UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 14)*

TransAtlantic Petroleum Ltd.

(Name of Issuer)

Common Shares, no par value

(Title of Class of Securities)

G89982113

(CUSIP Number)

Dalea Management, LLC

16803 Dallas Parkway Suite 300

Addison, Texas 75001

Attention: Christine Stroud

(972) 590-9879

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

April 7, 2016

(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 Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box ¨.

Note. Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of section 18 of the Securities Exchange Act of 1934 (the “Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Schedule 13D/A

Schedule 13D/A

Schedule 13D/A

Schedule 13D/A

Schedule 13D/A

Schedule 13D/A

Schedule 13D/A

Schedule 13D/A

AMENDMENT NO. 14 TO SCHEDULE 13D

This Amendment No. 14 to Schedule 13D (this “Fourteenth Amendment”) amends and supplements the Schedule 13D originally filed on April 17, 2008, as amended by Amendment No. 1 on June 25, 2008, Amendment No. 2 on August 28, 2008, Amendment No. 3 on September 29, 2008, Amendment No. 4 on December 30, 2008, Amendment No. 5 on July 2, 2009, Amendment No. 6 on December 3, 2009, Amendment No. 7 on September 13, 2010, Amendment No. 8 on May 17, 2011, Amendment No. 9 on March 23, 2012, Amendment No. 10 on January 10, 2014, Amendment No. 11 on January 14, 2015, Amendment No. 12 on May 5, 2015, and Amendment No. 13 on August 28, 2015 (collectively, the “Schedule 13D”). Unless otherwise indicated, all capitalized terms used but not defined herein shall have the same meaning ascribed to them in the Schedule 13D.

This Fourteenth Amendment is being filed to make updates and amendments to the Schedule 13D as follows:

Item 1. Security and Issuer

There are no changes to the Item 1 information previously filed.

Item 2. Identity and Background

Item 2 is hereby amended and supplemented by (i) revising the definition of “Reporting Persons” to also include ANBE Holdings and ANBE, LLC and (ii) adding the following paragraphs thereto:

ANBE Holdings, L.P. (“ANBE Holdings”), is a limited partnership organized under the laws of the State of Texas. Its principal business is to hold certain of the Mitchell Family’s investments. Each of Amy Mitchell and Mitchell’s four adult children, Alexandria Nicole Mitchell Jacobs, Noah Malone Mitchell, 4^th, Stevenson Briggs Mitchell and Elizabeth Lee Mitchell Howard, owns a 24.75% equity interest in ANBE Holdings and ANBE, LLC owns a 1% equity interest in ANBE Holdings.

ANBE, LLC is a limited liability company organized under the laws of the State of Texas. Its principal business is to manage ANBE Holdings. ANBE, LLC is the sole general partner of ANBE Holdings and is owned 50% by Mitchell and 50% by Amy Mitchell.

Item 3. Source and Amount of Funds or Other Consideration

Item 3 is hereby amended and supplemented by adding the following paragraphs thereto:

On December 30, 2015, the Issuer entered into a $5.0 million draw down convertible promissory note (the “ANBE Note”) with ANBE Holdings. The ANBE Note bears interest at a rate of 13.0% per annum and matures on June 30, 2016. On December 30, 2015, the Issuer borrowed $3.6 million (the “Initial Advance”) under the ANBE Note. Issuer can request subsequent advances under the ANBE Note prior to June 15, 2016. Each subsequent advance must be in a multiple of $500,000, or if the amount remaining for advance under the ANBE Note is less than $500,000, such lesser amount. The ANBE Note provides that advances under the ANBE Note are convertible into Issuer’s common shares, at the election of the holder, any time after the NYSE MKT approves the Issuer’s application to list the additional common shares issuable pursuant to the conversion feature of the ANBE Note, which approval was obtained on April 7, 2016, and prior to the maturity of the Note. The conversion price per Issuer’s common share for each advance is equal to 105% of the closing price of the Issuer’s common shares on the NYSE MKT on the trading date immediately prior to such advance. The conversion price of the Initial Advance is $1.3755 per share.

