Emulsion refers to an oil and water mixture that does not readily separate.
I usually assume that emulsion is 50% water, 50% crude. But that might not be correct since there’s no way (which I knew of) which can accurately determine how much water and oil content in an emulsion.
Therefore, I usually instruct operations team to check for both BS&W and emulsion levels in tanks nominated for loading. The priority is to ensure that BS&W does not exceed 0.5%. And emulsion would be aimed to be as low as reasonably practical.
We declare BS&W figure in our Certificate of Quality but not emulsion.
Therefore, I would issues Statement of Fact (SOF) or LOP (Letter of Protest) to highlight on the emulsion to both the seller and buyer.