the Warrantholder or the Person to
whom such shares are so issued.




8.  Transfer/Assignment.




(A)  Subject
to compliance with clauses (B) and (C) of this Section 8, this Warrant and all
rights hereunder are transferable, in whole or in part, upon the books of the
Corporation by the registered holder hereof in person or by duly authorized
attorney, and a new warrant shall be made and delivered by the Corporation, of
the same tenor and date as this Warrant but registered in the name of one or
more transferees, upon surrender of this Warrant, duly endorsed, to the office
or agency of the Corporation described in Section 3.  If this Warrant
is Transferred in part, such that the Warrantholder retains the right to acquire
Shares upon the exercise hereof, the Corporation shall, without limitation of
its obligations set forth in this clause (A), make and deliver a new warrant to
the Warrantholder of the same tenor and date as this Warrant but the number of
Shares issuable upon the exercise thereof shall be reduced to give effect to
such Transfer.  All expenses (other than stock transfer taxes) and
other charges payable in connection with the preparation, execution and delivery
of the new warrants pursuant to this Section 8 shall be paid by the
Corporation.




(B)  The
Warrantholder may not Transfer this Warrant or any Shares issued upon exercise
of this Warrant other than pursuant to an effective registration with the SEC,
in a sale exempt from registration under Rule 144 under the Securities Act, or,
in reliance upon an opinion of counsel reasonably acceptable to the Corporation,
in any other transaction exempt from registration under the Securities
Act.




(C)  This
Warrant and any new warrant certificate issued pursuant to the terms hereof
shall contain a legend as set forth below:




“THE
SECURITIES REPRESENTED BY THIS INSTRUMENT HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED, OR THE SECURITIES LAWS OF ANY STATE AND MAY
NOT BE TRANSFERRED, SOLD OR OTHERWISE DISPOSED OF EXCEPT WHILE A REGISTRATION
STATEMENT RELATING THERETO IS IN EFFECT UNDER SUCH ACT AND APPLICABLE STATE
SECURITIES LAWS OR PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER SUCH ACT OR
SUCH LAWS.”




(D)  If the
Warrantholder shall determine to Transfer all or any portion of this Warrant,
the Corporation shall provide, and shall cause its subsidiaries and their
respective officers, employees, representatives and advisors to provide, to the
Warrantholder such reasonable cooperation as the Warrantholder may request in
connection therewith, including, without limitation, participating in meetings
and due diligence sessions with any prospective transferee and providing to such
prospective transferee such information and documentation as such prospective
transferee may reasonably request in connection with its consideration of the
purchase of the Warrant (or any portion thereof) from the Warrantholder; provided, however, that the
Corporation shall not be required to take, or cause its subsidiaries or their
respective officers, employees, representatives or advisors to take, any of the
foregoing actions unless and until such prospective transferee shall have
executed and delivered to the Corporation a confidentiality agreement in form
and substance reasonably satisfactory to the Corporation; provided further, however, that the
Corporation shall not be obligated to provide any confidential information
pursuant to this section if the Corporation determines, in its reasonable
discretion, that any prospective transferee is a competitor of the
Corporation.




9.  Exchange and Registry of
Warrant.  This Warrant is exchangeable, upon the surrender
hereof by the Warrantholder to the Corporation, for a new warrant or warrants of
like tenor and representing the right to purchase the same aggregate number of
Shares.  The Corporation shall maintain a registry showing the name
and address of the Warrantholder as the registered holder of this
Warrant.  This Warrant may be surrendered for exchange or exercise, in
accordance with its terms, at the office of the Corporation, and the Corporation
shall be entitled to rely in all respects, prior to written notice to the
contrary, upon such registry.