ANBE Holdings used the proceeds from four loans from trusts of each of its limited partners, each in the original the principal amount $1.0 million, to fund the Initial Advance. The loans are evidenced by promissory notes dated December 28, 2015 made by ANBE Holdings in favor of each of Alexandria Nicole Mitchell Trust #2005 (the “Alexandria Trust Note”), Noah Malone Mitchell, 4th Trust #2005 (the “Noah Trust Note”), Stevenson Briggs Mitchell Trust #2005 (the “Stevenson Trust Note”), and Elizabeth Lee Mitchell Trust #2005 (the “Elizabeth Trust Note”), bearing interest at a rate of 13.0% per annum and maturing on June 30, 2016.

Item 4. Purpose of the Transaction

There are no changes to the Item 4 information previously filed.

Item 5. Interest in Securities of the Issuer

Items 5(a) and 5(b) are hereby amended and restated to read in their entirety as follows:

There are no further changes to the Item 5 information previously filed.

Item 6. Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer

There are no changes to the Item 6 information previously filed.

Item 7. Material to be Filed As Exhibits.

SIGNATURE

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

Exhibit 1

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) under the Securities and Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a Statement on Schedule 13D (including any and all amendments thereto) with respect to the common shares par value $.10 per share, of Transatlantic Petroleum Ltd., and further agree that this Joint Filing Agreement shall be included as an exhibit to such joint filings.

The undersigned further agree that each party hereto is responsible for the timely filing of such Statement on Schedule 13D and any amendments thereto, and for the accuracy and completeness of the information concerning such party contained therein; provided, however, that no party is responsible for the accuracy or completeness of the information concerning any other party, unless such party knows or has a reason to believe that such information is inaccurate.

This Joint Filing Agreement may be signed in counterparts with the same effect as if the signature on each counterpart were upon the same instrument.

IN WITNESS WHEREOF, the undersigned have hereunto set their hands as of the 12^th day of April, 2016.

Exhibit 3

Final Execution

PROMISSORY NOTE

FOR VALUE RECEIVED, the undersigned, ANBE Holdings, L.P., a Texas limited partnership (“Maker”), hereby promises to pay to the order of Alexandria Nicole Mitchell Trust #2005, (“Holder”), in lawful money of the United States of America, the principal sum of One Million Dollars and 00/100 ($1,000,000.00) (“Principal”), together with interest as set forth below (the “Note”).

Maturity Date: June 30, 2016

Interest Rate: Except as otherwise provided herein, this Note will bear interest from the execution date of this Note, until payment in full at a per annum rate equal to thirteen percent (13%). All interest will be compounded monthly and computed as a per diem charge for the actual number of days elapsed on the basis of a year consisting of three hundred sixty (360) days.

Default Rate: Each payment will be applied first to the payment of accrued unpaid interest and the balance, if any, will be applied to the unpaid principal balance of this Note. Any sum not paid when due will bear interest at a per annum rate equal to fifteen percent (15%) compounded monthly. Maker may prepay any amounts owed hereunder without premium or penalty.

If Maker fails to pay any amount when due under this Note, at the option of the Holder, the entire unpaid indebtedness evidenced by this Note will become due, payable and collectible then or thereafter as the Holder may elect, regardless of the date of maturity of this Note. Failure by the Holder to exercise such option will not constitute a waiver of the right to exercise the same in the event of any subsequent default.

Place for Payment: Principal and interest are payable to the Holder of this Note at 16803 Dallas Parkway, Addison, Texas 75001 or at any other address of which Payee may notify Maker in writing.

Prepayment of Principal: The Principal may be paid in whole or in part at any time before the Maturity Date, without penalty.

Terms of Payment of Principal and Interest: The Principal Amount and all accrued interest will be due in full at the Maturity Date.

To the extent permitted by applicable law, Maker waives notice, presentment, demand for payment, protest, notice of protest and non-payment or dishonor, notice of acceleration, notice of intent to accelerate, notice of intent to demand, diligence in collecting, grace, and all other formalities of any kind.

If this Note is place in the hands of an attorney for collection or if collection is attempted by suit or through probate, bankruptcy, insolvency, or other judicial proceedings, the Maker agrees to pay the collection expenses of the Payee, including reasonable attorneys’ fees. In the event judgment is rendered on any indebtedness evidenced by this Note, such amount shall bear interest at the highest lawful rate.

