UNITED STATES
               SECURITIES AND EXCHANGE COMMISSION

                    Washington, D.C.  20549


                          SCHEDULE 13D


           Under the Securities Exchange Act of 1934
                         AMENDMENT NO. 1


    Southwest Royalties Institutional Income Fund X-B, L.P.
                        (Name of Issuer)


                 Limited Partnership Interests
                 (Title of Class of Securities)


                         Not Applicable
                         (CUSIP Number)


                         L. Paul Latham
                 Clayton Williams Energy, Inc.
                   6 Desta Drive, Suite 6500
                   Midland, Texas 79705-5510
                         (432) 682-6324
                (Name, Address and Telephone Number of Person
       Authorized to Receive Notices and Communications)


                       September 30, 2005
    (Date of Event which Requires Filing of this Statement)


If the filing person has previously filed a statement on Schedule
13G  to  report  the  acquisition that is  the  subject  of  this
Schedule  13D,  and is filing this schedule because  of  240.13d-
1(e), 240.13d-1(f) or 240.13d-1(g), check the following box:  ?






                    CUSIP No. Not Applicable

  (1) Names of Reporting Persons         Clayton Williams Energy,
Inc.

 (2) Check the Appropriate Box          (a)
     if a Member of a Group             (b)  X

 (3) SEC Use Only

 (4) Source of Funds                    AF

 (5) Check if Disclosure of Legal
     Proceedings is Required
     Pursuant to Items 2(d) or 2(e)          Not Applicable

 (6) Citizenship or Place of
     Organization                       Delaware corporation


Number  of  Shares/Units  Beneficially Owned  by  Each  Reporting
Person With:


 (7) Sole Voting Power                  1,361.0 Units

 (8) Share Voting Power                 None

 (9) Sole Dispositive Power             1,361.0 Units

(10) Shared Dispositive Power           None

(11) Aggregate Amount Beneficially
     Owned by Each Reporting Person          1,361.0 Units

(12) Check if the Aggregate Amount
     in Row (11) Excludes Certain
     Shares                             Not Applicable

(13) Percent of Class Represented
     by Amount in Row (11)              12.2% of class of
                                   11,181 Units

                                            (14) Type of Reporting
                                       Person                  HC
                                       (sole  parent  company  of
                                       the    Managing    General
                                       Partner of Issuer)



Item 1.                                 Type     of     Security:
                                        Limited       Partnership
                                        Interests ("Units")

                                             Name of Issuer:
                                        Southwest Royalties
                                        Institutional Income X-B,
                                        L.P.

          Address of Issuer's           6 Desta Drive
          Principal Executive           Suite 6500
          Offices:                      Midland, Texas 79705

Item 2(a).     Name of Person
           Filing:                       Clayton Williams Energy,
Inc.

Item  2(b).     Address of Principal               6 Desta Drive,
Suite 6500
          Business Office:                   Midland, Texas 79705

Item 2(c).     Present Occupation:           Not Applicable

Item 2(d).     Criminal Convictions:              None

Item 2(e).     Civil Securities Laws
          Injunctions or
          Prohibitions:                 None

Item   2(f).       Citizenship:                         Delaware,
U.S.A.

Item 3.                                 Source of Funds:

     Southwest  Royalties, Inc., as Managing General  Partner  of
     the  Issuer, used its working capital to acquire Units  (see
     Item  4). As sole stockholder of Southwest Royalties,  Inc.,
     the  Reporting Person owns an indirect interest in the Units
     acquired by Southwest Royalties, Inc.

Item 4.   Purpose of Transactions:

     Southwest Royalties, Inc. satisfied the requirements of  the
     Right of Presentment contained in the Issuer's Agreement  of
     Limited  Partnership whereby Southwest Royalties,  Inc.,  as
     Managing  General  Partner, agrees  to  acquire  Units  from
     limited  partners  seeking an exit  from  the  Issuer  at  a
     formula price. The Reporting Person, as sole stockholder  of
     Southwest Royalties, Inc., owns an indirect interest in  the
     Units acquired.

Item 5.        Interest in Securities

     Southwest  Royalties,  Inc., which is the  Managing  General
     Partner  of  the Issuer, holds a total of 1,361.0  Units  of
     limited partnership interests over which it has sole  voting
     and dispositive powers. As the sole stockholder of Southwest
     Royalties,  Inc.,  the Reporting Person  holds  an  indirect
     interest of 1,361.0 limited partnership Units.  These  Units
     represent 12.2% of the total 11,181 Units, which are  issued
     and  outstanding. The purchase transactions, which  resulted
     in the indirect ownership of the Reporting Person increasing
     from  11.1%  to 12.2%, occurred between March 15,  2005  and
     September  30,  2005  when  the  Managing  General   Partner
     purchased  an  additional 117 Units as part of the  Issuer's
     Right of Presentment program. The price per unit ranged from
     $74.31 to $135.53.


Item 6.   Contracts, Arrangements,
          Undertakings or Relationships
          with Respect to Securities of
          the Issuer:                             Not Applicable

Item 7.   Material to Be Filed as
          Exhibits:                          Not Applicable



                           SIGNATURE


     After reasonable inquiry and to the best of my knowledge and
belief,  I  certify  that  the  information  set  forth  in  this
statement is true, complete and correct.





Date: October 5, 2005              By:  /s/ L. Paul Latham
                              ----------------------------------
                              L. Paul Latham, President and
                              Chief Executive Officer,
                              of Southwest Royalties, Inc.
                              the Managing General Partner