Controlled releases of asphaltene inhibitors by nanoemulsions

Abstract

Asphaltene precipitation is usually responsible for many flow assurance problems such as wettability changes and pore clogging in reservoirs, fouling in wellbore tubings and production surface facilities. This study develops a novel approach by using nanoemulsions (NE) for controlled delivery and release of asphaltene inhibitors (AI) to minimize asphaltene precipitation with reduced AI amount. LUMiSizer was utilised to study the effectiveness and performance of controlled release by three cases on asphaltene sedimentation: i) strong organic acids (dodecyl benzene sulfonic acid, DBSA), ii) nanoemulsions (blank NEs), and iii) nanoemulsions loaded with DBSA (DBSA NEs). The experiments suggested that the optimum inhibitor concentration for completely stabilizing asphaltene were 4 vol. % for DBSA. This amount of inhibitor can be significantly reduced by ~ 20 times by using the DBSA NEs, and the release time can be greatly extended. A mechanistic understanding of the controlled release effect is proposed based on interfacial properties and electron microscopic studies, which is related to the hydrophilicity of DBSA and the strong intermolecular interactions among all DBSA NE's components and the asphaltene molecules.

Molecular structure characterization of asphaltene in the presence of inhibitors with nanoemulsions

“…The total chemicals usage (% R TC ) are again lower than 4 vol% DBSA by a factor of 10%. These results in very good agreement with the previous work 27 for reducing AI amount and the total chemicals used, which found that 4 vol% DBSA and 20 vol% of DBSA NEs gave the same values of the instability indexes and the sedimentation rates.…”

“…Such a synergistic effect may overcome the hydrogen bond forces of water molecules and enhance the bounded molecules at the interface, resulting in more hydrophobicity of the oil phase. The procedure of synthesis of nanoemulsions with the presence and absence of AI was elaborated in the previous study, 27 as depicted in the schematic diagram in Fig. S1 in the ESI.…”

“…28 The procedure of asphaltene extraction was reported previously. 27 For preparation asphaltene solution, a (0.5 w/v %) of the asphaltene was dissolved in a mixture of two solvents: toluene/heptane (Heptol) volume ratio of 60 : 40. To observe the effect of DBSA, blank NEs, and DBSA NEs on asphaltene precipitation structure, samples were slowly added to the asphaltene solution under shear action in an (IKA T2S digital/Ultra-Turrax) homogenizer at a rotation speed of 7000 rpm until a complete combination of the NEs into the asphaltene solution.…”

“…As discussed in the previous study, 27 this system can overcome asphaltene intramolecular forces, creating new spaces, and involves multiple interactions between asphaltene and DBSA NE components including acid-base interactions, hydrogen bonding, polar-p interactions, cation-p interactions, and p-p interactions. These forces can provide additional electrostatic interactions with other ion-pair.…”

“…We have proposed a novel concept of using nanoemulsion as a carrier for AI and control its release inside asphaltene solution to increase asphaltene stability. 27 The ndings conrm that NEs could (i), signicantly decrease the inhibitors usage (ii) improve the asphaltene stability, and (iii) extend the treatment time via the slow release of AIs with high efficiency. However, a complete molecular analysis of asphaltene and a systematic understanding of how asphaltene molecular structure changes with the addition of inhibitors have not yet been achieved.…”