Abstract

The generation of stable emulsions at reservoir temperature was investigated as a possible mechanism of formation damage in the near well-bore area, Typically, emulsions have been considered a top-side process problem. Furthermore, experimentation is often based on a set of single events and a traditional conclusion would be that emulsions are of little concern in plugging mechanisms. However, in nature single event mechanisms are scarce. Under actual reservoir conditions both generation of scale and mobilization offines together with formation of emulsions might be simultaneous events. Thus, a combination of such mechanisms may lead to the plugging. In the present investigation a set of 11 different well parameters were tested in a factorial screening design for potentials in emulsion formation. The results from this screening design show that combinatorial effects are key events in fines stabilized emulsions. Two different North Sea degassed crudes gave emulsions under various combination of variable settings at reservoir temperature.

The present paper gives a survey on the influence of these variables on the stability and viscosity of the generated emulsions. Generation of emulsions and increase of flow viscosity might have great influence on well productivity.

Introduction

Production related formation damage has been estimated to reduce the income by more than 1 million NOK a day in some of the North Sea fields.

Although scale formation is touted as the most plausible damage mechanism it cannot explain the reduced productivity in many wells. For about 40% of these cases the exact mechanism of the formation damage is not known. In this respect combinatorial effects were sought as a possible explanation in an overall plugging mechanism.

The process of emulsification, that is, dispersion of liquids in liquids, is governed by surface forces.

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