CONCENTRATIONS, SIGNIFICANT CUSTOMERS, COMMITMENTS AND CONTINGENCIES - Customer Concentrations (Details) - Customer concentration risk	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Revenues | Customer 1
Revenue, Major Customer
Concentration percentage (as a percent)	38.00%	31.00%
Revenues | Customer 1 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	53.00%	36.00%
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)	12.00%	7.00%
Revenues | Customer 2 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	17.00%	8.00%
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)	3.00%	11.00%
Revenues | Customer 3 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	4.00%	12.00%
Revenues | Customer 3 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 3 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 4
Revenue, Major Customer
Concentration percentage (as a percent)	2.00%	4.00%
Revenues | Customer 4 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	2.00%	4.00%
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)	0.00%	0.00%
Revenues | Customer 5
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	17.00%
Revenues | Customer 5 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	20.00%
Revenues | Customer 5 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 5 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Receivables | Customer 1
Revenue, Major Customer
Concentration percentage (as a percent)	7.00%	20.00%
Receivables | Customer 2
Revenue, Major Customer
Concentration percentage (as a percent)	16.00%	14.00%
Receivables | Customer 3
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	8.00%
Receivables | Customer 4
Revenue, Major Customer
Concentration percentage (as a percent)	2.00%	10.00%
Receivables | Customer 5
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%