SpectraSphere* fluid mapping-whiledrilling service is the industry’s first to provide high-quality formation pressure measurements, reservoir representative fluid sampling, and in situ downhole fluid analysis—all in real time, and all while drilling.
Advanced PVT fluid properties play a vital role in estimating reserves, optimizing completions,designing surface facilities, and meeting production goals. However, these datasets are traditionally available only after performing conventional formation sampling. The unique ability to fully understand reservoir properties during drilling operations opens up new dimensions in well placement and reservoir characterization, while at the same time reducing costs. SpectraSphere service delivers these advantages in multiple environments, from enabling advanced knowledge of untapped reservoirs in exploration to de-risking fluid analysis and sampling in highly deviated development wells.
This module can operate on its own as a stand-alone formation pressure-while-drilling tool or be combined
with the SpectraSphere service pumpout module and sample carriers for fluid mapping operations. The
pretest module performs all the functionalities of the industry-proven StethoScope* formation pressurewhile-
drilling service, including time-optimized and pumps-off pretesting. This module also includes
■■ high-precision Axton quartz pressure gauge
■■ 30,000-psi pressure rating
■■ large-diameter probe.
Fluid mapping module
The downhole fluid analyzer (DFA) provides real-time reservoir fluid contamination estimation, compositional
analysis, and in-situ GOR measurements. The pumpout module (POM) contains an electromechanical positive
displacement unit that enables accurate pump control that drives the pump-out process.
The pump has a nominal operating range of between 0.1 cc/sec and 40 cc/sec. This system enables the
sampling operation to be driven at constant rate or constant drawdown pressure, providing precise flowline
control to ensure that phase integrity of the fluid is maintained.
The POM also has a resistivity cell, a temperature cell, and two sensor bays that house the DFA. Because
the POM requires mud circulation for generating power, the risk of differential sticking is reduced.
Sample carrier module (SCM)
The SpectraSphere service can be fitted with up to four carriers, each holding up to three Department of
Transportation (DOT)-certified PVT containers. They are either 450 cc or 250 cc, single-phase N2-compensated
bottles that are mounted on the outside of the drill collar and protected by articulated shields.
These DOT–certified containers are designed to be removed from the SCM on the rig for draining on
site or at a PVT laboratory. Up to four SCMs may be combined in a single BHA to increase the number
of sample bottles per run.
PVT lab testing validates results of fluid-profiling method in Gulf of Mexico
Eni US Operating Co. wanted to optimize formation sampling and 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 sampling method would need to be capable of acquiring pretests, capturing clean downhole samples and fully describing reservoir pressures at a cost and time savings.
Schlumberger recommended using fluid mapping to acquire samples, analyze them in real time, and measure formation pressures from the exploratory Mississippi Canyon well. This service is added to the downhole drilling assembly and collects reservoir-representative samples while drilling. Traditionally, sampling happens about a day after drilling, which often results in contamination of the reservoir by the drilling fluid filtrate. Fluid mapping while drilling accurately delivers individual compositions from C1 to C5, C6+, GOR, fluid color, hydrocarbon and water fractions, flowline fluid resistivity, temperature and pressure and formation volume factor, CO2—all during drilling.
Fluid mapping was used to collect and analyze six samples downhole in real time, setting an industry first for the transmission of detailed in situ fluid properties. Fluid mapping estimated contamination and cleanup time; performed fluid identification and typing; and measured GOR and fluid composition (C1 to C5, C6+, and CO2).
These results were verified 10 weeks later by lab results, which showed good agreement with field results on every measure. Contamination was estimated in real time to within ±2% of the laboratory-determined values. Pretests, pressure measurements, and fluid gradients were also successfully taken 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, Eni concluded that fluid mapping is a reliable method of gathering clean samples and good measurements while demonstrating a time savings of about 10 weeks.
Operator reduces risk and optimizes logging program with while-drilling formation pressure and fluid analysis in highly deviated wellbore
To further develop a field offshore Malaysia, the Hess Corporation needed a complete understanding of the reservoir, particularly fluid properties. Unfortunately, no critical data was available from the existing exploration well. As a result, Hess needed to obtain formation fluid and gas samples and formation pressure measurements from three wells. Because these three wells were highly deviated and the well paths would likely intersect pressure-depleted formations, Hess was concerned about differential sticking during sampling.
Schlumberger recommended obtaining the downhole pressure and fluid samples using fluid mapping to monitor the reservoir fluid properties and cleanup process as fluid is pumped through the flowline. When the pumped fluid meets the operator’s requirements, a downlink can be sent from surface to capture the formation fluid. Multiple sample bottles can be filled at a single sampling station, and as many as 12 fluid samples can be captured in a single run.
Using fluid mapping, Hess collected 4 fluid samples, 2 gas samples, and 21 formation pressure measurements over 12 hours while also avoiding differential sticking. Downhole testing showed the samples were contaminant-free, and later lab results confirmed that the samples were representative of the reservoir. Further sampling of the asset in a second and third well was deemed unnecessary, saving Hess 3 days.
This was the first sampling operation conducted by Hess in this field. With the collected water samples, the operator gained insight into formation water salinity, which is critical to calculating water saturation and optimizing completion design and production planning. The pressure data will help the operator understand zonal connectivity within the field.