MBW System
A brief consideration in using and installing watercut analyzers and the EESIFLO MBW system
Phil Hughes (EESIFLO International Pte Ltd)
Water in hydrocarbons has always been something to consider carefully in the oil industry and a common problem is water in crude oil. How it is measured or reported can affect either the buyer or seller financially. This may include:
- Custody Transfer
- Allocation
- Plant Balance (refinery input)
- Product Quality
- Sediment & Water
- Shrinkage (entrained gas)
- API gravity
- Contractual requirements
A barrel of water, can cost considerably more than a barrel of oil. Someone has to pay for the oil, pay for the water, pay for the disposal of water and pay for the process contamination. Everyone is looking for a quick fix and even today we find contracts written around spot sampling which can be completely unreliable if the sample is non representative of the liquids in the process stream. The lab results are thus invalid and the frustration simply increases because the measurements unfairly affect someone’s wallet. Could this be your wallet?
Fig. 1.0 Separation occurs in oil/water processes and spot sampling using the above method misses “bottom” water.
Laboratory analyses are generally accurate but are quite useless if the sample being analyzed is not representative of the TOTAL FLUID FLOW
The same applies online. Fig 1.1 World class watercut meter measuring a non-representative distribution of water and oil. Inevitable and problematic watercut measurements ,arguments, doubts and wasted time and money.
Additionally we have problematic calibration if watercut meters are calibrated to lab results from non representative spot sampling. Spending the money on a highly accurate instrument that is not sensing at a point where we have a homogeneous mixture is an exercise in futility.
The problem becomes chronic as oil wells depressurize and watercut increases to the point when there is more water than oil being produced . In small pipes the chances of getting proper mixing in a higher watercut situation is doubtful and in large (greater than 6 inches) pipes it is a pipe dream. Honest field operators will be familiar with the problems of laboratory prepared spot samples for calibration never tallying with the reported watercut .
The only known solution is to mix, so that our sampling or watercut instruments are gathering samples or data in a volume area where sample is representative and homogeneous! Whether we are taking spot samples, grab sampling or installing watercut meters, the same will apply if we have an uneven or unpredictable water distribution in the crude oil stream. Manufacturers of static mixers have proved this fact time and time again over the years. There is adequate data to show that mixing should not be considered an option.
