CONCENTRATIONS, SIGNIFICANT CUSTOMERS, COMMITMENTS AND CONTINGENCIES - Customer Concentrations (Details) - Customer concentration risk	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Revenues | Customer 1
Revenue, Major Customer
Concentration percentage (as a percent)	25.00%	38.00%
Revenues | Customer 1 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	46.00%	53.00%
Revenues | Customer 1 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 1 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 2
Revenue, Major Customer
Concentration percentage (as a percent)	10.00%	12.00%
Revenues | Customer 2 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	18.00%	17.00%
Revenues | Customer 2 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 2 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 3
Revenue, Major Customer
Concentration percentage (as a percent)	10.00%	3.00%
Revenues | Customer 3 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 3 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	27.00%	16.00%
Revenues | Customer 3 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 4 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 4 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 4 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	72.00%	22.00%
Receivables | Customer 1
Revenue, Major Customer
Concentration percentage (as a percent)	12.00%	7.00%
Receivables | Customer 2
Revenue, Major Customer
Concentration percentage (as a percent)	23.00%	16.00%
Receivables | Customer 3
Revenue, Major Customer
Concentration percentage (as a percent)	5.00%	7.00%