Document:

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                                                                   EXHIBIT 10(y)

                                 PROMISSORY NOTE

$10,000,000.00                                           Oklahoma City, Oklahoma
                                                               December 20, 2000

                  FOR VALUE RECEIVED, the undersigned, SEVEN SEAS PETROLEUM
INC., a Yukon Territory, Canada corporation (the "Borrower"), promises to pay to
the order of STILLWATER NATIONAL BANK AND TRUST COMPANY, N.A. (the payee, its
successors and assigns are hereinafter called the "Lender"), at 6305 Waterford
Boulevard, Suite 205, Oklahoma City, Oklahoma 73118, or at such other place as
may be designated in writing by the Lender, the principal sum of TEN MILLION
DOLLARS ($10,000,000.00), or so much thereof as is disbursed hereunder, together
with interest thereon at the rates hereinafter stated:

                  Prior to Default, advances under this Note will bear interest
                  from the date of advance at the per annum rate equal to the
                  Reference Rate plus 75/100 percent (.75%). All interest will
                  be computed for the actual number of days elapsed at a per
                  diem charge based on a year consisting of three hundred sixty
                  (360) days.

                  Provided that no event of Default has occurred or is
                  continuing under any of the Loan Documents, there will be no
                  required principal payments on this Note until December 31,
                  2001. Commencing on January 31, 2001, and on the last day of
                  each successive month thereafter until this Note is paid in
                  full, the Borrower will pay to the Bank all accrued unpaid
                  interest on this Note. The entire unpaid principal balance of
                  this Note plus all accrued and unpaid interest thereon will be
                  due and payable on December 31, 2001.

                  Unless otherwise defined herein, all terms defined or
referenced in that certain Loan Agreement of even date herewith between the
Borrower and the Lender (the "Loan Agreement") will have the same meanings
herein as therein.

                  This Note is executed and delivered in connection with the
Loan Agreement. Advances and payments hereunder may, at the option of the
Lender, be recorded on this Note or on the books and records of the Lender and
will be prima facie evidence of said advances, payments and unpaid balance of
this Note. It is specifically agreed that the aggregate of advances made during
the term of this Note may exceed the face amount hereof, but the unpaid
principal balance outstanding at any time will not exceed such face amount. All
payments will first be applied to the payment of accrued interest and the
balance will be applied in reduction of the principal balance hereof provided
that no payment will be applied to this Note until received by the Lender in
collected funds. All

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advances made or to be made under this Note will be made subject to the terms
and conditions stated in the Loan Agreement.

                  The Borrower will have the right at any time to prepay this
Note in whole or in part, without premium or penalty, but with interest accrued
to the date of prepayment.

                  The Borrower agrees that if, and as often as, this Note is
placed in the hands of an attorney for collection or to defend or enforce any of
the Lender's rights hereunder or under any instrument securing payment of this
Note, the Borrower will pay the Lender's reasonable attorneys' fees, all court
costs and all other expenses incurred by the Lender in connection therewith.

                  Any sum not paid when due, by acceleration or otherwise, will
bear interest at the per annum rate equal to the greater of (a) fifteen percent
(15%), or (b) the Reference Rate plus five percent (5%), and such interest which
has accrued will be paid at the time of and as a condition precedent to curing
any Default hereunder. During the existence of any such Default, the Lender may
apply any payments received on any amount due hereunder or under the terms of
any instrument now or hereafter evidencing or securing this indebtedness as the
Lender determines from time to time.

                  This Note is issued by the Borrower and accepted by the Lender
pursuant to a lending transaction negotiated, consummated and to be performed in
Oklahoma City, Oklahoma. Payment of this Note is secured by and subject to the
terms and conditions of the Loan Documents. This Note is to be construed
according to the internal laws of the State of Oklahoma. All actions with
respect to this Note, the Loan Documents or any other instrument securing
payment of this Note may be instituted in the courts of the State of Oklahoma
sitting in Oklahoma County, Oklahoma, or the United States District Court
sitting in Oklahoma City, Oklahoma, as the Lender may elect, and by execution
and delivery of this Note, the Borrower irrevocably and unconditionally submits
to the jurisdiction (both subject matter and personal) of each such court and
irrevocably and unconditionally waives: (a) any objection the Borrower might
now or hereafter have to the venue in any such court; and (b) any claim that any
action or proceeding brought in any such court has been brought in an
inconvenient forum.

                  On the occurrence of an event of Default or the breach of any
provision of this Note, any of the Loan Documents or any other instrument
securing payment of this Note, at the option of the Lender, the entire
indebtedness evidenced by this Note will become immediately due, payable and
collectible then or thereafter as the Lender might elect, regardless of the date
of maturity hereof. Failure by the Lender to exercise such option will not
constitute a waiver of the right to exercise the same in the event of any
subsequent Default.

