Document:

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                                                                    EXHIBIT 10.5

                    SOUTH TEXAS DRILLING & EXPLORATION, INC.
                                 1995 STOCK PLAN

         1. Purpose. This 1995 Stock Plan (the "Plan") is intended to provide
incentives (a) to the officers and employees of South Texas Drilling &
Exploration, Inc. (the "Company"), its parent (if any) and any present or future
subsidiaries of the Company (collectively, "Related Corporations"), by providing
them with opportunities to purchase stock in the Company pursuant to options
granted hereunder which qualify as "incentive stock options" under Section
422A(b) of the Internal Revenue Code of 1986 (the "Code") ("ISO" or "ISOs"); (b)
to directors, officers, employees and consultants of the Company and Related
Corporations, or any other person or entity, including persons providing regular
services to the Company or Related Corporations ("Other Person or Entity"), by
providing them with opportunities to purchase stock in the Company pursuant to
options granted hereunder which do not qualify as ISOs ("Non-Qualified Option"
or "Non-Qualified Options"); (c) to directors, officers, employees and
consultants of the Company and Related Corporations, or any Other Person or
Entity, by providing them with awards of stock in the Company ("Awards"); and
(d) to outside directors by providing each of them with a grant of five-year
options to purchase 10,000 shares of Common Stock upon becoming a director of
the Company and thereafter by providing each of them with annual grants of
five-year options to purchase 5,000 shares of Common Stock ("Outside Directors'
Options"). Anything in this Plan to the contrary notwithstanding, Stock Rights
(as defined below) shall not be granted or awarded hereunder to any
administrator or administrators if such grant, award or purchase would cause
such administrator or administrators not to satisfy the "disinterested person"
requirements of Rule 16b-3, or any successor or amended rule ("Rule 16b-3"),
promulgated by the Securities and Exchange Commission under the Securities
Exchange Act of 1934, as amended (the "1934 Act").

         ISOs, Non-Qualified Options and Outside Directors' Options are referred
to hereafter individually as an "Option" and collectively as "Options." Options
and Awards are referred to hereafter collectively as "Stock Rights." Recipients
of such Stock Rights are hereafter referred to individually as an "Optionee" and
collectively as "Optionees." As used herein, the terms "parent" and "subsidiary"
mean "parent corporation" and "subsidiary corporation" respectively, as those
terms are defined in Section 425 of the Code.

         2. Administration of the Plan. The Plan shall be administered (i) to
the extent required by Rule 16b-3, by an administrator or administrators in
compliance with Rule 16b-3, and (ii) in all other cases, by such administrator
or administrators as the Board of Directors (the "Board") may designate
(collectively, the "Administrators"). Subject to the terms of the Plan, the
applicable Administrator shall have the authority to (i) determine the employees
of the Company and Related Corporations (from among the class of employees
eligible under paragraph 1 to receive ISOs) to whom ISOs may be granted and to
determine (from among the class of individuals and entities eligible under
paragraph 1 to receive Non-Qualified Options or Awards) to whom Non-Qualified
Options or Awards may be granted; (ii) determine the time or times at which
Options or Awards may be granted; (iii) determine the option price of shares
subject to each Option (subject to the requirements of paragraph 4 with respect
to ISOs and paragraph 5 with respect to Non-Qualified Options); (iv) determine
whether each option granted shall be an ISO or a Non-Qualified Option; (v)
determine the time or times when each Option shall become

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exercisable and the duration of the exercise period (subject to paragraph 4 with
respect to ISOs and paragraph 5 with respect to Non-Qualified Options); (vi)
determine whether restrictions such as repurchase options are to be imposed on
shares subject to Stock Rights and the nature of such restrictions, if any; and
(vii) interpret the Plan and prescribe and rescind rules and regulations
relating to it; however, neither the Board nor the applicable Administrator
shall have any authority to determine whether or when an outside director shall
receive or exercise Outside Directors' Options (or to determine the exercise
price of such Outside Directors' Options) other than to ensure compliance with
the terms of the Plan with respect to Outside Directors. Options. With respect
to persons subject to Section 16 of the 1934 Act, transactions under the Plan
are intended to comply with all applicable conditions of Rule 16b-3. To the
extent any provision of the Plan or action by the applicable Administrator fails
to so comply, it shall be deemed null and void, to the extent permitted by law
and deemed advisable by the applicable Administrator. The interpretation and
construction by the applicable Administrator of any provisions of the Plan or of
any Stock Right granted under it shall be final unless otherwise determined by
the Board. Administrators or the Board may from time to time adopt such rules
and regulations for carrying out the Plan as they may deem best. No member of
the Board, any Administrator nor the Company shall be liable for any action or
determination made in good faith with respect to the Plan or any Stock Right
granted under it.

         3. Stock. The stock subject to the Stock Rights shall be authorized but
unissued shares of the Company's Common Stock, par value $.10 per share (the
"Common Stock"), or shares of Common Stock reacquired by the Company in any
manner. The aggregate number of shares of Common Stock which may be issued
pursuant to the Plan is 1,500,000; provided, however, that in no event shall the
number of shares of Common Stock subject to, and issued upon the exercise of,
ISOs exceed 1,500,000 in the aggregate; and provided, further that the maximum
number of shares of Common Stock issuable under the Plan to any employee of the
Company in any calendar year shall not exceed 1,200,000. The number of shares
authorized for the grant of Stock Rights under the Plan shall be subject to
adjustment as provided in paragraph 8. If any Option or any other Stock Right
granted under the Plan shall expire or terminate for any reason without having
been exercised in full or shall cease for any reason to be exercisable in whole
or in part, or if the Company shall reacquire any unvested shares issued
pursuant to any Stock Right, the unpurchased shares subject to such Options or
Stock Rights and any unvested shares so reacquired by the Company shall again be
available for grants of Stock Rights under the Plan to the extent permitted by
Rule 16b-3. -

         4. ISO Provisions. Any of the following provisions shall have no force
or effect if its inclusion in the Plan is not necessary for Options issued as
ISOs to qualify as ISOs pursuant to the Code and the regulations issued
thereunder.

