Page 44: of Offshore Engineer Magazine (Dec/Jan 2013)

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Subsea

Subsea multiphase sampling

Subsea sampling can

Time

Time help increase PVT

Stages in afecting taken well testing production accuracy and improve (hours) (hours) subsea multiphase meter

Connecting 2 to 43 well test performance. equipment

Test lines for subsea well

Building up 2 to 41.5 testing cost as much as pressure/fow

US$60 million and come

Testing 2 to 40 with logistical and well

Deconnecting 2 to 43 well test intervention challenges. equipment

Eivind Gransaether

Building up 2 to 41.5 explains. pressure/fow

Other lost 3 3 time he deployment of

Total 9 to 17 12 permanent subsea mul-

T tiphase meters as an

The steps needed to conduct a well test, and the period of time alternative to well testing and Source: Mirmorax.

production is lost.

as a way to increase recovery has become a priority for many operators. cuts, commingled well streams

Subsea multiphase meters from subsea tie backs, changes are viewed as a more fexible, in water properties from sea- or cost-effective and accurate freshwater-fooded wells, or option, compared to large and differences in salinity between maintenance-intensive test injected and reservoir water. separators. These changes are likely to

To be effective and accu- result in signifcant variations rate, subsea multiphase in PVT properties. Effective meters, which can cost up volumetric subsea sampling and to US$400,000 to buy and the accurate tracking of PVT integrate, need to be calibrated data can have a positive effect through quality, volumet- on the meters’ performance and

Computer-aided image of the sampling system. ric sampling over the feld’s operators’ production strategies

Image: Mirmorax.

lifetime. in these cases.

Fluctuations in PVT Data

This is particularly impor- The dangers of inaccurate tant as felds age and more reservoir One of the most important sources for PVT analysis were outlined in an SPE variables come into play, leading to an evaluating fuid properties and predict- paper by Adel M. Elsharkawy of Kuwait increase in the uncertainty of metering ing reservoir performance is pressure, University (SPE 37441). It illustrated systems. The majority of multiphase volume and temperature (PVT) data, how inaccurate PVT analysis resulted meters, for example, use a gamma source which is likely to change signifcantly in an underestimation of the ultimate that must be confgured with the fuid over the lifetime of the reservoir as fuid oil recovery from a particular feld by as properties of oil, water and gas, and ide- and process conditions change. much as 40%. ally must refect changing reservoir data Changes can include increased liquid Well test separators play an impor- over time. and water in the gas fow, higher water tant role in capturing PVT data by

December 2013 | OE oedigital.com 46 046_OE1213_Subsea1.indd 46 11/22/13 6:52 PM