Document:

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                                                                   EXHIBIT 10.16

             [EOTT ENERGY OPERATING LIMITED PARTNERSHIP LETTERHEAD]

December 19, 2000

                           CRUDE OIL PURCHASE CONTRACT

Coho Resources, Inc.
14785 Preston Road
Suite 865
Dallas, Texas 75240

Attn:     Mr. Gary Pittman
          Chief Financial Officer

Re:       EOTT CONTRACT NO. TP00-1018776
          COHO CONTRACT NO. ____________

Gentlemen:

When accepted by you in the manner hereinafter indicated, this shall evidence
the agreement ("Agreement") by and between COHO RESOURCES, INC., hereinafter
referred to as "COHO", and EOTT ENERGY OPERATING LIMITED PARTNERSHIP,
hereinafter referred to as "EOTT", under the terms of which, and in
consideration of the promises made hereunder and for other valuable
consideration received, such parties shall sell and buy the hereinafter
described crude oil and/or condensate ("crude oil") as follows:

I.        TERM:

          Commencing at 7:00 a.m. Central Time on November 1, 2000 to 7:00 a.m.
          Central Time on December 31, 2001. Termination shall not affect rights
          or obligations of either party accrued prior to the date of
          termination.

II.       TYPE OF OIL:

          Subject to the terms hereof, COHO shall deliver to EOTT COHO's owned
          or controlled production of Mississippi Light Sweet, Mississippi
          Light Sour and Mississippi Heavy Sour types of crude oil as listed on
          Attachment "A" hereto.

III.      QUANTITY:

          Volume to fluctuate with COHO's production from the Leases or Units
          listed on Attachment "A." Production from the properties listed on
          Attachment "A" currently averages eight thousand (8,000) barrels per
          day.

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IV.       DELIVERY:

          COHO shall deliver to EOTT at various lease sites, per Attachment "A",
          by tank gauges and/or meters into EOTT's designated carrier(s) with
          title and risk of loss to pass to EOTT as the oil passes through the
          outlet flange of COHO's tankage and/or meters. If Attachment "A" does
          not list all applicable leases, said leases shall nevertheless be
          covered hereunder and the parties hereto shall amend Attachment "A" as
          needed.

V.        PRICE:

          For each barrel of crude oil delivered to EOTT hereunder during each
          calendar month, EOTT shall pay EOTT's average daily posted price for
          the applicable calendar month, with adjustment made for gravity
          delivered, plus the applicable per barrel premium, as per Attachment
          "A" incorporated herein and made a part hereof for all purposes. For
          pricing purposes, all crude oil delivered hereunder during any
          calendar month will be considered to have been delivered in equal
          daily quantities during each such month.

VI.       PAYMENT:

          Payment shall be made by EOTT by open division order, less applicable
          production and severance taxes, by check, except COHO shall receive
          payment for its interest by wire transfer on the twentieth (20th) day
          of the calendar month following the calendar month of delivery.

VII.      DIVISION ORDERS:

          All division orders, division order documents and division order
          matters shall be sent to the following addresses:

          EOTT Energy Operating Limited         Coho Resources, Inc.
            Partnership                         Attn: Division Order Department
          Attn: Division Order Department       14785 Preston Road, Suite 860
          P.O. Box 4666                         Dallas, Texas 75240
          Houston, TX 77210-4666

          If any division orders are executed pursuant to this Agreement, and in
          the event of any irreconcilable conflict between the terms of any such
          division orders and this Agreement, the terms of this Agreement shall
          be deemed controlling, even if the division orders are dated
          subsequent to this Agreement.

VIII.     SPECIAL PROVISIONS:

          (A)     COHO shall fully defend and indemnify EOTT against, and hold
                  EOTT fully harmless from, any claim, action, suit, demand or
                  complaint (of any nature whatsoever) which any interest owner
                  in any well (on any lease which is covered or affected hereby)
                  may bring in connection with (i) COHO's ability to enter into
                  this Agreement with EOTT, or (ii) any production proceeds paid
                  out by EOTT to COHO pursuant to this Agreement. COHO warrants
                  unto EOTT that COHO has full right and authority to enter into
                  this Agreement for all of the crude oil committed by COHO
                  hereunder, and that COHO is violating no duty or obligation
                  which it may have to any third party in entering into this
                  Agreement, provided, however, EOTT acknowledges that under
                  certain agreements between COHO and other working interest
                  owners COHO's authority to market crude oil is limited to
                  periods not exceeding one year, but EOTT may rely upon COHO's
                  authority to market in the case of any and all crude oil
                  actually delivered to EOTT hereunder.