10.  Loss, Theft, Destruction or
Mutilation of Warrant.  Upon receipt by the Corporation of
evidence reasonably satisfactory to it of the loss, theft, destruction or
mutilation of this Warrant, and in the case of any such loss, theft or
destruction, upon receipt of a bond, indemnity or security reasonably
satisfactory to the Corporation, or, in the case of any such mutilation, upon
surrender and cancellation of this Warrant, the Corporation shall make and
deliver, in lieu of such lost, stolen, destroyed or mutilated Warrant, a new
warrant of like tenor and representing the right to purchase the same aggregate
number of Shares as provided for in such lost, stolen, destroyed or mutilated
Warrant.  Notwithstanding the foregoing, so long as this Warrant is
held by the Investor or any other member of the Investor Group, in the event of
the loss, theft or destruction of this Warrant, the Corporation shall accept
from the Investor or any other member of the Investor Group that may hold all or
any portion of this Warrant from time to time an unsecured indemnity, and shall
not require a bond or other security.




11.  Saturdays, Sundays,
Holidays, etc.  If the last or appointed day for the taking of
any action or the expiration of any right required or granted herein shall not
be a Business Day, then such action may be taken or such right may be exercised
on the next succeeding day that is a Business Day and, for the avoidance of
doubt, if the Expiration Time is not a Business Day, the Expiration Time shall
automatically be extended to the first Business Day immediately following the
previously scheduled Expiration Date.




12.  Rule 144
Information.  The Corporation covenants that it will use its
commercially reasonable efforts to timely file all reports and other documents
required to be filed by it under the Exchange Act and the rules and regulations
promulgated by the SEC thereunder (or, if the Corporation is not required to
file such reports, it will, upon the request of the Warrantholder, make publicly
available such information as necessary to permit sales pursuant to Rule 144 or
Regulation S under the Securities Act), and it will use commercially reasonable
efforts to take such further action as the Warrantholder may reasonably request,
in each case to the extent required from time to time to enable the
Warrantholder to, subject to the terms set forth in this Warrant and the Warrant
Agreement, sell this Warrant and the shares of Common Stock issuable upon
exercise hereof without registration under the Securities Act within the
limitation of the exemptions provided by (A) Rule 144 or Regulation S under the
Securities Act, as such rules may be amended from time to time, or (B) any
successor rule or regulation hereafter adopted by the SEC.  Upon the
written request of the Warrantholder, the Corporation will deliver to the
Warrantholder a written statement that it has complied with such
requirements.




13.  Adjustments and Other
Rights.  The Exercise Price and the number of Shares issuable
upon exercise of this Warrant shall be subject to adjustment from time to time
as follows:




(A)  Stock Splits, Subdivisions,
Reclassifications or Combinations. If the Corporation shall (i) declare
and pay a dividend or make a distribution on its Common Stock in shares of
Common Stock, (ii) subdivide or reclassify the outstanding shares of Common
Stock into a greater number of shares, or (iii) combine or reclassify the
outstanding shares of Common Stock into a smaller number of shares, the number
of Shares issuable upon exercise of this Warrant at the time of the record date
for such dividend or distribution or the effective date of such subdivision,
combination or reclassification shall be proportionately adjusted so that the
Warrantholder after such date shall be entitled to purchase the number of shares
of Common Stock which such holder would have owned or been entitled to receive
in respect of the shares of Common Stock subject to this Warrant after such date
had this Warrant been exercised immediately prior to such date.  In
such event, the Exercise Price in effect at the time of the record date for such
dividend or distribution or the effective date of such subdivision, combination
or reclassification shall be adjusted to the number obtained by dividing (x) the
product of (1) the number of Shares issuable upon the exercise of this Warrant
before such adjustment and (2) the Exercise Price in effect immediately prior to
the record or effective date, as the case may be, for the dividend,
distribution, subdivision, combination or reclassification giving rise to such
adjustment by (y) the new number of Shares issuable upon exercise of the Warrant
determined pursuant to the immediately preceding sentence.




