SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* CHESAPEAKE ENERGY CORP (Last) (First) (Middle) 6100 NORTH WESTERN AVENUE (Street) OKLAHOMA CITY OK 73118 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Bronco Drilling Company, Inc. [ BRNC ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 06/06/2011
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock, par value $0.01 per share(1)(2)	06/06/2011		P		24,278,257	A	$11	24,278,257	I	See Footnote(3)
Common Stock, par value $0.01 per share(4)	06/06/2011		P		63,550,899	A	$11	87,829,156	I	See Footnote(3)
Common Stock, par value $0.01 per share	06/06/2011		P		4,521,802(5)	A	$11	1,000(6)	I	See Footnote(3)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person* CHESAPEAKE ENERGY CORP (Last) (First) (Middle) 6100 NORTH WESTERN AVENUE (Street) OKLAHOMA CITY OK 73118 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* CHESAPEAKE OPERATING INC (Last) (First) (Middle) 6100 NORTH WESTERN AVENUE (Street) OKLAHOMA CITY OK 73118 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* CHESAPEAKE OILFIELD SERVICES LLC (Last) (First) (Middle) 6100 NORTH WESTERN AVENUE (Street) OKLAHOMA CITY OK 73118 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* NOMAC DRILLING LLC (Last) (First) (Middle) 6100 NORTH WESTERN AVENUE (Street) OKLAHOMA CITY OK 73118 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Nomac Acquisition, Inc. (Last) (First) (Middle) 6100 NORTH WESTERN AVENUE (Street) OKLAHOMA CITY OK 73118 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. This form is a joint filing by Chesapeake Energy Corporation ("Chesapeake"), Chesapeake Operating, Inc., a direct wholly owned subsidiary of Chesapeake ("Operating"), Chesapeake Oilfield Services, L.L.C. ("Oilfield"), a direct wholly owned subsidiary of Operating, Nomac Drilling, L.L.C., a direct wholly owned subsidiary of Oilfield ("Drilling") and Nomac Acquisition Inc., a direct wholly owned subsidiary of Drilling ("Nomac").

2. Shares of Common Stock, par value $0.01 per share (the "Shares"), of Bronco Drilling Company, Inc. ("Bronco") acquired pursuant to the tender offer effected pursuant to the Agreement and Plan of Merger, dated as of April 14, 2011 and amended as of May 17, 2011 (as so amended, the "Merger Agreement"), by and among Chesapeake, Nomac and Bronco (such tender offer, the "Offer").

3. Shares were held by Nomac. As Nomac is an indirect wholly owned subsidiary of Chesapeake, Operating and Oilfield and a direct wholly owned subsidiary of Drilling, each of Chesapeake, Operating, Oilfield and Drilling may be deemed to have acquired indirect beneficial ownership of the Shares.

4. Shares acquired pursuant to the exercise of "top-up" option to purchase additional shares from Bronco, at $11.00 per share, under the terms of the Merger Agreement.

5. Reflects all of the outstanding shares of Bronco Drilling Company, Inc. not tendered in the Offer, which may be deemed to have been acquired by Chesapeake and Nomac pursuant to the consummation of the Merger (as defined below).

6. Following the exercise of the "top-up" option, Nomac was merged with and into Bronco, with Bronco surviving the Merger as an indirect wholly owned subsidiary of Chesapeake pursuant to a "short-form merger" under Delaware law (the "Merger"). At the effective time of the Merger, all of Bronco's previously outstanding stock held by the registrants were canceled. Prior to the Merger, Drilling directly held, and therefore Chesapeake, Operating and Oilfield may be deemed to have indirectly held, 1,000 shares of Nomac, which represented all of the issued and outstanding capital stock of Nomac. At the effective time of the Merger, each share of Nomac was converted into a share of the surviving company's stock.

Remarks:

Exhibit List: Exhibit 99.1 - Joint Filer Information; Exhibit 99.2 - Joint Filer Signatures

	/s/ Domenic J. Dell'Osso, Jr., Executive Vice President and Chief Financial Officer for CHESAPEAKE ENERGY CORPORATION	06/07/2011
	/s/ Domenic J. Dell'Osso, Jr., Executive Vice President and Chief Financial Officer for CHESAPEAKE OPERATING, INC.	06/07/2011
	/s/ Domenic J. Dell'Osso, Jr., Executive Vice President and Chief Financial Officer for CHESAPEAKE OILFIELD SERVICES, L.L.C.	06/07/2011
	/s/ Domenic J. Dell'Osso, Jr., Executive Vice President and Chief Financial Officer for NOMAC DRILLING, L.L.C.	06/07/2011
	/s/ Domenic J. Dell'Osso, Jr., Executive Vice President and Chief Financial Officer for NOMAC ACQUISITION, INC.	06/07/2011
	** Signature of Reporting Person	Date
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