                  The makers, endorsers, sureties, guarantors and all other
persons who may become liable for all or any part of this obligation severally
waive presentment for payment, protest and notice of nonpayment. Said parties
consent to any extension of time (whether one or more) of payment hereof,
release of all or any part of the security for the payment hereof or release of
any party liable for the payment of this obligation. Any such extension or
release may be made without notice to any such party and without discharging
such party's liability hereunder.

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                  IN WITNESS WHEREOF, the Borrower has executed this instrument
effective the date first above written.

                                   SEVEN SEAS PETROLEUM INC., a Yukon
                                   Territory, Canada corporation

                                   By /s/ LARRY A. RAY
                                     --------------------------------
                                     Larry A. Ray, President

                                   (the "Borrower")

                                      - 3 -<PAGE>   1
                                                                   EXHIBIT 10(z)

                             STOCK PLEDGE AGREEMENT

                  THIS STOCK PLEDGE AGREEMENT is executed effective the 20th day
of December, 2000, by SEVEN SEAS PETROLEUM INC., a Yukon Territory, Canada
corporation (the "Borrower"), SEVEN SEAS PETROLEUM HOLDINGS INC., a Cayman
Islands corporation ("SSPH"), and SEVEN SEAS PETROLEUM COLUMBIA INC., a Cayman
Islands corporation ("SSPC" and jointly and severally with the Borrower and
SSPH, the "Debtors"), each having a notice address at 5555 San Felipe, Suite
1700, Houston, Texas 77056, in favor of STILLWATER NATIONAL BANK AND TRUST
COMPANY, N.A. (the "Secured Party"), having a notice address at 6305 Waterford
Boulevard, Suite 205, Oklahoma City, Oklahoma 73118.

                                   WITNESSETH:

                  WHEREAS, the Borrower is liable to the Secured Party under
that certain Promissory Note of even date herewith in the principal amount of
Ten Million Dollars ($10,000,000.00) (the "Note"), in connection with that
certain Loan Agreement of even date herewith between the Borrower and the
Secured Party (the "Loan Agreement"); and

                  WHEREAS, each of SSPH and SSPC is a direct or indirect wholly
owned subsidiary of the Borrower and the Debtors have agreed to secure payment
of the Note and all other Obligations of the Borrower to the Secured Party by
granting the Secured Party a lien, security interest and pledge covering certain
assets of the Debtors.

                  NOW, THEREFORE, in consideration of the premises and the
agreements herein contained and for other good and valuable consideration, the
receipt and sufficiency of all of which are hereby acknowledged, the Debtors
hereby agree with the Secured Party as follows:

1. Definitions. Unless otherwise defined herein, all terms used herein which are
defined in the Loan Agreement will have the same meanings herein unless the
context otherwise requires and all terms used herein which are defined in the
Oklahoma Uniform Commercial Code (the "UCC") will have the same meanings herein
unless the context otherwise requires.

2. Security Interest. Each of the Debtors hereby grants to the Secured Party a
first and prior security interest in the stock currently owned by the Debtors
described in Schedule "A" attached hereto as a part hereof (the "Pledged
Stock"), together with all additions and substitutions of shares of the Pledged
Stock or certificates, all of the Debtors' interest and rights in the Pledged
Stock, whether now owned or hereafter acquired, all cash and stock dividends
attributable to the Pledged Stock, all increases relating to the Pledged Stock
as a result of stock splits, mergers or any other reorganization, all monies and
claims for monies due and to become due to the Debtors as dividends or arising
under accounts, contracts, agreements and general intangibles relating to the
Pledged Stock and all proceeds and products thereof (the Pledged Stock and the
foregoing items are hereafter called the "Collateral"). This Agreement is
intended for security only and is to secure the Obligations of the Debtors owing
to the Secured Party as herein described. It is understood that the Secured
Party does not hereby assume any of the obligations of the Debtors in connection
with the Collateral.

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         2.1      Voting Rights. Absent an event of Default (as hereinafter
                  defined) under this Agreement or the other Loan Documents, the
                  Debtors will retain all voting rights with respect to the
                  Pledged Stock. On or after the occurrence of an event of
                  Default and without further notice to the Debtors, the Secured
                  Party will have the right to exercise all voting rights, all
                  conversion, exchange, subscription and other rights pertaining
                  to the Pledged Stock, whether or not the Pledged Stock has
                  been registered in the Secured Party's name. Each of the
                  Debtors hereby appoints the Secured Party as such Debtor's
                  lawful attorney-in-fact and proxy to exercise the foregoing
                  rights after the occurrence of an event of default. Each of
                  the Debtors agrees that the foregoing proxy is coupled with an
                  interest and is irrevocable.

