The prospect of using permanent downhole sensors for monitoring oilfield scales

This paper aims to extend the scope of a previous investigation of the applicability of combined electrical resistivity and temperature logs for monitoring scale in carbonate formations during carbon dioxide sequestration in saline carbonate aquifer or during CO₂-EOR projects. This study intends to extend the scope of resistivity and temperature logs to a new area of importance which is scale monitoring in real time and in-situ in porous media, completion, and surface facilities. Previous works have focused on the use of electrical resistivity measurements to track carbon dioxide migration by observing time lapse resistivity change based on the understanding that electrical resistivity only changes when rock fluid saturation or rock content changes. Such experiments were also conducted only within several hours or less. They did not consider the effect of fluid rock interaction on formation resistivity. Also, in field application, time lapse in the range of months is often considered thereby neglecting vital information from the reservoirs if measurements were taken continuously. It is discussed in this paper that such voluminous data often ignored or not taken during logging has a lot to tell about the processes going on in the reservoir or in production facilities particularly during CO₂projects. Furthermore, no real time and in-situ down-hole scale monitoring technique currently exists. Current practice involves frequent and continuous geochemical and petrographic analysis of produced formation water cuttings. The technique proposed in the current study comes with no additional cost as it utilizes permanent down-hole sensors such as temperature and resistivity.