COMMON UNIT PURCHASE AGREEMENT

Exhibit 1.2

COMMON UNIT PURCHASE AGREEMENT

by and among

ENTERPRISE PRODUCTS OPERATING LLC

ENTERPRISE GTM HOLDINGS L.P.

as Sellers

and

DUNCAN ENERGY PARTNERS L.P.

as Buyer

Dated as of June 15, 2009

TABLE OF CONTENTS

COMMON UNIT PURCHASE AGREEMENT

     THIS COMMON UNIT PURCHASE AGREEMENT (this “ Agreement ”) dated as of June 15, 2009, is made and entered into by and among Enterprise Products Operating LLC, a Texas limited liability company (“ EPO ”), and Enterprise GTM Holdings L.P., a Delaware limited partnership (“ Enterprise GTM ”, and together with EPO, the “ Sellers ”; and each a “ Seller ”), as Sellers, and Duncan Energy Partners L.P., a Delaware limited partnership (the “ Partnership ” and the “ Buyer ”), as Buyer. The above-named entities are sometimes referred to in this Agreement each as a “ Party ” and collectively as the “ Parties .” Certain capitalized terms used are defined in Article I hereof.

RECITALS

     WHEREAS, EPO currently owns 5,393,100 common units representing limited partner interests in the Partnership (“ Common Units ”) and Enterprise GTM currently owns 37,333,887 Common Units; and

     WHEREAS, the Partnership is willing to repurchase all 5,393,100 of such Common Units owned directly by EPO and up to 3,806,900 Common Units owned directly by Enterprise GTM (or such other number of Common Units agreed upon by Enterprise GTM and the Partnership on or after the date hereof), such aggregate number of Common Units to equal the number of Common Units the Partnership will concurrently issue and sell to other investors in connection with the Offering (described below); and

     WHEREAS, in order to accomplish the objectives and purposes in the preceding recital, concurrently with the consummation of the transactions contemplated hereby, each of the following matters shall occur:

          1. The Partnership, through a group of underwriters (the “ Underwriters ”), proposes to issue up to 8,000,000 Common Units (or up to 9,200,000 Common Units if the Underwriters exercise any option to purchase up to an additional 1,200,000 Common Units to cover over-allotments), through a public offering (the “ Offering ”);

          2. The public, through the Underwriters, will contribute all of the Offering proceeds, net of the underwriters’ discounts and commissions (but without giving effect to any reimbursement by the Underwriters to the Partnership for expenses), to the Partnership in exchange for the Common Units issued in the Offering (such net Offering proceeds, the “ Offering Proceeds ”); and

          3. The Partnership will use the Offering Proceeds to repurchase an aggregate number of Common Units owned directly by EPO and Enterprise GTM (the “ Subject Interests ”) equal to the aggregate number of, and at the same net purchase price per Common Unit as, the Common Units offered and sold in the Offering.

     NOW, THEREFORE, in consideration of their mutual undertakings and agreements hereunder, the Parties undertake and agree as follows:

ARTICLE I
DEFINITIONS; RECORDATION

      1.1 Definitions . Capitalized terms used herein and not defined elsewhere in this Agreement shall have the meanings given such terms as is set forth below.

     “ Agreement ” has the meaning assigned to such term in the first paragraph of this Agreement.

     “ Buyer ” has the meaning assigned to such term in the first paragraph of this Agreement.

     “ Cash Consideration ” has the meaning assigned to such term in Section 2.1 .

     “ Common Units ” has the meaning assigned to such term in the recitals to this Agreement.

     “ Closing ” means the closing of the sale of the Subject Interests pursuant to this Agreement, which shall occur concurrent with the applicable closing of the Offering (including, as applicable, any over-allotment closing of the Offering).

     “ Effective Date ” means June 15, 2009.

     “ EPO ” has the meaning assigned to such term in the first paragraph of this Agreement.

     “ Laws ” means any and all laws, statutes, ordinances, rules or regulations promulgated by a governmental authority, orders of a governmental authority, judicial decisions, decisions of arbitrators or determinations of any governmental authority or court.

     “ Offering ” has the meaning assigned to such term in the recitals to this Agreement.

     “ Offering Proceeds ” has the meaning assigned to such term in the recitals to this Agreement.

     “ Partnership ” has the meaning assigned to such term in the first paragraph of this Agreement.

     “ Partnership Agreement ” means the Amended and Restated Agreement of Limited Partnership, dated as of February 5, 2007, of the Partnership, as amended on the date hereof.

     “ Party ” and “ Parties ” have the meanings assigned to such terms in the first paragraph of this Agreement.

     “ Seller ” and “ Sellers ” have the meanings assigned to such terms in the first paragraph of this Agreement.

     “ Subject Interests ” has the meaning assigned to such term in the recitals to this Agreement.

     “ Underwriters ” has the meaning assigned to such term in the recitals to this Agreement.

     “ Underwriting Agreement ” has the meaning assigned to such term in Section 4.1 .

ARTICLE II
THE OFFERING AND RELATED TRANSACTIONS

      2.1 Pricing for Subject Interests . Buyer and Sellers hereby agree that the pricing of the Offering, and the cash consideration at which the Subject Interests shall be acquired by Buyer from Sellers equal to the Offering Proceeds (the “ Cash Consideration ”), shall be established by mutual written consent of Buyer and Sellers on or after the date hereof (no later than June 18, 2009) (which written consent may be evidenced in the form attached hereto as Annex A ). If the pricing of the Offering does not occur by June 18, 2009, this Agreement shall terminate and be of no further force or effect.

      2.2 Buyer’s Purchase, and Sellers’ Sale, of Common Units . At the Closing, each of the Sellers hereby agrees to sell, and the Buyer hereby agrees to purchase, the Subject Interests consisting of first, all 5,393,100 of such Common Units owned directly by EPO and second, up to 3,806,900 Common Units owned directly by Enterprise GTM (including with respect to up to 1,200,000 Common Units in connection with the exercise by the Underwriters of their over-allotment option), or such other number of Common Units agreed upon by Enterprise GTM and the Partnership on or after the date hereof, for the Cash Consideration agreed to by Buyer and Sellers as set forth in Section 2.1 above. Buyer and Enterprise GTM hereby agree that the number of Common Units to be purchased by Buyer from Enterprise GTM shall be confirmed by mutual written consent of Buyer and Enterprise GTM on or after the date hereof (which written consent may be evidenced in the form attached hereto as Annex