         2.2      Cash Dividends. Absent an event of Default, the Debtors will
                  have the right to receive and retain for the Debtors' use all
                  cash dividends paid on the Pledged Stock. On or after the
                  occurrence of an event of Default and without further notice
                  to the Debtors, the Secured Party will have the right to
                  receive such cash dividends and to apply the same toward
                  satisfaction of the Secured Indebtedness (as hereinafter
                  defined) or hold the same as part of the Collateral under this
                  Agreement.

         2.3      Stock Dividends. In the event any stock dividends are paid on
                  the Pledged Stock, or if any stock or other securities are
                  delivered to the Debtors in connection with any stock split,
                  merger or reorganization affecting the Pledged Stock, the
                  Debtors will immediately deliver to the Secured Party the
                  certificates representing such stock dividends, other stock or
                  securities, together with executed endorsements or appropriate
                  powers. Any such stock dividend, other stock or securities
                  will be held by the Secured Party as part of the Collateral
                  under the terms of this Agreement.

3. Secured Indebtedness. The security interest granted hereby in the Pledged
Stock is given to secure the Borrower's payment of: (a) the Note together with
interest thereon; (b) any and all other or additional Obligations of the
Borrower to the Secured Party; (c) all extensions, renewals, amendments,
modifications, substitutions and changes in form to the Note; (d) all costs and
expenses incurred in connection with the collection of the Note and any other
Obligations and enforcement of the Loan Documents and the Secured Party's rights
under this Agreement and all other Loan Documents including, without limitation,
the collection or enforcement of the Loan Documents whether by judicial
proceedings, proceedings under Chapter 7 or 11 of the Bankruptcy Code or any
successor statute thereto, or otherwise, and including attorneys' fees and
expenses; (e) all advances made by the Secured Party to protect the security
hereof, including advances made for or on account of levies, taxes and for
maintenance or recovery of the Pledged Stock, together with interest thereon at
the Default rate specified in the Note; (f) all future advances and any and all
other indebtedness, liabilities and obligations of the Borrower to the Secured
Party (whether primary, secondary, direct or indirect, absolute or contingent,
sole, joint, or several) whether now owing or hereafter incurred; and (g)
performance of the agreements herein set forth (the foregoing items (a) through
(g) are collectively referred to herein as the "Secured Indebtedness").

4. Debtors' Agreements. Until payment in full of the Secured Indebtedness, the
Debtors jointly and severally will perform or cause to be performed the
following agreements:

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         4.1      Possession of Collateral. The Debtors agree to deliver the
                  Pledged Stock to the Secured Party, appropriately endorsed to
                  the Secured Party or with stock powers in form and substance
                  satisfactory to the Secured Party in favor of the Secured
                  Party. The Debtors will provide the name and address of the
                  stock transfer agent to the Secured Party. Regardless of the
                  form of any endorsement to the Secured Party, the Debtors
                  waive presentment, demand, notice of dishonor, protest, notice
                  of protest and all other notices with respect thereto.

         4.2      Additional Documents. The Debtors agree to execute and deliver
                  any documents which are necessary in the judgment of the
                  Secured Party to obtain, maintain and perfect a security
                  interest under this Agreement and to enable the Secured Party
                  to comply with any foreign, federal or state law to obtain or
                  perfect the Secured Party's security interest in the
                  Collateral or otherwise applicable to the Secured Party.

         4.3      Creation of Liens. The Debtors will not create, assume or
                  suffer to exist any claim, pledge, security interest,
                  encumbrance or other lien (including the lien of an
                  attachment, judgment or execution) affecting any or all of the
                  Collateral, excluding only liens held by the Secured Party.

5. Debtors' Representations and Covenants. The Debtors jointly and severally
hereby warrant, represent and agree as follows:

         5.1      Principal Place of Business. The principal place of business
                  in the United States of each of the Debtors is 5555 San
                  Felipe, Suite 1700, Houston, Texas 77056.

         5.2      Title. Each of the Debtors has absolute title to the Pledged
                  Stock owned by such Debtor free and clear of all liens,
                  encumbrances and security interests except for the security
                  interest hereby granted to the Secured Party and such other
                  rights, if any, of the Secured Party, and each of the Debtors
                  warrants and will defend the same unto the Secured Party
                  against the claims and demands of all persons and parties
                  whomsoever. The Debtors are not in default in the performance
                  of any obligation or the payment of any sum owing with respect
                  to the Pledged Stock. The Debtors will take all steps
                  necessary to cause or permit the Secured Party to cause the
                  Pledged Stock to be registered in the name of the Secured
                  Party and new share certificates to be issued.

