Chemical scavenging of hydrogen sulfide and mercaptans

Emulsion separation

Keywords
Emulsionseparationdemulsificationemulsificationcrude oilcoalescenceoilfield processingdemulsifierchemicalselectrocoalescencemechanical internalsheating.

Crude oil and formation water from a reservoir is produced under conditions that often favor the formation and flow of emulsions towards and inside the processing facility. Except for crude oil desalting, the occurrence of emulsions is undesirable, as it creates the potential to impede the formation of bulk crude oil and produced water phases. The formation of emulsions often cannot be completely prevented, even though measures are usually taken to at least mitigate their occurrence. The residence time in a multiphase separator is typically limited to a few minutes, which puts an upper limit on the maximum allowed lifetime of an emulsion if bulk separation of oil and water is to be accomplished. For these reasons, an understanding of the conditions that favor emulsion formation in upstream crude oil processing is required, as also how to accelerate the breakage rate of emulsions in a way that crude oil treatment remains an economically feasible affair. In this chapter, we aim to outline the fundamental scientific and technological aspects relevant to emulsion separation in crude oil processing. We first discuss the key factors that govern emulsion formation, stabilization, and separation. Building up from these principles, we describe approaches for analyzing and predicting the separation process, which can serve as a basis for the design of oil–water separators. The main driving force for the separation of the two liquid phases is gravity, but often additional mechanisms are required to enhance the separation rate. In the last section of this chapter, we will review heating, mechanical internals for separator vessels, and chemical as well as electrostatic demulsification techniques as the four primary means to boost bulk oil–water separation.

Foam control

Keywords: Antifoam
defoamer
crude oil separator
antifoaming mechanism
foam stabilizer
water-based foam
oil-based foam
silicone antifoam, nonsilicone antifoam

Unwanted foaming occurs in many oilfield applications, and although it can be eliminated by mechanical means, the use of antifoams and defoamers is the most common and effective technique. The chemistry and operation of antifoams depend strongly on whether the system is water- or oil-based, due to their different surface chemistry. The nature of the foam also depends on the chemistry of the foam stabilizers in the system, such as surfactants, macromolecules, and solid particles. In oil-based systems, silicone antifoams with three different chemistries are used almost exclusively: polydimethylsiloxane (PDMS), organomodified silicones, and fluorosilicones, and the most important applications are related to crude oil separators. In water-based systems, silica-filled PDMS and organics (such as polyalkylene glycols) are the most typical antifoams. The foam control mechanisms of the various systems will be reviewed in detail herein, as well as their relevance to several water- and oil-based oilfield applications.