Published: 01/01/2007
Published: 01/01/2007
Determining fluid density is a primary objective of formation evaluation because that measurement significantly influences field production and economics. The ability to obtain quantitative fluid density measurements at reservoir conditions and in real time from a deepwater vertical appraisal well drilled with oil-base mud was planned to improve understanding of the formation fluids and the reservoir for optimizing a subsequent drillstem test.
The InSitu Density sensor was deployed with innovative Quicksilver Probe
focused extraction, which diverts filtrate-contaminated fluid to the perimeter
of the probe to collect pure reservoir fluid into the extraction flowline. The
separation of pure reservoir fluid makes it possible to accurately conduct
downhole fluid analysis, even in oil-base mud. Under flowing conditions, the
InSitu Density sensor uses dual resonance modes to directly compute density
from resonator-fluid interaction, with the measurement quality assessed against
standard-fluid characterization parameters.
The toolstring was also
configured with optical fluid analyzers, conducted pressure pretests, and
collected PVT fluid samples.
InSitu Density sensor measurements shown on the log from three sampling
stations in the oil zone are consistent and comparable with values determined
by pressure gradient analysis and were confirmed by subsequent PVT sample
analysis. Because real-time measurement of fluid density directly yields the
slope of the pressure gradient, the fluid contacts can be readily identified.
The log shows three pressure gradients, corresponding to gas, oil, and water
and all in pressure communication. There are no indicators of
compartmentalization or compositional grading.
The composition of the
oil was also determined in real time by downhole fluid analysis of the fluid
density measurements and optical spectrometry data.
With this
information available during logging, the operator was able to rapidly assess
the fluid composition and location of fluid contacts to guide the operation and
then design a drillstem test.
Challenge: Dynamically investigate formation fluid density at reservoir conditions in an appraisal well drilled with oil-base mud.
Solution: Combine InSitu Density reservoir fluid density sensor with Quicksilver Probe focused extraction to obtain accurate density measurements under flowing conditions and conduct downhole fluid analysis.
Results: Acquired accurate density data input for real-time downhole fluid analysis to optimize the logging investigation and subsequent operations.
