Permeability damage due to water injection containing oil droplets and solid particles at residual oil saturation

Abstract

Re-injection of produced water is of increasing importance as water cuts continue to increase worldwide. It provides an environmentally acceptable solution to the disposal of produced water, and contributes to pressure maintenance when injection takes place into the reservoir itself. Injection can take place under matrix injection or fracturing conditions. In both cases, the performance of the injection well and the distribution of the injected water are strongly influenced by the build-up of formation impairment around the wellbore or the fracture face. Solid particles and small oil droplets dispersed in the injection water are deposited in the formation by a process of filtration, and therefore will cause this impairment. As part of a study on formation damage, different concentrations of oil droplets and hematite particles suspended in water were injected into sandstone core samples. A particle analyzer was used to measures the inlet and outlet concentrations of each particle type, concentration and size. The analysis confirms the high impact of oil concentration with the presence of solid particle on permeability damage. Preparation of oily-water emulsion is very challenging to achieve without chemical agents or mechanical devices. The presence of solid particles present in oily-water emulsion act as emulsion stability agents. Hematite particles being oil-wet, improved emulsion stability. Permeability impairment due to oily-water alone at residual oil formation is insignificant, and the size of oil droplets does not play a big role in injecivtivity decline. However, oily-water containing solid particles causes severe permeability damage. Furthermore, if the deposition of solids increases to a critical concentration, it could create a high differential pressure mobilizing some of the trapped residual oil. Copyright 2005, Society of Petroleum Engineers Inc.

Publication Title

SPE Middle East Oil and Gas Show and Conference, MEOS, Proceedings

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