(B)  Business
Combinations.  In case of any Business Combination,
reclassification of Common Stock (other than a reclassification of Common Stock
referred to in Section 13(A)), capital reorganization of the Common Stock or any
other transaction or event in which the shares of Common Stock are exchanged for
or converted into the right to receive any stock or other securities or property
(including cash), and subject to the right of the Warrantholder set forth in
Section 15, the Warrantholder’s right to receive Shares upon exercise of this
Warrant (with the number of Shares issuable upon exercise of this Warrant being
determined, for purposes of this clause (B), without giving effect to the
limitation on exercise set forth in Section 13(H) hereof) shall be converted
into the right to exercise this Warrant to acquire the number of shares of stock
or other securities or property (including cash) which the Common Stock issuable
upon exercise of this Warrant immediately prior to such Business Combination,
reclassification, capital reorganization or other transaction or event would
have been entitled to receive upon consummation of such Business Combination,
reclassification, capital reorganization or other transaction or event; and in
any such case, if necessary, the provisions set forth herein with respect to the
rights and interests thereafter of the Warrantholder shall be appropriately
adjusted so as to be applicable to the Warrantholder’s right to exercise this
Warrant in exchange for any shares of stock or other securities or property
(including cash) pursuant to this paragraph.  In determining the kind
and amount of stock, securities or the property (including cash) receivable upon
exercise of this Warrant following the consummation of such Business
Combination, reclassification, capital reorganization or other transaction or
event, if the holders of Common Stock have the right to elect the kind or amount
of consideration receivable upon consummation of such Business Combination,
reclassification, capital reorganization or other transaction or event, then the
Warrantholder shall be deemed to have elected the types and amounts of
consideration received by the majority of all holders of the shares of Common
Stock that affirmatively make such an election in connection therewith (or of
all such holders if none make an election).




(C)  Rounding of Calculations;
Minimum Adjustments.  All calculations under this Section 13
shall be made to the nearest one-tenth (1/10th) of a cent or to the nearest
one-hundredth (1/100th) of a share, as the case may be.  Any provision
of this Section 13 to the contrary notwithstanding, no adjustment in the
Exercise Price or the number of Shares into which this Warrant is exercisable
shall be made if the amount of such adjustment would be less than $0.01 or
one-tenth (1/10th) of a share of Common Stock, but any such amount shall be
carried forward and an adjustment with respect thereto shall be made at the time
of and together with any subsequent adjustment which, together with such amount
and any other amount or amounts so carried forward, shall aggregate $0.01 or
1/10th of a share of Common Stock, or more.


-3-





(D)  Timing of Issuance of
Additional Common Stock Upon Certain Adjustments.  In any case
in which the provisions of this Section 13 shall require that an adjustment
shall become effective immediately after a record date for an event, the
Corporation may defer until the occurrence of such event (i) issuing to the
Warrantholder to the extent it has exercised this Warrant after such record date
and before the occurrence of such event the additional shares of Common Stock
issuable upon such exercise by reason of the adjustment required by such event
over and above the shares of Common Stock issuable upon such exercise before
giving effect to such adjustment and (ii) paying to such Warrantholder any
amount of cash in lieu of a fractional share of Common Stock; provided, however, that the
Corporation upon request shall deliver to such Warrantholder a due bill or other
appropriate instrument evidencing such Warrantholder’ s right to receive such
additional shares, and such cash, upon the occurrence of the event requiring
such adjustment.





(E)  Other
Events.  For so long as the Warrantholder holds this Warrant or
any portion thereof, if any event occurs as to which the provisions of this
Section 13 are not strictly applicable or, if strictly applicable, would not, in
the good faith judgment of the Board of Directors, fairly and adequately protect
the purchase rights of the Warrantholder pursuant to this Warrant in accordance
with the essential intent and principles of such provisions, then the Board of
Directors shall make such adjustments in the application of such provisions, in
accordance with such essential intent and principles, as shall be reasonably
necessary, in the good faith opinion of the Board of Directors, to protect such
purchase rights as aforesaid.  The Exercise Price and the number of
Shares into which this Warrant is exercisable shall not be adjusted in the event
of a change in the par value of the Common Stock.




(F)  Statement Regarding
Adjustments.  Whenever the Exercise Price or the number of
Shares into which this Warrant is exercisable shall be adjusted as provided in
this Section 13, the Corporation shall forthwith file at the principal office of
the Corporation a statement showing in reasonable detail the facts requiring
such adjustment and the Exercise Price that shall be in effect and the number of
Shares into which this Warrant shall be exercisable after such adjustment, and
the Corporation shall also cause a copy of such statement to be sent by mail,
first class postage prepaid, to the Warrantholder at the address appearing in
the Corporation’s records.