          (B)     All crude oil delivered to EOTT hereunder will be crude oil
                  delivered in accordance with the quality standards set forth
                  herein (including the General Provisions attached hereto), and
                  COHO will fully indemnify EOTT against and hold EOTT harmless
                  from any loss, damage, harm, liability, claim, action, suit,
                  demand or complaint, of any nature whatsoever, which EOTT may

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                  suffer as a result of receiving non-standard crude oil from
                  COHO at the point of title transfer set forth herein as a
                  consequence of COHO's intentional addition in such crude oil
                  of any contaminant.

          (C)     This Agreement is subject to the General Provisions which are
                  attached hereto and made a part hereof for all purposes.

IX.       ADDITIONAL LEASE PRODUCTION:

          EOTT agrees that any production which is subsequently owned,
          developed, controlled, or acquired by COHO where COHO has the right to
          market the production, in the State of Mississippi during the Term of
          this Agreement shall be automatically added to this Agreement,
          provided the said production is a type of crude oil then being
          purchased by EOTT and is located in an area from which EOTT then
          makes crude oil purchases. The pricing for any additional production
          added to this Agreement under this Paragraph IX shall be priced
          according to crude oil grade as follows:

          (i)     For Mississippi Light Sweet type crude oil: EOTT's posted
                  price for South Louisiana Sweet, with adjustment made for
                  gravity delivered, plus $1.50 per barrel premium, based on
                  deemed equal daily deliveries during each calendar month.

          (ii)    For Mississippi Light Sour type crude oil: EOTT's posted price
                  for Mississippi Light Sour, with adjustment made for gravity
                  delivered, plus $1.70 per barrel premium, based on deemed
                  equal daily deliveries during each calendar month.

          (iii)   For Mississippi Heavy Sour type crude oil transported by
                  pipeline: EOTT's posted price for Mississippi Light Sour, with
                  adjustment made for gravity delivered, plus $1.70 per barrel
                  premium, based on deemed equal daily deliveries during each
                  calendar month. For Mississippi Heavy Sour type crude oil
                  transported by truck: EOTT's posted price for Mississippi
                  Light Sour, with adjustment made for gravity delivered, plus
                  $1.00 per barrel premium, based on deemed equal daily
                  deliveries during each calendar month.

X.        OTHER PRODUCTION:

          COHO also grants EOTT the right of first refusal to purchase any
          "other" production which is owned, developed, controlled, or acquired
          at any time by COHO where COHO has the right to market the production
          in the states of Mississippi or Alabama during the Term of this
          Agreement (meaning any crude oil type which is not being purchased by
          EOTT or any crude oil in any area from which EOTT does not make crude
          oil purchases). The notice period for the right of first refusal shall
          be for a period of thirty (30) days from the date EOTT receives notice
          from COHO of any offers. As to such "other" production, EOTT shall
          have the right, but not the obligation, to add same to this Agreement.
          The price structure for any other grade of Mississippi crude oil or
          for any additional crude oil production in the State of Alabama which
          becomes subject to this Agreement shall be negotiated at the time of
          COHO's acquisition of such production. In the event EOTT and COHO
          cannot agree upon the applicable pricing structure for any such
          production, the matter shall be submitted to arbitration for binding
          resolution.

XI.       RIGHT TO SWITCH PRICING METHOD:

          Reference is made to the one-time right to switch the pricing method
          (which is described in parts I, II and III of Attachment "A"). Subject
          to the same timing and other requirements set forth in Attachment "A,"
          COHO shall have the same, one-time right to switch the pricing method
          as to each of the crude types set forth in Paragraphs IX(i), IX(ii),
          and IX(iii) above, as follows:

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          (a)     For the Mississippi Light Sweet type crude covered under
                  Paragraph IX(i) above, COHO may elect to switch the pricing to
                  the average of Plains Marketing's and EOTT's daily posted
                  prices for Louisiana Light Sweet crude oil during the
                  applicable calendar month of delivery hereunder, with
                  adjustment made for gravity delivered, plus $1.50 per barrel.

          (b)     For the Mississippi Light Sour type crude covered under
                  Paragraph IX(ii) above, COHO may elect to switch the pricing
                  to the average of Equiva's and EOTT's daily posted prices for
                  Mississippi Sour crude oil during the applicable calendar
                  month of delivery hereunder, with adjustment made for gravity
                  delivered, plus $1.70 per barrel.

