Nanoemulsion-Enhanced Treatment of Oil-Contaminated Cuttings

Abstract

This article, written by Dennis Denney, contains highlights of paper SPE 162401, ’Nanoemulsion-Enhanced Treatment of Oil-Contaminated Oil-Based Drill Solids,’ by Wasan Saphanuchart, SPE, Yoong Shang Loke, SPE, and Chun Hwa See, SPE, BCI Chemical Corporation, prepared for the 2012 Abu Dhabi International Petroleum Exhibition & Conference, Abu Dhabi, 11-14 November. The paper has not been peer reviewed. When oil-based mud is used, the drilled formation solids (cuttings) are regarded as controlled or hazardous waste. As such, they can be disposed of in three ways: decontamination treatment followed by discharge into the sea, injection of the cuttings into the well, or transfer to a controlled hazardous-waste landfill. The lowest environmental effect for solids disposal, especially for offshore operation, is decontamination treatment followed by discharge. However, conventional decontamination technology exhibits limited efficiency in extracting oil from the drill solids. Introduction One function of drilling mud is a washing action to remove cuttings from the wellbore. The mud returns to the surface with entrained cuttings and, typically, flows through shale shakers, desanders, desilters, hydrocyclones, centrifuges, or other devices to separate the cuttings from the mud. Conventional decontamination technology yields an oil content in the treated cuttings of >1% in the dried solids, which does not meet strict environmental regulations in many highly ecologically sensitive countries (e.g., the UK and North Sea countries). Apart from cuttings reinjection, all other treatment methods require land-based waste treatment. Nanoemulsion technology can improve oil-removal efficiency by providing ultralow oil/water interfacial tension (IFT). Heavy- and light-oil extraction from the cuttings surface is enhanced. The cuttings-treatment process proposed in this paper can achieve oil content of <1%. Nanoemulsion Nanoemulsions are clear and thermodynamically stable. In typical nanoemulsions, the droplet size ranges from 10 to 100 nm, which is much smaller than the wavelength of visible light. Hence, nanoemulsions generally are weak scatterers of light, making them transparent. Nanoemulsions can be formulated with a single phase or multiple phases. The IFT between the aqueous and hydrocarbon phases in nanoemulsion systems can be as low as 0.0001 mN/m, compared with an ordinary emulsion or macroemulsion (approximately 0.1 to 30 mN/m). A nanoemulsion might be a dispersion of water in oil or oil in water (in which the second solution is the dispersion medium or solvent). There may also be a bicontinuous structure in which both water and oil are continuous.