Evaluation of Polyamidoamine-Assisted Scale Inhibitors for Silicate Scale Mitigation at Simulated Near-Wellbore Conditions
Authors: Tan B. C. , Saaid I. M. , Mahat S. Q. A. , Zainal S. , Bhaskoro P. T. , Anuar A. 
Published: February 2025

Summary
Silicate scaling is a challenge that can result in formation damage and flow assurance issues in production systems due to alkali-based chemical flooding. Previous research has indicated that the classic scale inhibitor chemicals, such as phosphonates and phosphinopolyacrylates, exhibit poor efficiency in silicate scale inhibition. Polyamidoamine (PAMAM) dendrimers have gained considerable attention in the search for silicate scale mitigation along with other polymeric inhibitors to build synergism. The contribution of silicate scale inhibition has received little attention within the petroleum industry. In this paper, we aim to investigate the performance of PAMAM-assisted inhibitors for silicate scale mitigation under simulated near-wellbore region conditions. A static bottle experiment was carried out to assess the effectiveness of folic acid (PteGlu), PAMAM dendrimers of Generations 1.0 (PAMAM G-1) and 2.0 (PAMAM G-2), and their synergistic formulations (PAMAM G-1/PteGlu and PAMAM G-2/PteGlu) in silicate scale inhibition at increasing temperatures. A dynamic scale loop experiment was also performed to determine the minimum inhibitor concentrations (MIC) of pure scale inhibitor chemicals and their effectiveness in hindering silicate precipitation under fluid flow condition. To mimic a squeeze operation, a coreflooding experiment was conducted to evaluate the dynamic adsorption and desorption characteristics of the PAMAM-assisted scale inhibitors in sandstone formation. Static bottle test results revealed that the presence of inhibitors yields better scale inhibition as the temperature increases gradually. The findings show that PAMAM G-2/PteGlu silicate scale inhibitor outperforms the other inhibitors under static and dynamic conditions at all tested temperatures. This inhibitor reduced the turbidity of brine mixture by 84.1% at room condition, and the turbidity reduced further by 94.8% at a temperature of 90°C. When tested with the silicomolybdate method, PAMAM G-2/PteGlu inhibitor was 42.6% effective in preventing silicate scale formation at room temperature. Surprisingly, its silicate scale inhibition increased to 52.6% at 95°C after 72 hours. Moreover, PAMAM G-2/PteGlu inhibitor was able to delay scale precipitation remarkably by 48-fold as compared with that without inhibition in the dynamic scale loop test. The coreflooding results showed that the dynamic adsorption and desorption of PAMAM/PteGlu inhibitors were slightly better than that of phosphonate inhibitor. Maximum adsorption was achieved after 3 pore volumes (PV) of PAMAM G-2/PteGlu inhibitor injection and required 1,420 PV of post-flush brine to reach its 10 mg/L MIC in Berea core. Meanwhile, PAMAM G-1/PteGlu inhibitor exhibited similar performances in silicate scale inhibition up to 50.2% effectiveness, delayed scale buildup by 45-fold, achieved maximum adsorption in the core with 3-PV inhibitor injection, and required 1,200 PV of post-flush brine to reach 10 mg/L MIC. In this work, the ascending sequence of silicate scale inhibition performance is PAMAM G-1 &lt; PAMAM G-2 &lt; PteGlu &lt; PAMAM G-1/PteGlu &lt; PAMAM G-2/PteGlu. This study implies that silicate scale treatment using synergistic PAMAM-assisted scale inhibitors is possible for oilfield conditions. Additionally, these scale inhibitors are deemed environmentally friendly chemicals that could offer alternatives to commercial scale inhibitors.