Gran Tierra Energy (GTE) 10-Q 2 May 18 2018 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 27, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	GRAN TIERRA ENERGY INC.
Entity Central Index Key	1,273,441
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		385,258,378
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
OIL AND NATURAL GAS SALES (NOTES 3 and 7)	$ 138,228	$ 94,659
EXPENSES
Operating	26,265	23,937
Transportation	6,997	6,942
Depletion, depreciation and accretion (Note 3)	39,461	26,593
Asset impairment	0	283
General and administrative (Note 3)	11,160	8,712
Equity tax	0	1,224
Foreign exchange gain	(942)	(1,847)
Financial instruments loss (gain) (Note 10)	6,946	(5,439)
Interest expense (Note 5)	5,495	3,095
EXPENSES	95,382	63,500
INTEREST INCOME	786	408
INCOME BEFORE INCOME TAXES (NOTE 3)	43,632	31,567
INCOME TAX EXPENSE
Current (Note 8)	12,289	7,417
Deferred (Note 8)	13,482	11,379
INCOME TAX EXPENSE	25,771	18,796
NET INCOME AND COMPREHENSIVE INCOME	$ 17,861	$ 12,771
NET INCOME PER SHARE - BASIC AND DILUTED (in dollars per share)	$ 0.05	$ 0.03
WEIGHTED AVERAGE SHARES OUTSTANDING - BASIC (in shares)	391,294,042	399,007,086
WEIGHTED AVERAGE SHARES OUTSTANDING - DILUTED (in shares)	391,379,013	399,046,114

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents (Note 11)	$ 160,474	$ 12,326
Restricted cash and cash equivalents (Note 11)	3,294	11,787
Accounts receivable	49,239	45,353
Investment (Note 10)	21,265	25,055
Derivatives (Note 10)	3,769	302
Taxes receivable	55,024	40,831
Other current assets	10,952	9,591
Total Current Assets	304,017	145,245
Oil and Gas Properties (using the full cost method of accounting)
Proved	676,520	629,081
Unproved	452,865	464,948
Total Oil and Gas Properties	1,129,385	1,094,029
Other capital assets	4,802	5,195
Total Property, Plant and Equipment (Notes 3 and 4)	1,134,187	1,099,224
Other Long-Term Assets
Deferred tax assets	43,547	57,310
Investment (Note 10)	15,964	19,147
Other long-term assets (Note 11)	6,492	6,112
Goodwill (Note 3)	102,581	102,581
Total Other Long-Term Assets	168,584	185,150
Total Assets	1,606,788	1,429,619
Current Liabilities
Accounts payable and accrued liabilities	126,756	125,876
Derivatives (Note 10)	21,672	21,151
Taxes payable	23,203	9,324
Asset retirement obligation	111	323
Equity compensation award liability (Note 10)	8,633	295
Total Current Liabilities	180,375	156,969
Long-Term Liabilities
Long-term debt (Notes 5 and 10)	397,568	256,542
Deferred tax liabilities	26,467	28,417
Asset retirement obligation	33,405	31,241
Share-based Compensation Arrangement, Recorded Liability, Fair Value Disclosure, Noncurrent	5,724	11,135
Other long-term liabilities	9,610	8,980
Total Long-Term Liabilities	472,774	336,315
Contingencies (Note 9)
Shareholders’ Equity
Common Stock (Note 6) (384,959,730 and 385,191,042 shares of Common Stock and 5,908,065 and 6,111,665 exchangeable shares, par value $0.001 per share, issued and outstanding as at March 31, 2018, and December 31, 2017, respectively)	10,295	10,295
Additional paid in capital	1,326,687	1,327,244
Deficit	(383,343)	(401,204)
Total Shareholders’ Equity	953,639	936,335
Total Liabilities and Shareholders’ Equity	$ 1,606,788	$ 1,429,619

Condensed Consolidated Balance4

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common Stock, shares issued (in shares)	384,959,730	385,191,042
Common Stock, shares outstanding (in shares)	384,959,730	385,191,042
Exchangeable shares, shares issued (in shares)	5,908,065	6,111,665
Exchangeable shares, shares outstanding (in shares)	5,908,065	6,111,665
Common Stock and exchangeable shares, par value (in dollars per share)	$ 0.001	$ 0.001

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net income	$ 17,861	$ 12,771
Adjustments to reconcile net income to net cash provided by operating activities:
Depletion, depreciation and accretion (Note 3)	39,461	26,593
Asset impairment	0	283
Deferred tax expense	13,482	11,379
Stock-based compensation (Note 6)	3,309	1,203
Amortization of debt issuance costs (Note 5)	670	605
Cash settlement of restricted share units	(120)	(318)
Unrealized foreign exchange gain	(1,044)	(2,819)
Financial instruments loss (gain) (Note 10)	6,946	(5,439)
Cash settlement of financial instruments (Note 10)	(5,817)	768
Cash settlement of asset retirement obligation	(192)	(13)
Net change in assets and liabilities from operating activities (Note 11)	(3,464)	4,930
Net cash provided by operating activities	71,092	49,943
Investing Activities
Additions to property, plant and equipment (Note 3)	(72,694)	(46,160)
Deposit received for sale of Brazil business unit	0	3,500
Changes in non-cash investing working capital	1,957	(1,797)
Net cash used in investing activities	(70,737)	(44,457)
Financing Activities
Proceeds from bank debt, net of issuance costs (Note 5)	4,988	18,471
Repayment of bank debt (Note 5)	(153,000)	(23,000)
Proceeds exercise of stock options (Note 6)	74	0
Repurchase of shares of Common Stock (Note 6)	(1,194)	0
Proceeds from issuance of Senior Notes, net of issuance costs (Note 5)	288,368	0
Net cash provided by (used in) financing activities	139,236	(4,529)
Foreign exchange gain on cash, cash equivalents and restricted cash and cash equivalents	663	474
Net increase in cash, cash equivalents and restricted cash and cash equivalents	140,254	1,431
Cash, cash equivalents and restricted cash and cash equivalents, beginning of period (Note 11)	26,678	43,267
Cash, cash equivalents and restricted cash and cash equivalents, end of period (Note 11)	$ 166,932	$ 44,698

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Share Capital	Additional Paid in Capital	Deficit
Increase (Decrease) in Stockholders' Equity
Cumulative adjustment for accounting change related to tax reorganizations				$ 124,476
Balance, beginning of period at Dec. 31, 2016		$ 10,303	$ 1,342,656	(493,972)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (Note 6)			0
Stock-based compensation (Note 6)			709
Repurchase of Common Stock (Note 6)			0
Net income (loss)	$ 12,771			12,771
Balance, end of period at Mar. 31, 2017	996,943	10,303	1,343,365	(356,725)
Increase (Decrease) in Stockholders' Equity
Cumulative adjustment for accounting change related to tax reorganizations				0
Balance, beginning of period at Dec. 31, 2017		10,295	1,327,244	(401,204)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (Note 6)			74
Stock-based compensation (Note 6)			563
Repurchase of Common Stock (Note 6)			(1,194)
Net income (loss)	17,861			17,861
Balance, end of period at Mar. 31, 2018	$ 953,639	$ 10,295	$ 1,326,687	$ (383,343)

