Identify new sampling method to save time and money in future
Eni US Operating Co. wanted to optimize formation testing processes to
save time and money in future wells. The operator conducted a field test while
drilling an exploratory well in the Mississippi Canyon area of the Gulf of
Mexico in Miocene turbiditic sands. The target zone was located at a water
depth of about 5,800 ft with uncertain reservoir characteristics and fluid
properties. A new reservoir fluid mapping method would need to be capable of
acquiring pretests, capturing clean downhole samples, and fully describing
reservoir fluids at a cost and time savings.
Acquire individual fluid composition analysis up to C5 with
Schlumberger recommended using the SpectraSphere service to measure
formation pressures, acquire samples, and analyze the fluid characteristics in
real time from the exploratory Mississippi Canyon well. This service is added
to the downhole drilling assembly and collects reservoir-representative samples
while performing accurate fluid analysis before sampling while drilling.
Traditionally, sampling happens about a day after drilling, which often results
in deeper invasion of the reservoir by the drilling fluid filtrate. The
SpectraSphere service accurately delivers the following in situ hydrocarbons
properties: individual compositions from C1 to C5,
C6+, GOR, fluid color, hydrocarbons and water fractions, flowline
fluid resistivity, temperature and pressure, and CO2.
Transmitted individual hydrocarbon analysis in situ, delivered
lab-quality fluid profiling
The SpectraSphere service analyzed and collected six samples downhole in
real time, setting an industry first for the transmission of detailed in situ
fluid properties. The SpectraSphere service estimated contamination and time to
clean up, performed fluid identification and typing and measured GOR and fluid
composition (C1 to C5, C6+, and
These results were verified 10 weeks later by lab results. Contamination
was estimated in real time to within ±2% of the laboratory-determined
values. Pressure measurements and fluid gradients were also successfully
obtained during the operation. A total of 28 pretests were taken—17 while
drilling and 11 while pulling out—that provided Eni a full description of
the reservoir pressure and fluid gradients.
By delivering lab-quality results while drilling, SpectraSphere service
proved its capability of gathering good measurements and clean samples, saving
Eni about 10 weeks.
PVT lab analysis results show good agreement with real-time, in situ
analysis of fluid properties.
Eni determined that the quality and amount of real-time data (shown
above) from the SpectraSphere service would enable it to accurately determine
pressures, fluid composition, and fluid fraction in future wells.