Formation Damage Assessment and Adsorption/Desorption Profile of New Phosponate-Based Scale Inhibitor at 350°F

Abstract

Abstract The formation of calcite scale is induced generally through a change in pressure and temperature, which affects the saturation level of calcium and bicarbonate as the CO2 gas is released. Prevention of calcite precipitation through scale inhibitor squeezing job treatment is a well-known method for minimizing potential scaling. The selection of suitable scale inhibitor is important as its performance can be affected by the lithology and reservoir conditions. In this study, a scheme of screening new scale inhibitors was evaluated. The proposed scheme included the study of the adsorption/desorption characteristics of the scale inhibitor and its efficiency at higher temperature. The proposed scale inhibitor treatment design included pre-flush/post-flush fluid and the SI main fluid in addition to the synthetic formation water (SFW). Lithium chloride was introduced to the main SI fluid as a tracer. To study the SI fluid-rock interaction, core flood testing was conducted on the Outcrop Torrey Buff sandstone core plug. The results of the core flood was used to determine the change in permeability during the SI soaking and assess the formation damage. Ca, Mg and total iron in the effluents samples were used to study the dissolution of the plug. P and Li analysis were used to study the absorption/desorption behavior of the scale inhibitor during the 5 days of flooding and compared to the minimum inhibition concentration (MIC). Core flood data showed the differential pressures versus the cumulative pore volume of the injected fluids revealed that around 20% of formation damage was encountered during the SI flooding, which is anticipated in sandstone rock due to high adsorption of the scale inhibitor on the rock. The desorption profile of the scale inhibitor showed that the proposed treatment scale inhibitor could keep its concentration above the MIC at ultra-high temperature. The study revealed that the proposed phosphonate-based inhibitor showed effective performance at higher temperature. The desorption rate is adequate to keep the scale inhibitor concentration above the MIC. The scheme of study can be used to screen different scale inhibitors at higher temperature and to assess their adsorption/desorption characteristic.