Description of Business

Description of Business	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Gran Tierra Energy Inc., a Delaware corporation (the “Company” or “Gran Tierra”), is a publicly traded company focused on oil and natural gas exploration and production in Colombia.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies These interim unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”). The information furnished herein reflects all normal recurring adjustments that are, in the opinion of management, necessary for the fair presentation of results for the interim periods. The note disclosure requirements of annual consolidated financial statements provide additional disclosures to that required for interim unaudited condensed consolidated financial statements. Accordingly, these interim unaudited condensed consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements as at and for the year ended December 31, 2017 , included in the Company’s 2017 Annual Report on Form 10-K, filed with the SEC on February 27, 2018 . The Company’s significant accounting policies are described in Note 2 of the consolidated financial statements which are included in the Company’s 2017 Annual Report on Form 10-K and are the same policies followed in these interim unaudited condensed consolidated financial statements, except as noted below. The Company has evaluated all subsequent events through to the date these interim unaudited condensed consolidated financial statements were issued. Recently Adopted Accounting Pronouncements Revenue from Contracts with Customers The Company adopted Accounting Standard Codification ("ASC") 606 Revenue from Contracts with Customers with a date of initial application of January 1, 2018 in accordance with the modified retrospective approach without using the practical expedients. Except for providing enhanced disclosures about the Company's revenue transactions, the application of ASC 606 did not have an impact on the Company’s consolidated financial position, results of operations or cash flows. a) Significant Accounting Policy The Company's revenue relates to oil and natural gas sales in Colombia. The Company recognizes revenue when it transfers control of the product to a customer. This generally occurs at the time the customer obtains legal title to the product and when it is physically transferred to the delivery point agreed with the customer. Payment terms are generally within three business days following delivery of an invoice to the customer. Revenue is recognized based on the consideration specified in contracts with customers. Revenue represents the Company's share and is recorded net of royalty payments to governments and other mineral interest owners. The Company evaluates its arrangement with third parties and partners to determine if the Company acts as a principal or an agent. In making this evaluation, management considers if the Company obtains control of the product delivered, which is indicated by the Company having the primary responsibility for the delivery of the product, having ability to establish prices or having inventory risk. If the Company acts in the capacity of an agent rather than as a principal in transaction, then the revenue is recognized on a net-basis, only reflecting the fee realized by the Company from the transaction. Tariffs, tolls and fees charged to other entities for use of pipelines owned by the Company are evaluated by management to determine if these originate from contracts with customers or from incidental arrangements. In the comparative period, revenue from the production of oil and natural gas was recognized when the customer took title and assumed the risks and rewards of ownership, prices were fixed or determinable, the sale was evidenced by a contract and collection of the revenue was reasonably assured. b) Significant Judgments When determining if the Company acted as a principal or as an agent in transactions, management determines if the Company obtains control of the product. As part of this assessment, management considered detailed criteria for revenue recognition set out in ASC 606. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, "Recognition and Measurement of Financial Assets and Financial Liabilities". ASU 2016-01 addressed certain aspects of recognition, measurement, presentation and disclosure of financial instruments. ASU 2016-01 was effective for annual reporting periods and interim reporting periods within those annual reporting periods, beginning after December 15, 2017. The implementation of this update did not impact on the Company’s consolidated financial position, results of operations or cash flows or disclosure. In February 2018, the FASB issued ASU 2018-03, "Recognition and Measurement of Financial Assets and Financial Liabilities". ASU 2018-03 clarifies certain aspects of the guidance in ASU 2016-01. ASU 2018-03 is effective for annual reporting periods beginning after December 15, 2017 and interim reporting periods within those annual reporting periods beginning after June 15, 2018. Early adoption is permitted upon adoption of ASU 2016-01.The amendments should be applied retrospectively with a cumulative-effect adjustment to the effective date of ASU 2016-01. The Company early adopted this update on January 1, 2018. The implementation of this update did not impact on the Company’s consolidated financial position, results of operations or cash flows or disclosure.

Segment and Geographic Reportin

Segment and Geographic Reporting	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment and Geographic Reporting	Segment and Geographic Reporting The Company is primarily engaged in the exploration and production of oil and natural gas. Commencing in 2018, the Company has one reportable segment based on geographic organization, Colombia. Prior to the sale of the Company's Brazil business unit effective June 30, 2017 and its Peru business unit effective December 18, 2017, Brazil and Peru were reportable segments. The "All Other" category represents the Company’s corporate, Brazil and Peru activities until the date of sale. The following tables present information on the Company’s reportable segments and other activities: Three Months Ended March 31, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 138,228 $ — $ 138,228 Depletion, depreciation and accretion 38,499 962 39,461 General and administrative expenses 6,809 4,351 11,160 Income (loss) before income taxes 61,151 (17,519 ) 43,632 Segment capital expenditures 72,561 133 72,694 Three Months Ended March 31, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 90,464 $ 4,195 $ 94,659 Depletion, depreciation and accretion 24,935 1,658 26,593 General and administrative expenses 4,832 3,880 8,712 Income (loss) before income taxes 37,144 (5,577 ) 31,567 Segment capital expenditures 42,840 3,320 46,160 As at March 31, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Property, plant and equipment $ 1,132,626 $ 1,561 $ 1,134,187 Goodwill 102,581 — 102,581 All other assets 182,440 187,580 370,020 Total Assets $ 1,417,647 $ 189,141 $ 1,606,788 As at December 31, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Property, plant and equipment $ 1,096,833 $ 2,391 $ 1,099,224 Goodwill 102,581 — 102,581 All other assets 176,980 50,834 227,814 Total Assets $ 1,376,394 $ 53,225 $ 1,429,619

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment (Thousands of U.S. Dollars) As at March 31, 2018 As at December 31, 2017 Oil and natural gas properties Proved $ 2,896,700 $ 2,810,796 Unproved 452,865 464,948 3,349,565 3,275,744 Other 23,633 26,401 3,373,198 3,302,145 Accumulated depletion, depreciation and impairment (2,239,011 ) (2,202,921 ) $ 1,134,187 $ 1,099,224 The Company used an average Brent price of $56.92 per bbl for the purposes of the March 31, 2018 ceiling test calculations ( December 31, 2017 - $54.19 ).