          (c)     For the Mississippi Heavy Sour type crude covered under
                  Paragraph IX(iii) above, COHO may elect to switch the pricing
                  to the average of Equiva's and EOTT's daily posted prices
                  Mississippi Sour crude oil during the applicable calendar
                  month of delivery hereunder, with adjustment made for gravity
                  delivered, plus $1.70 per barrel for those barrels gathered by
                  pipeline or plus $1.00 per barrel for those barrels gathered
                  by truck.

          This one-time right to switch the pricing method shall be exercisable
          by thirty (30) days' written notice from COHO to EOTT, to be effective
          on the first day of any calendar month after the notice period as
          designated by COHO in such notice.

XII.      RENEWAL TERMS:

          Prior to the expiration of this Agreement, EOTT and COHO shall
          endeavor to negotiate a new, mutually-agreeable agreement, or a
          mutually-agreeable extension of this Agreement. Should the parties be
          unable to agree upon the terms for a new agreement or an extension, or
          should COHO notify EOTT that it does not wish to negotiate a new
          agreement or an extension, EOTT and COHO shall be bound by the
          following terms and conditions:

          (i)     COHO shall solicit bonafide competitive bids from other
                  purchasers (unrelated to COHO) for purchases to be made on or
                  after January 1, 2002, and EOTT shall have the right and
                  option, but not the obligation, to match any bonafide written
                  offer (from any bonafide crude oil purchaser) which COHO will
                  otherwise act upon. COHO shall submit any such bonafide
                  written offer to EOTT no later than December 1, 2001, and EOTT
                  shall advise COHO, no later than December 19, 2001, as to
                  whether EOTT will match such written offer.

          (ii)    If COHO proceeds under Paragraph XII(i) above, and if EOTT
                  elects not to match an applicable bonafide written offer from
                  a bonafide crude oil purchaser, EOTT shall, at COHO's option,
                  enter into a buy/sell agreement with COHO whereby EOTT shall
                  purchase a volume and quality of Mississippi/Alabama crude oil
                  equal to the lease production covered under this Agreement as
                  of December 31, 2001, and sell back to COHO a corresponding
                  volume of crude oil of the grade(s) and quality(ies) provided
                  below. Such delivery back to COHO shall be at either Genesis
                  Pipeline Company's Liberty, Mississippi Station or within
                  TEPPCO Pipeline's facilities at Cushing, Oklahoma, or any
                  combination of these locations, at COHO's option. In the case
                  of deliveries back to COHO at Genesis Pipeline Company's
                  Liberty, Mississippi Station, EOTT shall deliver back to COHO
                  substantially the same grades and qualities of crude oil as
                  are delivered by COHO to EOTT in the applicable calendar
                  month. In the case of deliveries back to COHO within TEPPCO
                  Pipeline's facilities at Cushing, Oklahoma, EOTT shall deliver
                  back to COHO West Texas Intermediate type crude oil. All
                  deliveries made by EOTT to COHO shall be subject to location
                  differentials (in favor of EOTT) and shall be established when
                  the buy/sell agreement is negotiated, with binding arbitration
                  to be used if such differentials cannot be agreed upon.
                  Subject to the location differentials described in the
                  preceding sentences of this Paragraph XII(ii), (a) pricing
                  for all deliveries made by COHO to EOTT pursuant to the
                  buy/sell agreement shall be based upon mutually-agreeable area
                  posted prices for the grades and qualities of crude oil
                  delivered by COHO to EOTT thereunder, (b) pricing for all
                  deliveries made by EOTT back to

                                       A-4

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                  COHO at Genesis Pipeline Company's Liberty, Mississippi
                  Station pursuant to the buy/sell agreement shall be based
                  upon the same posted prices determined in accordance with
                  part (a) of this sentence, and (c) pricing for all
                  deliveries made by EOTT back to COHO within TEPPCO
                  Pipeline's facilities at Cushing, Oklahoma pursuant to the
                  buy/sell agreement shall be based upon mutually-agreeable
                  posted prices for West Texas Intermediate type crude oil. If
                  agreement cannot be reached on a specific posted price, then
                  an average of all market related area posted prices for
                  grade and quality of oil delivered shall be used.

XIII.     ARBITRATION:

          Wherever in this Agreement a provision is made for resolution of a
          disagreement between the parties by arbitration, such arbitration
          proceedings shall be conducted in accordance with the commercial
          arbitration rules, then in effect, of the American Arbitration
          Association. All such arbitration proceedings shall be conducted in
          Houston, Texas unless otherwise agreed upon by the parties.