               A. Grant of ISO. All ISOs shall be granted under the Plan within
ten (10) years of the date of the Plan's adoption by the Board or the date the
Plan receives the requisite shareholder approval, whichever is earlier.

               B. Minimum Option Price for ISOs.

                    (i) The price per share specified in the agreement relating
               to each ISO granted under the Plan shall not be less than the
               fair market

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               value per share of Common Stock on the date of such grant. In the
               case of an ISO to be granted to an employee owning stock
               representing more than ten percent of the total combined voting
               power of all classes of stock of the Company or any Related
               Corporation, the price per share specified in the agreement
               relating to such ISO shall not be less than 110 percent of the
               fair market value per share of Common Stock on the date of grant.

                    (ii) In no event shall the aggregate fair market value
               (determined at the time an ISO is granted) of Common Stock for
               which ISOs granted to any employee are exercisable for the first
               time by such employee during any calendar year (under all stock
               option plans of the Company and any Related Corporation) exceed
               $100,000.

                    (iii) If, at the time an ISO is granted under the Plan, the
               Company's Common Stock is publicly traded, "fair market value"
               shall be determined as of the last business day for which the
               prices or quotes discussed in this sentence are available prior
               to the date such Option is granted and shall mean (a) the last
               reported sales price of the Common Stock on the principal
               national securities exchange on which the Common Stock is traded,
               if the Common Stock is then traded on a national securities
               exchange; or (b) the last reported sale price (on that date) of
               the Common Stock on the NASDAQ National Market List, if the
               Common Stock is not then traded on a national securities
               exchange; or (c) the closing bid price (or the average of bid
               prices) last quoted (on that date) by an established quotation
               service for over-the-counter securities, if the Common Stock is
               not reported on the NASDAQ National Market List. However, if the
               Common Stock is not publicly traded at the time an ISO is granted
               under the Plan, "fair market value" shall be deemed to be the
               fair market value of the Common Stock as determined by the
               applicable Administrator after taking into consideration all
               factors which it deems appropriate, including, without
               limitation, recent sale and offer prices of the Common Stock in
               private transactions negotiated at arm's length.

               C. Duration of ISOs. Subject to earlier termination as provided
in subparagraphs F and G hereunder, each ISO shall expire on the date specified
by the applicable Administrator, but not more than (i) ten years from the date
of grant in the case of ISOs generally, and (ii) five years from the date of
grant in the case of ISOs granted to an employee owning stock possessing more
than ten percent of the total combined voting power of all classes of stock of
the Company or any Related Corporation. Subject to the foregoing provisions and
such earlier termination as provided in said subparagraphs F and G, the term of
each ISO shall be the term set forth in the original instrument granting such
ISO, except with respect to any part of such ISO that is converted into a
Non-Qualified Option pursuant to subparagraph K below.

               D. Eligible Employees. ISOs may be granted to any employee of the
Company or any Related Corporation. Those officers and directors of the Company
who are not employees may not be granted ISOs under the Plan.

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               E. Acceleration of Exercise of ISOs. The Administrator shall not,
without the consent of the Optionee, accelerate the exercise date of any
installment of any ISO granted to any employee (and not previously converted
into a Non-Qualified Option pursuant to subparagraph K below) if such
acceleration would violate the annual vesting limitation contained in Section
422A(d) of the Code, as described in subparagraph B(ii) hereinabove.

               F. Effect of Termination of Employment on ISOs. If an ISO
Optionee ceases to be employed by the Company or any Related Corporation other
than by reason of death or disability (as such term is defined in subparagraph G
hereunder), any ISO granted to such Optionee within the six-month period
immediately preceding such termination shall be cancelled forthwith. With
respect to any ISOs granted to such Optionee more than six months prior to such
termination, no further installments of such ISOs shall become exercisable and
his ISOs shall terminate after the passage of 90 days from the date of
termination of his employment, but in no event later than on their specified
expiration dates, except to the extent that such ISOs (or unexercised
installments thereof) have been converted into Non-Qualified Options pursuant to
subparagraph K below. Leave of absence with the written approval of the
applicable Administrator shall not be considered an interruption of employment
under the Plan, provided that such written approval contractually obligates the
Company or any Related Corporation to continue the employment of the employee
after the approved period of absence. Employment shall also be considered as
continuing uninterrupted during any other bona fide leave of absence (such as
those attributable to illness, military obligations or governmental service)
provided that the period of such leave does not exceed 90 days or, if longer,
any period during which such Optionee's right to reemployment is guaranteed by
statute. ISOs granted under the Plan shall not be affected by any change of
employment within or among the Company and Related Corporations, so long as the
Optionee continues to be an employee of the Company or any Related Corporation.

               G. Effect of Death or Disability on ISOs. If an Optionee ceases
to be employed by the Company or any Related Corporation by reason of his death,
any ISO of his may be exercised, to the extent of the number of shares with
respect to which he could have exercised it on the date of his death, by his
estate, personal representative or beneficiary who has acquired the ISO by will
or by the laws of descent and distribution, at any time prior to the earlier of
the date specified in the ISO agreement, the ISO's specified expiration date or
one year of the death of the Optionee.