Debt and Debt Issuance Costs

Debt and Debt Issuance Costs	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt and Debt Issuance Costs	Debt and Debt Issuance Costs The Company's debt at March 31, 2018 and December 31, 2017 was as follows: (Thousands of U.S. Dollars) As at March 31, 2018 As at December 31, 2017 Senior notes $ 300,000 $ — Convertible notes 115,000 115,000 Revolving credit facility — 148,000 Unamortized debt issuance costs (17,432 ) (6,458 ) Long-term debt $ 397,568 $ 256,542 Senior Notes On February 15, 2018 , Gran Tierra Energy International Holdings Ltd. ("GTEIH"), an indirect, wholly owned subsidiary of the Company, issued $300 million of 6.25% Senior Notes due 2025 (the "Senior Notes"). The Senior Notes are fully and unconditionally guaranteed by the Company and certain subsidiaries of the Company that guarantee its revolving credit facility. Net proceeds from the sale of the Senior Notes were $288.4 million , after deducting the initial purchasers' discounts and commission and the offering expenses payable by the Company. The Senior Notes bear interest at a rate of 6.25% per year, payable semi-annually in arrears on February 15 and August 15 of each year, beginning on August 15, 2018 . The Senior Notes will mature on February 15, 2025 , unless earlier redeemed or repurchased. Before February 15, 2022 , GTEIH may, at its option, redeem all or a portion of the Senior Notes at 100% of the principal amount plus accrued and unpaid interest and a make-whole premium. Thereafter, the Company may redeem all or a portion of the Senior Notes plus accrued and unpaid interest applicable to the date of the redemption at the following redemption prices: 2022 - 103.125% ; 2023 - 101.563% ; 2024 and thereafter - 100% . Interest Expense The following table presents total interest expense recognized in the accompanying interim unaudited condensed consolidated statements of operations: Three Months Ended March 31, (Thousands of U.S. Dollars) 2018 2017 Contractual interest and other financing expenses $ 4,825 $ 2,490 Amortization of debt issuance costs 670 605 $ 5,495 $ 3,095

Share Capital

Share Capital	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share Capital	Share Capital The Company’s authorized share capital consists of 595,000,002 shares of capital stock, of which 570 million are designated as Common Stock, par value $0.001 per share, 25 million are designated as Preferred Stock, par value $0.001 per share, one share is designated as Special A Voting Stock, par value $0.001 per share, and one share is designated as Special B Voting Stock, par value $0.001 per share. Shares of Common Stock Exchangeable Shares of Gran Tierra Exchangeco Inc. Exchangeable Shares of Gran Tierra Goldstrike Inc. Balance, December 31, 2017 385,191,042 4,422,776 1,688,889 Options exercised 30,000 — — Shares repurchased and canceled (464,912 ) — — Exchange of exchangeable shares 203,600 (203,600 ) — Balance, March 31, 2018 384,959,730 4,219,176 1,688,889 On March 7, 2018 , the Company announced that it intended to implement a share repurchase program (the “2018 Program”) through the facilities of the Toronto Stock Exchange ("TSX") and eligible alternative trading platforms in Canada. Under the 2018 Program, the Company is able to purchase at prevailing market prices up to 19,269,732 shares of Common Stock, representing approximately 5.00% of the issued and outstanding shares of Common Stock as of March 8, 2018 . Shares purchased pursuant to 2018 Program will be canceled. The 2018 Program will expire on March 11, 2019 , or earlier if the 5.00% share maximum is reached. Equity Compensation Awards The following table provides information about p erformance stock units (“PSUs”), deferred share units (“DSUs”), restricted stock units (“RSUs”) and stock option activity for the three months ended March 31, 2018 : PSUs DSUs RSUs Stock Options Number of Outstanding Share Units Number of Outstanding Share Units Number of Outstanding Share Units Number of Outstanding Stock Options Weighted Average Exercise Price/Stock Option ($) Balance, December 31, 2017 6,131,951 455,768 122,090 8,960,692 3.65 Granted 3,305,486 67,926 — 1,890,413 2.47 Exercised — — (48,600 ) (30,000 ) (2.46 ) Forfeited (108,195 ) — (1,822 ) (349,878 ) (5.17 ) Expired — — — (8,334 ) (3.50 ) Balance, March 31, 2018 9,329,242 523,694 71,668 10,462,893 3.39 Stock-based compensation expense for the three months ended March 31, 2018 , was $3.3 million and was primarily recorded in general and administrative ("G&A") expenses ( three months ended March 31, 2017 - $1.2 million ). At March 31, 2018 , there was $22.0 million ( December 31, 2017 - $13.7 million ) of unrecognized compensation cost related to unvested PSUs, RSUs and stock options which is expected to be recognized over a weighted average period of 2.0 years. Net Income per Share Basic net income per share is calculated by dividing net income by the weighted average number of shares of Common Stock and exchangeable shares issued and outstanding during each period. Diluted net income per share is similarly calculated except that the common shares outstanding for the period is increased using the treasury stock method to reflect the potential dilution that could occur if outstanding stock awards were vested at the end of the applicable period plus potentially issuable shares on conversion of the convertible notes. Anti-dilutive shares represent potentially dilutive securities that are excluded from the computation of diluted income or loss per share as their impact would be anti-dilutive. Weighted Average Shares Outstanding Three Months Ended March 31, 2018 2017 Weighted average number of common and exchangeable shares outstanding 391,294,042 399,007,086 Shares issuable pursuant to stock options 867,427 635,484 Shares assumed to be purchased from proceeds of stock options (782,456 ) (596,456 ) Weighted average number of diluted common and exchangeable shares outstanding 391,379,013 399,046,114 For the three months ended March 31, 2018 , 8,599,422 options, on a weighted average basis, ( three months ended March 31, 2017 - 9,210,869 options) were excluded from the diluted income per share calculation as the options were anti-dilutive. Shares issuable upon conversion of the 5.00% Convertible Notes due 2021 ("Convertible Notes") were anti-dilutive and excluded from the diluted income per share calculation.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Most of the Company's revenues are from oil sales at prices which reflect the blended prices received upon shipment by the purchaser at defined sales points or are defined by contract relative to ICE Brent and adjusted for quality each month. For the three months ended March 31, 2018 , 100% (three months ended March 31, 2017 - 100% ) of the Company's revenue resulted from oil sales. In the three months ended March 31, 2018 , quality and transportation discounts were 16% of the ICE Brent price (three months ended March 31, 2017 - 22% ). During the three months ended March 31, 2018 , the Company's production was sold primarily to four major customers in Colombia (three months ended March 31, 2017 - three ). As at March 31, 2018 , accounts receivable included $7.1 million of accrued sales revenue which related to March 2018 production ( December 31, 2017 - $11.1 million which related to December 31, 2017 production). December 31, 2017 accrued sales revenue was collected during the three months ended March 31, 2018 without significant adjustment to revenue for that period.

Taxes

Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Taxes	Taxes The Company's effective tax rate was 59% in the three months ended March 31, 2018 , compared with 60% in the comparable period in 2017 . Current income tax expense was higher in the three months ended March 31, 2018 , compared with the corresponding period in 2017 , primarily as a result of higher taxable income in Colombia. The deferred income tax expense of $13.5 million for the three months ended March 31, 2018 , was primarily due to excess tax depreciation compared with accounting depreciation in Colombia. For the three months ended March 31, 2018 , the difference between the effective tax rate of 59% and the 21% U.S. statutory rate was primarily due to an increase to the impact of foreign taxes, valuation allowance, other permanent differences, non-deductible third party royalty in Colombia, stock based compensation, other local taxes and foreign currency translation. For the comparable period in 2017 , the effective rate differed from the U.S. statutory rate of 35% primarily due to an increase to the valuation allowance, which was largely attributable to losses incurred in the United States, Brazil and Colombia, as well as the impact of a non-deductible third-party royalty in Colombia, foreign taxes, local taxes, and stock-based compensation. These items were partially offset by foreign currency translation adjustments and other permanent differences.