This Note shall be governed in all respects by the laws of the State of Texas, not including its conflict of law provisions.

ANBE HOLDINGS, L.P. PROMISSORY NOTE - PAGE 1 OF 2

ANBE HOLDINGS, L.P. PROMISSORY NOTE - PAGE 2 OF 2

Exhibit 4

Final Execution

PROMISSORY NOTE

FOR VALUE RECEIVED, the undersigned, ANBE Holdings, L.P., a Texas limited partnership (“Maker”), hereby promises to pay to the order of Noah Malone Mitchell, 4^th Trust #2005, (“Holder”), in lawful money of the United States of America, the principal sum of One Million Dollars and 00/100 ($1,000,000.00) (“Principal”), together with interest as set forth below (the “Note”).

Maturity Date: June 30, 2016

Interest Rate: Except as otherwise provided herein, this Note will bear interest from the execution date of this Note, until payment in full at a per annum rate equal to thirteen percent (13%). All interest will be compounded monthly and computed as a per diem charge for the actual number of days elapsed on the basis of a year consisting of three hundred sixty (360) days.

Default Rate: Each payment will be applied first to the payment of accrued unpaid interest and the balance, if any, will be applied to the unpaid principal balance of this Note. Any sum not paid when due will bear interest at a per annum rate equal to fifteen percent (15%) compounded monthly. Maker may prepay any amounts owed hereunder without premium or penalty.

If Maker fails to pay any amount when due under this Note, at the option of the Holder, the entire unpaid indebtedness evidenced by this Note will become due, payable and collectible then or thereafter as the Holder may elect, regardless of the date of maturity of this Note. Failure by the Holder to exercise such option will not constitute a waiver of the right to exercise the same in the event of any subsequent default.

Place for Payment: Principal and interest are payable to the Holder of this Note at 16803 Dallas Parkway, Addison, Texas 75001 or at any other address of which Payee may notify Maker in writing.

Prepayment of Principal: The Principal may be paid in whole or in part at any time before the Maturity Date, without penalty.

Terms of Payment of Principal and Interest: The Principal Amount and all accrued interest will be due in full at the Maturity Date.

To the extent permitted by applicable law, Maker waives notice, presentment, demand for payment, protest, notice of protest and non-payment or dishonor, notice of acceleration, notice of intent to accelerate, notice of intent to demand, diligence in collecting, grace, and all other formalities of any kind.

If this Note is place in the hands of an attorney for collection or if collection is attempted by suit or through probate, bankruptcy, insolvency, or other judicial proceedings, the Maker agrees to pay the collection expenses of the Payee, including reasonable attorneys’ fees. In the event judgment is rendered on any indebtedness evidenced by this Note, such amount shall bear interest at the highest lawful rate.

This Note shall be governed in all respects by the laws of the State of Texas, not including its conflict of law provisions.

ANBE HOLDINGS, L.P. PROMISSORY NOTE - PAGE 1 OF 2

ANBE HOLDINGS, L.P. PROMISSORY NOTE - PAGE 2 OF 2

Exhibit 5

Final Execution

PROMISSORY NOTE

FOR VALUE RECEIVED, the undersigned, ANBE Holdings, L.P., a Texas limited partnership (“Maker”), hereby promises to pay to the order of Stevenson Briggs Mitchell Trust #2005, (“Holder”), in lawful money of the United States of America, the principal sum of One Million Dollars and 00/100 ($1,000,000.00) (“Principal”), together with interest as set forth below (the “Note”).

Maturity Date: June 30, 2016

Interest Rate: Except as otherwise provided herein, this Note will bear interest from the execution date of this Note, until payment in full at a per annum rate equal to thirteen percent (13%). All interest will be compounded monthly and computed as a per diem charge for the actual number of days elapsed on the basis of a year consisting of three hundred sixty (360) days.

Default Rate: Each payment will be applied first to the payment of accrued unpaid interest and the balance, if any, will be applied to the unpaid principal balance of this Note. Any sum not paid when due will bear interest at a per annum rate equal to fifteen percent (15%) compounded monthly. Maker may prepay any amounts owed hereunder without premium or penalty.

