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Schedule of Revenue by Major Customers by Reporting Segments (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Oct. 31, 2021
Oct. 31, 2020
Oct. 31, 2021
Oct. 31, 2020
Product Information [Line Items]        
Revenues  $ 247 $ 118 $ 519 $ 287
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Eni S.p.A [Member]        
Product Information [Line Items]        
Revenues  14 72 14 99
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Department of Energy [Member]        
Product Information [Line Items]        
Revenues  81 81
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | EGP [Member]        
Product Information [Line Items]        
Revenues  14 42 163 157
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Clark Hill [Member]        
Product Information [Line Items]        
Revenues  30 37
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Matthews [Member]        
Product Information [Line Items]        
Revenues  30 30
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Valaris [Member]        
Product Information [Line Items]        
Revenues  47 135
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Other [Member]        
Product Information [Line Items]        
Revenues  31 4 59 31
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Customer [Member]        
Product Information [Line Items]        
Revenues  $ 247 $ 118 $ 519 $ 287