         If an Optionee ceases to be employed by the Company and all Related
Corporations by reason of his disability, he shall have the right to exercise
any ISO held by him on the date of termination of employment, to the extent of
the number of shares with respect to which he could have exercised it on that
date, at any time prior to the earlier of the date specified in the ISO
agreement, the ISO's specified expiration date or one year from the date of the
termination of the Optionee's employment. For the purposes of the Plan, the term
"disability" shall mean "permanent and total disability" as defined in Section
22(e)(3) of the Code or successor statute.

               H. Adjustments. Any adjustment made pursuant to paragraphs 8(A)
or (B) with respect to ISOs shall be made only after the applicable
Administrator, after consulting with counsel for the Company, determines whether
such adjustments would constitute a "modification" of such ISOs (as that term is
defined in Section 425 of the Code) or would cause

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any adverse tax consequences for the holders of such ISOs. If the applicable
Administrator determines that such adjustments made with respect to ISOs would
constitute a modification of such ISOs, it may refrain from making such
adjustments.

               I. Notice to Company of Disqualifying Dispositions. Each employee
who receives an ISO must agree to notify the Company in writing immediately
after the employee makes a "disqualifying disposition" of any Common Stock
acquired pursuant to the exercise of an ISO. A "disqualifying disposition" is
any disposition (including any sale) of such Common Stock before the later of
(a) two years after the date the employee was granted the ISO, or (b) one year
after the date the employee acquired Common Stock by exercising the ISO. If the
employee has died before such stock is sold, these holding period requirements
do not apply and no Disqualifying Disposition can occur thereafter.

               J. Other Requirements. ISOs shall be issued subject to such
additional requirements as may be imposed from time to time by the Code or the
regulations issued thereunder.

               K. Conversion of ISOs into Non-Qualified Options: Termination of
ISOs. The applicable Administrator, at the written request of any Optionee, may
in its discretion take such actions as may be necessary to convert such
Optionee's ISOs (or any installments or portions of installments thereof) that
have not been exercised on the date of conversion into Non-Qualified Options at
any time prior to the expiration of such ISOs, regardless of whether the
Optionee is an employee of the Company or a Related Corporation at the time of
such conversion. Such actions may include, but not be limited to, extending the
exercise period or reducing the exercise price of the appropriate installments
of such Options. At the time of such conversion, the applicable Administrator
(with the consent of the Optionee) may impose such conditions on the exercise of
the resulting Non-Qualified Options as the applicable Administrator in its
discretion may determine, provided that such conditions shall not be
inconsistent with the provisions of paragraph 5 or any other paragraph of the
Plan. Nothing in the Plan shall be deemed to give any Optionee the right to have
such Optionee's ISOs converted into Non-Qualified Options, and no such
conversion shall occur until and unless the Administrator takes appropriate
action. The applicable Administrator, with the consent of the Optionee, may also
terminate any portion of any ISO that has not been exercised at the time of such
termination.

         5. Non-Qualified Options.

               A. Minimum Option Price. The price per share specified in the
agreement relating to each Non-Qualified Option granted under the Plan shall not
be less than the fair market value per share of Common Stock on the date of such
grant. If, at the time a Non-Qualified Option is granted under the Plan, the
Company's Common Stock is publicly traded, "fair market value" shall be
determined as of the last business day for which the prices or quotes discussed
in this sentence are available prior to the date such Non-Qualified Option is
granted and shall mean (i) the last reported sales price of the Common Stock on
the principal national securities exchange on which the Common Stock is traded,
if the Common Stock is then traded on a national securities exchange; or (ii)
the last reported sale price (on that date) of the Common Stock on the NASDAQ
National Market List, if the Common Stock is not then traded on a national
securities exchange; or (iii) the closing bid price (or the average of bid
prices) last

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quoted (on that date) by an established quotation service for
over-the-counter securities, if the Common Stock is not reported on the NASDAQ
National Market List. However, if the Common Stock is not publicly traded at the
time a Non-Qualified Option is granted under the Plan, "fair market value" shall
be deemed to be the fair market value of the Common Stock as determined by the
applicable Administrator after taking into consideration all factors which it
deems appropriate, including, without limitation, recent sale and offer prices
of the Common Stock in private transactions negotiated at arm's length.

               B. Duration of Non-Qualified Options. Each Non-Qualified Option
shall expire on the date specified by the applicable Administrator, but not more
than ten (10) years from the date of grant.

               C. Vesting of Non-Qualified Options. Subject to any shorter or
longer vesting period and any termination provisions which the applicable
Administrator may impose, a Non-Qualified Option shall be exercisable as
follows: (i) 20% of the shares under the Non-Qualified Option shall be
exercisable one calendar year after the date of its grant, (ii) an additional
20% of the shares under the Non-Qualified Option shall be exercisable two
calendar years after the date of its grant, (iii) an additional 20% of the
shares under the Non-Qualified Option shall be exercisable three calendar years
after the date of its grant, (iv) an additional 20% of the shares under the
Non-Qualified Option shall be exercisable four calendar years after the date of
its grant, and (v) the last 20% of the shares under the Non-Qualified Option
shall be exercisable five calendar years after the date of its grant.

               D. Maintain Non-ISO Status. If the applicable Administrator
determines to issue a Non-Qualified Option, it shall take whatever actions it
deems necessary, under Section 422A of the Code and the regulations promulgated
thereunder, to ensure that such Non-Qualified Option is not treated as an ISO.

         6. Outside Directors' Options.

               A. Grant. Upon becoming a director of the Company each outside
director shall receive an option to purchase 10,000 shares of Common Stock and
on June 15 of each calendar year after the date the Plan is approved by the
shareholders of the Company, each outside director then serving shall receive an
option to purchase 5,000 shares of Common Stock (individually, an "Outside
Director's Option," and collectively, "Outside Directors' Options"). In order to
phase in the Company's Outside Director's Option program, current outside
directors shall be granted an Outside Director's Option to purchase 10,000
shares on June 15, 1995.

