QEMSCAN WellSiteUnprecedented cuttings analysis in a field-tested solution for the well site
Particles to Cuttings | Cuttings to Lithologies | Lithologies to Properties | Properties to Logs
2Advanced MudloggingQEMSCAN WellSite is a solution facilitating advanced mudlogging
services during remote on- and off-shore drilling operations.
Mudlogging commonly complements down-hole (in-situ) logging
using remote sensing technologies known as wireline or logging-
while-drilling (LWD). Rock cuttings, returned to the surface through
the circulating drilling mud, represent the tangible evidence
of the subsurface geology, and therefore a description and/or
analysis of cuttings is a cost effective method to obtaining valuable
complementary data on the stratigraphy of the drilled sequence.
Optical description of cuttings is a common activity of mudlogging
services; however, the process of optical cuttings description is manual,
labor-intensive and qualitative, as echoed by well-site geologists:
we always ask for an experienced mudlogger, but never get one.
QEMSCAN WellSite was developed with 2 objectives in mind:
descriptions, providing more accurate and detailed information
than manual and qualitative methods.
quantitative cuttings descriptions in near real-time at the well
site, ready for seamless integration with logging data provided by
integrated and independent service providers, particularly LWD
Whereas many emerging advanced mudlogging technologies are
primarily bulk cuttings analysis methods, QEMSCAN WellSite is
essentially an imaging technique providing petrographic images
of individual particles in a mud sample. QEMSCAN WellSite uses
this feature to digitally screen particles in a mud sample in order
to separate cuttings particles from other particles such as cavings,
deconvolutes a bulk sample into cuttings properties on a lithology
basis, providing superior confidence in rock properties obtained from
3Cuttings PetrographyQEMSCAN WellSite is actually an automated petrography solution
developed since the late eighties primarily for the mining industry.
QEMSCAN enables access to two primary components of petrography
analysis: mineralogy and texture (i.e. microstructure). The primary
output of QEMSCAN WellSite is 2D numerical mineral and texture
maps of cuttings. These maps form the basis of subsequent image
and chemical analysis on a cutting-by-cutting basis. The visual nature
of the color-coded petrographic images make QEMSCAN WellSite
data readily accessible to a wide range of professionals at the rig (both
geologists and petrophysicists).
SystemBased on a product platform consisting of a compact, rugged and
mobile Scanning Electron Microscope (SEM), energy dispersive
spectrometers (EDS) and QEMSCAN Automated Petrography
measurement and analysis routines, QEMSCAN WellSite has been
designed for, and tested at, remote on- and off-shore well-site
Schematic of the sample measurement process. The electron beam is scanned across the sample surface; at each measurement point (also called a pixel) the BSE and x-ray signals are used for mineral identification by analyzing the EDX spectrum for chemical composition and subsequent classification based on known mineral chemical compositions.
locations. The physical dimensions easily permit placement in 30
foot or larger mudlogging units, or even smaller
4Optimized Sample Preparation WorkflowSamples for QEMSCAN WellSite are presented in the form of 30 mm
diameter resin blocks containing an average of 1,0002,000 cuttings
particles/block, depending on the average size of the cuttings. The
with resin, curing the resin block, cutting and cross-sectioning the
block with a diamond saw, and finally coating the sample surface
with a conductive carbon film. Each device used in the sample
preparation process has a small enough footprint to be placed on
desktops typically found in a mudlogging unit. An additional benefit
of the sample preparation process is that the resulting resin blocks
improve handling and archiving, making cuttings readily available
for complementary analysis at a later stage at a central storage or
Near Real-time Data AcquisitionThe development phase of QEMSCAN WellSite included two extensive
field tests: in the highlands of Papua New Guinea, and off-shore Qatar,
aimed primarily at testing the feasibility and value of near real-time
data acquisition. Whereas time-to-data and throughput may vary
significantly as a function of primary data required, these field tests
yielded near real-time results.
From the time cuttings are collected at the shaker station, cleaned
and dried, it takes less than 30 minutes to prepare a resin block for
analysis. Samples are typically loaded in the system in batches of 6,
with measurement times of around 30 minutes per sample. The initial
data, therefore, are available one hour after collection of cuttings from
the first sampling horizon.
Experience from the first two field tests has demonstrated that up
to 35 cuttings samples can be measured in a 24 hour interval, with
an average of 22 samples if interruptions in the drilling process are
included. Sample preparation efficiency can exceed sample analysis
as demonstrated by one trial where 55 samples were prepared in a
24 hour period. At high drilling rates typically > 100 foot per hour, a
backlog of samples may accumulate; however, during both field tests,
drilling downtime due to e.g. cementation runs, allowed operators to
catch up on the backlog.