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies The Agencia Nacional de Hidrocarburos (National Hydrocarbons Agency) (“ANH") and Gran Tierra are engaged in ongoing discussions regarding the interpretation of whether certain transportation and related costs are eligible to be deducted in the calculation of an additional royalty (the "HPR royalty"). Based on the Company's understanding of the ANH's position, the estimated compensation which would be payable if the ANH’s interpretation is correct could be up to $51.8 million as at March 31, 2018 . At this time no amount has been accrued in the interim unaudited condensed consolidated financial statements as Gran Tierra does not consider it probable that a loss will be incurred. In addition to the above, the Company has a number of other lawsuits and claims pending. Although the outcome of these other lawsuits and disputes cannot be predicted with certainty, the Company believes the resolution of these matters would not have a material adverse effect on the Company’s consolidated financial position, results of operations or cash flows. Gran Tierra records costs associated with these lawsuits and claims as they are incurred or become probable and determinable. Letters of credit and other credit support At March 31, 2018 , the Company had provided letters of credit and other credit support totaling $76.5 million ( December 31, 2017 - $76.0 million ) as security relating to work commitment guarantees contained in exploration contracts and other capital or operating requirements.

Financial Instruments and Fair

Financial Instruments and Fair Value Measurement	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Measurement	Financial Instruments and Fair Value Measurement Financial Instruments At March 31, 2018 , the Company’s financial instruments recognized in the balance sheet consisted of: cash and cash equivalents; restricted cash and cash equivalents; accounts receivable; investments; derivatives, accounts payable and accrued liabilities, long-term debt and equity compensation award liability. Fair Value Measurement The fair value of certain investments, derivatives and equity compensation award (PSU, DSU and RSU) liabilities are remeasured at the estimated fair value at the end of each reporting period. The fair value of the short-term portion of the Company's investment in Sterling Resources Ltd. ("Sterling") was estimated using quoted prices at March 31, 2018 and the foreign exchange rate at that time. The fair value of the long-term portion of the investment restricted by escrow conditions was estimated using observable and unobservable inputs; factors that were evaluated included quoted market prices, precedent comparable transactions, risk-free rate, measures of market risk volatility, estimates of the Company's and Sterling's costs of capital and quotes from third parties. The fair value of commodity price and foreign currency derivatives is estimated based on various factors, including quoted market prices in active markets and quotes from third parties. The Company also performs an internal valuation to ensure the reasonableness of third party quotes. In consideration of counterparty credit risk, the Company assessed the possibility of whether the counterparty to the derivative would default by failing to make any contractually required payments. Additionally, the Company considers that it is of substantial credit quality and has the financial resources and willingness to meet its potential repayment obligations associated with the derivative transactions. The fair value of the PSU liability was estimated based on option pricing model using inputs such as quoted market prices in an active market, and PSU performance factors. The fair value of the DSU and RSU liabilities were estimated based on quoted market prices in an active market. The fair value of derivatives and RSU, PSU and DSU liabilities at March 31, 2018 , and December 31, 2017 , were as follows: (Thousands of U.S. Dollars) As at March 31, 2018 As at December 31, 2017 Investment - current and long-term assets $ 37,229 $ 44,202 Foreign currency derivative asset 3,769 302 $ 40,998 $ 44,504 Commodity price derivative liability $ 21,672 $ 21,151 Equity compensation award liability - current and long-term 14,357 11,430 $ 36,029 $ 32,581 The following table presents gains or losses on financial instruments recognized in the accompanying interim unaudited condensed consolidated statements of operations: Three Months Ended March 31, (Thousands of U.S. Dollars) 2018 2017 Commodity price derivative loss (gain) $ 4,995 $ (4,703 ) Foreign currency derivatives gain (3,970 ) (736 ) Investment loss 5,921 — Financial instruments loss (gain) $ 6,946 $ (5,439 ) These gains and losses are presented as financial instrument gains and losses in the interim unaudited condensed consolidated statements of operations and cash flows. Investment loss for the three months ended March 31, 2018 related to the fair value loss on the Sterling shares Gran Tierra received or subscribed for in connection with the sale of its Peru business unit in December 2017. For the three months ended March 31, 2018 , this investment loss was unrealized. Financial instruments not recorded at fair value include the Senior Notes and the Convertible Notes. At March 31, 2018 , the carrying amounts of the Senior Notes and the Convertible Notes were $288.5 million and $111.2 million , respectively, which represented the aggregate principal amount less unamortized debt issuance costs, and the fair values were $292.5 million and $130.0 million , respectively. The fair value of long-term restricted cash and cash equivalents and the revolving credit facility approximated their carrying value because interest rates are variable and reflective of market rates. The fair values of other financial instruments approximate their carrying amounts due to the short-term maturity of these instruments. GAAP establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. This hierarchy consists of three broad levels. Level 1 inputs consist of quoted prices (unadjusted) in active markets for identical assets and liabilities and have the highest priority. Level 2 and 3 inputs are based on significant other observable inputs and significant unobservable inputs, respectively, and have lower priorities. The Company uses appropriate valuation techniques based on the available inputs to measure the fair values of assets and liabilities. At March 31, 2018 , the fair value of the current portion of the investment, DSU and RSU liability was determined using Level 1 inputs, the fair value of derivatives and PSUs was determined using Level 2 inputs and the fair value of the long-term portion of the investment restricted by escrow conditions was determined using Level 3 inputs. The table below presents the fair value of the long-term portion of the investment: Three Months Ended Year Ended March 31, 2018 December 31, 2017 (Thousands of U.S. Dollars) Opening balance $ 19,147 $ — Acquisition — 19,091 Unrealized valuation (loss) gain (2,703 ) 56 Unrealized foreign exchange loss (480 ) — Closing balance $ 15,964 $ 19,147 The Company uses available market data and valuation methodologies to estimate the fair value of debt. The fair value of debt is the estimated amount the Company would have to pay a third party to assume the debt, including a credit spread for the difference between the issue rate and the period end market rate. The credit spread is the Company’s default or repayment risk. The credit spread (premium or discount) is determined by comparing the Company’s Senior Notes, Convertible Notes and revolving credit facility to new issuances (secured and unsecured) and secondary trades of similar size and credit statistics for both public and private debt. The disclosure above regarding the fair value of the Convertible Notes was determined using Level 2 inputs based on the indicative pricing published by certain third-party services or trading levels of the Convertible Notes, which are not listed on any securities exchange or quoted on an inter-dealer automated quotation system. The disclosure in the paragraph above regarding the fair value of cash and restricted cash and cash equivalents, revolving credit facility and Senior Notes was based on Level 1 inputs. The Company’s non-recurring fair value measurements include asset retirement obligations. The fair value of an asset retirement obligation is measured by reference to the expected future cash outflows required to satisfy the retirement obligation discounted at the Company’s credit-adjusted risk-free interest rate. The significant level 3 inputs used to calculate such liabilities include estimates of costs to be incurred, the Company’s credit-adjusted risk-free interest rate, inflation rates and estimated dates of abandonment. Accretion expense is recognized over time as the discounted liabilities are accreted to their expected settlement value, while the asset retirement cost is amortized over the estimated productive life of the related assets. Commodity Price Derivatives The Company utilizes commodity price derivatives to manage the variability in cash flows associated with the forecasted sale of its oil production, reduce commodity price risk and provide a base level of cash flow in order to assure it can execute at least a portion of its capital spending. At March 31, 2018 , the Company had outstanding commodity price derivative positions as follows: Period and type of instrument Volume, Reference Sold Swap ($/bbl, Weighted Average) Purchased Call ($/bbl, Weighted Average) Swaps: April 1, to December 31, 2018 5,000 ICE Brent $ 55.90 n/a Participating Swaps: April 1, to December 31, 2018 5,000 ICE Brent $ 52.50 $ 56.11 Foreign Currency Derivatives The Company utilizes foreign currency derivatives to manage the variability in cash flows associated with the Company's forecasted Colombian peso ("COP") denominated expenses. At March 31, 2018 , the Company had outstanding foreign currency derivative positions as follows: Period and type of instrument Amount Hedged U.S. Dollar Equivalent of Amount Hedged (Thousands of U.S. Dollars) (1) Reference Purchased Call Sold Put (COP, Weighted Average) Collars: April 1, 2018 to December 31, 2018 130,500 46,935 COP 3,000 3,107 (1) At March 31, 2018 foreign exchange rate.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information The following table provides a reconciliation of cash, cash equivalents and restricted cash and cash equivalents with the Company's interim unaudited condensed consolidated balance sheet that sum to the total of the same such amounts shown in the interim unaudited condensed consolidated statements of cash flows: (Thousands of U.S. Dollars) As at March 31, As at December 31, 2018 2017 2017 2016 Cash and cash equivalents $ 160,474 $ 26,716 $ 12,326 $ 25,175 Restricted cash and cash equivalents - current 3,294 7,663 11,787 8,322 Restricted cash and cash equivalents - long-term (included in other long-term assets) 3,164 10,319 2,565 9,770 $ 166,932 $ 44,698 $ 26,678 $ 43,267 Net changes in assets and liabilities from operating activities were as follows: Three Months Ended March 31, (Thousands of U.S. Dollars) 2018 2017 Accounts receivable and other long-term assets $ (1,982 ) $ (2,428 ) Derivatives 1,847 — Inventory (1,785 ) 207 Prepaids 1,498 1,078 Accounts payable and accrued and other long-term liabilities (2,495 ) 4,310 Taxes receivable and payable (547 ) 1,763 Net changes in assets and liabilities from operating activities $ (3,464 ) $ 4,930 The following table provides additional supplemental cash flow disclosures: Three Months Ended March 31, (Thousands of U.S. Dollars) 2018 2017 Non-cash investing activities: Net liabilities related to property, plant and equipment, end of period $ 70,108 $ 54,875

