The composition of acid/oil interface in acid oil emulsions

Yulia M Ganeeva,Ekaterina E Barskaya,Vladimir I Morozov,Ekaterina S Okhotnikova,Alina Kh Valiullova,Tatiana N Yusupova,Lucia F Davletshina

doi:10.1007/s12182-020-00447-9

Abstract

In well stimulation treatments using hydrochloric acid, undesirable water-in-oil emulsion and acid sludge may produce and then cause operational problems in oil field development. The processes intensify in the presence of Fe(III), which are from the corroded surfaces of field equipment and/or iron-bearing minerals of the oil reservoir. In order to understand the reasons of the stability of acid emulsions, acid emulsions were prepared by mixing crude oil emulsion with 15% hydrochloric acid solutions with and without Fe(III) and then separated into free and upper (water free) and intermediate (with water) layers. It is assumed that the oil phase of the free and upper layers contains the compounds which do not participate in the formation of acid emulsions, and the oil phase of the intermediate layers contains components involved in the formation of oil/acid interface. The composition of the oil phase of each layer of the emulsions was studied. It is found that the asphaltenes with a high content of sulfur, oxygen and metals as well the flocculated material of protonated non-polar oil components are concentrated at the oil/acid interface. In addition to the above, in the presence of Fe(III) the Fe(III)-based complexes with polar groups of asphaltenes are formed at the acid/oil interface, contributing to the formation of armor films which enhance the emulsion stability.

Highlights

During well operations, reservoir porosity and permeability of bottomhole rock deteriorate as a result of clay swelling, mineral scaling, asphaltene and wax deposition, formation of high viscosity water-in-oil emulsions, etc
It was assumed that the oil phase of the free and upper layers contains the compounds which do not participate in the formation of acid emulsions, and the oil phase of the intermediate layers, on the contrary, contains components involved in the formation of armor films at the oil/acid interface
The quantitative and qualitative redistributions of asphaltenes and waxes in acid emulsions were investigated by mixing crude oil emulsion with 15% hydrochloric acid solutions with and without Fe(III)

Summary

Introduction

Reservoir porosity and permeability of bottomhole rock deteriorate as a result of clay swelling, mineral scaling, asphaltene and wax deposition, formation of high viscosity water-in-oil emulsions, etc. To improve wellto-reservoir connectivity and restore rock permeability in the bottomhole formation zone, well stimulation treatments with various acids are used. During acid treatment there is an interaction of Edited by Yan-Hua Sun. The operational effective factors affecting the acid oil emulsion and sludge formation are compiled by Shirazi et al (2019) and are: acid type and strength, additives, temperature, iron concentration ferric, exposure time, mixing rate and acid mixture ratio. It is generally believed that the formation of stable waterin-oil emulsion is caused by the adsorption at the oil/water interface the surface-active compounds, such as asphaltenes, resins and naphthenic acids present in the oil

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