Abstract
Abstract Pyridine, 2-hydroxy-6-methylpyridine, 3-hydroxypyridine, and 4-methoxypyridine are evaluated as potential phase-partitioning oil field tracers. Their stability is tested in a brine for 12 weeks at temperatures between 25 °C–150 °C, and at initial pH values of 5,5; 7,1; 8,0. Interactions with kaolinite clay, Berea sandstone and limestone are also evaluated. The main results are as follows: pyridine is stable up to 12 weeks at 150 °C, and not influenced by the rock substrates or pH. 2-hydroxy-6-methylpyridine becomes unstable at T ≥ 50 °C, is not affected by the rock substrates, and exihibts slower degradation kinetics at higher pH values. 3-hydroxypyridine is unstable at T ≥ 75 °C, sensitive to the presence of kaolinite in a combined effect with pH, and exihibts slower degradation kinetics at higher pH. 4-methoxypyridine degrades at T ≥ 75 °C, is characterised by a strong interaction with kaolinite, and is insensitive to pH. The degradation of 4-methoxypyridine in the absence of kaolinite clay follows pseudo first-order kinetics. This compound could indicate the temperature in the swept volumes, and in conjunction with a fully conservative tracer indicate the presence of clays. Pyridine exhibits the required stability and lack of interaction with rock materials to be used as PITT tracer in oil reservoirs. However, it is present in oils and its concentration levels in production waters should be evaluated prior to its use.
Highlights
Knowledge of the residual oil saturation (SOR) in the swept volumes of oil reservoirs can be used both to improve reservoir management, and in the design and evaluation of EOR/IOR projects [1,2]
In this document we present the stability assessment performed on 4 pyridines that are partitioning inter-well tracer test (PITT) tracer candidates
It is the precursor to some pesticides, such as paraquat and diquat [16], industrially used as solvent, in the production of dyes, explosives, pharmaceuticals, etc. [17,18], and is used as a ligand in coordination chemistry [19]. 4-Methoxypyridine is mostly used as a ligand in coordination chemistry [20,21], and in the synthesis of pharmaceutical compounds [22]. 3-Hydroxypyridine has been considered as a precursor for the production of nitrogen-rich polymers for CO2 adsorption [23], used as additive to improve optical properties of hydrophilic ophthalmic lenses [24], and as precursor for pharmaceutical active principles [25]. 2-Hydroxy-6-methylpyridine has no significant industrial use and we only found it reported as a ligand in the preparation of metal-lanthanide complexes or special metal complexes [26,27]
Summary
Knowledge of the residual oil saturation (SOR) in the swept volumes of oil reservoirs can be used both to improve reservoir management, and in the design and evaluation of EOR/IOR projects [1,2]. The poor knowledge about the behaviour and geochemical interactions of the compounds used as PITT tracers lead to many unsuccessful tests in the past [4,6]. In recent years, this type of tracer test has received increasing attention due to the importance of the information it provides [7,8]. The study of tracer compounds prior to their use on the field is crucial, to ensure the accuracy of the tests, and to evaluate the possibility of using tracers to retrieve other type of relevant information [10,11,12]. The influence of temperature, pH, time, salinity, and different rock materials, on the stability and behaviour of pyridine, 4-methoxypyridine, 3-hydroxypyridine, and 2-Hydroxy-6-methylpyridine was investigated
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