               B. Minimum Purchase Price. The exercise price per share of the
Outside Directors' Options shall not be less than the fair market value per
share of Common Stock on the date of such grant. If, at the time an Outside
Director's Option is granted under the Plan, the Company's Common Stock is
publicly traded, "fair market value" shall be determined as of the last business
day for which the prices or quotes discussed in this sentence are available
prior to the date such Outside Director's Option is granted and shall mean (i)
the last reported sales price of the Common Stock on the principal national
securities exchange on which the Common Stock is traded, if the Common Stock is
!hen traded on a national securities exchange; or (ii) the last reported sale
price (on that date) of the Common Stock on the NASDAQ National Market List, if

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the Common Stock is not then traded on a national securities exchange; or (iii)
the closing bid price (or the average of bid prices) last quoted (on that date)
by an established quotation service for over-the-counter securities, if the
Common Stock is not reported on the NASDAQ National Market List. However, if the
Common Stock is not publicly traded at the time an Outside Director's Option is
granted under the Plan, "fair market value" shall be the average of the three
most recent sale and offer prices of the Common Stock in private transactions
negotiated at arm's length.

               C. Duration of Outside Directors' Options. Each Outside
Director's Option shall expire five (5) years from the date of grant; otherwise,
an Outside Director's Option shall not be subject to forfeiture or termination.

               D. Exercise. An outside director may exercise an Outside
Director's Option, if exercisable, by providing written notice to the Company
addressed to the Secretary of the Company at 9310 Broadway, Bldg. I, San
Antonio, Texas 78217. The written notice shall specify the number of options
being exercised, and by paying the full exercise price. The written notice shall
also include such written representations, warranties and covenants as may be
required by the Company, Company counsel or the applicable Administrator.

               E. Maintain Non-ISO Status. The applicable Administrator shall
take whatever actions it deems necessary, under Section 422A of the Code and the
regulations promulgated thereunder, to ensure that any such Outside Director's
Option is not treated as an ISO.

               F. Holding Period and Termination. An outside director may not
dispose of any shares acquired as a result of the exercise of an Outside
Director's Option until six months after the date of the "grant" of the Outside
Director's Option, as determined in accordance with Rule 16(b)-3. Upon the
termination of the Plan or the unavailability of shares of Common Stock for
issuance under the Plan, no additional Outside Directors' Options shall be
granted.

         7. Written Agreements. Stock Rights shall be evidenced by instruments
(which need not be identical) in such forms as the applicable Administrator may
from time to time approve. Such instruments shall conform to such terms,
conditions and provisions as are applicable hereunder and may contain such other
terms and conditions and provisions as the applicable Administrator deems
advisable which are not inconsistent with the Plan, including restrictions
applicable to shares of Common Stock issuable upon exercise of Stock Rights. A
Stock Right may provide for acceleration of exercise in the event of a change in
control of the Company, in the discretion of and as defined by the applicable
Administrator. The applicable Administrator may from time to time confer
authority and responsibility on one or more of its own members and/or one or
more officers of the Company to execute and deliver such instruments. The proper
officers of the Company are authorized and directed to take any and all action
necessary or advisable from time to time to carry out the terms of such
instruments.

         8. Adjustments. Upon the happening of any of the following described
events, an Optionee's rights with respect to Options granted to him hereunder,
and the recipient's rights with respect to Common Stock to be acquired pursuant
to an Award hereunder, shall be adjusted as

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hereinafter provided, unless otherwise specifically provided, in addition or to
the contrary, in the written agreement between the recipient and the Company
relating to such Stock Right.

               A. Certain Corporate Events. In the event shares of Common Stock
shall be subdivided or combined into a greater or smaller number of shares or
if, upon a merger, consolidation, reorganization, split-up, liquidation,
combination, recapitalization or the like of the Company, the shares of Common
Stock shall be exchanged for other securities of the Company or of another
corporation, each grantee of a Stock Right shall be entitled, subject to the
conditions herein stated, to purchase (or have used for measurement purposes)
such number of shares of Common Stock or amount of other securities of the
Company or such other corporation as were exchangeable for the number of shares
of Common Stock which such grantee would have been entitled to purchase (or have
used for measurement purposes) except for such action, and appropriate
adjustments shall be made in the purchase price per share to reflect such
subdivision, combination or exchange.

               B. Stock Dividends. In the event the Company shall issue any of
its shares as a stock dividend upon or with respect to the shares of stock of
the class which at the time shall be subject to a Stock Right hereunder, each
grantee upon exercising a Stock Right shall be entitled to receive (for the
purchase price paid upon such exercise) (or have used for measurement purposes)
the shares or other consideration as to which he is exercising his Stock Right
and, in addition thereto (at no additional cost), such number of shares of the
class or classes in which such stock dividend or dividends were declared or
paid, and such amount of cash in lieu of fractional shares, or other
consideration as he would have received if he had been the holder of the shares
as to which he is exercising (or which are used for measurement in connection
with) his Stock Right at all times between the date of grant of such Stock Right
and the date of its exercise.

               C. New Securities. If any person or entity owning restricted
Common Stock obtained by exercise of a Stock Right made hereunder receives new
or additional or different shares or securities ("New Securities") in connection
with a corporate transaction described in subparagraph A above or a stock
dividend described in subparagraph B above as a result of owning such restricted
Common Stock, such New Securities shall be subject to all of the conditions and
restrictions applicable to the restricted Common Stock with respect to which
such New Securities were issued.

