ATP monitoring in the context of crude oil presents unique challenges due to the complex nature of the sample matrix and the harsh conditions often associated with oil extraction, transportation, and processing. This article explores a situation where obtaining a water sample becomes problematic or where water there is little to no water content, necessitating the collection of a crude oil sample.
For customers operating in midstream (crude oil distribution) where the extraction of water from a sample collection point might be difficult, LuminUltra adopted a modified procedure. Treating a crude oil sample as a solid using LuminUltra modified procedure only becomes necessary when the amount filterable using QGOM falls below 1 mL. Otherwise, QGOM remains the preferred method.
Here are some struggles associated with ATP monitoring in crude oil:
- Sample Preparation: Extracting ATP from 100% Crude Oil Samples is challenging. Crude oil is often viscous and can contain solids, emulsions, and water. The sample preparation process becomes crucial in releasing ATP from microorganisms present in the oil.
- Baseline Variation: Establishing a consistent baseline for ATP levels in crude oil environments can be difficult due to the variability in the type of crude oil, geographical location, extraction methods, and source water. However, without a reliable baseline, it becomes challenging to interpret ATP measurements accurately and to set appropriate standards.
Modified Sample Preparation Procedure
If your sample is a 100% oil sample (no water) and filtration is not possible, treating the samples as a solid will produce successful results for analysis. Using the solids method, the result will be in Total ATP (tATP), a measurement of both the cellular and extracellular (dissolved) ATP.
- Add 1 mL of crude oil to a 5 mL Ultralyse 7 (Extraction) Tube. Invert 3x and allow the oil and extractant to separate into two layers.
- Allow at least 5 minutes for ATP extraction in the UltraLyse 7 (Extraction) Tube. Ensure the same extraction time is used for each sample to get comparable results between samples.
- Transfer 1 mL of the aqueous layer from the UltraLyse 7 (Extraction) Tube to a 9 mL UltraLute (Dilution) Tube.
- Pipet 100 µL of the UltraLute (Dilution) solution into a 12x55 mm test tube with 100 µL Luminase and take reading.
Tips for Success:
- For enhanced accuracy and comparability, it is advisable to maintain consistent timing and sampling practices between samples. Establish standardized sampling protocols to ensure uniform ATP measurements.
Calculating your tATP value:
Replace the area with 1 mL if using the sampling technique above
Comparing Readings Between Different Sample Matrices:
Directly comparing ATP readings between crude oil and an oil-associated water sample is not advised due to the variance in composition and capacity to host active microorganisms. For baseline establishment and trending, it is advised to compare only between similar sample types (i.e., produced water to other produced water samples, or crude oil to other crude oil samples). Trying to directly compare ATP readings from crude oil samples with those from water samples can lead to inaccurate interpretations.
Here's why this distinction is important:
- Diverse Composition: Microorganisms live in water. Crude oil can contain small water droplets that host microbial growth, however the amount of water droplets and therefore the amount of microbial activity in a crude oil can differ depending on its composition. Water will, in most cases, have much higher microbial activity than crude oil.
- Baseline Variability: Establishing consistent baselines for ATP readings requires considering the natural variations within each type of sample. Crude oil and water will have different ATP [DN7] baseline levels. Comparing ATP levels without accounting for these baseline differences can lead to misinterpretation of contamination levels.
- Accuracy and Applicability: The purpose of ATP monitoring in oil and gas systems from upstream through to downstream is to assess the level of microbial contamination and the efficacy of mitigation strategies. By comparing readings between the same sample type, such as crude oil with crude oil and water with water, you can accurately determine if microbial growth standards are being met. This approach provides relevant and actionable insights for microbial management.
In summary, the primary reason for comparing ATP readings within the same type of sample (crude oil with crude oil and water with water) is to ensure accurate and meaningful assessments of microbial contamination and efficacy of mitigation strategies. Attempting to directly compare disparate substances like crude oil and water can lead to inaccurate conclusions, as the properties and components of these sample types are unique.