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                                                                    EXHIBIT 10.7

                         FIRST AMENDMENT OF AGREEMENT

     THIS FIRST AMENDMENT OF AGREEMENT is made this 31st day of July, 2001, by
and between UNICORP, INC., a Nevada corporation having its principal office and
place of business in Harris County, Texas ("Unicorp"), EQUITABLE ASSETS,
INCORPORATED, a Belize corporation having its principal office and place of
business in Belize City, Belize ("Equitable"), TEXAS NEVADA OIL & GAS CO., a
Texas corporation having its principal office and place of business in Harris
County, Texas ("TNOG"), and HOUSTON AMERICAN ENERGY CROP., a Delaware
corporation having its principal office and place of business in Harris County,
Texas ("HAEC") and the successor to Opportunity Acquisition Company, a Texas
corporation ("Opportunity").

     WHEREAS, the parties previously entered into that certain Agreement dated
March 23, 2001 (the "Original Agreement"); and

     WHEREAS, the parties now desire to amend the Original Agreement as set
forth herein;

     NOW, THEREFORE, in consideration of the foregoing and the following mutual
covenants and agreements, the parties do hereby agree as follows:

     1.  Amendment of Original Agreement.  Paragraphs 2 and 4 of the Original
Agreement are hereby amended in their entirety to read as follows:

     "2.  Merger.  As of July 31, 2001 HAEC, as successor to Opportunity, will
     enter into an agreement of merger (the "Merger Agreement") with TNOG,
     whereby TNOG will, following the effectiveness of the Exchange Act
     Registration, merge with HAEC (the "Merger") pursuant to Section
     368(a)(1)(A) of the Internal Revenue Code of 1986, as amended.  HAEC will
     be the surviving entity.  The Merger Agreement will provide that the shares
     of the common stock of HAEC (the "HAEC Stock") following the Merger will be
     held approximately five percent by the Unicorp Shareholders and 95 percent
     by the shareholders of HAEC before the Merger."

     "4.  Registration of Opportunity's Stock.  In conjunction with the
     Information Statement, and as part of the Merger, an S-4 Registration
     Statement (the "Securities Act Registration") in accordance with the
     Securities Act will be prepared and filed by HAEC to register the HAEC
     Stock to be received by the Unicorp Shareholders."

Additionally, all references in the Original Agreement to "Opportunity" shall
hereafter refer to "HAEC."

     2.  Attorney's Fees.  In the event that it should become necessary for any
party entitled hereunder to bring suit against any other party to this First
Amendment for enforcement of the covenants herein contained, the parties hereby
covenant and agree that the party who is found to be in violation of said
covenants shall also be liable for all reasonable attorney's fees and costs of
court incurred by the other parties hereto.

     3.  Mediation and Arbitration.  All disputes arising or related to this
First Amendment must exclusively be resolved first by mediation with a mediator
selected by the parties, with such mediation to be held in Houston, Texas. If
such mediation fails, then any such dispute shall be resolved by binding
arbitration under the Commercial Arbitration Rules of the American Arbitration
Association in effect at the time the arbitration proceeding commences, except
that (a) Texas law and the Federal Arbitration Act must govern construction and
effect, (b) the locale of any arbitration must be in Houston, Texas, and (c) the
arbitrator must with the award provide written findings of fact and conclusions
of law. Any party may seek from a court of competent jurisdiction any
provisional remedy that may be necessary to protect its rights or assets pending
the selection of the arbitrator or the arbitrator's determination of the merits
of the controversy. The exercise of such arbitration rights by any party will
not preclude the exercise of any self-help remedies (including without
limitation, setoff rights) or the exercise of any non-judicial foreclosure
rights. An arbitration award may be entered in any court having jurisdiction.
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     4.  Benefit.  All the terms and provisions of this First Amendment shall be
binding upon and inure to the benefit of and be enforceable by the parties
hereto, and their respective heirs, executors, administrators, personal
representatives, successors and permitted assigns.

     5.  Notices.  All notices, requests, demands, and other communications
hereunder shall be in writing and delivered personally or sent by registered or
certified United States mail, return receipt requested with postage prepaid, if
to Unicorp, Equitable, or TNOG, addressed to Mr. Louis Mehr at 1907 Tarpley,
Katy, Texas 77493, with a copy to M. Stephen Roberts, Esquire, at P.O. Box
981021, Houston, Texas 770098, telecopier (713) 961-1148, and e-mail
sroberts@bigfoot.com; and if to HAEC, addressed to Mr. John F. Terwilliger at
801 Travis Street, Suite 1425, Houston, Texas 77002, telecopier (713) 221-8845,
and e-mail mooseoil@swbell.net, with a copy to Norman T. Reynolds, Esquire,
Jackson Walker L.L.P. at 1100 Louisiana Street, Suite 4200, Houston, Texas
77002, telecopier (713) 752-4221, and e-mail nreynolds@jw.com. Any party hereto
may change its address upon 10 days' written notice to any other party hereto.

