Abstract
In the present document, we report the development of an analytical method consisting of a sequential direct-immersion/headspace solid-phase microextraction (DI-HS-SPME) followed by gas-phase chromatography and tandem mass spectrometry (GC-MS/MS) for simultaneous analysis of 4-chlorobenzyl alcohol, 2,6-dichlorobenzyl alcohol, 4-methoxybenzyl alcohol, 3,4-dimethoxybenzyl alcohol, pyridine, and 2,3-dimethylpyrazine in oilfield production waters. These compounds are under evaluation for use as phase-partitioning tracers in oil reservoirs. To the best of our knowledge, this is the first time SPME has been applied to the analysis of these compounds in production waters, or any other type of matrix where the compounds targeted are the base for a technical application. Relevant extraction parameters, such as the adsorbent phase of the fiber, direct immersion or headspace, addition of salt, temperature and time of extraction were investigated. The final optimal operation conditions consist on extracting 5 mL of sample at pH 9.0 with 1.8 g of NaCl with constant stirring during 5 minutes of DI-SPME followed by 15 minutes of HS-SPME at 70 °C using a DVB/CAR/PDMS (50/30 µm) fiber. The limits of quantification (LOQ), linearity, precision and accuracy of the method were evaluated. Analyses of the tracer compounds and recovery studies were also performed on production waters from 8 different oilfields of the Norwegian continental shelf. LOQs between 0.080 and 0.35 µg L-1 were obtained. The recovery yields of the method were consistently higher than 85% and RSDs less than 13%. None of the tracer compounds was found in the real samples processed, which is consistent with one of the requirements for an artificial tracer in an oilfield: absence or constant and low background in the traced fluid. The performance of the method developed, combined with its easiness to automate, introduce a new, accurate and cost-efficient technique to process the hundreds of samples required by an inter-well tracer test.
Highlights
Nowadays, tracer tests are routinely used by the oil industry to retrieve information about the reservoir
The growing attention on partitioning inter-well tracer test (PITT) leads to a need for developing new oil/water partitioning tracers qualified for this application in order to minimize the risk of unsuccessful field tests due to the use of inadequate tracer compounds [3,10]. 4-Chlorobenzyl alcohol; 2,6-dichlorobenzyl alcohol; 4-methoxybenzyl alcohol; 3,4dimethoxybenzyl alcohol; pyridine; and 2,3-dimethylpyrazine were identified as relevant compounds in an ongoing comprehensive R&D project to introduce new oil/water partitioning tracers for the inter-well region of oil reservoirs [3,11,12]
We propose a methodology for analysis of the compounds identified as interesting PITT tracers in production waters from oilfields based on Solid-phase microextraction (SPME)-GC-mass spectrometer (MS)/MS, with a sequential DI-SPME and HS-SPME extraction
Summary
Tracer tests are routinely used by the oil industry to retrieve information about the reservoir. One type of such tests is the partitioning inter-well tracer test (PITT). The determination of the delay in the arrival of the partitioning tracers relies on the quantification of the tracer compounds often in several hundreds of produced water samples, collected during the test’s timeframe, to build the tracer production curves. 4-Chlorobenzyl alcohol; 2,6-dichlorobenzyl alcohol; 4-methoxybenzyl alcohol; 3,4dimethoxybenzyl alcohol; pyridine; and 2,3-dimethylpyrazine were identified as relevant compounds in an ongoing comprehensive R&D project to introduce new oil/water partitioning tracers for the inter-well region of oil reservoirs [3,11,12]. An analytical method to identify and quantify these compounds in production waters from oilfields is required
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