XIV.      ASSIGNABILITY:

          This Agreement, or any portion thereof, shall not be assignable by
          either party without the prior written consent from the other party,
          which consent shall not be unreasonably withheld. No assignment shall
          be binding on either party unless and until the other party has
          received written notice of the assignment and provided its written
          consent.

XV.       NO PARTNERSHIP OR JOINT VENTURE:

          Nothing contained herein is intended to constitute a partnership or
          joint venture between the parties.

          If the foregoing accurately reflects our agreement, please execute
this document in the space provided below and return a fully executed
counterpart hereof to EOTT for its files.

Sincerely,

EOTT ENERGY OPERATING LIMITED PARTNERSHIP
By:  EOTT Energy Corp., its General Partner

By:     /s/ DAN E. COLE
   -----------------------------------------
            Dan E. Cole
            General Manager
            Gulf Coast Region

ACCEPTED AND AGREED TO THIS 18TH DAY OF JANUARY, 2001

BY:  COHO RESOURCES, INC.

By:    /s/ GARY L. PITTMAN
    ------------------------------------------
Title:     CFO
       ---------------------------------------

                                       A-5<PAGE>   1

                                                                    EXHIBIT 10.8

              SECOND AMENDMENT TO DEVELOPMENT AND SUPPLY AGREEMENT

     This Second Amendment to Development and Supply Agreement ("Amendment"),
effective as of June 12, 2000, is made by and between Luminex Corporation, a
Delaware corporation ("LUMINEX"), and Bio-Rad Laboratories, Inc., a Delaware
corporation ("BIO-RAD") (LUMINEX and BIO-RAD collectively, the "Parties"), and
amends that certain Development and Supply Agreement dated as of March 19, 1999
between the Parties (as previously amended by amendment dated January 13, 2000,
the "Agreement").

     The Parties hereby agree as follows, for the purpose of amending the
Agreement in the following respects:

1.   Amendments. The Parties hereby agree to amend the Agreement in the
     following respects:

     1.1  Magnetic Bead Amendments.

          1.1.1 Section 2.1(d) of the Agreement is hereby amended to delete all
sentences in that section except the first two sentences and add the following
as the third and fourth sentences of such section:

          "Exhibit F sets forth the criteria for BIO-RAD's supply of Magnetic
          Beads to LUMINEX and LUMINEX's treatment of such Magnetic Beads. The
          tolling fees payable by BIO-RAD to LUMINEX with respect to Magnetic
          Beads shall be the prices set forth in Exhibit G (the "Magnetic Bead
          Prices")."

          1.1.2 Section 2.2 of the Agreement is hereby amended to delete the
phrase in the last sentence "or the Development Agreement."

          1.1.3 Sections 1.4, 4.2, 4.3, 4.4, 4.5, 4.8, 4.10, 4.15, 4.16 and
Article 7 of the Agreement are hereby amended to delete all instances of the
word "Standard" when preceding the word "Beads."

          1.1.4 Section 4.6(b) of the Agreement is hereby amended to delete the
last sentence of such section and replace it with the following:

          "The amounts of the tolling fees for Magnetic Beads shall be as set
          forth in Exhibit G. These Magnetic Bead Prices will be effective
          during the first [**] of this Agreement, after which time LUMINEX may,
          [**]. Such increases may occur no more frequently than [**]. Each [**]
          increase during the [**]."

          1.1.5 Section 4.9 of the Agreement is hereby amended to add the phrase
", Magnetic Bead Prices" following the phrase "Payment of the Unit Transfer
Fee."

          1.1.6 Exhibits F and G attached to this Amendment are hereby added as
Exhibits to the Agreement.

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requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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     1.2  Standard Bead Pricing Amendments.

          1.2.1 The first sentence of Section 4.6(a) of the Agreement is hereby
                amended by deleting the phrase "[**] for ever [**] units of
                Standard Beads purchased, where a "unit" of Standard Beads is
                equal to one microsphere bead ("Unit Transfer Fee") and
                substituting therefor:

          "for Beads purchased hereunder according to the prices set forth on
          Exhibit H, as amended ("Unit Transfer Fees")."

          1.2.2 All references in the Agreement to "Unit Transfer Fee" are
hereby amended to be references to "Unit Transfer Fees."

          1.2.3 Exhibit H, attached to this Amendment, is hereby added as an
Exhibit to the Agreement.

          1.2.4 Exhibit I, [**], rev. C, attached to this Amendment, is hereby
added as an Exhibit to the Agreement.

          1.2.5 The end of the first sentence of Section 9.1 is hereby amended
to add the phrase ", and Beads for BIO-RAD's [**] shall be [**]."