               D. Cash Dividends. No adjustments shall be made for dividends
paid in cash or in property other than securities of the Company, unless
specified to the contrary by the applicable Administrator in the instrument
evidencing such Stock Right.

               E. Fractional Shares. No fractional shares shall actually be
issued under the Plan. Any fractional shares which, but for this subparagraph E,
would have been issued to a grantee pursuant to a Stock Right shall be deemed to
have been issued and immediately sold to the Company for their fair market
value, and the grantee shall receive from the Company cash in lieu of such
fractional shares.

               F. Adjustments. Upon the happening of any of the foregoing events
described in subparagraphs A or B above, the class and aggregate number of
shares set forth in

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paragraph 3 hereof that are subject to Stock Rights which previously have been
or subsequently may be granted under the Plan shall also be appropriately
adjusted to reflect the events described in such subparagraphs. The Board shall
determine the specific adjustments to be made under this paragraph 8 and,
subject to paragraph 4(H), its determination shall be conclusive.

         9. Means of Exercising Stock Rights. A Stock Right (or any part or
installment thereof) shall be exercised as specified in the written instrument
granting such Stock Right, which instrument may specify any legal method of
exercise. The holder of a Stock Right exercisable for shares shall not have the
rights of a shareholder with respect to the shares covered by his Stock Right
until the date of issuance of a stock certificate to him for such shares. Except
as expressly provided above in paragraph 8 with respect to changes in
capitalization and stock dividends, no adjustment shall be made for dividends or
similar rights for which the record date is before the date such stock
certificate is issued.

         10. Transferability of Stock Rights. Except as otherwise provided in
the Plan, no Stock Right granted under the Plan shall be transferrable by an
Optionee other than by (i) will or the laws of descent and distribution, or (ii)
pursuant to a qualified domestic relations order as defined by the Code or Title
I of the Employee Retirement Income Security Act, or the rules thereunder.

         11. Term of the Plan. This Plan was adopted by the Board as of April
21, 1995, effective as of May 1, 1995, subject to approval of the Plan by the
holders of a majority of the outstanding shares of the Company at the next
meeting of shareholders present in person or by proxy at the next meeting of
shareholders. Stock Rights may be granted under the Plan at any time on or after
May 1, 1995, even if prior to the date of shareholder approval of the Plan;
provided, however, that such date shall not be prior to the date on which the
applicable Administrator acts to approve the grant or award. If the requisite
shareholder approval is not obtained by April 21, 1996, any grants of ISOs under
the Plan and any grants of Stock Rights to officers and directors, as the case
may be, made prior to that date will be automatically rescinded, except in the
case of an ISO granted to Wm. Stacy Locke which, in such event, shall remain in
effect but without the benefits of this Plan.

         12. Termination; Amendment. The Board may terminate or amend the Plan
in any respect at any time, except that (i) no amendment requiring shareholder
approval under provisions of the Code and related regulations relating to ISOs
or under Rule 16b-3 will be effective without approval of shareholders as
required and within the times set by such rules, and (ii) no amendment may be
made more than once every six (6) months to the provisions of the Plan dealing
with, related to, affecting or governing Outside Directors' Options (other than
those required to comport with changes in the Code, the Employee Retirement
Income Security Act, or the rules thereunder, or Rule 16b-3).

         13. Application of Funds. The proceeds received by the Company from the
sale of shares pursuant to Stock Rights authorized under the Plan shall be used
for general corporate purposes.

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         14. Governmental Regulation. The Company's obligation to sell and
deliver shares of the Common Stock under this Plan is subject to the approval of
any governmental authority required in connection with the authorization,
issuance or sale of such shares.

         15. Withholding of Additional Income Taxes. Upon the exercise of a
Non-Qualified Option, an Outside Director's Option, the grant of an Award, the
making of a Purchase of Common Stock for less than its fair market value, the
making of a Disqualifying Disposition (as defined in paragraph 4(I)), the
vesting of restricted Common Stock acquired on the exercise of a Stock Right
hereunder, or any other event in connection with a Stock Right, the Company, in
accordance with Section 3402(a) of the Code, may require the Optionee, Award
recipient, purchaser, or holder or exerciser of a Stock Right to pay additional
withholding taxes in respect of the amount that is considered compensation
includable in such person's gross income.

         16. Governing Law; Construction. The validity and construction of the
Plan and the instruments evidencing Stock Rights shall be governed by the laws
of the State of Texas. In construing this Plan, the singular shall include the
plural and the masculine gender shall include the feminine and neuter, unless
the context otherwise requires.

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                    OUTSIDE DIRECTORS' STOCK OPTION AGREEMENT

         THIS OPTION AGREEMENT is made as of the ____ day of ___________, 19___,
("Date of Grant") by and between South Texas Drilling & Exploration, Inc., with
its principal place of business at 9310 Broadway, Building 1, San Antonio, Bexar
County, Texas (hereinafter called the "Company"), and ______________________
(hereinafter called the "Director"), a Director of the Company. This is an
"Outside Directors' Option" issued pursuant to the Company's 1995 Stock Plan.

         WHEREAS, the Company desires to afford the Director an opportunity to
purchase shares of the $.10 par value voting common stock of the Company
(hereinafter called the "stock"), pursuant to and in accordance with the terms
and provisions of the Company's 1995 Stock Plan applicable to Outside Directors'
Options (hereinafter referred to as the "Plan") and as hereinafter provided.

