Effect of supercritical CO2 flooding on the produced water quality and performance of the scale inhibitors in a typical tight sandstone oilfield

In order to enhance oil recovery, supercritical CO2 (scCO2) flooding has been applied in many oilfields to extract oil and gas post primary recovery. However, it causes serious scaling problems in the reservoir, oil well and production tubing. In this article, the produced water quality before and after scCO2 flooding in carbonate reservoirs are analyzed. The scaling trend of produced water before and after scCO2 flooding was calculated by using the Davis-stiff saturation index and Ryznar stability index methods. Static experiments and scanning electron microscope (SEM) are used to study the scale inhibition performance and mechanism of HEDP, ATMP, MA-AA, and PAA on CaCO3 in produced water before and after scCO2 flooding. The results show that after scCO2 flooding, the quality of produced water changes obviously, thus the scaling trend of produced water increases, the growth of CaCO3 crystal is affected and the scale inhibition efficiency of conventional scale inhibitors decreases.