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Summary of Significant Accounting Policies - Schedule of Revenue by Major Customers by Reporting Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Revenues	$ 317	$ 725	$ 604	$ 1,131
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Eni S.P.A [Member]
Revenues	34	42	135	118
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Premier Oil UK Limited [Member]
Revenues		5	27	126
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | EGP [Member]
Revenues	223	678	379	774
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | ACET [Member]
Revenues	33		37
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Other [Member]
Revenues	$ 27		$ 26	$ 113

X

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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