(Left) Wet cuttings sample, direct from a shale shaker, with resin impregnated block of same sample, for comparison.(Right) Multiple cuttings samples, prepared, labelled and laid out in stratigraphic order.
5Three MapViews showing a cuttings sample before digital or contextual screening (left), after digital screening to remove drilling mud particles (middle), and after contextual screening to remove cavings, swarf and drilling additives (right).
Particles to CuttingsOnce the numerical mineral maps have been acquired by the system,
image analysis allows for digital screening to remove particles
below a size attributed to drilling mud typically < 63 micrometers.
Subsequent contextual screening removes particles attributed to
caving, swarf and drilling additives, each identified on the basis of
textural and/or compositional properties that differentiate them from
Relevant parameters derived from this screening include cuttings
versus drilling additives ratio (measure of percentage returns), or
cuttings size and shape (measure on drilling performance and stress
Cuttings to LithologiesThe nature of cuttings collection at a constant sampling (i.e. depth)
interval ensures that multiple rock types (lithologies) are likely to be
represented within a single sampling interval. While bulk cuttings
analysis techniques cannot take this lithology variation into account,
QEMSCAN WellSite separates the cuttings into lithology classes, using
mineralogy and texture-based lithology classification rulesets.
While QEMSCAN WellSite comes pre-configured with standard
lithology rulesets, these can be customized at the well site prior to
cuttings collection, or applied retrospectively during or after the
drilling activities, on- or off-site.Schematic diagram illustrating that a cuttings sample may contain multiple lithologies.
6Lithology to PropertiesThe next level of analysis is the determination of specific lithology
properties, such as:
A variety of preconfigured reports are available for reporting each of
the above properties for any given batch of depth intervals. Additional
report templates can easily be created and retained for future use.
Lithology classes from a siliciclastic reservoir sequence.
Property sheet for lithology class calc-cmt-si (calcareous cemented silt) based on combined cuttings. This cuttings class comprises siltstone cuttings cemented by calcite.
calc-cmt-crs-qtz ark-crs-qtz cl-crs-qtz crs-qtz calc-cmt-si cl-si si calc-cl cl cmt uclass
7Properties to LogsFinally, each of these properties can be easily exported for
incorporation into 3rd party logging software, such as ODM, for
subsequent interpretation by petrophysicists or reservoir evaluation
specialists. Results from the two field tests demonstrate excellent
consistency between the conventional mudlog cuttings descriptions
and those obtained by QEMSCAN WellSite on the one side, but on the
other side superior resolution and detail of mineralogy and texture,
from which specific properties such as cuttings / additives ratio,
lithology, clay type, or calculated matrix density can be derived with
Retrospective Data InterrogationAnother key feature of QEMSCAN WellSite solution is that all of the
raw data is retained in datastores (databases) that can be revisited
retrospectively with the help of off-line software on workstations at
oil and gas company operational centers. As insights into formation
evaluation continue to develop, it is anticipated that these quantitative
cuttings databases will carry significant value over time
for historical interrogation studies.
Collaborative DevelopmentQEMSCAN WellSite requirements have been gathered in close
collaboration with many major oil and gas companies and service
providers, whose input is greatly acknowledged. Furthermore, field
tests have been conducted in Papua New Guinea in close collaboration
with Halliburton (Houston, Texas) and OilSearch (Sydney, Australia),
and off-shore Qatar. Further development and testing is ongoing with
independent surface logging company GEOLOG at its R&D facilities in
For a full description of the field tests, we refer to application
notes available upon request and for download on
Integrated ODM log juxtaposing QEMSCAN data with selected down-hole data.
FEI CompanyFEI is a leading developer and manufacturer of electron and ion beam
microscopes, headquartered in Oregon, USA, and is listed on the
New York NASDAQ Stock Market. The Natural Resources business unit
is dedicated to the development, marketing, sales and support of
technology solutions for the mining, oil & gas, and geosciences sectors.
Demonstration facilities are available in Australia, The Netherlands
For more information please visit: www.fei-natural-resources.com
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2011. We are constantly improving the performance of our products, so all specifications are subject to change without notice.QEMSCAN, WellSite and the FEI logo are trademarks of FEI Company, and FEI is a registered trademark of FEI Company. All other trademarks belong to their respective owners. BR00?? ??-2011
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