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

Abstract

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.

Keywords:

• ScCO₂ flooding
• scaling trend
• scale inhibitor
• CaCO₃ crystal

Acknowledgments

This work was supported by the scientific research program funded by Shaanxi provincial education department (21JK0984), the natural science basic research project of Shaanxi province (2021JQ-633) and innovation and entrepreneurship training program for college students of Shaanxi province (S202110719016, S202110719098), which are gratefully acknowledged.