A New Logistically Simple Solution for Implementing Alkali-Surfactant-Polymer/Alkali-Cosolvent-Polymer in Difficult Environments: Evaluation of Concept with High Total Acid Number Viscous Crude Oil

Abstract

Summary Research on alkali-assisted chemical enhanced oil recovery (EOR) technology [alkali-surfactant-polymer (ASP)/alkali-cosolvent-polymer (ACP)] with high total acid number (TAN) crude oils has led to developments with liquid organic alkalis and cosolvents (Southwick et al. 2020; Fortenberry et al. 2015; Schumi et al. 2019; Upamali et al. 2018). Both concepts afford potential significant cost reduction in field operations, but to date it has not been demonstrated that these two concepts can work together. Monoethanolamine (MEA) alkali and a wide variety of liquid cosolvents are evaluated with high TAN crude oil (1.5 mg KOH/g oil). Formulations are found that give ultralow interfacial tension (UL-IFT) at a specified injection salinity. Fine tuning the formulation to different injection salinities can be done by choosing alternate cosolvents (or a cosolvent blend). A formulation comprising 1% MEA and a novel high molecular weight (3152 g/gmol) cosolvent, 0.5% glycerin alkoxylate with 30 mol of propylene oxide and 35 mol of ethylene oxide (glycerin-30PO-35EO), gave UL-IFT in 21,000 total dissolved solids (TDS) injection brine and gave 100% oil recovery in Bentheimer sandstone with 3,500 ppm FP 3630Ss (SNF Flopaam 3630Sis partially hydrolyzed polyacrylamide) as mobility control agent. All oil was produced clean, no separation of emulsion was needed to measure oil recovery. Alkali consumption tests were also performed with a high-permeability reservoir sandstone. Results confirmed earlier data published with Boise outcrop sandstone (Southwick et al. 2020) showing low alkali consumption with MEA. On a mass basis, only 12% of the amount of MEA is consumed relative to the amount of sodium carbonate consumed. This reduces the logistical challenges of shipping chemicals to remote locations. MEA is also a low-viscosity liquid which further simplifies field handling.