(G)  Notice of Adjustment
Event.  In the event that the Corporation shall propose to take
any action of the type described in this Section 13 or the Corporation shall
declare any cash dividend upon its Common Stock or make any special dividend or
other distribution to the holders of its Common Stock, or the Corporation shall
offer for subscription pro rata to the holders of its Common Stock any
additional shares of stock of any class or other rights, or there shall be any
capital reorganization or reclassification of the capital stock of the
Corporation, or any Business Combination, the Corporation shall give written
notice to the Warrantholder, which notice shall specify the record date, if any,
with respect to any such action and the approximate date on which such action is
to take place.  Such notice shall also set forth the facts with
respect thereto as shall be reasonably necessary to indicate the effect on the
Exercise Price and the number, kind or class of shares or other securities or
property which shall be deliverable upon exercise of this Warrant.  In
the case of any action which would require the fixing of a record date, such
notice shall be given at least ten (10) days prior to the date so fixed, and in
case of all other action, such notice shall be given at least fifteen (15) days
prior to the taking of such proposed action.




(H)  Limitations on
Exercise.  Notwithstanding anything to the contrary contained
herein, (i) the aggregate number of Shares that may be acquired by the
Warrantholder upon the exercise of this Warrant shall not exceed 19.99% of the
number of shares of Common Stock that are issued and outstanding on the Issue
Date, provided that the number of Shares referred to in this clause (i) shall be
subject to proportional increase or decrease, as applicable, upon the occurrence
of any event referred to in Section 13(A) hereof, and (ii) the number of Shares
that may be acquired by the Warrantholder upon any exercise of the Warrant shall
be limited to the extent necessary to ensure that, immediately after giving
effect to the exercise of this Warrant, the total number of shares of Common
Stock owned by the Warrantholder and its Affiliates and any other Person whose
ownership of Common Stock would be aggregated with the Warrantholder’s for
purposes of Section 13(d) of the Exchange Act, does not exceed 19.99% of the
total number of shares of Common Stock that are outstanding immediately after
giving effect to such exercise of this Warrant.  Nothing contained in
this clause (H) shall limit the terms set forth in, or the amounts payable to
any member of the Investor Group (or, in the case of Section 15, any
Warrantholder) pursuant to the terms of, Sections 15 and 16 of this
Warrant.




(I)  Proceedings Prior to Any
Action Requiring Adjustment. As a condition precedent to the taking of
any action which would require an adjustment pursuant to this Section 13, the
Corporation shall take any action which may be necessary, including obtaining
regulatory approvals or exemptions, in order that the Corporation may thereafter
validly and legally issue as fully paid and nonassessable all shares of Common
Stock that the Warrantholder is entitled to receive upon exercise of this
Warrant pursuant to this Section 13.




(J)  Adjustment
Rules.  Any adjustments pursuant to this Section 13 shall be
made successively whenever an event referred to herein shall
occur.  If an adjustment in Exercise Price made hereunder would reduce
the Exercise Price to an amount below the par value of the Common Stock, then
such adjustment in the Exercise Price made hereunder shall reduce the Exercise
Price to the par value of the Common Stock and then, upon the Corporation’s
satisfaction of its obligations under Section 4, to such lower par value as may
then be established.




(K)  No
Impairment.  The Corporation will not, by amendment of its
certificate of incorporation or through any reorganization, transfer of assets,
consolidation, merger, dissolution, issue or sale of securities or any other
voluntary action, avoid or seek to avoid the observance or performance of any of
the terms to be observed or performed hereunder by the Corporation, but will at
all times in good faith assist in the carrying out of all the provisions of this
Warrant and in taking of all such action as may be necessary or appropriate in
order to protect the rights of the Warrantholder.