Significant Accounting Polici18

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Revenue from Contracts with Customers The Company adopted Accounting Standard Codification ("ASC") 606 Revenue from Contracts with Customers with a date of initial application of January 1, 2018 in accordance with the modified retrospective approach without using the practical expedients. Except for providing enhanced disclosures about the Company's revenue transactions, the application of ASC 606 did not have an impact on the Company’s consolidated financial position, results of operations or cash flows. a) Significant Accounting Policy The Company's revenue relates to oil and natural gas sales in Colombia. The Company recognizes revenue when it transfers control of the product to a customer. This generally occurs at the time the customer obtains legal title to the product and when it is physically transferred to the delivery point agreed with the customer. Payment terms are generally within three business days following delivery of an invoice to the customer. Revenue is recognized based on the consideration specified in contracts with customers. Revenue represents the Company's share and is recorded net of royalty payments to governments and other mineral interest owners. The Company evaluates its arrangement with third parties and partners to determine if the Company acts as a principal or an agent. In making this evaluation, management considers if the Company obtains control of the product delivered, which is indicated by the Company having the primary responsibility for the delivery of the product, having ability to establish prices or having inventory risk. If the Company acts in the capacity of an agent rather than as a principal in transaction, then the revenue is recognized on a net-basis, only reflecting the fee realized by the Company from the transaction. Tariffs, tolls and fees charged to other entities for use of pipelines owned by the Company are evaluated by management to determine if these originate from contracts with customers or from incidental arrangements. In the comparative period, revenue from the production of oil and natural gas was recognized when the customer took title and assumed the risks and rewards of ownership, prices were fixed or determinable, the sale was evidenced by a contract and collection of the revenue was reasonably assured. b) Significant Judgments When determining if the Company acted as a principal or as an agent in transactions, management determines if the Company obtains control of the product. As part of this assessment, management considered detailed criteria for revenue recognition set out in ASC 606. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, "Recognition and Measurement of Financial Assets and Financial Liabilities". ASU 2016-01 addressed certain aspects of recognition, measurement, presentation and disclosure of financial instruments. ASU 2016-01 was effective for annual reporting periods and interim reporting periods within those annual reporting periods, beginning after December 15, 2017. The implementation of this update did not impact on the Company’s consolidated financial position, results of operations or cash flows or disclosure. In February 2018, the FASB issued ASU 2018-03, "Recognition and Measurement of Financial Assets and Financial Liabilities". ASU 2018-03 clarifies certain aspects of the guidance in ASU 2016-01. ASU 2018-03 is effective for annual reporting periods beginning after December 15, 2017 and interim reporting periods within those annual reporting periods beginning after June 15, 2018. Early adoption is permitted upon adoption of ASU 2016-01.The amendments should be applied retrospectively with a cumulative-effect adjustment to the effective date of ASU 2016-01. The Company early adopted this update on January 1, 2018. The implementation of this update did not impact on the Company’s consolidated financial position, results of operations or cash flows or disclosure.

Segment and Geographic Report19

Segment and Geographic Reporting (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Schedule of Information on Reportable Segments and Other Activities	The following tables present information on the Company’s reportable segments and other activities: Three Months Ended March 31, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 138,228 $ — $ 138,228 Depletion, depreciation and accretion 38,499 962 39,461 General and administrative expenses 6,809 4,351 11,160 Income (loss) before income taxes 61,151 (17,519 ) 43,632 Segment capital expenditures 72,561 133 72,694 Three Months Ended March 31, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 90,464 $ 4,195 $ 94,659 Depletion, depreciation and accretion 24,935 1,658 26,593 General and administrative expenses 4,832 3,880 8,712 Income (loss) before income taxes 37,144 (5,577 ) 31,567 Segment capital expenditures 42,840 3,320 46,160
Schedule of Long-lived Assets by Geographical Area	As at March 31, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Property, plant and equipment $ 1,132,626 $ 1,561 $ 1,134,187 Goodwill 102,581 — 102,581 All other assets 182,440 187,580 370,020 Total Assets $ 1,417,647 $ 189,141 $ 1,606,788 As at December 31, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Property, plant and equipment $ 1,096,833 $ 2,391 $ 1,099,224 Goodwill 102,581 — 102,581 All other assets 176,980 50,834 227,814 Total Assets $ 1,376,394 $ 53,225 $ 1,429,619