         NOW, THEREFORE, in consideration of the mutual covenants hereinafter
set forth and Director's service as a director of the Company, the parties
hereto agree as follows:

         1. The Plan. This Option Agreement is made pursuant to and in
accordance with the terms and provisions of the Plan as adopted by the Board of
Directors of the Company on April 21, 1995, and subject to the approval by a
vote of a majority in interest of the stockholders of the Company on or before
April 21, 1996. Anything in this Option Agreement to the contrary
notwithstanding, the terms and provisions of the Plan applicable to Outside
Directors' Options, all of which are incorporated herein by reference, shall be
controlling in the event of any inconsistency herewith. By signing this
Agreement, the Director acknowledges that he has received a copy of the Plan.

         2. Grant of Option. The Company hereby irrevocably grants to the
Director the right

                                       1
<PAGE>   12

and option (hereinafter called the "Option") to purchase all or any part of an
aggregate of ______ shares of the stock (subject to adjustment as provided in
the Plan) on the terms and conditions hereinafter set forth. The Date of the
Grant of the Option is _____________.

         3. Purchase Price. The purchase price of the shares of the stock
covered by the Option shall be $_______ per share (subject to adjustment as
provided in the Plan), which the Company believes is the fair market value of
the stock as of the Date of the Grant.

         4. Time Option is Exercisable. Until this Option is terminated, the
Director shall have the right to purchase all or a portion of the stock subject
to this Option at such times, and from time to time, as he might desire, subject
to the terms and provisions hereinafter set forth. There is no obligation on the
Director to purchase any of the stock subject to the Option.

         5. Exercise of Option. The Director may exercise this Option by giving
written notice to the Company specifying the number of full shares to be
purchased and accompanied by payment of the full price thereof. No exercise of
the Option shall be complete and no stock shall be delivered to the Director
prior to the time that the full purchase price for such stock has been paid. The
purchase price shall be paid in cash. During the lifetime of the Director, the
Option may not be exercised by any person (including the spouse of the Director)
other than by the Director. Upon the death of the Director, the Option may be
exercised by the personal representative, legatees or heirs of the Director
until the earlier to occur of (a) the termination of the Option or the Plan by
their terms or (b) the date one (1) year after the date of death of the
Director.

         6. Nontransferability of Option. This Option is not transferable except
by Will or by the laws of descent and distribution. This Option may not be
assigned, transferred, pledged or hypothecated in any manner and shall not be
subject to any form of execution, attachment or

                                       2
<PAGE>   13

similar process. Any attempted assignment, transfer, pledge, hypothecation or
other disposition of this Option contrary to the provisions of this Agreement
and the Plan, or the levy of any execution, attachment or similar process upon
the Option, shall be null and void and of no effect.

         7. Stockholder Rights. The Director shall not have any of the rights of
a stockholder merely because of his ownership of the Option granted by this
Agreement.

         8. Holding Period of Underlying Stock. The Director shall not dispose
of any stock acquired as a result of the exercise of the Option until six months
after the date of the grant of this Option.

         9. Requirements of Law. If any law or regulation of the Securities and
Exchange Commission or any other federal or state commission or agency having
jurisdiction requires the Company or the Director to take any action with
respect to the stock acquired by the exercise of this Option, then the date upon
which the Company shall deliver the stock shall be postponed until full
compliance has been made with all such legal or regulatory requirements.
Further, at or before the time of the delivery of the stock, the Director shall,
if requested by the Company, deliver to the Company his written statement that
he intends to hold the stock so acquired by him on exercise of this Option for
investment and not with a view of resale or other distribution thereof to the
public. Further, in the event the Company shall determine that, in compliance
with the Securities Act of 1933, as amended, or any other applicable federal or
state statute or regulation, it is necessary to register any of the shares of
stock with respect to which an exercise of this Option has been made, or to
qualify any such shares for exemption from any of such requirements, the Company
shall take such action at its own expense, but not until such action has been
completed shall the Option shares be delivered to the Director.

                                       3
<PAGE>   14

         IN WITNESS WHEREOF, the Company has caused this Outside Directors'
Stock Option Agreement to be executed by an authorized officer, and the Director
has hereunto set his hand, all as of the day and year first above written.

                                            SOUTH TEXAS DRILLING &
                                               EXPLORATION, INC.

                                            By:
                                               --------------------------------

                                            DIRECTOR:

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

                                       4
<PAGE>   15
                        INCENTIVE STOCK OPTION AGREEMENT

         THIS OPTION AGREEMENT is made as of the ____ day of ___________, 19___,
("Date of Grant") by and between South Texas Drilling & Exploration, Inc., with
its principal place of business at 9310 Broadway, Building 1, San Antonio, Bexar
County, Texas (hereinafter called the "Company"), and ______________________
(hereinafter called the "Employee"), an employee of the Company.

         WHEREAS, the Company desires to afford the Employee an opportunity to
purchase shares of the $.10 par value voting common stock of the Company
(hereinafter called the "stock"), pursuant to and in accordance with the terms
and provisions of the Company's 1995 Stock Plan (hereinafter referred to as the
"Plan") and as hereinafter provided.

         NOW, THEREFORE, in consideration of the mutual covenants hereinafter
set forth and Employee's employment by the Company, the parties hereto agree as
follows:

         1. The Plan. This Option Agreement is made pursuant to and in
accordance with the terms and provisions of the Plan as adopted by the Board of
Directors of the Company on April 21, 1995, and subject to the approval by a
vote of a majority in interest of the stockholders of the Company on or before
April 21, 1996. Anything in this Option Agreement to the contrary
notwithstanding, the terms and provisions of the Plan, all of which are
incorporated herein by reference, shall be controlling in the event of any
inconsistency herewith. By signing this Agreement, the Employee acknowledges
that he has received a copy of the Plan.