14.  Certain Issuances of Common
Stock or Convertible Securities.  Without the prior written
consent of the Warrantholder, other than in Permitted Transactions (as defined
below), or as expressly referred to in Section 13(A), the Corporation shall not
issue any shares of Common Stock (or rights or warrants or other securities
exercisable or convertible into or exchangeable for shares of Common Stock) (A)
without consideration, or (B) at a consideration per share (or having a
conversion, exercise or exchange, as applicable, price per share) that is less
than 95% of the Market Price on the trading day immediately preceding the date
of the execution of the agreement in respect of the pricing of such shares (or
such rights, warrants or other securities) or, if no such pricing event shall
occur, on the last trading day immediately preceding the date of the issuance or
grant of such shares (or such rights, warrants or other securities); provided, however, that if the
Corporation shall undertake a registered underwritten public offering of shares
of Common Stock (or rights or warrants or other securities exercisable or
convertible into or exchangeable for shares of Common Stock), the price at which
such shares of Common Stock (or rights or warrants or other securities
exercisable or convertible into or exchangeable for shares of Common Stock)
shall be deemed to have been issued for purposes of this Section 14 will be
determined without giving effect to any underwriting discount or selling
commission granted or paid, as applicable, to the underwriters in connection
therewith.  For purposes hereof, “Permitted
Transactions” shall mean the issuance of shares of Common Stock (i) upon
the exercise of stock options or similar equity awards granted by the
Corporation pursuant to the terms of an employee benefit plan adopted in the
ordinary course of business and consistent with past practice that is approved
by the Board of Directors and, if required by applicable law or regulation, the
stockholders of the Corporation, provided that the exercise or similar price of
any such stock option or equity award is at least equal to the Market Price on
the date of grant of such stock option or equity award, or (ii) in connection
with the exercise or conversion, in accordance with the terms set forth therein
on the Issue Date, of any securities of the Corporation that are outstanding as
of the Issue Date that are exercisable for or convertible into Common Stock and
that are disclosed pursuant to the applicable sections of the Warrant
Agreement.




15.  Business Combination
Payment.  In the event of the occurrence of a Business
Combination in which the consideration payable to the holders of Common Stock
does not consist exclusively of cash, in lieu of the treatment of this Warrant
specified in Section 13(B) hereof, if so elected by the Warrantholder by written
notice to the Corporation delivered at least five (5) Business Days prior to the
closing of such Business Combination, the Warrantholder’s right to receive stock
or other securities or property at or following the closing of such Business
Combination upon exercise of this Warrant pursuant to Section 13(B) hereof shall
be converted, effective upon the closing of such Business Combination, into the
right to receive a payment from the Corporation in cash equal to the amount
obtained by multiplying (i) the number of Shares issuable upon exercise of this
Warrant pursuant to Section 2 hereof immediately prior to the consummation of
such Business Combination, by (ii) the Business Combination Payment Amount that
is applicable to such Business Combination.  The amounts payable by
the Corporation pursuant to this Section 15 shall be paid concurrently with the
closing of such Business Combination in U.S. dollars in immediately available
funds to such account(s) designated by the Warrantholder in writing to the
Corporation.