If Maker fails to pay any amount when due under this Note, at the option of the Holder, the entire unpaid indebtedness evidenced by this Note will become due, payable and collectible then or thereafter as the Holder may elect, regardless of the date of maturity of this Note. Failure by the Holder to exercise such option will not constitute a waiver of the right to exercise the same in the event of any subsequent default.

Place for Payment: Principal and interest are payable to the Holder of this Note at 16803 Dallas Parkway, Addison, Texas 75001 or at any other address of which Payee may notify Maker in writing.

Prepayment of Principal: The Principal may be paid in whole or in part at any time before the Maturity Date, without penalty.

Terms of Payment of Principal and Interest: The Principal Amount and all accrued interest will be due in full at the Maturity Date.

To the extent permitted by applicable law, Maker waives notice, presentment, demand for payment, protest, notice of protest and non-payment or dishonor, notice of acceleration, notice of intent to accelerate, notice of intent to demand, diligence in collecting, grace, and all other formalities of any kind.

If this Note is place in the hands of an attorney for collection or if collection is attempted by suit or through probate, bankruptcy, insolvency, or other judicial proceedings, the Maker agrees to pay the collection expenses of the Payee, including reasonable attorneys’ fees. In the event judgment is rendered on any indebtedness evidenced by this Note, such amount shall bear interest at the highest lawful rate.

This Note shall be governed in all respects by the laws of the State of Texas, not including its conflict of law provisions.

ANBE HOLDINGS, L.P. PROMISSORY NOTE - PAGE 1 OF 2

ANBE HOLDINGS, L.P. PROMISSORY NOTE - PAGE 2 OF 2

Exhibit 6

Final Execution

PROMISSORY NOTE

FOR VALUE RECEIVED, the undersigned, ANBE Holdings, L.P., a Texas limited partnership (“Maker”), hereby promises to pay to the order of Elizabeth Lee Mitchell Trust #2005, (“Holder”), in lawful money of the United States of America, the principal sum of One Million Dollars and 00/100 ($1,000,000.00) (“Principal”), together with interest as set forth below (the “Note”).

Maturity Date: June 30, 2016

Interest Rate: Except as otherwise provided herein, this Note will bear interest from the execution date of this Note, until payment in full at a per annum rate equal to thirteen percent (13%). All interest will be compounded monthly and computed as a per diem charge for the actual number of days elapsed on the basis of a year consisting of three hundred sixty (360) days.

Default Rate: Each payment will be applied first to the payment of accrued unpaid interest and the balance, if any, will be applied to the unpaid principal balance of this Note. Any sum not paid when due will bear interest at a per annum rate equal to fifteen percent (15%) compounded monthly. Maker may prepay any amounts owed hereunder without premium or penalty.

If Maker fails to pay any amount when due under this Note, at the option of the Holder, the entire unpaid indebtedness evidenced by this Note will become due, payable and collectible then or thereafter as the Holder may elect, regardless of the date of maturity of this Note. Failure by the Holder to exercise such option will not constitute a waiver of the right to exercise the same in the event of any subsequent default.

Place for Payment: Principal and interest are payable to the Holder of this Note at 16803 Dallas Parkway, Addison, Texas 75001 or at any other address of which Payee may notify Maker in writing.

Prepayment of Principal: The Principal may be paid in whole or in part at any time before the Maturity Date, without penalty.

Terms of Payment of Principal and Interest: The Principal Amount and all accrued interest will be due in full at the Maturity Date.

To the extent permitted by applicable law, Maker waives notice, presentment, demand for payment, protest, notice of protest and non-payment or dishonor, notice of acceleration, notice of intent to accelerate, notice of intent to demand, diligence in collecting, grace, and all other formalities of any kind.

If this Note is place in the hands of an attorney for collection or if collection is attempted by suit or through probate, bankruptcy, insolvency, or other judicial proceedings, the Maker agrees to pay the collection expenses of the Payee, including reasonable attorneys’ fees. In the event judgment is rendered on any indebtedness evidenced by this Note, such amount shall bear interest at the highest lawful rate.

This Note shall be governed in all respects by the laws of the State of Texas, not including its conflict of law provisions.

ANBE HOLDINGS, L.P. PROMISSORY NOTE - PAGE 1 OF 2

ANBE HOLDINGS, L.P. PROMISSORY NOTE - PAGE 2 OF 2