         2. Grant of Option. The Company hereby irrevocably grants to the
Employee the right and option (hereinafter called the "Option") to purchase all
or any part of an aggregate of ______ shares of the stock (subject to adjustment
as provided in the Plan) on the terms and conditions hereinafter set forth. The
Date of the Grant of the Option is _____________.

                                       1
<PAGE>   16

         3. Purchase Price. The purchase price of the shares of the stock
covered by the Option shall be $_______ per share (subject to adjustment as
provided in the Plan), which the Company believes is the fair market value of
the stock as of the Date of the Grant.

         4. Time Option is Exercisable. Until this Option is terminated, the
Employee shall have the right to purchase all or a portion of the stock subject
to this Option at such times, and from time to time, as he might desire, subject
to the terms and provisions hereinafter set forth. There is no obligation on the
Employee to purchase any of the stock subject to the Option. The Option shall be
exercised as follows:

                  (1) Twenty percent (20%) of the shares under Option shall
                  become exercisable on __________, 199_.

                  (2) An additional twenty percent (20%) (being forty percent
                  (40%) of the total shares under Option) shall become
                  exercisable __________, 199_, two (2) years after Date of
                  Grant.

                  (3) An additional twenty percent (20%) (being sixty percent
                  (60%) of the total shares under Option) shall become
                  exercisable ____________, 199_.

                  (4) An additional twenty percent (20%) (being eighty percent
                  (80%) of the total shares under Option) shall become
                  exercisable _______________, 199_.

                  (5) An additional twenty percent (20%) (being one hundred
                  percent (100%) of the total shares under Option) shall become
                  exercisable ___________, 2000.

         5. Exercise of Option. The Employee may exercise this Option by giving
written notice to the Company specifying the number of full shares to be
purchased and accompanied by payment of the full price thereof. No exercise of
the Option shall be complete and no stock shall be delivered to the Employee
prior to the time that the full purchase price for such stock has been

                                       2
<PAGE>   17

paid. The purchase price shall be paid in cash. During the lifetime of the
Employee, the Option may not be exercised by any person (including the spouse of
the Employee) other than by the Employee. Upon the death of the Employee, the
Option may be exercised by the personal representative, legatees or heirs of the
Employee until the earlier to occur of (a) the termination of the Option or the
Plan by their terms or (b) the date one (1) year after the date of death of the
Employee.

         6. Nontransferability of Option. This Option is not transferable except
by Will or by the laws of descent and distribution. This Option may not be
assigned, transferred, pledged or hypothecated in any manner and shall not be
subject to any form of execution, attachment or similar process. Any attempted
assignment, transfer, pledge, hypothecation or other disposition of this Option
contrary to the provisions of this Agreement and the Plan, or the levy of any
execution, attachment or similar process upon the Option, shall be null and void
and of no effect.

         7. Stockholder Rights. The Employee shall not have any of the rights of
a stockholder merely because of his ownership of the Option granted by this
Agreement.

         8. Employment. The grant of this Option shall not impose upon the
Company any obligation whatsoever to retain the Employee in its employ for any
period. This Option is personal to the Employee and may be exercised by him as
provided in the Plan only if he is continuously employed by the Company from the
date of the granting of this Option to the date of its exercise, except as
otherwise provided herein and in the Plan. Should such employment be terminated
by the Company (for any reason whatsoever or for no reason) or by the voluntary
action of the Employee for any reason (other than by reason of the death of the
Employee), this Option, to the extent that it has not been exercised, shall
terminate three (3) months after the date of termination of employment (the
"Termination Date") and shall not be exercised after the

                                       3
<PAGE>   18

Termination Date.

         9. Requirements of Law. If any law or regulation of the Securities and
Exchange Commission or any other federal or state commission or agency having
jurisdiction requires the Company or the Employee to take any action with
respect to the stock acquired by the exercise of this Option, then the date upon
which the Company shall deliver the stock shall be postponed until full
compliance has been made with all such legal or regulatory requirements.
Further, at or before the time of the delivery of the stock, the Employee shall,
if requested by the Company, deliver to the Company his written statement that
he intends to hold the stock so acquired by him on exercise of this Option for
investment and not with a view of resale or other distribution thereof to the
public. Further, in the event the Company shall determine that, in compliance
with the Securities Act of 1933, as amended, or any other applicable federal or
state statute or regulation, it is necessary to register any of the shares of
stock with respect to which an exercise of this Option has been made, or to
qualify any such shares for exemption from any of such requirements, the Company
shall take such action at its own expense, but not until such action has been
completed shall the Option shares be delivered to the Employee.

         10. Tax Benefits. Under the terms of Sections 421 and 422A of the Code,
the Employee is entitled to certain federal income tax advantages upon exercise
of this incentive stock option. The tax benefits are available, however, only if
the Employee does not dispose of stock acquired pursuant to this Agreement
within two (2) years from the date the Option was granted nor within one (1)
year after the transfer of the shares to the Employee upon exercise of the
Option.

         IN WITNESS WHEREOF, the Company has caused this Incentive Stock Option

                                       4
<PAGE>   19

Agreement to be executed by an authorized officer, and the Employee has hereunto
set his hand, all as of the day and year first above written.

                                            SOUTH TEXAS DRILLING &
                                               EXPLORATION, INC.

                                            By:
                                               --------------------------------

                                            EMPLOYEE:

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

                                       5<PAGE>   1

                                                                    EXHIBIT 10.6

                      NON-STATUTORY STOCK OPTION AGREEMENT

         This OPTION AGREEMENT (this "Agreement") is made as of the 18th day of
June, 1997, by and between SOUTH TEXAS DRILLING & EXPLORATION, INC., a Texas
corporation, with its principal place of business in San Antonio, Bexar County,
Texas (hereinafter called the "Company"), and SAN PATRICIO CORPORATION, a Texas
corporation, with its principal place of business in Corpus Christi, Nueces
County, Texas (hereinafter called "SP").