16.  Make Whole
Payment.  If (i) the Investor or any other member of the
Investor Group that may hold all or any portion of the Warrant from time to time
shall Transfer the Warrant, in whole or in part, at any time or from time to
time prior to the Expiration Time, to any Person that is not a member of the
Investor Group as of the date of such Transfer, (ii) the consideration received
by the Investor or such other member of the Investor Group in respect of each
share of Common Stock that is issuable upon exercise of that portion of the
Warrant that is being Transferred is less than the Spread Value, and (iii) the
Investor (or, if applicable, such other member of the Investor Group) shall have
(A) solicited multiple parties in respect of the proposed Transfer of this
Warrant (or portion thereof) in good faith, and (B) determined to Transfer this
Warrant (or portion thereof) to the party that has proposed terms and conditions
that are, in the good faith judgment of the Investor (or, if applicable, such
other member of the Investor Group), the most favorable to the Investor (or, if
applicable, such other member of the Investor Group) compared to the proposed
terms and conditions proposed by any other party or parties that are solicited
(and make a definitive proposal) in connection with the proposed Transfer of
this Warrant (or any portion thereof), in all cases taking into account all
facts and circumstances that the Investor (or, if applicable, such other member
of the Investor Group) determines in good faith to be relevant, including,
without limitation, the proposed purchase price for this Warrant (or portion
thereof) subject to such Transfer, the manner in which the purchase of this
Warrant (or any portion thereof) by any such party will be financed, the ability
of such party to timely consummate the purchase of this Warrant (or portion
thereof), and any other legal or regulatory matters that the Investor (or, if
applicable, such other member of the Investor Group) may, in good faith,
determine to be relevant in connection with the proposed Transfer of this
Warrant (or any portion thereof), then the Warrantholder shall be entitled to
receive a payment from the Corporation in cash equal to the amount obtained by
multiplying (A) the positive difference, if any, between (x) the Spread Value
and (y) the Net Per Share Consideration paid to the Investor or such other
member of the Investor Group in connection with such Transfer, by (B) the number
of Shares issuable upon exercise of that portion of the Warrant subject to such
Transfer (such cash payment is referred to as the “Make Whole
Payment”).  The amounts payable by the Corporation pursuant to
this Section 16 shall be paid within five (5) Business Days of the occurrence of
such Transfer in U.S. dollars in immediately available funds to such account(s)
designated by the Investor (or, if applicable, such other member of the Investor
Group) in writing to the Corporation.  It is understood and agreed
that if the Transfer of the Warrant occurs in more than one transaction, the
Investor (and, if applicable, the other members of the Investor Group) shall be
entitled to the Make Whole Payment with respect to each such transaction in
which the Make-Whole Payment is a positive amount, with each such payment to be
made within five (5) Business Days of the occurrence of each such Transfer and,
if applicable, a new warrant evidencing the remaining shares of Common Stock
covered by the portion of the Warrant, if any, not subject to such Transfer
shall be issued in the name of the Investor (or, if applicable, the applicable
member of the Investor Group) in accordance with the terms set forth
herein.  Notwithstanding anything in this Warrant to the contrary, the
rights set forth in this Section 16 are solely for the benefit of the Investor
and the other members of the Investor Group (it being agreed that such rights
may be Transferred or assigned to any member of the Investor Group in connection
with the Transfer of all or any portion of this Warrant to any such member of
the Investor Group), and, except as expressly provided in the immediately
preceding parenthetical, are not transferable or assignable in whole or in part
to any other Person.


-4-





17.  Governing
Law. THIS WARRANT SHALL BE GOVERNED BY, AND CONSTRUED AND ENFORCED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF DELAWARE (WITHOUT REGARD TO ITS
CONFLICTS OF LAWS PRINCIPLES).





18.  Waiver of Jury Trial,
Consent to Jurisdiction.




(A)  Waiver of Jury
Trial.  THE PARTIES HERETO VOLUNTARILY AND INTENTIONALLY WAIVE
ANY RIGHT ANY OF THEM MAY HAVE TO A TRIAL BY JURY IN RESPECT OF ANY LITIGATION
OR OTHER CLAIM ARISING OUT OF, UNDER OR IN CONNECTION WITH THIS
WARRANT.




(B)  Consent to
Jurisdiction.Any suit, action or
proceeding arising out of or relating to this Warrant or otherwise to enforce
any judgment in respect of any breach under this Warrant may be brought by any
party hereto in any federal district court located in Delaware or any Delaware
state court as such party may in its sole discretion elect, and by the execution
and delivery of this Warrant, the parties hereto irrevocably and unconditionally
submit to the non-exclusive in personam jurisdiction of each such court, and
each of the parties hereto irrevocably waive and agree not to assert in any
proceeding before any tribunal, by way of motion, as a defense or otherwise, any
claim that it is not subject to the in personam jurisdiction of any such
court.  In addition, each of the parties hereto irrevocably waive, to
the fullest extent permitted by law, any objection that it may now or hereafter
have to the laying of venue in any suit, action or proceeding arising out of or
relating to this Warrant brought in any such court, and hereby irrevocably
waives any claim that any such suit, action or proceeding brought in any such
court has been brought in an inconvenient forum.




