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Asset Retirement Obligations (Details Narrative) (USD $)
 9 Months Ended
Jan. 31, 2015
Apr. 30, 2014
Asset Retirement Obligation, future liability $ 1,142,723us-gaap_RestructuringReserveCurrent $ 1,087,292us-gaap_RestructuringReserveCurrent
Costs are expected to be incurred, minimum period 1 year  
Credit-adjusted risk-free discount rate 10.00%PTRC_CreditAdjustedRiskFreeDiscountRate  
Percentage of inflation rate 2.00%PTRC_AssetRetirementObligationsInflationRate  
Reclamation deposits $ 0PTRC_ReclamationDeposits $ 0PTRC_ReclamationDeposits
Minimum [Member]    
Costs are expected to be incurred, minimum period 1 year  
Maximum [Member]    
Costs are expected to be incurred, minimum period 24 years