CONVERTIBLE SENIOR SECURED PROMISSORY NOTE

Exhibit 99.1

THIS CONVERTIBLE SENIOR SECURED PROMISSORY NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED. NO SALE OR DISPOSITION MAY BE EFFECTED EXCEPT IN COMPLIANCE WITH RULE 144 UNDER SAID ACT OR AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN OPINION OF COUNSEL FOR THE HOLDER SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE ACT OR RECEIPT OF A NO-ACTION LETTER FROM THE SECURITIES AND EXCHANGE COMMISSION.

CONVERTIBLE SENIOR SECURED PROMISSORY NOTE

FOR VALUE RECEIVED, HEARTLAND OIL AND GAS CORP. (“ Maker ,” or, the “ Company ”), whose address is 1625 Broadway, Suite 1480, Denver, Colorado 80202, promises to pay to the order of                      (“ Payee ”), at places designated in writing in advance by Payee, when due, the principal sum of                      ($              ) (the “ Principal Amount ”), which amount constitutes the sum of $              delivered to the Company by Payee on the date hereof, plus $              representing the total number of shares of the Company’s Series B Preferred Stock held by Payee immediately prior to the issuance of this Note and exchanged therefore. The obligations of Maker under this Note are secured by the Security Agreement of even date herewith, as it may be amended from time to time, between Maker and Payee.

1. Interest . No interest shall accrue on the Principal Amount.

2. Payments . The Principal Amount shall be due and payable on the earlier of (a) March 28, 2007 and (b) the closing date of any Subsequent Financing (the “ Maturity Date ”). All amounts payable hereunder are payable in lawful money of the United States of America. Payment shall be deemed made and effective at 11:59 p.m. Colorado time on the date of payment, regardless of the actual time of delivery of such payment. “ Subsequent Financing ” means a financing occurring after the date hereof and on or prior to the Maturity Date in which Maker issues (i) equity or equity-linked securities, or (ii) debt which is convertible into equity, in which there is an equity component, or which could otherwise result in the issuance of equity securities (“ Additional Securities ”).

3. Prepayment at Option of Maker . Maker may prepay in cash all (but not less than all) of the Principal Amount of this Note prior to the Maturity Date without the prior written consent of Payee.

4. Consent Requirements . So long as any Principal Amount remains outstanding hereunder, Maker shall not, in each case without first obtaining the prior written consent of Payee:

(a) redeem, repurchase or otherwise acquire, or declare or pay any cash dividend or distribution on, any capital stock of Maker;

(b) increase the par value of Maker’s common stock;

(c) create or issue any debt securities or incur any indebtedness or redeem, repurchase, prepay or otherwise acquire any outstanding debt securities or indebtedness of Maker (other than trade payables incurred in the ordinary course of business consistent with past practice), except as expressly required by the terms of such securities or indebtedness;

(d) sell all or substantially all of Maker’s assets or stock, or consolidate or merge with another entity;

(e) liquidate, dissolve, recapitalize or reorganize;

(f) enter into any agreement, commitment, understanding or other arrangement to take any of the foregoing actions; or

(g) cause or authorize any subsidiary of Maker to engage in any of the foregoing actions.

5. Optional Conversion .

(a) Subject to Sections 6 and 7, Payee may convert this Note on the Maturity Date into that number of shares of common stock of Maker that results from dividing the Principal Amount by $0.04.

(b) Payee shall effect the conversion of this Note pursuant to this Section 5 by providing notice to Maker of its intent to convert and surrendering this Note to Maker. Not later than three trading days after receipt of such notice and the surrendered Note from Payee, Maker shall deliver to Payee a certificate or certificates representing the number of shares of common stock being acquired upon the conversion of this Note.

(c) In case Maker shall, after the original issue date of this Note (i) subdivide its outstanding shares of common stock into a greater number of shares or issue additional shares of common stock for no consideration as a stock dividend, (ii) combine its outstanding shares of common stock into a smaller number of shares of common stock, or (iii) issue any shares of its capital stock in a reclassification of the common stock, then the number of common shares receivable upon conversion of this Note immediately prior thereto shall be adjusted so that Payee shall be entitled to receive the kind and number of common shares or other securities of Maker which it would have owned or have been entitled to receive had this Note

been converted in advance thereof. An adjustment made pursuant to this paragraph shall become effective immediately after the effective date of such event retroactive to the record date, if any, for such event.

6. Conversion Upon a Qualified Financing . Subject to Section 7, the holder of this Note shall participate in a Qualified Financing (as defined below), in accordance with the following provisions:

(a) At least ten (10) trading days prior to the anticipated closing of a Qualified Financing, the Company shall deliver a notice (the “ Notice ”) to the holder stating (A) its bona fide intention to offer such Additional Securities, (B) the number of such Additional Securities to be offered, (C) the price and terms upon which it proposes to offer such Additional Securities, and (D) the anticipated closing date of the sale of such Additional Securities.

(b) At the closing of such Qualified Financing, the holder shall (i) purchase, at the price and on the terms specified in the Notice, that portion of such Additional Securities that have a total purchase price equal to $              ; and (ii) surrender this Note to the Company in consideration for such Additional Securities. The remaining Principal Amount not converted into such Additional Securities in accordance with this Section 6 shall be deemed satisfied in full upon surrender of this Note in accordance with this Section 6.

(c) In addition to the Additional Securities purchased by the holder of this Note in accordance with Section 6(b), at the closing of such Qualified Financing, the holder of this Note may purchase, together with the other holder(s) of Senior Secured Convertible Promissory Note(s) issued by the Company of like kind (together, the “ Note Holders ”), Additional Securities having an aggregate purchase price equal to $2,000,000, at the price and on the terms specified in the Notice, the purchase price for which shall be paid by wire transfer of immediately available funds to such account as the Company shall designate for such purpose. Notwithstanding Section 6(b), if the Note Holders do not purchase Additional Securities in a Qualified Financing accordance with this Section 6(c), then upon the closing of such Qualified Financing, this Note shall automatically convert into (i) that number of Additional Securities being issued and sold in such Qualified Financing that results from dividing $              by the purchase price per share of such Additional Securities paid by the investor(s) in such Qualified Financing, and (ii)                   shares of the Company’s Series B Preferred Stock or such other series or class of the Company’s preferred stock as shall have equivalent terms and preferences as set forth in the Certificate on the date hereof (excluding the rights set forth in Article XIII of the Certificate of Designation, Preferences and Rights relating to the Company’s Series B Preferred Stock (the “ Certificate ”)). Any preferred shares issued pursuant to 6(c)(ii) are referred to herein as “ Preferred Shares ”) For the avoidance of doubt, the remedies set forth in this Section 6(c) shall be the Company’s exclusive remedies for the failure by the Note Holders to purchase Additional Securities in a Qualified Financing