(C)  Service of
Process.  Each party hereto irrevocably agrees that process
personally served or served by registered mail or served in the manner provided
for communications in this Warrant shall constitute, to the extent permitted by
law, adequate service of process in any suit, action or proceeding arising out
of or relating to this Warrant, or any action or proceeding to execute or
otherwise enforce any judgment in respect of any breach
hereunder.  Receipt of process so served shall be conclusively
presumed as evidenced by a delivery receipt furnished by the postal service or
any commercial delivery service.




(D)  Other
Forums.  Nothing herein shall in any way be deemed to limit the
ability of any party hereto to serve any writs, process or summonses in any
manner permitted by applicable law or to obtain jurisdiction over any other
party hereto in such other jurisdiction, and in such other manner, as may be
permitted by applicable law.




(E)  Credit Agreement
Provisions.  Notwithstanding anything contained in this Warrant
to the contrary, the terms set forth in this Section 18 and Section 17 shall not
affect or modify the related or similar terms contained in the Credit Agreement
(as defined in the Warrant Agreement) or any other instrument or document
executed in connection therewith, which shall remain in full force and effect
and shall not be affected hereby, it being understood and agreed that in the
event of any action, suit, proceeding, claim or similar matter arising under or
out of or in connection with the Credit Agreement or such other instruments or
documents, the terms set forth in the Credit Agreement or such other instruments
or documents shall control.




19.  Binding
Effect.  This Warrant shall be binding upon any successors or
permitted assigns of the Corporation, and, without the prior written consent of
the Warrantholder, the Corporation shall not be permitted to assign any of its
rights or obligations under this Warrant except in connection with a Business
Combination, and if a Business Combination shall occur, the terms set forth in
Section 13(B) hereof (and if, applicable, Section 15 hereof) shall apply with
respect thereto and if the Corporation shall not be the continuing entity in
such Business Combination, the successor thereto shall assume in a writing
delivered to the Warrantholder prior to the consummation thereof (which writing
shall be reasonably satisfactory in form and substance to the Warrantholder) the
obligations of the Corporation hereunder.




20.  Amendments.  This
Warrant may be amended and the observance of any term of this Warrant may be
waived only with (i) in the case of an amendment, the written consent of the
Corporation and the Warrantholder, and (ii) in the case of a waiver, the Person
waiving rights hereunder.




21.  Prohibited Actions.
The Corporation agrees that it will not take any action which would entitle the
Warrantholder to an adjustment of the Exercise Price if the total number of
shares of Common Stock issuable after such action upon exercise of this Warrant,
together with all shares of Common Stock then outstanding and all shares of
Common Stock then issuable upon the exercise of all outstanding options,
warrants, conversion and other rights, would exceed the total number of shares
of Common Stock then authorized by its certificate of
incorporation.




22.  Notices. All
communications hereunder, including any notice, request, instruction or other
document to be given hereunder by any party to the other, shall be in writing,
shall be delivered by hand, registered or certified mail (postage prepaid),
nationwide overnight courier, or facsimile or other electronic transmission
(confirmed by delivery by nationwide overnight courier sent on the day of the
sending of such facsimile or other electronic transmission), and (A) if to the
Warrantholder, addressed to it at the addresses specified on Schedule I or at such
other address as such Warrantholder shall have specified to the Corporation in
writing in accordance with the terms hereof, and (B) if to the Corporation,
addressed to it at Bronco Drilling Company, Inc., 16217 North May Avenue,
Edmond, Oklahoma 73013, Attention:  D. Frank Harrison
(Fax:  (405) 285-9234), with a copy to Thompson & Knight LLP, 333
Clay Street, Suite 3300, Houston, TX  77002, Attention:  William
T. Heller IV (Fax:  (832) 397-8071), or at such other address as the
Corporation shall have specified to the Warrantholder in writing in accordance
with the terms hereof.  Any notice so addressed shall be deemed to be
given:  if delivered by hand, by facsimile or other electronic
communication, on the date of such delivery (subject to compliance with the term
set forth above in respect of facsimile or other electronic communications); if
mailed by national overnight courier, on the first Business Day following the
date of such mailing; and if mailed by registered or certified mail, on the
second Business Day after the date of such mailing.