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	(Thousands of U.S. Dollars) As at March 31, 2018 As at December 31, 2017 Oil and natural gas properties Proved $ 2,896,700 $ 2,810,796 Unproved 452,865 464,948 3,349,565 3,275,744 Other 23,633 26,401 3,373,198 3,302,145 Accumulated depletion, depreciation and impairment (2,239,011 ) (2,202,921 ) $ 1,134,187 $ 1,099,224

Debt and Debt Issuance Costs (T

Debt and Debt Issuance Costs (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Debt	The Company's debt at March 31, 2018 and December 31, 2017 was as follows: (Thousands of U.S. Dollars) As at March 31, 2018 As at December 31, 2017 Senior notes $ 300,000 $ — Convertible notes 115,000 115,000 Revolving credit facility — 148,000 Unamortized debt issuance costs (17,432 ) (6,458 ) Long-term debt $ 397,568 $ 256,542
Schedule of Interest Expense Recognized	The following table presents total interest expense recognized in the accompanying interim unaudited condensed consolidated statements of operations: Three Months Ended March 31, (Thousands of U.S. Dollars) 2018 2017 Contractual interest and other financing expenses $ 4,825 $ 2,490 Amortization of debt issuance costs 670 605 $ 5,495 $ 3,095

Share Capital (Tables)

Share Capital (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Common Stock	Shares of Common Stock Exchangeable Shares of Gran Tierra Exchangeco Inc. Exchangeable Shares of Gran Tierra Goldstrike Inc. Balance, December 31, 2017 385,191,042 4,422,776 1,688,889 Options exercised 30,000 — — Shares repurchased and canceled (464,912 ) — — Exchange of exchangeable shares 203,600 (203,600 ) — Balance, March 31, 2018 384,959,730 4,219,176 1,688,889
Schedule of PSU, DSU, RSU and Stock Option Activity	The following table provides information about p erformance stock units (“PSUs”), deferred share units (“DSUs”), restricted stock units (“RSUs”) and stock option activity for the three months ended March 31, 2018 : PSUs DSUs RSUs Stock Options Number of Outstanding Share Units Number of Outstanding Share Units Number of Outstanding Share Units Number of Outstanding Stock Options Weighted Average Exercise Price/Stock Option ($) Balance, December 31, 2017 6,131,951 455,768 122,090 8,960,692 3.65 Granted 3,305,486 67,926 — 1,890,413 2.47 Exercised — — (48,600 ) (30,000 ) (2.46 ) Forfeited (108,195 ) — (1,822 ) (349,878 ) (5.17 ) Expired — — — (8,334 ) (3.50 ) Balance, March 31, 2018 9,329,242 523,694 71,668 10,462,893 3.39
Schedule of Weighted Average Shares Outstanding	Weighted Average Shares Outstanding Three Months Ended March 31, 2018 2017 Weighted average number of common and exchangeable shares outstanding 391,294,042 399,007,086 Shares issuable pursuant to stock options 867,427 635,484 Shares assumed to be purchased from proceeds of stock options (782,456 ) (596,456 ) Weighted average number of diluted common and exchangeable shares outstanding 391,379,013 399,046,114

Financial Instruments and Fai23

Financial Instruments and Fair Value Measurement (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Derivatives and RSU, PSU and DSU Liabilities	The fair value of derivatives and RSU, PSU and DSU liabilities at March 31, 2018 , and December 31, 2017 , were as follows: (Thousands of U.S. Dollars) As at March 31, 2018 As at December 31, 2017 Investment - current and long-term assets $ 37,229 $ 44,202 Foreign currency derivative asset 3,769 302 $ 40,998 $ 44,504 Commodity price derivative liability $ 21,672 $ 21,151 Equity compensation award liability - current and long-term 14,357 11,430 $ 36,029 $ 32,581
Schedule of Gains or Losses on Financial Instruments Recognized	The following table presents gains or losses on financial instruments recognized in the accompanying interim unaudited condensed consolidated statements of operations: Three Months Ended March 31, (Thousands of U.S. Dollars) 2018 2017 Commodity price derivative loss (gain) $ 4,995 $ (4,703 ) Foreign currency derivatives gain (3,970 ) (736 ) Investment loss 5,921 — Financial instruments loss (gain) $ 6,946 $ (5,439 )
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	The table below presents the fair value of the long-term portion of the investment: Three Months Ended Year Ended March 31, 2018 December 31, 2017 (Thousands of U.S. Dollars) Opening balance $ 19,147 $ — Acquisition — 19,091 Unrealized valuation (loss) gain (2,703 ) 56 Unrealized foreign exchange loss (480 ) — Closing balance $ 15,964 $ 19,147
Schedule of Commodity Price Derivative Positions and Commodity Foreign Currency Contracts	At March 31, 2018 , the Company had outstanding commodity price derivative positions as follows: Period and type of instrument Volume, Reference Sold Swap ($/bbl, Weighted Average) Purchased Call ($/bbl, Weighted Average) Swaps: April 1, to December 31, 2018 5,000 ICE Brent $ 55.90 n/a Participating Swaps: April 1, to December 31, 2018 5,000 ICE Brent $ 52.50 $ 56.11
Schedule of Outstanding Foreign Currency Derivative Positions	At March 31, 2018 , the Company had outstanding foreign currency derivative positions as follows: Period and type of instrument Amount Hedged U.S. Dollar Equivalent of Amount Hedged (Thousands of U.S. Dollars) (1) Reference Purchased Call Sold Put (COP, Weighted Average) Collars: April 1, 2018 to December 31, 2018 130,500 46,935 COP 3,000 3,107 (1) At March 31, 2018 foreign exchange rate.

Supplemental Cash Flow Inform24

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash and cash equivalents with the Company's interim unaudited condensed consolidated balance sheet that sum to the total of the same such amounts shown in the interim unaudited condensed consolidated statements of cash flows: (Thousands of U.S. Dollars) As at March 31, As at December 31, 2018 2017 2017 2016 Cash and cash equivalents $ 160,474 $ 26,716 $ 12,326 $ 25,175 Restricted cash and cash equivalents - current 3,294 7,663 11,787 8,322 Restricted cash and cash equivalents - long-term (included in other long-term assets) 3,164 10,319 2,565 9,770 $ 166,932 $ 44,698 $ 26,678 $ 43,267
Schedule of Net Changes in Assets and Liabilities	Net changes in assets and liabilities from operating activities were as follows: Three Months Ended March 31, (Thousands of U.S. Dollars) 2018 2017 Accounts receivable and other long-term assets $ (1,982 ) $ (2,428 ) Derivatives 1,847 — Inventory (1,785 ) 207 Prepaids 1,498 1,078 Accounts payable and accrued and other long-term liabilities (2,495 ) 4,310 Taxes receivable and payable (547 ) 1,763 Net changes in assets and liabilities from operating activities $ (3,464 ) $ 4,930
Schedule of Additional Supplemental Cash Flow Disclosures	The following table provides additional supplemental cash flow disclosures: Three Months Ended March 31, (Thousands of U.S. Dollars) 2018 2017 Non-cash investing activities: Net liabilities related to property, plant and equipment, end of period $ 70,108 $ 54,875

Significant Accounting Polici25

Significant Accounting Policies Significant Accounting Policies (Details)	3 Months Ended
	Mar. 31, 2018day
Accounting Policies [Abstract]
Payment terms, number of days	3