6. Default. As used herein "Default" means the occurrence of any event of
Default under the Loan Agreement or the failure by any of the Debtors to keep,
observe, comply with and perform all of the obligations and undertakings under
this Agreement or any of the other Loan Documents or failure to pay any
principal or interest on the Note when due and, in any such event, the Secured
Party may, at its option and without notice to any party, declare all or any
portion of the Secured Indebtedness to be immediately due and payable and may
proceed to enforce payment of the same, to exercise any or all rights and
remedies provided herein, in the other Loan Documents, and by the UCC and
otherwise available at law or in equity. All remedies hereunder are cumulative,
and any indulgence or waiver by the Secured Party will not be construed as an
abandonment of any other right hereunder or of the power to enforce the same or
another right at a later time.

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7. Remedies. On the occurrence of an event of Default, the Secured Party may
take the following actions:

         7.1      Remedy. The Secured Party may (a) exercise in respect of the
                  Collateral or any portion thereof all of the rights and
                  remedies of a secured party under the UCC, or (b) at any time
                  and from time to time sell, resell, assign and deliver, in the
                  Secured Party's discretion, all or any part of the Collateral,
                  in one or more parcels at the same or different times, and all
                  right, title and interest, claim and demand therein and right
                  of redemption thereof, at public or private sale on
                  commercially reasonable terms. In connection therewith, the
                  Secured Party may bid on such Collateral for its own account
                  and each of the Debtors hereby waives and releases any and all
                  equity or right of redemption. To effect any sale, transfer or
                  other disposal of any of the Collateral, the Secured Party has
                  the right, for and in the name, place and stead of the
                  Debtors, to execute endorsements, assignments or other
                  instruments of conveyance or transfer with respect to all or
                  any of the Collateral.

         7.2      Sale Procedure. Except as expressly provided for herein, no
                  demand or advertisement, all of which are hereby expressly
                  waived by the Debtors, will be required in connection with any
                  sale or other disposition of any part of the Collateral which
                  threatens to decline speedily in value or which is of a type
                  customarily sold on a recognized market. In all other events,
                  the Secured Party will give the Debtors, at least ten (10)
                  days prior notice of the time and place of any public sale and
                  of the time after which any private sale or other disposition
                  is to be made, which notice the Debtors agree is reasonable,
                  all other demands and advertisements being hereby waived. The
                  Secured Party will not be obligated to make any sale of
                  Collateral, regardless of the fact that notice of sale may
                  have been given. The Secured Party may adjourn any public or
                  private sale or cause the same to be adjourned from time to
                  time by announcement at the time and place fixed for sale, and
                  such sale may be made at the time and place to which the same
                  was so adjourned. Upon each public or private sale of
                  Collateral, the Secured Party or any holder of the Note, or
                  any of their respective affiliates, may purchase all or any of
                  the Collateral being sold, free from any equity or right of
                  redemption, which is hereby waived and released by the
                  Debtors, and may make payment therefor in cash or, at the
                  Secured Party's or such holder's option (by endorsement
                  without recourse), by tendering or releasing principal or
                  accrued and unpaid interest on the Note, in lieu of cash, in a
                  face amount equal to the amount of the purchase price. The
                  Debtors agree to pay all reasonable costs and expenses of
                  every kind for sale or delivery, including brokers' and
                  attorneys' fees, and after deducting such costs and expenses
                  from the proceeds of sale, the Secured Party will apply any
                  residue to the payment of the Secured Indebtedness and the
                  Debtors will continue to be liable for any deficiency in
                  accordance with the Loan Documents. The balance, if any,
                  remaining after payment in full of all of the Secured
                  Indebtedness will be paid to the Debtors or as otherwise
                  directed by any court having appropriate jurisdiction.

