Compositional Variations between Precipitated and Organic Solid Deposition Control (OSDC) Asphaltenes and the Effect of Inhibitors on Deposition by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometry

Abstract

Organic solid deposition control (OSDC) is a live oil test capable of simulating the production conditions of oil streams and can generate asphaltene deposits under production system conditions. OSDC can also simulate gas lift conditions because the producers are looking for artificial lift methods to produce oil from low-energy reservoirs. In this paper, we present the first compositional study on the OSDC deposits under gas lift conditions and compare it to C7 asphaltenes from the same crude oil precipitated in the laboratory, by use of ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry. Furthermore, deposits collected from chemically treated fluids were also studied. The negative-ion mass spectra of OSDC deposits from untreated crude oil and asphaltene inhibitor (AI)-treated crude oil are richer in acidic species, such as the Ox and SxOy polar classes, relative to the parent crude oil. The molecular-weight differences for treated deposits relative to the untreated sample may help explain the deposition tendency in the tests. We infer that a correlation of field asphaltene deposition tendency with laboratory screening tests is essential for the advancement of asphaltene research.