Segment and Geographic Report26

Segment and Geographic Reporting - Schedule of Information on Reportable Segments and Other Activities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)segment	Mar. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	1
Oil and natural gas sales	$ 138,228	$ 94,659
Depletion, depreciation and accretion	39,461	26,593
General and administrative expenses	11,160	8,712
Income (loss) before income taxes	43,632	31,567
Segment capital expenditures	72,694	46,160
Reportable Segments | Colombia
Segment Reporting Information [Line Items]
Oil and natural gas sales	138,228	90,464
Depletion, depreciation and accretion	38,499	24,935
General and administrative expenses	6,809	4,832
Income (loss) before income taxes	61,151	37,144
Segment capital expenditures	72,561	42,840
All Other
Segment Reporting Information [Line Items]
Oil and natural gas sales	0	4,195
Depletion, depreciation and accretion	962	1,658
General and administrative expenses	4,351	3,880
Income (loss) before income taxes	(17,519)	(5,577)
Segment capital expenditures	$ 133	$ 3,320

Segment and Geographic Report27

Segment and Geographic Reporting - Schedule of Long-lived Assets by Geographical Area (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Property, plant and equipment	$ 1,134,187	$ 1,099,224
Goodwill	102,581	102,581
All other assets	370,020	227,814
Total Assets	1,606,788	1,429,619
Reportable Segments | Colombia
Segment Reporting Information [Line Items]
Property, plant and equipment	1,132,626	1,096,833
Goodwill	102,581	102,581
All other assets	182,440	176,980
Total Assets	1,417,647	1,376,394
All Other
Segment Reporting Information [Line Items]
Property, plant and equipment	1,561	2,391
Goodwill	0	0
All other assets	187,580	50,834
Total Assets	$ 189,141	$ 53,225

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Oil and natural gas properties	$ 3,373,198	$ 3,302,145
Accumulated depletion, depreciation and impairment	(2,239,011)	(2,202,921)
Total Property, Plant and Equipment (Notes 3 and 4)	1,134,187	1,099,224
Oil and natural gas properties
Property, Plant and Equipment [Line Items]
Oil and natural gas properties	3,349,565	3,275,744
Proved
Property, Plant and Equipment [Line Items]
Oil and natural gas properties	2,896,700	2,810,796
Unproved
Property, Plant and Equipment [Line Items]
Oil and natural gas properties	452,865	464,948
Other
Property, Plant and Equipment [Line Items]
Oil and natural gas properties	$ 23,633	$ 26,401

Property, Plant and Equipment29

Property, Plant and Equipment - Property, Plant and Equipment (Narrative) (Details) - $ / bbl	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Crude Oil and NGL
Property, Plant and Equipment [Line Items]
Average Brent price per bbl (in dollars per barrel)	56.92	54.19

Debt and Debt Issuance Costs -

Debt and Debt Issuance Costs - Schedule of Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (17,432)	$ (6,458)
Long-term debt	397,568	256,542
Convertible notes
Debt Instrument [Line Items]
Convertible senior notes and revolving credit facility	115,000	115,000
Revolving credit facility | Revolving credit facility
Debt Instrument [Line Items]
Convertible senior notes and revolving credit facility	0	148,000
Senior Notes Unsecured 6.25% | Senior notes
Debt Instrument [Line Items]
Convertible senior notes and revolving credit facility	$ 300,000	$ 0

Debt and Debt Issuance Costs 31

Debt and Debt Issuance Costs - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Line of Credit Facility [Line Items]
Proceeds from issuance of Senior Notes, net of issuance costs (Note 5)	$ 288,368	$ 0
Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Long-term debt, gross	$ 300,000		$ 0
Debt instrument, interest rate, stated percentage	6.25%
Proceeds from issuance of Senior Notes, net of issuance costs (Note 5)	$ 288,400
Prior to February 15th, 2022 | Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	100.00%
2022 | Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	103.125%
2023 | Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	101.563%
2024 and thereafter | Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	100.00%

Debt and Debt Issuance Costs 32

Debt and Debt Issuance Costs - Schedule of Interest Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Debt Disclosure [Abstract]
Contractual interest and other financing expenses	$ 4,825	$ 2,490
Amortization of debt issuance costs	670	605
Total interest expense recognized	$ 5,495	$ 3,095

Share Capital - Additional Info

Share Capital - Additional Information (Details) - $ / shares	Mar. 08, 2018	Mar. 31, 2018	Mar. 07, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized share capital (in shares)		595,000,002
Authorized share capital, Common Stock (in shares)		570,000,000
Common Stock, par value (in dollars per share)		$ 0.001		$ 0.001
Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized share capital, Preferred Stock (in shares)		25,000,000
Preferred Stock, par value (in dollars per share)		$ 0.001
Special A Voting Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized share capital, Preferred Stock (in shares)		1
Preferred Stock, par value (in dollars per share)		$ 0.001
Special B Voting Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized share capital, Preferred Stock (in shares)		1
Preferred Stock, par value (in dollars per share)		$ 0.001
The 2018 Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under the 2018 Program (up to) (in shares)			19,269,732
Shares authorized representing issued and outstanding shares of Common Stock (as a percent)	5.00%

Share Capital - Schedule of Com

Share Capital - Schedule of Common Stock (Details)	3 Months Ended
	Mar. 31, 2018shares
Increase (Decrease) in Common Stock
Beginning balance (in shares)	385,191,042
Exercised (in shares)	30,000
Ending balance (in shares)	384,959,730
Shares of Common Stock
Increase (Decrease) in Common Stock
Beginning balance (in shares)	385,191,042
Exercised (in shares)	30,000
Shares repurchased and canceled (in shares)	(464,912)
Exchange of exchangeable shares (in shares)	203,600
Ending balance (in shares)	384,959,730
Shares of Common Stock | Exchangeable Shares of Gran Tierra Exchangeco Inc.
Increase (Decrease) in Common Stock
Beginning balance (in shares)	4,422,776
Exercised (in shares)	0
Shares repurchased and canceled (in shares)	0
Exchange of exchangeable shares (in shares)	(203,600)
Ending balance (in shares)	4,219,176
Shares of Common Stock | Exchangeable Shares of Gran Tierra Goldstrike Inc.
Increase (Decrease) in Common Stock
Beginning balance (in shares)	1,688,889
Exercised (in shares)	0
Shares repurchased and canceled (in shares)	0
Exchange of exchangeable shares (in shares)	0
Ending balance (in shares)	1,688,889

