Though the API is currently in late stages of balloting a draft.
There are however standards in place for fiscal automatic sampling of crude oil namely API 8.2 and ISO 3171.
[1] Water cut meters are typically used in the petroleum industry to measure the water cut of oil flowing from a well, produced oil from a separator, crude oil transfer in pipelines and in loading tankers.
The main technologies are dielectric measurements using radio or microwave frequency and NIR measurements and less common are gamma ray based instruments.
The water cut in waterdrive reservoirs can reach very high values.