[DIAMOND M ONSHORE, INC. LETTERHEAD]


                                December 31, 1996



Drillers, Inc.
625 Paragon Center One
450 Gears Road
Houston, Texas 77067


Gentlemen:

                  Reference is hereby made to that certain Asset Purchase
Agreement, dated as of November 12, 1996 (the "Purchase Agreement"), between
Diamond M Onshore, Inc. (the "Company") and Drillers, Inc. ("Buyer"), to which
Diamond Offshore Drilling, Inc. is a party for the purposes of Article 12 and
Section 8.5 thereof and DI Industries, Inc. is a party for the purposes of
Article 13 thereof. All capitalized terms used in this letter (this "Agreement")
and not otherwise defined shall have the meanings assigned to them in the
Purchase Agreement.

                  The Purchase Agreement is hereby amended, effective as of the
Closing Date, as follows:

                  1.       Subsection 3.1(b)(iii)(y) is hereby amended to read
                           in its entirety as follows: "any necessary consents
                           to transfer or assign Contracts or Permits, to the
                           extent the same are transferable or assignable".

                  2.       Subsection 3.1(k) is hereby amended to insert the
                           word "not" in the third line of the first sentence
                           thereof immediately after the word "would" and
                           immediately before the word "result".

                  3.       Section 10.14 is hereby amended to read in its
                           entirety as follows:

                           "10.14 Survival. Except as provided in Sections 3.3
                           and 3.4, no representations, warranties, covenants or
                           agreements in this Agreement






                           shall survive the Closing except for Articles 6, 8,
                           9, 10, 12 and 13 and Sections 1.2, 1.6, 2.4 and
                           4.12."

                  Except as expressly herein amended, the Purchase Agreement
shall remain in full force and effect. All references to the Purchase Agreement
in the legal opinions, certificates, ancillary agreements and other documents
delivered at or in connection with the Closing shall be deemed to refer to the
Purchase Agreement as hereby amended.

                  This Agreement shall be governed by and construed in
accordance with the laws of the State of Texas, without giving effect to
conflict of laws rules or principles, and shall inure to the benefit of and be
binding upon the successors and assigns of the parties hereto; provided that
this Agreement may not be assigned by any party without the prior written
consent of all other parties. No provision of this Agreement may be amended,
modified or waived, except as a written document signed by all parties hereto.
This Agreement may be executed in counterparts, each of which shall be deemed to
be an original, but all of which, taken together, shall constitute one and the
same Agreement. This Agreement is not intended to be for the benefit of, and
shall not be enforceable by, any person or entity that is not a party hereto.

                  Please acknowledge receipt of this letter and confirm your
agreement concerning the matters stated herein by signing and returning the
enclosed copy hereof, whereupon this Agreement and your acceptance of the terms
and conditions herein provided shall constitute a binding Agreement between us.


Very truly yours,

DIAMOND M ONSHORE, INC.


By: /s/ Richard L. Lionberger
         Richard L. Lionberger
         Vice President

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Accepted and agreed to as of the date above first written:

DRILLERS, INC.


By: /s/ Ronnie McBride
Name:   Ronnie McBride
Title:    Sr. V.P. - Domestic Ops.


DI INDUSTRIES, INC.


By: /s/ Ronnie McBride
Name:   Ronnie McBride
Title:    Sr. V.P. - Domestic Ops.






DIAMOND OFFSHORE DRILLING, INC.


By: /s/ Richard L. Lionberger
Name:   Richard L. Lionberger
Title:    Vice President



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