QEMSCAN^® WellSite™ data analysis and reporting follows a structured workflow:

• Particles to Cuttings
• Cuttings to Lithologies
• Lithologies to Properties
• Properties to Logs

The first step involves image-based filters and particle classification to digitally separate genuine drill cuttings from other particles that commonly contaminate the samples, including solid drilling fluid additives. In contrast to bulk sample analysis techniques such as from XRF, XRD and LIBS, QEMSCAN WellSite can report these properties separately and calculate the percentage return of the cuttings. The second level of information includes reports on the composition of representative drill cuttings within a sample sequence. The genuine cuttings are sorted in lithology classes, based on mineral and texture rule-sets. Mineral and lithology contribution can be reported for any selected sampling sequence, providing mineral stratigraphy and lithology logs. Thirdly, for each lithology class, lithology-based properties are measured including modal mineralogy, clay typing, grain size and calculated matrix density. Finally, QEMSCAN reports can be integrated in the form of log data with conventional Formation Evaluation Logs and downhole instrument logs such as wireline and Logging While Drilling (LWD) data for interpretation.

Particles to Cuttings

Once 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 particles – typically <63 micrometers. Subsequent contextual screening removes particles attributed to caving, swarf and drilling additives (see figure below). 

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 fields). The ability to digitally screen a cuttings sample is a major differentiator between QEMSCAN® WellSite and bulk cutting analysis methods (LIBS, XRF and XRD).

Cuttings to Lithologies

The 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 analysis 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. 

Linking quantitative cuttings properties to lithology is a key feature of QEMSCAN WellSite. 

Lithology to Properties

The next level of analysis is the determination of specific lithology properties, such as:

• Modal mineralogy
• Clay typing (glauconite, micas, radioactive clays, swelling clays) 
• K-feldspar abundance 
• Quartz grain size 
• Calculated matrix density 
• Trace mineralogy such as pyrite or apatite 
• Calculated matrix elemental chemistry 
• Organic particles abundance, commonly encountered in gas and oil shale plays 

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. 

Properties to Logs

Finally, 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 inferred matrix density can be derived with confidence.

Retrospective Data Interrogation

Another key feature of the QEMSCAN WellSite solution is that both raw and processed data is saved in databases that can be revisited off-line at oil and gas company operational centers. As insights into reservoir evaluation continue to develop, it is anticipated that these quantitative cuttings databases will carry significant value over time for historical interrogation studies.