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Need to monitor drill cuttings in new wells to see if crude oil, drilling muds or both are present?  An evaluation study was performed testing eight samples for Horizon Well Logging, Inc. in California.  The samples were tested for GRO, Total PAH and Target PAH using Sitelab's UVF-3100D analyzer and Heavy PAHs using the TD-500D analyzer.  The types and quantities of aromatic hydrocarbons that exist in crude oil fluoresce very differently and at much higher intensity compared to oil based drilling muds and their additives.  Sitelab's UVF technology can detect how much and what type of hydrocarbon is present, including a rough estimation of the API gravity in the oils or drill cuttings.

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Report below courtesy of Horizon Well Logging, Inc.


Drilling for oil using an oil based mud (OBM) facilitates the drilling process but is often confusing for the mudlogging geologist.  Some of the formation oil qualities that are readily apparent in water based systems are bright fluorescence and solvent cuts.  Both of these attributes are also present when using OBM whether there is any formation oil present or not.  Often OBM is used where the target is a high gravity oil that doesn’t stain the cuttings brown from the oil.  Steve Greason of Sitelab Corporation in West Newbury, MA graciously agreed to test a set of eight samples for OBM vs formation oil.  Three different tests on each of the eight samples were performed using Sitelab’s UVF-3100D.  An additional test using Sitelab’s TD-500D analyzer was also performed on all eight samples.  The test data shows marked elevation of Polyaromatic Hydrocarbons (PAH’s) in the crude oils plus in the OBM that contained crude oils.  Very low values for these same PAH’s were observed in the unused OBM, pure LVT (mineral oil base of the OBM), and in CFR (a mud additive that also fluoresces).

The eight samples tested are listed below:

A - LVT - nearly pure hydro treated mineral oil, this is OBM base oil

B - OBM - from the mud company before being used to drill (contains LVT, Mul I & II (oil/water emulsifiers), Lime, and Claytone (clay that is receptive to oil - fairly inert)

C - Crude oil - 30 gravity (fairly high)

D - Crude oil - 44 gravity (high gravity - runny like water)

E - OBM with some crude oil - used in drilling

F - Crude oil - same oil in OBM above - skimmed from sump - may have some rig oils but believed fairly pure crude

G - CFR - mud additive that also has a characteristic fluorescence

H - Crude oil - 35 gravity - from a different well but brings participation from another major - sitting 3 years

The equipment shows a clear distinction between the OBM and formation oil when they are extracted from their liquid state. Further tests should include testing of the actual cuttings during realtime drilling.             

Oil response varies depending on the types and quantities of aromatic hydrocarbons detected:

Fingerprinting "signatures" or
ratios can be used to estimate the API gravity in crude oils:

Both analyzers show the same trend.  PAHs are proportionate to the API gravity.  Lighter crude oils exhibit higher ratios, while heavier crude oils exhibit lower ratios.

The GRO ratios were also proportionate, except for the 35 API gravity oil.  Why?  BTEX compounds degrade more quickly than PAH compounds.  The oil from this well is likely older and weathered, while the other two wells have fresher oil.
              Need to Test Contaminated Drill Cuttings?

If laboratory testing is required for remediating, disposing or investigating sites contaminated with drill cuttings, contact Sitelab to see which instrument is most suitable.  Drill cuttings are prepared and analyzed similar to soil samples.  Test results take about 5 minutes from start to finish using our sample extraction kits.  Click the video below or see our TEST PROCEDURES for step-by-step test procedures.


Learn more about Oil Forensic Applications...


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