X-Ray Fluorescence and X-Ray Diffraction with Drill Cuttings: Real-Time Oilfield Geochemistry

      The techniques of X-ray diffraction (XRD) and X-ray fluorescence (XRF) enable the identification of the elemental components of any sample. When I was an undergraduate geology student several decades ago, we had a very large XRD machine that had its own little room. I only had a brief introduction to it in one class, but professors and grad students used it in their research.  

     Fast forward to now, we have portable XRF and XRD instruments that are much less expensive and accurate enough for most field work, although the more sophisticated stationary units give better quality results. Portable hand-held XRF devices are now in common use to examine outcrops, cores, and well cuttings.

     Beginning in earnest in the 2010s, some mudlogging companies began to experiment with and offer geochemical logging services that rely on XRF and XRD. Samples are analyzed at spaced intervals and analyzed for elemental content of certain elements, and these changing levels of different elements are logged with measured depth (MD) and then correlated back to true vertical depth (TVD). Gamma ray logs are the standard for measurement while drilling (MWD). The goal of geochemical logging is usually to define a gamma ray section by its elemental content, which can be used as a second data source to support or refute different gamma ray interpretations. This can be done in real-time or in near real-time. Geochemical logging is a form of chemo-stratigraphy, defining stratigraphic intervals by elemental composition. Some XRF geochemical logs are shown below.

     Some companies, such as Field Geo Services, also host advanced geochemical laboratories. They note that in addition to service for oil & gas companies, they offer services to the geothermal, mining, environmental, and material science sectors.

“From reservoir characterization and mineral exploration to cement, ceramic, and metals testing, our lab’s capabilities are designed to support not just energy projects, but any application that requires a deeper understanding of material composition and performance.” 

     They also point out that while mudlogging offers a qualitative description of rocks, geochemistry offers quantitative confirmation. They also utilize mass spectrometry in their in-house lab.  

“Using mass spectrometry, we can track vapor chemistry signatures with unparalleled sensitivity, revealing compartmentalization, aromatics, and subtle geochemical shifts invisible to conventional gas detection.”

“XRF gives elemental profiles of drill cuttings in minutes, offering real-time chemostratigraphy and formation characterization. XRD provides mineralogical data that’s crucial for understanding reservoir quality, swelling clays, or frac potential.”

     They suggest their geochemical service for exploration and appraisal wells, production studies, reservoirs with complex mineralogy, compartmentalization, or situations where target zone certainty is needed.  

     As noted in the summary below, other material besides rocks can be characterized for elemental composition, including drilling mud, which often contains chemical additives. Chemostratigraphy can be used to find the best target intervals in horizontal wells by focusing on the optimal mineralogy for porosity & permeability, organic matter preservation, and brittleness, which aids hydraulic fracturing.

     It should also be pointed out that elemental components in drilling mud can alter the results of XRF analysis and need to be considered when interpreting drill-site XRF data. Geologist Preston Monaghan’s CrustCore Insights explains how the periodic mud report should be utilized to adjust and correctly interpret XRF data. His post, entitled How the Mud Report Is Used in XRF Interpretation, is reproduced below.

How the Mud Report Is Used in XRF Interpretation

In unconventional drilling, cuttings-based XRF is only as reliable as the context behind the data. The daily mud report provides that context. Here’s how:

1.        Identifies Additives That Alter Elemental Signatures.

Mud reports list treatments such as:

CaCO₃ / lime → inflates Ca, Mg signals,

Barite (BaSO₄) → raises Ba, suppresses Th & U detection

Graphite → mimics organic-rich (reducing) intervals

LCM pills → introduce foreign minerals

Gypsum / salts → alter sulfur and chloride response

If XRF spikes align with additive additions, the change is not geological.

2.        Reveals Contamination Timing.

XRF trends must be compared to:

torque events, lost circulation, LCM sweeps,bridging material additions.

These events often overlay contamination on cuttings.

      3.   Explains False Brittleness Indicators

Calcium spikes from CaCO₃ sweeps can mimic:

limestone streaks, carbonate cement, brittle intervals.

Mud report → tells you whether it’s rock or chemistry.

     4.   Tracks OBM Dilution & Surfactants

OBM system treatments introduce trace metals:

Zn, Cu, Fe, Cr

Those appear in XRF models as “mineralization.”

Mud report → shows they came from the mud.

     5.   Prevents Misinterpretation of Redox Conditions

Graphite pills and surfactants can mimic:

reducing facies, elevated TOC, migration signatures.

Without the mud report, this looks like reservoir change.

     6.   Helps Identify Suppressed Elements

Barite’s density acts like a spectral blanket and suppresses ppm-level signals (Th, U).

Mud report → tells you when suppression begins.

     7.   Separates Cavings From True Formation Entry

Bit balling → shale cavings

Seating bit → limestone cavings

Swab/surge → heterolithic blends

Mud report + drilling narrative = avoids wrong formation picks.

     8.   Supports Machine Learning QC

If barite sweeps coincide with flattened variability, the model is no longer learning the rock — it’s learning the additive schedule.

Mud report = metadata.

Why Most People Ignore It

Office geoscientists often never:

washed cuttings, smelled OBM smoke, watched pills pump downhole, saw coatings on grains.

So they assume XRF = rock.

The mud report reminds you:

> XRF = rock + mud + additives + workflow bias.

Bottom Line

The mud report is the context layer that prevents:

false depositional interpretations, wrong facies boundaries, bad brittleness models, landing zone errors.

Without it, you’re not analyzing the reservoir.

You’re analyzing drilling contamination.

Professional takeaway

If you’re using XRF on cuttings:

Always cross-check additive timing.

Flag element spikes during sweeps.

Watch for suppressed trace elements.

Correlate fluorescence changes with mud treatment.

Respect the mud report.

Respect the context.

   

 

 

References:

 

More Than Mudlogging: Field Geo Services’ Advanced Geochemistry Lab. Field Geo Services, Inc., November 11, 2025. (26) More Than Mudlogging: Field Geo Services’ Advanced Geochemistry Lab | LinkedIn

How the Mud Report Is Used in XRF Interpretation. Preston Monaghan. CrustCore Insights. Posted on LinkedIn. (26) Post | Feed | LinkedIn

Mudlogging vs. Geochemistry: The Case for Stacked Services. Field Geo Services, Inc. August 18, 2025. (26) Mudlogging vs. Geochemistry: The Case for Stacked Services | LinkedIn

X-Ray Fluorescence (XRF): Wellsite XRF sample collection and analysis. Field Geo Services. X-Ray Fluorescence (XRF) - Field Geo Services Inc