         WHEREAS, incident to the transactions contemplated by the Asset
Purchase Agreement dated May 23, 1997, by and between the Company, SP and
Richard Phillips ('Phillips"), the Company desires to afford SP an opportunity
to purchase shares of the $0.10 par value common stock of the Company
(hereinafter called the "Stock").

         NOW, THEREFORE, in consideration of the mutual covenants hereinafter
set forth, the parties hereto agree as follows:

         1. Corporate Authority. This Agreement is made pursuant to and in
accordance with the terms and provisions of a resolution adopted by the Board of
Directors of the Company on April 25, 1997.

         2. Grant of Option. The Company hereby irrevocably grants to SP the
right and option to purchase all or any part of an aggregate of 150,000 shares
of the Stock on the terms and conditions hereinafter set forth (hereinafter
referred to individually as an "Option" and collectively as the "Options").

<PAGE>   2

         3. Purchase Price. The purchase price of the shares of the Stock
covered by the Options shall be $1.50 per share (subject to adjustment as
provided in Section 11).

         4. Time Option is Exercisable. SP shall have the right to purchase all
or a portion of the Stock subject to the Option at such times, and from time to
time, until June 18, 2002, at which time the Options shall terminate. There is
no obligation on SP to purchase any of the Stock subject to the Options.

         5. Exercise of Options. SP may exercise an Option by giving written
notice to the Company specifying the number of full shares to be purchased and
accompanied by payment of the full price thereof. No exercise of an Option shall
be complete and no Stock shall be delivered to SP prior to the time that the
full purchase price for such Stock has been paid. The purchase price shall be
paid in cash.

         6. Transferability of Options. The Options may only be assigned,
transferred, pledged or hypothecated to Phillips. Otherwise, the Options may not
be assigned, transferred, pledged or hypothecated in any manner and shall not be
subject to any form of execution, attachment or similar process. Any attempted
assignment, transfer, pledge, hypothecation or other disposition of the Options
contrary to the provisions of this Agreement, or the levy of any execution,
attachment or similar process upon the Options, shall be null and void and of no
effect. However, Phillips may assign the Options upon his death.

         7. Stockholder Rights. SP, (or Phillips, if the Options are so
transferred) shall not have any of the rights of a stockholder merely because of
its/his ownership of the Options granted by this Agreement.

                                       2

<PAGE>   3

         8. Requirements of Law. If any law or regulation of the Securities and
Exchange Commission (the "SEC") or any other federal or state commission or
agency having jurisdiction requires the Company or SP to take any action with
respect to the Stock acquired by the exercise of the Options, then the Company
shall take such required actions within a reasonable period of time and the date
upon which the Company shall deliver the Stock shall be postponed until full
compliance has been made with all such legal or regulatory requirements.
Further, at or before the time of the delivery of the Stock, SP shall, if
requested by the Company, deliver to the Company its written statement that it
intends to hold the Stock so acquired by him on exercise of any Option for
investment and not with a view to resale or other distribution thereof to the
public. Further, in the event the Company shall determine that, in compliance
with the Securities Act of 1933, as amended (the "Act"), or any other applicable
federal or state statute or regulation, it is necessary to register any of the
shares of Stock with respect to which an exercise of any Option has been made,
or to qualify any such shares for exemption from any of such requirements, the
Company shall take such action at its own expense and within a reasonable period
of time, but not until such action has been completed shall the Option shares be
delivered to SP.

         9. Restrictions on Sale or Other Transfer of Stock. SP (or Phillips)
may not sell, assign or otherwise transfer any shares of Stock purchased
pursuant to the exercise of any Option granted hereunder in any manner that
violates the Act, or the Rules and Regulations of the SEC issued thereunder, or
any other federal or state laws, rules, and regulations applicable to the sale
or transfer of securities.

         10. Capital Adjustments Affecting Stock. In the event of a capital
adjustment resulting from a stock dividend, stock split, reorganization, merger,
consolidation, or a combination or

                                       3

<PAGE>   4

exchange of shares, the number of shares of Stock under Option shall be adjusted
consistent with such capital adjustment. The price of any share under Option
shall be adjusted so that there will be no change in the aggregate purchase
price payable under exercise of any such Option. The granting of an Option
pursuant to this Agreement shall not affect in any way the right or power of the
Company to make adjustments, reorganizations, reclassifications or changes of
its capital or business structure or to merge, consolidate, dissolve, liquidate,
or sell or transfer all or any part of its business or assets.

         11. Dissolution, Liquidation and Reorganization. In the event of the
dissolution or liquidation of the Company, any Option granted under this
Agreement shall terminate as of a date to be fixed by the Board, provided that
not less than thirty (30) days' written notice of the date so fixed shall be
given to SP, and SP shall have the right during such period to exercise all or
any part of his Options without regard to the limitations of Section 4.

         IN WITNESS WHEREOF, the Company has caused this Agreement to be
executed by an authorized officer, and SP has hereunto set its hand, all as of
the day and year first above written.

                                        SOUTH TEXAS DRILLING & EXPLORATION, INC.

                                        By: /s/ Wm. Stacy Locke
                                           ------------------------------------

                                        Name: Wm. Stacy Locke
                                             ----------------------------------

                                        Title: President
                                              ---------------------------------

                                       4

<PAGE>   5

                                        SAN PATRICIO CORPORATION

                                        By: /s/ Richard Phillips
                                           ------------------------------------

                                        Name: Richard Phillips
                                             ----------------------------------

                                        Title: President
                                              ---------------------------------

ABB0E8A6

                                       5

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