Note 10 - Asset Retirement Obligations - Estimated Amounts and Timing of Cash Flows and Assumptions Used for ARO Estimates (Details)	Jan. 31, 2020 USD ($) yr	Jul. 31, 2019 USD ($) yr
Undiscounted amount of estimated cash flows | $	$ 8,221,018	$ 8,221,018
Measurement Input, Expected Term [Member] | Minimum [Member]
Asset retirement obligations, measurement input (Year)	9	9
Measurement Input, Expected Term [Member] | Maximum [Member]
Asset retirement obligations, measurement input (Year)	21	21
Measurement Input, Inflation Rate [Member] | Minimum [Member]
Asset retirement obligations, measurement input (Year)	0.0156	0.0156
Measurement Input, Inflation Rate [Member] | Maximum [Member]
Asset retirement obligations, measurement input (Year)	0.0217	0.0217
Measurement Input, Discount Rate [Member] | Minimum [Member]
Asset retirement obligations, measurement input (Year)	0.055	0.055
Measurement Input, Discount Rate [Member] | Maximum [Member]
Asset retirement obligations, measurement input (Year)	0.0596	0.0596