Share Capital - Schedule of PSU

Share Capital - Schedule of PSU, DSU, RSU and Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Number of Outstanding Stock Options
Beginning Balance (in shares)	8,960,692
Granted (in shares)	1,890,413
Exercised (in shares)	(30,000)
Forfeited (in shares)	(349,878)
Expired (in shares)	(8,334)
Ending Balance (in shares)	10,462,893
Weighted Average Exercise Price/Stock Option ($)
Beginning balance (in dollars per share) | $ / shares	$ 3.65
Granted (in dollars per share) | $ / shares	2.47
Exercised (in dollars per share) | $ / shares	(2.46)
Forfeited (in dollars per share) | $ / shares	(5.17)
Expired (in dollars per share) | $ / shares	(3.50)
Ending balance (in dollars per share) | $ / shares	$ 3.39
PSUs
Number of Outstanding Share Units
Beginning Balance (in shares)	6,131,951
Granted (in shares)	3,305,486
Exercised (in shares)	0
Forfeited (in shares)	(108,195)
Expired (in shares)	0
Ending Balance (in shares)	9,329,242
DSUs
Number of Outstanding Share Units
Beginning Balance (in shares)	455,768
Granted (in shares)	67,926
Exercised (in shares)	0
Forfeited (in shares)	0
Expired (in shares)	0
Ending Balance (in shares)	523,694
RSUs
Number of Outstanding Share Units
Beginning Balance (in shares)	122,090
Granted (in shares)	0
Exercised (in shares)	(48,600)
Forfeited (in shares)	(1,822)
Expired (in shares)	0
Ending Balance (in shares)	71,668

Share Capital - Equity Compensa

Share Capital - Equity Compensation Awards (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 22		$ 13.7
Weighted average period for recognition	2 years
General and administrative (G&A) expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3.3	$ 1.2

Share Capital - Schedule of Wei

Share Capital - Schedule of Weighted Average Shares Outstanding (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted average number of common and exchangeable shares outstanding (in shares)	391,294,042	399,007,086
Shares issuable pursuant to stock options (in shares)	867,427	635,484
Shares assumed to be purchased from proceeds of stock options (in shares)	(782,456)	(596,456)
Weighted average number of diluted common and exchangeable shares outstanding (in shares)	391,379,013	399,046,114

Share Capital - Weighted Averag

Share Capital - Weighted Average Shares Outstanding (Narrative) (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Convertible notes | Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate	5.00%
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options excluded from diluted income (loss) per share calculation (in shares)	8,599,422	9,210,869

Revenue (Details)

Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Concentration Risk [Line Items]
Variable adjustment for transportation, location, quality, and other elements, percentage	(15.95713%)	(22.42956%)
Accrued sales revenue	$ 7.1		$ 11.1
Product Concentration Risk | Revenue from Contract with Customer [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	99.86399%	99.63765%

Taxes (Details)

Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Effective tax rate	59.00%	60.00%
Deferred (Note 8)	$ 13,482	$ 11,379

Contingencies (Details)

Contingencies (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Letters of credit and other credit support provided	$ 76,500,000	$ 76,000,000
Pending Litigation Royalty, Transportation and Related Costs
Loss Contingencies [Line Items]
Estimated compensation which would be payable if the ANH's interpretation is correct	51,800,000
Amount accrued	$ 0

Financial Instruments and Fai42

Financial Instruments and Fair Value Measurement - Schedule of Fair Value of Derivatives and RSU, PSU and DSU Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Investment - current and long-term assets	$ 37,229	$ 44,202
Foreign currency derivative asset	3,769	302
Assets, fair value disclosure	40,998	44,504
PSU, DSU and RSU liability - current and long-term	14,357	11,430
Liabilities, fair value disclosure	36,029	32,581
Foreign currency derivative asset
Derivatives, Fair Value [Line Items]
Foreign currency derivative asset	3,769	302
Commodity Hedge
Derivatives, Fair Value [Line Items]
Commodity price derivative liability	$ 21,672	$ 21,151

Financial Instruments and Fai43

Financial Instruments and Fair Value Measurement - Schedule of Gains or Losses on Financial Instruments Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Investment loss	$ (5,921)	$ 0
Financial instruments loss (gain)	6,946	(5,439)
Commodity price derivative loss (gain)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative (loss) gain	4,995	(4,703)
Foreign currency derivatives gain
Derivative Instruments, Gain (Loss) [Line Items]
Derivative (loss) gain	$ (3,970)	$ (736)

Financial Instruments and Fai44

Financial Instruments and Fair Value Measurement - Narrative (Details) $ in Millions	Mar. 31, 2018USD ($)
Carrying amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, fair value disclosure	$ 288.5
Value of the notes	111.2
Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, fair value disclosure	292.5
Value of the notes	$ 130

Financial Instruments and Fai45

Financial Instruments and Fair Value Measurement - Rollforward of Level 3 Financial Asset (Details) - Equity Securities - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Opening balance	$ 15,964	$ 19,147	$ 0
Acquisition	0	19,091
Unrealized valuation (loss) gain	(2,703)	56
Unrealized foreign exchange loss	(480)	0
Closing balance	$ 15,964	$ 19,147

Financial Instruments and Fai46

Financial Instruments and Fair Value Measurement - Schedule of Commodity Price Derivative Positions and Commodity Foreign Currency Contracts (Details) - Commodity Hedge bbl in Thousands	3 Months Ended
	Mar. 31, 2018$ / bblbbl
Commodity Foreign Currency Contract, Swap April 1 To December 31, 2018 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (in barrels of oil per day) | bbl	5
Commodity Foreign Currency Contract, Swap April 1 To December 31, 2018 [Member] | Purchased | Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Floor price (in dollars per barrel)	55.9
Participating Swaps: April 1, to December 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (in barrels of oil per day) | bbl	5
Participating Swaps: April 1, to December 31, 2018 | Purchased | Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Floor price (in dollars per barrel)	52.5
Participating Swaps: April 1, to December 31, 2018 | Purchased | Call
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Floor price (in dollars per barrel)	56.11

Financial Instruments and Fai47

Financial Instruments and Fair Value Measurement - Schedule of Outstanding Foreign Currency Derivative Positions (Details) - Collars: April 1, 2018 to December 31, 2018 $ in Thousands, $ in Millions	Mar. 31, 2018COP ($)$ / collar	Mar. 31, 2018USD ($)$ / collar
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount Hedged	$ 130,500	$ 46,935
Purchased | Call
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Purchased Call (in COP per collar)	3,000	3,000
Sold | Put
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Sold Put (in COP per collar)	3,107	3,107

Supplemental Cash Flow Inform48

Supplemental Cash Flow Information - Reconciliation of Cash, Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 160,474	$ 12,326	$ 26,716	$ 25,175
Restricted cash and cash equivalents - current	3,294	11,787	7,663	8,322
Restricted cash and cash equivalents - long-term (included in other long-term assets)	3,164	2,565	10,319	9,770
Cash, cash equivalents and restricted cash and cash equivalents	$ 166,932	$ 26,678	$ 44,698	$ 43,267

Supplemental Cash Flow Inform49

Supplemental Cash Flow Information - Schedule of Net Changes in Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Accounts receivable and other long-term assets	$ (1,982)	$ (2,428)
Derivatives	1,847	0
Inventory	(1,785)	207
Prepaids	1,498	1,078
Accounts payable and accrued and other long-term liabilities	(2,495)	4,310
Taxes receivable and payable	(547)	1,763
Net changes in assets and liabilities from operating activities	$ (3,464)	$ 4,930

Supplemental Cash Flow Inform50

Supplemental Cash Flow Information - Schedule of Additional Supplemental Cash Flow Disclosures (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Net liabilities related to property, plant and equipment, end of period	$ 70,108	$ 54,875