     6.  Construction.  Words of any gender used in this First Amendment shall
be held and construed to include any other gender, and words in the singular
number shall be held to include the plural, and vice versa, unless the context
requires otherwise. In addition, the pronouns used in this First Amendment shall
be understood and construed to apply whether the party referred to is an
individual, partnership, joint venture, corporation or an individual or
individuals doing business under a firm or trade name, and the masculine,
feminine and neuter pronouns shall each include the other and may be used
interchangeably with the same meaning.

     7.  Waiver.  No course of dealing on the part of any party hereto or its
agents, or any failure or delay by any such party with respect to exercising any
right, power or privilege of such party under this First Amendment or any
instrument referred to herein shall operate as a waiver thereof, and any single
or partial exercise of any such right, power or privilege shall not preclude any
later exercise thereof or any exercise of any other right, power or privilege
hereunder or thereunder.

     8.  Cumulative Rights.  The rights and remedies of any party under this
First Amendment and the instruments executed or to be executed in connection
herewith, or any of them, shall be cumulative and the exercise or partial
exercise of any such right or remedy shall not preclude the exercise of any
other right or remedy.

     9.  Invalidity.  In the event any one or more of the provisions contained
in this First Amendment or in any instrument referred to herein or executed in
connection herewith shall, for any reason, be held to be invalid, illegal or
unenforceable in any respect, such invalidity, illegality, or unenforceability
shall not affect the other provisions of this First Amendment or any such other
instrument.

     10.  Time of the Essence.  Time is of the essence of this First Amendment.

     11.  Headings.  The headings used in this First Amendment are for
convenience and reference only and in no way define, limit, simplify or describe
the scope or intent of this First Amendment, and do not effect or constitute a
part of this First Amendment.

     12.  Excusable Delay.  None of the parties hereto shall be obligated to
perform and none shall be deemed to be in default hereunder, if the performance
of a non-monetary obligation is prevented by the occurrence of any of the
following, other than as the result of the financial inability of the party
obligated to perform: acts of God, strikes, lock-outs, other industrial
disturbances, acts of a public enemy, wars or war-like action (whether actual,
impending or expected and whether de jure or de facto), arrest or other
restraint of governmental (civil or military) blockades, insurrections, riots,
epidemics, landslides, lightning, earthquakes, fires, hurricanes, storms,
floods, washouts, sink holes, civil disturbances, explosions, breakage or
accident to equipment or machinery, confiscation or seizure by any government of
public authority, nuclear reaction or radiation, radioactive contamination or
other causes, whether of the kind herein enumerated, or otherwise, that are not
reasonably within the control of the party claiming the right to delay
performance on account of such occurrence.

     13.  No Third-Party Beneficiary.  Any agreement to pay an amount and any
assumption of liability herein contained, express or implied, shall be only for
the benefit of the undersigned parties and their respective

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successors and permitted assigns (as herein expressly permitted), and such
agreements and assumptions shall not inure to the benefit of the obligees or any
other party, whomsoever, it being the intention of the parties hereto that no
one shall be or be deemed to be a third-party beneficiary of this First
Amendment.

     14.  Multiple Counterparts.  This First Amendment may be executed in one or
more counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

     15.  Governing law; Jurisdiction.  This First Amendment shall be governed
by and construed in accordance with the laws of the State of Texas, without
regard to any conflicts of laws provisions thereof. Each party hereby
irrevocably submits to the personal jurisdiction of the United States District
Court for Harris County, Texas, as well as of the District Courts of the State
of Texas in Harris County, Texas over any suit, action or proceeding arising out
of or relating to this First Amendment. Each party hereby irrevocably waives, to
the fullest extent permitted by law, any objection which it may now or hereafter
have to the laying of the venue of any such mediation, arbitration, suit, action
or proceeding brought in any such county and any claim that any such mediation,
arbitration, suit, action or proceeding brought in such county has been brought
in an inconvenient forum.

     16.  Perfection of Title.  The parties hereto shall do all other acts and
things that may be reasonably necessary or proper, fully or more fully, to
evidence, complete or perfect this First Amendment, and to carry out the intent
of this First Amendment.

     17.  Entire Agreement.  This instrument contains the entire understanding
of the parties with respect to the subject matter hereof, and may not be changed
orally, but only by an instrument in writing signed by the party against whom
enforcement of any waiver, change, modification, extension, or discharge is
sought.

     IN WITNESS WHEREOF, this First Amendment has been executed in multiple
counterparts on the date first written above.

                                            UNICORP, INC.


                                            By   /s/ Louis G. Mehr
                                              ---------------------------------
                                              Louis G. Mehr, President



                                            EQUITABLE ASSETS, INCORPORATED


                                            By   /s/ Louis G. Mehr
                                              ---------------------------------
                                              Louis G. Mehr, President



                                            TEXAS NEVADA OIL & GAS CO.


                                            By   /s/ Louis G. Mehr
                                              ---------------------------------
                                              Louis G. Mehr, President



                                            HOUSTON AMERICAN ENERGY CORP.


                                            By   /s/ John F. Terwilliger
                                              ---------------------------------
                                              John F. Terwilliger, President

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