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         7.3      Private Sales. The Debtors recognize that the Secured Party
                  may be unable to effect a public sale of all or part of the
                  Collateral by reason of certain prohibitions contained in the
                  Securities Act of 1933, as amended, as now or hereafter in
                  effect, or in applicable blue sky or other state securities
                  laws, as now or hereafter in effect, but may be compelled to
                  resort to one or more private sales to a restricted group of
                  purchasers who will be obliged to agree, among other things,
                  to acquire such Collateral for their own account, for
                  investment and not with a view to the distribution or resale
                  thereof. The Debtors agree that private sales so made may be
                  at prices and other terms less favorable to the Debtors than
                  if such Collateral were sold at public sales, and that the
                  Secured Party has no obligation to delay sale of any such
                  Collateral for the period of time necessary to permit the
                  issuer of such Collateral, even if such issuer would agree, to
                  register such Collateral for public sale under such applicable
                  securities laws. The Debtors agree that private sales, absent
                  other adverse circumstances, will not be deemed to have been
                  made in a commercially unreasonable manner. In connection with
                  the foregoing, the Secured Party may, at the Debtors' expense,
                  consult with counsel to determine whether a public or private
                  sale of Collateral is necessary or appropriate.

8. Miscellaneous. It is further agreed as follows:

         8.1      Time. Time is of the essence of this Agreement and each
                  provision of this Agreement.

         8.2      Notices. Any notice required or permitted to be given by this
                  Agreement will be deemed to have been given on the date such
                  notice is delivered personally or by telefacsimile to the
                  party designated to receive such notice, on the date sent by
                  overnight courier or on the date deposited in the United
                  States mail, postage prepaid, and directed to the notice
                  address specified in the initial paragraph of this Agreement,
                  the Loan Agreement or otherwise provided to the Secured Party
                  in writing.

         8.3      Cumulative Remedies. No failure on the part of the Secured
                  Party to exercise, and no delay in exercising any right under
                  this Agreement will operate as a waiver thereof, nor will any
                  single or partial exercise by the Secured Party of any right
                  under this Agreement preclude any other or further right of
                  exercise thereof or the exercise of any other right except as
                  provided in the Loan Documents.

         8.4      Construction. This Agreement is to be construed according to
                  the internal laws of the State of Oklahoma. All actions with
                  respect to this Agreement may be instituted in the Courts of
                  the State of Oklahoma or the United States District Court
                  sitting in Oklahoma County, Oklahoma and each of the Debtors
                  hereby consents to the jurisdiction and venue of any such
                  courts.

         8.5      Amendment. Neither this Agreement nor any of the provisions
                  hereof can be changed, waived, discharged or terminated,
                  except by an instrument in writing signed by the party against
                  whom enforcement of the change, waiver, discharge or
                  termination is sought.

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         8.6      Severability. The provisions of this Agreement are severable,
                  and if any clause or provision is held invalid, illegal or
                  unenforceable in any respect in any jurisdiction, the
                  validity, legality and enforceability of the remaining
                  provisions contained herein will not be in any way affected or
                  impaired thereby.

         8.7      Binding Effect. This Agreement will be binding on the Debtors
                  and the Debtors' successors and permitted assigns, and will
                  inure to the benefit of the Secured Party and the Secured
                  Party's successors and assigns.

         8.8      Continuing Agreement. This is a continuing Agreement and the
                  grant of a security interest hereunder will remain in full
                  force and effect and all the rights, powers and remedies of
                  the Secured Party hereunder will continue to exist until all
                  of the Secured Indebtedness is paid in full as the same
                  becomes due and payable and until the Secured Party, upon
                  request of the Debtors, has executed a written termination
                  statement, reassigned to the Debtors, without recourse, the
                  Collateral and all rights conveyed hereby and returned
                  possession of any Collateral in the Secured Party's possession
                  to the Debtors.

                  IN WITNESS WHEREOF, the Debtors and the Secured Party have
executed and delivered this Agreement effective the date first above written.

                                SEVEN SEAS PETROLEUM INC., a Yukon
                                Territory, Canada corporation

                                By /s/ LARRY A. RAY
                                  -----------------------------------
                                       Larry A. Ray, President

                                SEVEN SEAS PETROLEUM HOLDINGS INC., a
                                Cayman Islands corporation

                                By /s/ LARRY A. RAY
                                  -----------------------------------
                                Name:  Larry A. Ray
                                     --------------------------------
                                Title: President
                                      -------------------------------

                                      - 6 -

<PAGE>   7

                              SEVEN SEAS PETROLEUM COLOMBIA INC., a
                              Cayman Islands corporation

                              By /s/ LARRY A. RAY
                                ---------------------------------------------
                              Name:  Larry A. Ray
                                   ------------------------------------------
                              Title: President
                                    -----------------------------------------

                              (jointly and severally, the "Debtors")

                              STILLWATER NATIONAL BANK AND TRUST
                              COMPANY, N.A.

                              By /s/ G.P. JOHNSON HIGHTOWER
                                ---------------------------------------------
                                G.P. Johnson Hightower, Senior Vice President

                              (the "Secured Party")

                                      - 7 -

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