Heavy Acidic Oil Transportation By Emulsion In Water

Abstract

This paper sets out to demonstrate, at lab scale, the feasibility of the twomain phases of the process, namely the emulsification of a heavy Venezuelanacidic crude oil (ZUATA), and the subsequent breaking of the oil-in-wateremulsion. The heavy ZUATA crude can be emulsified directly by making use of thesurfactants naturally present in this rich acid oil. These potentialsurfactants, mainly represented by naphthenic acids, become effectiveemulsifiers when salified into naphthenate anions by the addition of bases(soda, ammonia). Stable oil-in-water emulsions, typically with 60 to 65% oil, are obtained byusing these two bases. There are a number of advantages to be gained in usingammonia to form the oil-in-water emulsions as opposed to other bases (soda forexample) for emulsion breaking and phase separation. The paper demonstrates that it suffices to heat the emulsion to break it. Itdescribes the conditions required for ammonia removal and recovery, and theresulting emulsion breaking. An industrial process for achieving the separation is then proposed. Introduction Extra heavy oils (viscosity >10,000 cP, 7<°API<12) can betransported1–3 by heated pipelines, or regular heating of the crude, or dilution with a lighter crude or a naphtha. Of all these different transportmeans, dilution is the most economical and currently the most widely used. The dilution ratio varies between 30 and 40% depending on the transportationspecifications of the pipelines (19°API and crude viscosity<350 cP forCanada, 400 cP for Venezuela). Using the diluent affects the capacity of thepipeline, which is reduced from 30 to 40% and this entails the necessity ofeither having a second pipeline for diluent return, or purchasing more diluenton the production site. Moreover, as the diluent is extracted from the crudeduring atmospheric distillation in the upgrader unit or in the customer'srefinery, the crude desalting, heating and atmospheric distillation units areover-sized by 30 to 40%. The transportation of heavy crude oil by emulsification in water4can be made economically attractive, in comparison with other means such asdilution, provided the surfactant stabilizing the emulsion can be recovered.The lower viscosity of the oil-in-water emulsion significantly increases thetransportation capability. Using water instead of diluent simplifies the crudetreatment process. This paper sets out to demonstrate, at lab scale, the feasibility of the twomain phases of the process, firstly, emulsification of a heavy Venezuelanacidic crude oil (ZUATA) and, secondly, the subsequent breaking of theoil-in-water emulsion. Emulsification of heavy ZUATA oil The ZUATA oil can be emulsified directly, without any added externalsurfactant, owing to the surfactants naturally present in this rich acid heavyoil (°API: 7.8, Total Acidity: 4.3 mg KOH/g). The relevant "potential"surfactants are chiefly represented by naphthenic acids, which become"effective" surfactants when transformed into naphthenate anions by addition ofa base (NaOH, NH4OH)5.These naphthenate salts assume therole of "effective" surfactants, enabling oil-in-water emulsions to be obtainedat various oil-to-water ratios.

Crude Oil Emulsion Properties and Their Application to Heavy Oil Transportation

“…The second way is to "activate" the natural surfactants which are part of heavy crude oil composition: one can make these surfactants more hydrophilic by ionizing the acid functional groups carried by the fatty acids and asphaltenes (from low molecular weight species to carboxylic functions carried by asphaltenes) with a strong base like soda. Addition of strong bases is a well know process in enhanced oil recovery by decreasing interfacial tension to very low values [32][33][34][35][36][37][38]. The presence of natural saponifiable acids in some crudes may eliminate the need for expensive commercial surfactants.…”

“…Ammonia can then be recovered and recycled [35]. Breaking these emulsions is a challenge for different reasons: -The density of heavy oil is very close to the density of water.…”

Influence of pH on Stability and Dynamic Properties of Asphaltenes and Other Amphiphilic Molecules at the Oil−Water Interface

“…Because asphaltenes are surface-active, water-in-oil emulsions are formed when oil and water are stirred together, for instance, during the production processes. Many studies of these emulsions can be found in the literature. − Very early, the oil−water interfacial properties in the presence of asphaltenes have been shown to be very peculiar, with long adsorption times and formation of rigid skins at the interface. − The influence of pH has been studied on model emulsions with asphaltenes or on water−crude oil emulsions. ,,− There are basically two ways to obtain oil-in-water emulsions: through the addition of water-soluble surfactants and/or the addition of bases to saponify amphiphilic molecules contained in the oil, making their compounds (such as naphthenic acids, asphaltenes, ...) more hydrophilic. The aim of the present study is to investigate, in more detail, the role of pH on interfacial properties of asphaltenes and asphaltene/surfactant mixtures at the oil/water interface and to study the relationship between interfacial properties and the stability of model emulsions as a function of pH.…”

Required Viscosity Values To Ensure Proper Transportation of Crude Oil by Pipeline

“…(d) For diluted extra heavy oils with naphtha or lighter crude for transportation by pipeline API gravity is 19 and viscosity is <350 cP (∼ < 355 cSt) for Canada and 400 cP (∼420 cSt) for Venezuela …”