23.  Multiple
Warrantholders.  If, on any date of determination, there shall
be more than one Warrantholder as a result of a Transfer of a portion of this
Warrant, then with respect to any consent or approval required of the
Warrantholders under the Warrants, such consent or approval shall be binding on
all Warrantholders if consented to or approved in writing by the Warrantholder
or Warrantholders that own Warrants representing a majority of the Shares
issuable upon exercise of all Warrants held by all such Warrantholders as of
such date of determination.




24.  Entire
Agreement.  This Warrant (including the forms attached hereto),
the Warrant Agreement and the Transaction Documents, contain the entire
agreement between the parties with respect to the subject matter hereof and
supersede all prior and contemporaneous arrangements or undertakings with
respect thereto, provided that for the avoidance of doubt, nothing contained
herein shall affect the terms set forth in the Credit Agreement (as defined in
the Warrant Agreement) or the other documents and instruments being executed in
connection therewith, all of which shall remain in full force and
effect.




[Remainder
of page intentionally left blank]




-5-


IN
WITNESS WHEREOF, the Corporation has caused this Warrant to be executed in its
corporate name by one of its officers thereunto duly authorized all as of the
day and year first above written.









BRONCO
DRILLING COMPANY, INC.









By:/s/ MARK
DUBBERSTEIN


Mark
Dubberstein,


President








ACKNOWLEDGED
AND AGREED


AS OF THE
DATE FIRST WRITTEN ABOVE





CARSO
INFRAESTRUCTURA Y


CONSTRUCCIÓN,
S.A.B. DE C.V.








By:/s/ QUINTIN BOTAS
HERNANDEZ


Quintin
Botas Hernandez,


Attorney-in-fact








By:/s/ ALEJANDRO ARCHONDIA
BECERRA


Alejandro
Archondia Becerra,


Attorney-in-fact


-6-


[FORM
OF NOTICE OF EXERCISE]














TO:           Bronco
Drilling Company, Inc.





RE:           Election
to Purchase Common Stock





The undersigned, pursuant to the
provisions set forth in the attached Warrant, hereby agrees to subscribe for and
purchase the number of shares of Common Stock set forth below covered by such
Warrant.  The undersigned, in accordance with Section 3 of this
Warrant, hereby agrees to pay the aggregate Exercise Price for such shares of
Common Stock.  A new warrant evidencing the remaining shares of Common
Stock covered by such Warrant, but not yet subscribed for and purchased, if any,
should be issued in the name of the holder set forth below.








Number of
Shares of Common Stock: __________________





Method of
Payment of Exercise Price (note if cash exercise pursuant to Section 3(i) or
cashless exercise pursuant to Section 3(ii) of the Warrant):
__________________





Aggregate
Exercise Price: __________________














Holder:
_________________________________





By:
____________________________________





Name:
__________________________________





Title:
___________________________________





Date:
___________________________________





-7-


SCHEDULE
I




SCHEDULE
OF WARRANTHOLDERS







Warrantholder
            Address
            Initial Number of Shares Subject to
      WarrantsCarso
      Infraestructura y
              Construcción,
      S.A.B. de C.V.
            Carso
      Infraestructura y
              Construcción,
      S.A.B. de C.V.
              Jaime
      Balmes No. 11, Torre C,
              piso
      4,
              Col
      Los Morales Polanco,
              C.P.
      11510, Mexico, D.F.
              Attention:
      Guillermo Barbosa Araujo
              Facsimile:
      (52) 55 5255 1686
              Confirmation
      No.: (52) 55 5255 1686
              
              with
      a copy (which shall not constitute notice) to:
              Willkie
      Farr & Gallagher LLP
              787
      Seventh Avenue
              New
      York, New York 10019
              Attention:  Russell
      L. Leaf
              Facsimile:  (212)
      728-8111
              Confirmation
      No.:  (212) 728-8000
            5,440,770










-8-