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Asset Retirement Obligations (Details 1) (USD $)
9 Months Ended 12 Months Ended
Jan. 31, 2015
Jan. 31, 2014
Apr. 30, 2014
Apr. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]        
2015     $ 460,778us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths  
2016     81,181us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo  
2017     212,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree  
2018         
2019         
Thereafter     388,764us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive  
Total, before discount     1,142,723PTRC_AssetRetirementObligationBeforeDiscount  
Effect of discount 38,060us-gaap_AssetRetirementObligationAccretionExpense 40,985us-gaap_AssetRetirementObligationAccretionExpense (234,139)us-gaap_AssetRetirementObligationAccretionExpense  
Asset Retirement Obligations $ 908,584us-gaap_AssetRetirementObligation   $ 908,584us-gaap_AssetRetirementObligation $ 763,036us-gaap_AssetRetirementObligation