| OMB APPROVAL                                                                                                       |
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| OMB Number:  3235-0058Expires:  April 30, 2012Estimated average burdenhours per response  2.50 |
| SEC FILE NUMBER000-49674                                                                                           |
| CUSIP NUMBER                                                                                                  |

| (Check one): |   | x Form 10-K   Form 20-F   Form 11-K   Form 10-Q   Form 10-D   Form N-SAR    Form N-CSR |
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|   |   | For Period Ended: December 31, 2011                                                                                  |
|--------|--------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |   |                                                                                                                                                                                                                                                                    |   | Transition Report on Form 10-K |
|   |   |                                                                                                                                                                                                                                                                    |   | Transition Report on Form 20-F |
|   |   |                                                                                                                                                                                                                                                                    |   | Transition Report on Form 11-K |
|   |   |                                                                                                                                                                                                                                                                    |   | Transition Report on Form 10-Q |
|   |   |                                                                                                                                                                                                                                                                    |   | Transition Report on Form N-SAR |
|   |   | For the Transition Period Ended:                                        |

| Read Instruction (on back page) Before Preparing Form. Please Print or TypeNothing in this form shall be construed to imply that the Commission has verified any information contained herein. |
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| PART I — REGISTRANT INFORMATION                     |
| Colorado 2001B Limited Partnership                        |
| Full Name of Registrant                                   |
|                                                      |
| Former Name if Applicable                                 |
|                                                      |
| 1775 Sherman Street, Suite 3000                           |
| Address of Principal Executive Office (Street and Number) |
|                                                      |
| Denver, CO  80203                               |
| City, State and Zip Code                                  |
|                                                      |

|   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |   |     |
|--------|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------|----------|
| (a)    |   | The reason described in reasonable detail in Part III of this form could not be eliminated without unreasonable effort or expense                                                                                                                                                                                                                                                                                                                                                                            |   |   x |
| (b)    |   | The subject annual report, semi-annual report, transition report on Form 10-K, Form 20-F, Form 11-K, Form N-SAR or Form N-CSR, or portion thereof, will be filed on or before the fifteenth calendar day following the prescribed due date; or the subject quarterly report or transition report on Form 10-Q, or subject distribution report on Form 10-D, or  portion thereof, will be filed on or before the fifth calendar day following the prescribed due date; and |   |     |
| (c)    |   | The accountant’s statement or other exhibit required by Rule 12b-25(c) has been attached if applicable.                                                                                                                                                                                                                                                                                                                                                                                           |   |     |

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|            |                                                                          |
|-----------------|-------------------------------------------------------------------------------|
| (1)   | Name and telephone number of person to contact in regard to this notification |

| R. Scott Meyers                    |        |               |
|------------------------------------|-------------|--------------------|
| Chief Accounting Officer           |        |               |
| Petroleum Development Corporation, |        |               |
| Managing General Partner           | 304         | 842-3597           |
| (Name)                             | (Area Code) | (Telephone Number) |

| (2)   | Have all other periodic reports required under Section 13 or 15(d) of the Securities Exchange Act of 1934 or Section 30 of the Investment Company Act of 1940 during the preceding 12 months or for such shorter period that the registrant was required to file such report(s) been filed?  If answer is no, identify report(s).          Yes    No x                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|-----------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|            |  Form 10-K for the period from September 5, 2001 (date of inception) to December 31, 2001 (filing subsequently withdrawn)Form 10-Q for the quarter ended March 31, 2002 (filing subsequently withdrawn)Form 10-Q for the quarter ended June 30, 2002 (filing subsequently withdrawn) Form 10-Q for the quarter ended September 30, 2002 (filing subsequently withdrawn)Form 10-K for the year ended December 31, 2002 (filing subsequently withdrawn)Form 10-Q for the quarter ended March 31, 2003 (filing subsequently withdrawn)Form 10-Q for the quarter ended June 30, 2003 (filing subsequently withdrawn)Form 10-Q for the quarter ended September 30, 2003 (filing subsequently withdrawn)Form 10-K for the year ended December 31, 2003 (filing subsequently withdrawn)Form 10-Q for the quarter ended March 31, 2004 (filing subsequently withdrawn)Form 10-Q for the quarter ended June 30, 2004 (filing subsequently withdrawn)Form 10-Q for the quarter ended September 30, 2004 (filing subsequently withdrawn)Form 10-K for the year ended December 31, 2004 (filing subsequently withdrawn)Form 10-Q for the quarter ended March 31, 2005 (filing subsequently withdrawn)Form 10-Q for the quarter ended June 30, 2005Form 10-Q for the quarter ended September 30, 2005Form 10-K for the year ended December 31, 2005 |

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|   |   Form 10-Q for the quarter ended March 31, 2006Form 10-Q for the quarter ended June 30, 2006Form 10-Q for the quarter ended September 30, 2006Form 10-K for the year ended December 31, 2006Form 10-Q for the quarter ended March 31, 2007Form 10-Q for the quarter ended June 30, 2007Form 10-Q for the quarter ended September 30, 2007Form 10-K for the year ended December 31, 2007Form 10-Q for the quarter ended March 31, 2008Form 10-Q for the quarter ended June 30, 2008Form 10-Q for the quarter ended September 30, 2008Form 10-K for the year ended December 31, 2008Form 10-Q for the quarter ended March 31, 2009Form 10-Q for the quarter ended June 30, 2009Form 10-Q for the quarter ended September 30, 2009Form 10-K for the year ended December 31, 2009Form 10-Q for the quarter ended March 31, 2010Form 10-Q for the quarter ended June 30, 2010Form 10-Q for the quarter ended September 30, 2010Form 10-K for the year ended December 31, 2010Form 10-Q for the quarter ended March 31, 2011Form 10-Q for the quarter ended June 30, 2011Form 10-Q for the quarter ended September 30, 2011Form 10-K for the year ended December 31, 2011 |
|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (3)   | Is it anticipated that any significant change in results of operations from the corresponding period for the last fiscal year will be reflected by the earnings statements to be included in the subject report or portion thereof?           Yes   No x If so, attach an explanation of the anticipated change, both narratively and quantitatively, and, if appropriate, state the reasons why a reasonable estimate of the results cannot be made. We cannot comment on the results of our operations for the years ended December 31, 2011 and 2010 until the ultimate resolution of the matter discussed above. |
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|  Colorado 2001B Limited Partnership     |
|----------------------------------------------|
| ________________________________             |
| (Name of Registrant as specified in charter) |
|                                         |

|                           |   |   |   |                                                                               |
|--------------------------------|--------|--------|--------|------------------------------------------------------------------------------------|
| Date:  April 2, 2012 |   | By     |   | /s/ Gysle R. Shellum                                                               |
|                           |   |   |   | Gysle R. Shellum,Chief Financial Officer of Petroleum Development Corporation |