     1.3  Luminex 100 System Pricing Amendments.

          1.3.1 Exhibit E to the Agreement is hereby amended by deleting such
Exhibit in its entirety and substituting therefor Exhibit E attached to this
Amendment.

          1.3.2 Exhibit J, "[**], attached to this Amendment, is hereby added as
an Exhibit to the Agreement.

     1.4  Warranty Amendments.

          1.4.1 Section 6.1 of the Agreement is hereby amended by adding the
following to the end of such Section:

          [**]

          1.4.2 In Exhibit C of the Agreement, the first sentence of the
paragraph "Limited Warranty" is hereby amended by deleting the phrase "one year
from delivery to an End User, but no more than fifteen (15) months from delivery
to BIO-RAD" and substituting therefor:

          [**]

     1.5  Defined Terms Amendments.

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          1.5.1 Section 1.5 is hereby amended by deleting such Section in its
entirety.

          1.5.2 Section 1.11 is hereby amended by deleting such Section in its
entirety and substituting therefor the following

          "Luminex Systems" means the following laser based fluorescent
analytical test systems:

                                               Luminex Part Number

          Standard Luminex 100                        [**]
          [**]                                        [**]
          [**]                                        [**]
          Luminex Sheath Delivery System              CNS001-01
          Luminex XY Platform                         CNX002-01

          * Defined further below

          [**] (for BIO-RAD's Life Sciences Group):

          [**]

          [**] (for BIO-RAD's Clinical Diagnostics Division):

          [**]

          1.5.3 All references in the Agreement to "Bio-Rad System" or
"Luminex100 System" are hereby amended to be references to "Luminex Systems."

          1.5.4 All references in the Agreement to "Luminex100 Purchase Price"
(including the definition of such term) are hereby amended to be references to
"System Purchase Price."

2.   Effect of Amendment.

     2.1 This Amendment amends the Agreement to incorporate the terms and
conditions set forth in this Amendment. The relationship of the Parties shall
continue to be governed by the terms and conditions of the Agreement, as amended
herein; and in the event that there is any conflict between the terms and
conditions of the Agreement and this Amendment, the terms and conditions of this
Amendment shall control.

     2.2 As used in this Amendment, all capitalized terms shall have the
meanings defined for such terms in this Amendment or, if not defined in the
Amendment, the meanings defined in the Agreement.

     2.3 This Amendment (including the Exhibits hereto) constitute the entire
agreement between the Parties in connection with the subject matter hereof and
supersede all prior and contemporaneous

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requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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agreements, understandings, negotiations and discussions, whether oral or
written, of the Parties with respect to such subject matter.

         IN WITNESS WHEREOF, the Parties have executed this Amendment to be
effective as of the date first written above.

LUMINEX CORPORATION                    BIO-RAD CORPORATION

By: /s/ RANDEL S. MARFIN               By: /s/ SANFORD S. WADLER
   ---------------------------            ----------------------------
Name:   Randel S. Marfin               Name:    Sanford S. Wadler
     -------------------------              --------------------------
Title: Vice President                  Title: Vice President
      ------------------------               -------------------------

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requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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                                    EXHIBIT E

                             SYSTEM PURCHASE PRICING

[**]

These System Purchase Prices will be effective until [**], after which time
LUMINEX may, at its option, [**] increase the System Purchase Prices effective
on [**] written notice to BIO-RAD, provided that such increases (i) may occur no
more frequently than [**] and (ii) shall not exceed (a) [**] during the [**]
period beginning [**] and (b) the [**] increase in the [**] beginning on or
after [**]. Any increase in the System Purchase Prices shall be effective for
all Luminex Systems ordered after such notice. [**]

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requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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                                    EXHIBIT F

                BIO-RAD CARBOXYLATED MULTI-ANALYTE MAGNETIC BEADS

[**]

LUMINEX will treat the Magnetic Beads to meet the required performance
specifications listed in the table below.

[**]

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requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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                                    EXHIBIT G

                       BIO-RAD MAGNETIC BEAD TOLLING FEES

[**]

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requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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                                    EXHIBIT H

                              BIO-RAD BEAD PRICING

                                      [**]

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requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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                                    EXHIBIT I

                                      [**]

Following are the mutually [**].  These Specifications [**].

[**]

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requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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                                    EXHIBIT J

                                      [**]

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[**] Indicates that material has been omitted and confidential treatment
requested therefor. All such material has been filed separately with the
Commission pursuant to Rule 24b-2.

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