Preparation and Performance Evaluation of Amphiphilic Polymers for Enhanced Heavy Oil Recovery.

The continuous growth in global energy and chemical raw material demand has drawn significant attention to the development of heavy oil resources. A primary challenge in heavy oil extraction lies in reducing crude oil viscosity. Alkali-surfactant-polymer (ASP) flooding technology has emerged as an effective method for enhancing heavy oil recovery. However, the chromatographic separation of chemical agents presents a formidable obstacle in heavy oil extraction. To address this challenge, we utilized a free radical polymerization method, employing acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, lauryl acrylate, and benzyl acrylate as raw materials. This approach led to the synthesis of a multifunctional amphiphilic polymer known as PAALB, which we applied to the extraction of heavy oil. The structure of PAALB was meticulously characterized using techniques such as infrared spectroscopy and Nuclear Magnetic Resonance Spectroscopy. To assess the effectiveness of PAALB in reducing heavy oil viscosity and enhancing oil recovery, we conducted a series of tests, including contact angle measurements, interfacial tension assessments, self-emulsification experiments, critical association concentration tests, and sand-packed tube flooding experiments. The research findings indicate that PAALB can reduce oil-water displacement, reduce heavy oil viscosity, and improve swept volume upon injection into the formation. A solution of 5000 mg/L PAALB reduced the contact angle of water droplets on the core surface from 106.55° to 34.95°, shifting the core surface from oil-wet to water-wet, thereby enabling oil-water displacement. Moreover, A solution of 10,000 mg/L PAALB reduced the oil-water interfacial tension to 3.32 × 10-4 mN/m, reaching an ultra-low interfacial tension level, thereby inducing spontaneous emulsification of heavy oil within the formation. Under the condition of an oil-water ratio of 7:3, a solution of 10,000 mg/L PAALB can reduce the viscosity of heavy oil from 14,315 mPa·s to 201 mPa·s via the glass bottle inversion method, with a viscosity reduction rate of 98.60%. In sand-packed tube flooding experiments, under the injection volume of 1.5 PV, PAALB increased the recovery rate by 25.63% compared to traditional hydrolyzed polyacrylamide (HPAM) polymer. The insights derived from this research on amphiphilic polymers hold significant reference value for the development and optimization of chemical flooding strategies aimed at enhancing heavy oil recovery.

Method for Judging the Stability of Asphaltenes in Crude Oil.

The colloidal instability index (CII) has been widely used for testing the stability of asphaltenes as a classical method. In this study, five oil samples were tested by the CII method; the results obtained greatly differ from the real field results. In our investigation, we combined the Turbiscan LAB stability analyzer and saturate, aromatic, resin, and asphaltene (SARA) analysis to further investigate the asphaltene stability by heptane titration. The results revealed that there exists a threshold volume ratio before the asphaltenes destabilize. The stability of crude oil is related to the saturation solubility of asphaltenes. By testing the CII value of the crude oil in its current state and the CII value of the dissolved asphaltenes in its saturated state, we were able to propose a new way to judge the oil stability.